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Q: Hi Tim,

My tech says I need a fm circuit board for my Marantz 2245, am works fm does not. Do have any idea where I can locate one? Is this interchangeable with any other 22xx series board?


A: Hello John,

Sounds more like you need a new tech. This era of technology was not designed to be board swap-able. The units were designed to be repaired to the component level. Virtually all modern electronics are designed to either be recycled or repaired by changing out large blocks of components. Unless your tech is older, he probably has little or no experience with component level repairs. The only reason to swap out an entire board would be if it is physically damaged beyond repair. You'll have to find another 2245 for parts to get an entire circuit board.


Q: I have 4 Pioneer Spec II Amplifiers that I purchased in the late 70's. 3 out of 4 of them have begun to do the same thing. If I let them sit for a while, they work fine initilally, but if I leave them on for a day or so without turning them off, they go into overload. After turning them off, unless I let them sit for a long while before turning them back on again, they will not turn back on since they still remain in overload unless allowed to sit for a day or so.

Someone told me to check the output transistors, and reseat them suggesting that it was heat related. I took an infrared thermometer to them after having the amps on for a while and compared their measurements to the amp that works perfectly. I did not see a lot of difference in comparing them with the same wattage on the meters, but did notice a few that were warmer then others, so I reseated them. It didn't change anything after turning them on again.

If I leave the amps on very long, even before they go into overload protection, they will pop through the speakers when I turn the amp off.

If I try turning the amp on before waiting very long (yet long enough that they will still turn on)after shutting it off, it will also pop immediately after the protection mode red light goes out. Also, the needles will display watts as high as 10 watts when immediately after turning the switch one, then when the relay switches on that takes it through the overload protection testing phase, the meter goes back down to 0. If it doesn't go down to zero when the relay kicks in, the amp stays in protection mode and doesn't come back on.

Since these amps are doing exactly the same thing, I assume it is an age related thing. The one amp that works fine has been used much less then the others.

Any advice you could give me would be much appreciated.

I have the Spec II service manual and would like to repair them myself.

Where can I find specialty parts for these amps, and to bring these amps back to new, what parts would you recommend replacing to give me another 30 years.


A: Hello Bob,

Sounds like DC on the outputs. If you insist on "do it yourself", replace all of the electrolytic capacitors except the large ones in the power supply and cross your fingers. Of course, without the proper test equipment you won't really know what the amps are doing, even if they seem to be working fine.


Q: Hi Tim.

I have a Marantz 2275 and upon taking the cover off I noticed that the output transistors are not original Marantz.

I was told this makes a difference to the Marantz warm sound.

Is this true?

Also , what do you recommend or use too replace the output transistors , if i can't find originals.



A: Hello Tom,

Love those "urban legends". Provided they are the correct substitution, and there are no other problems, there will be no deterioration in the sound. To ensure that all is correct power/distortion/noise/frequency tests need to be performed. For those that insist there is a difference, I must insist that something else is wrong with the unit.


Q: Hi,

I have 2 questions....

I have a Marantz 2250B. Is it OK to use 8v 250ma dial lamps. Will the plastic shroud melt? I cant find 8v 200ma lamps anywhere.

Also, what is the difference between the Marantz 2250 and 2250B?

Love your web site for many years...Thanks so much

Regards, Craig

A: Hello Craig,

Yes, its OK. Most sources that claim that lamp will cause damage are selling some other type. I've installed hundreds with no problems. The very few times I've seen damaged plastic it appeared that the entire unit was subjected to overheating.

Marantz used the "B" designation for varying reasons. In the case of the 2250 and 2250B, the 2250 is an earlier model and the 2250B has an overall improved design.

(Many models used 300 ma lamps stock. Using an infrared thermometer, the 300 ma lamps run at a peak temperature of 130 degrees F. The 250 ma lamps run at a peak of 115 degrees F.)


Q: Hi, I have kenwood 9600 that was working well until a digital tuner into the phono jacks. as i turned up the volume all of the sound went dead.after removing everything and the cover i found two blown fuses.I replaced them ,but evertime I turn the power back on, those same two fuses blow. Ihave lights but no sound from any channel, and no meter movement. What should i do next? thanks andy.

A: Hello Andy,

Well, you're not going to like this answer. Chances are good that you blew one or more of the output ICs. Now the bad news, they are no longer available. Do any fishing?

There is a chance that the problem is in the power supply and not the output section. You may want to invest in determining that.

(The IC in question, the TA-200W, can occasionally be found on eBay. Condition unknown and, if you don't know excactly what your doing, you may lose your investment in a flash.)


Q: I just bought a vintage Marantz 2500 and when I turned it on for the first time the volume knob was turned all the way down but it about put me out of my seat. It was very loud! There are 2 set screws on the volume knob, with these removed the knob still does not want to come off and fear of breaking something I thought I would ask to get some info on it. It appears to have been pryed on before becouse there are a couple of nicks on the back side of the knob so I'm figuring someone has messed up the volume knob. It is a 250 watts per channel so no room for mistakes> ha! suggestions before surgery? thanks claydo77

A: Hello,

Never had one of those. I have seen knobs that have been super glued on. Get out the Dremel tool. Regardless of how the knob is attached, at full counterclockwise there should be no volume.


Q: Hi Tim,

I just took the plunge and bought a Sansui AU-717 on ebay. I've heard many people caution against buying vintage gear on ebay, but I guess my heart won out over my head. In any event, the amp is on its way. It looks to be in near mint condition cosmetically.

My question is, any advice you can give, in terms of what I should be looking for to evaluate that it's all right? Or, any steps I should take, in terms of cleaning, et cetera?

Also, this amp has two phonos. Do you know if one is for MM and one for MC cartridges, or is it just two of the same?

Lastly, there are three outlets on the back. One is "switched." What does that mean?


A: Hello Jim,

Ideally, you should have the unit tested for power output and distortion. Noise and frequency response would also be a good idea. Finding someone that can perform these tests may be difficult, and may require shipping the unit.

Both phono inputs are MM.

"Switched" in reference to the AC outlets simply means that it turns on and off with the front panel power switch.

On a side note, some time ago I purchased an AU-717 that I auditioned in my home. It was connected to a pair of Klipsch LaScalas and sounded fine. Subsequent testing revealed that both channels clipped below 2 watts RMS. The Klipsch are so efficient that the amp was not driven to clipping even at a very low level. The moral of the story is you can't always believe your ears.


Q: Tim,

I have fond memories of my old Onkyo TX-8500 receiver from the late '70's. It was a behemoth at 60 pds, with discrete PS for each channel. My question is -

with most speakers of the era being rated at an impedance of 8 ohms, most amps/receivers were designed to handle this load. I find that my tastes run to ribbon speakers (Apogee), which usually present an amp a load of 4 ohms or below. Would one of the quality vintage receivers like my old Onkyo be able to "comfortably" drive a pair of these 4 ohm nominally-rated ribbon speakers to "healthy" volume levels without clipping or overheating?

Apogees came out in the mid-eighties - 5-10 years after the last of the "monster receivers" were manufactured. When many stand-alone power amps of the day were used with the Apogees, they either shut down or burned up. Krell made their reputation in driving the low impedance load Apogees presented. Many say that the old amps/receivers from the '70's were much better built than many of today's products; could they have handled ribbon speaker low impedance loads - given that part quality and design have improved, yet most amps still struggle with this load?

I am curious because at some point I may try a restored vintage receiver with my Apogee speakers. Thanks.

A: Hello Joe,

Those are very hungry speakers. I don't know what the recommended minimum power rating is for them, but I wouldn't ignore it. All of the name brand amplifiers from the 70's will drive 4 ohm loads. If the Apogees dip below that, the amp may shut down. You may want to consider a McIntosh power amp, many of those will drive 2 ohm loads or less.


Q: I recently purchased an Altec Lansing speaker with a 604B speaker, N-1000-B crossover, with both enclosed in a 605A furniture cabinet. It is a very nice looking and sounding speaker, but the problem is that neither my Sansui 8080DB receiver or Pioneer SX-727 receiver is equipped to drive a 16 ohm speaker, which is what the Altec is.

I would love to use a Pioneer receiver (the receiver will also be driving a pair of Pioneer CS-99A speakers), but I have not been able to find any Pioneer receiver equipped to drive a 16 ohm speaker. Any suggestions you might be able to give regarding an appropriate receiver to use with this speaker would be most appreciated. I don't want to spend a lot of money for a receiver to drive this speaker, but I do want it to sound good!

A: Hello Gene,

Any receiver, including your Pioneer and Sansui, that is rated to drive 8 ohm loads will drive 16 ohm loads with no problem. The output of the receiver will be half that of it's 8 ohm rating.


Q: Hi Tim,

I recently acquired a 1975 Toshiba stereo console which has a Pioneer
SX-770 receiver, 3-speed BSR record changer and uses a pair of Pioneer
CS-66A speakers. I'd like to upgrade this system to 4-channel matrix sound
in order to enjoy matrix-encoded quadraphonic LP records without buying an
additional amplifier & decoder, as I have an extra pair of JVC bookshelf
speakers that I want to use. I've heard that such upgrade was possible, and
after extensive Internet research, I found a "4-channel matrix decoder"
circuit, which is attached to this e-mail.

Legend: Black box - stereo receiver, brown boxes - speakers.

The wiring connections were simple to do, but as you can see in the
circuit, it requires the bridging of the negative speaker terminals. I'm not
sure if the Pioneer SX-770 can handle the bridging of its negative speaker
terminals, as I am aware that some amplifiers cannot. I do not want to
damage the power transistors!

However, when I repaired this SX-770's "A" and "B" speaker terminals
recently, I saw that all the negative terminals are wired together,

With all that said, is it OK for me to use this "4-channel matrix
decoder" circuit on the Pioneer SX-770 receiver?

My front speakers are the Pioneer CS-66A units with 8-ohm impedance
each, and for the rear speakers, I plan to use the JVC bookshelf units with
6-ohm impedance each.

As an alternative to the JVCs, I can use a pair of 1968 Philips portable
full-range speakers with 5-ohm impedance each, as the rear speakers.

Thanks in advance for your help!


A: Hello Jonathan,

What you are proposing will work, and do no harm to your Pioneer. But, it is not a 4 channel matrix decoder. This is a variation on a technique sometimes referred to as "hot wiring". By using the hot terminals of an amplifier to drive a pair of speakers, the difference (left minus right) signal is produced. This renders an interesting sound, mostly reverb and whatever is not common to both channels, but does not reproduce matrix encoded 4 channel sources. For that you need an active matrix decoder. If you eliminate the 8 ohm resistor and the volume control in your diagram, you'll get a quick idea of what it will sound like. Those extra components allow for a certain amount of control over the L-R signal.

Then there's the question of "matrix". There are two common forms of matrix encoding, "regular" and "SQ". SQ recordings are fairly common, while I've had a hard time finding regular matrix recordings. Most four channel receivers included a regular matrix decoder, some also included SQ. The more expensive the receiver, the more likely it will include both matrix decoders as well as a CD-4 decoder. A couple that come to mind are the Pioneer QX-949 and Sansui QRX-7500.



Q: I sold two Marantz #3800 control stereo console units recently. I was selling these on ebay for my husband's employer. As far as I knew, these items were in working condition. The buyer has said that "speaker outputs are bad, a VU meter that doesn't work, and switches need cleaning". What does a repair like this typically cost? The buyer wants some help on the repairs and I offered to pay half. I just want to know an approximate cost so I don't get ripped off. I am by no means an expert on this equipment. Thanks in advance for your help.

A: First things first. The 3800 has no internal amplifier. The speaker outputs only function when an external amplifier is connected to the speaker inputs. Same goes for the headphones. The VU meter only functions when the unit is in Dolby mode. Dirty switches are par for the course for a unit this age. In my opinion, that should be expected on a unit that has not been recently serviced. A general cleaning and testing will run around $100.00 at most competent shops.


Q: hello. I own a marantz 2285. what does biasing this sort of amp mean . I always read about it but i dont really know what it means.What are the signs that an amp needs to be biased? Thanks . patrick.

A: Hello Patrick,

Bias is essential in a class AB amplifier to prevent excessive crossover distortion. Too much bias will cause the amp to run hot and shorten it's life. Too little bias will introduce unwanted distortion. Your vintage amp should be checked whenever it's serviced, or every few years. If, at idle, it runs hot or stone cold, have it looked at ASAP.


Q: Hi Tim -
I just purchased my first Marantz piece of equipment, a 2270 receiver. It is an excellent unit, but I have one problem that I hope you can help me with. Everything that gets plugged into the inputs gets shorted to ground when it's function is not selected to play. In other words, my tape deck's output gets shorted (thereby knocking out the meters while I'm recording) if I switch from monitor to source on the 2270. The aux input gets shorted to ground if aux is not selected, even the outputs of the phono preamp circuit board in the receiver get shorted to ground if phono 1 or 2 is not selected. Does this sound like a wiring defect to you or could they possibly have meant it to be this way? I would NEVER short the outputs of my tape machines or my cd burner together, much less to the chassis of the receiver. I don't have any other Marantz equipment to check this against, but no other piece I own, from the cheapest Kenwood reciever to the McIntosh system, does anything like this. Am I wrong to assume that shorting a line level output is bad for that device's output amp? Sounds like a REALLY bad idea!
Thanks in advance

A: Hello Matt,

Pretty sure that's normal, I've experienced it in other units. The reason for that, I suppose, is to prevent cross talk from other sources. Shorting the output of almost any line-level consumer device does no harm.



Q: Hi! Recently been given an old Marantz MR230 which is in cood cosmetic condition, however all outputs are blown up. It uses 2SD718 and 2SB688. Would I gain some more power (say 20 WATTS or more) If i had to substitute the original outputs (2SB688 and 2SD 718) with some higher wattage outputs? (either 2SB1429 and 2SD2155 or TIP142 and TIP147) Thanks!!

A: Hello Chris,

No. Power output is determined primarily by the capabilities of the power supply.


Q: I recently bought a Kenwood kr 9600 from E-Bay. It was in mint condition as advertised and worked perfectly. I built 300 W speaker to handle the tremendous power. After about a week I decided to really crank it up. After that it has a very weak output from one channel and is "crackling".
I put an external preamp to the input so it is definately the Power Amp.
There is an IC (A TA-200W) and a small circuit board that it is connected to. I have been unable to locate that IC. Several websites in China claim to have them but they are not ten pin. Any idea where I can find one. I would think that the IC is shot and not the small board that it is attached to.


A: Hello Ernie,

Yes, it's probably the IC. They show up on eBay from time to time. The last one I saw went for $125.00, and of course, the condition is unknown.

On another note, it is unwise to build speakers without proper design criteria. You can easily create a system that produces a load that will damage your amp.



A: Hello William,

You may be better off in the long run just having the 2270's FM section aligned. Output voltage is related to output power. For example, 10 volts across 8 ohms = 12.5 watts. There are a couple of problems with measuring power this way. First, you need a non-reactive precision 8 ohm load, not just a speaker. Second, and most important, there is no measurement of distortion.


Q: You almost answered my question back on 08-15 of 04

When running two pairs of speakers with my Marantz 2230 receiver in the mode where both main and remote speakers are played at the same time, will it damage my receiver if one set of speakers is 8 ohms (Pioneer CS-G403s my mains)and the other pair (Pioneer CS-A31s my remotes) are 16 ohm?

If my math is right this would mean that I am producing a load to the amplifier of right at 4 ohms. (correct)

Is that going to be a problem?

Thanks for your time,


A: Hello Mike,

Back to school for you. Resistance in parallel is calculated by the formula Rt = R1xR2/R1+R2, which in your case equals 5.3 ohms. The 2230 will drive loads down to 4 ohms, so you're fine.


Q: I own a Sansui 9090 receiver and a pair of Sansui SP-7500X speakers! The receiver functions great and the sound is amazing! There is only one thing wrong woth the receiver. The top row of lights on the face aren't working. There are 2 gauges on the top left (not sure what they read), along with the actual tuning needle display on the right side, that don't light up. The receiver is able to tune and receive radio stations with no problem! Does this sound like a blown fuse/bulb or maybe something greater? Please advise! I am looking to sell this system once I get it functioning properly! Thank you in advance for your time!


A: Hello Mike,

This is a common problem on the 9090. The dial lamps are controlled by the function selector switch. The part of that switch that controls the lamps has failed. The solution is to bypass that part of the switch, leaving the dial lamps on all the time. Probably a job best left to a pro.


Q: I enjoy reading "ask the tech" very much - often my questions are answered before I can ask them! In one of the posts a while ago someone mentioned a Marantz receiver that had most of it's bulbs burned out and some melting issues. I am currently (no pun intended) working on a Sansui QRX5500 with similar bulb issues, but much more serious power supply issues as well (burned out regulator Q's, fried resistors, etc.).

Well, it turns out that this Vietnam era unit was purchased overseas at a military PX, and when brought back here the voltage selector was set for 100 volts instead of 120. I think this oversight all those years ago may be what has caused so much carnage. Have you ever encountered this before? Do you feel it is worth mentioning to your readers? I'm sure that many of these classics from the late 60's and early 70's came back from overseas and have 220, 120 and 100 volt taps on their transformers.


A: Hello Matt,


I have heard stories of problems with heat and lamps on various models, but have seen little evidence of it. Since a lot of manufacturers used a tap directly off the transformer, that is non-regulated, to drive the lamps your explanation has much merit. An increase in the secondary voltage of the transformer, caused by essentially miss-tapping the primary, would produce a higher voltage for the unregulated lamp circuit thereby producing more heat. Of course the same condition would effect other non-regulated circuits, and may very well stress out the regulated circuits. I would expect that the problem would most likely occur when the 100V voltage selector position was used instead of 110V or 120V.


Q: I was recently given a sansui 9090db.
Sounds good to this point.
Any idiocycratic behaviors from this unit and what service-inspections should I have performed on it.
Is it a durable design?

A: Hello Andy,

Yes, it is a very durable design. The 9090DB has a problem with the Dolby control section that will cause one or both channels to go out. It's a major repair job, so you might just wait until it becomes a problem. Otherwise, have the services described here performed:


Q: I have a Marantz 2235 and want to add another amplifier to take advantage of the biamp capabilities of my ADS 1290 floor standers. If I use the 2325 as a preamp for the 2nd unit, how do I ensure that the preamp output from the 2325 is compatible with the main in of the 2nd amp so I don't get different volume levels between the low frequency drivers and the mid range/tweeter?

You seem to be a fan of Marantz and the 2325 in particular. I have read that Marantz had "average" tuners compared to other manufacturers in the '70's, but I find the 2325 FM section to be excellent!! Any other comments on the performance of the 2325 vs. competitors of the era?


A: Hello Barry,

The 2325 is one of Marantz's finest, and it has an excellent tuner section. The ADS are designed to be used with an electronic crossover, which would handle the different power levels needed. You can use the 2325's pre-out to feed another amplifier, just make sure you go in before the volume control, i.e. into an AUX or Tape input, so that you can adjust the power level of the second amplifier. Then the 2325 will control the overall volume of the system.


Q: I have a Pioneer Spec 2 bought DOA from an auction site. I had a noteworthy technician repair it. All the output transistors had to be replaced and he replaced many of the electrolytic caps, out of tolerance resistors, and repaired a damaged temp sensor on the left channel heat sink. He did a 3-day burn in test also.

I am using a Pioneer Spec 1 pre-amp and Pioneer HPM 150 Speakers. The following has happened twice now: Shortly after getting the amp back, I was letting the tone arm descend onto an LP and the needle skipped with a loud pop and the amp went into protection. Turned out that a couple of the output transistors in the left channel blew out. The tech repaired it on his dime as it was under the 90 day warranty and it was felt that one or more of the output transistor(s)may have let go due to a manufacturing defect. This past weekend, I connected my Pioneer 8 track cartridge recorder to the unit (I still use 8 tracks in a couple of my classic cars) to make some tapes. All was good until I removed the tape cartridge from the player and there was a loud pop, and the amp again went into protection. I isolated the outputs by disconnecting the connector at the top of each board (pins 16 - 21 from memory). Again, the left channel has created a short which blows the related fuse. Before I have this repaired again, is there anything my tech should look for that would allow a momentary "pop" to create such havoc and blow out the output transistors? The output transistors he used are NTE285's and NTE383's.

Thank you in advance for any ideas you have on this.


A: Hello Mike,

First, I suggest that you use the subsonic filter on the SPEC-1 at all times. A sharp transient should engage the protect circuit, but not take out any output devices. Since the problem only occurs in one channel, while the transient occurs in both, it points to a problem in that channel. Have your tech do a power vs. distortion check, and a signal to noise check. Also check the bias and DC offset for both channels. You should probably also have him check out the SPEC-1.


Q: Looking for advice. I have a Sansui SE-88 equalizer that I was trying to find a replacement AC transformer for. Any tips on where to locate one or find help cross referencing to a comparable replacement? The only marking on the original is a Sansui label w/ C1630XX and D591 indicated. The service manual does indicate a Sansui stock number of 15022404 for the T1 transformer but I am clueless on who could recognize that part number. Just thought I would ask as the web search is comoing up blank.Either way, keep up the good work.

Cheers, Derek


Q: It's the same old story. I bought an early model Marantz 2270 (with the champagne face) off of ebay and it's not all original as stated. I noticed that the transistors are Marantz on one side and not the other. How does this affect the sound and if I was to look for some replacement Marantz ones what should I be looking for?

A: Hello Joe,

Replacement output transistors are common and should not degrade the performance at all. The question is, were the correct replacements used and any other associated problems resolved? The only way to know for sure is to have a performance verification test performed on the unit. I wouldn't worry so much about finding original Marantz transistors, as they would be used and in unknown condition.


Q: I have seen equipment for sale on eBay that claims to have been serviced or "checked by tech". What do you think of that?


A: Hello Fred,

Based on my experience buying equipment with that statement attached, I believe it means very little. From what I have seen, I'm convinced that "tech" is the name of the family dog.

Equipment that has been serviced is worth significantly more than equipment that has not. But the work has to have been done correctly. Any competent repair shop will provide a receipt and hopefully a description of the work done and ideally some test results to go with all that. If the seller cannot produce a receipt for the alleged service from a legitimate shop, don't buy it.


Q: I have a pioneer sx-650 am/fm receiver that I used happily for decades until it stopped working a couple years ago...I have a friend that works on stereos and could probably fix, but he left a job where he had access to replacement parts. If I have him troubleshoot the problem, what are the odds that we can order replacement parts from you?

I'd like to figure out some way to put it back in action, because the new "surround sound" receiver I just bought is way more complicated than I want to deal with... the pioneer has a "classic" look and simple operation.

I'd appreciate any suggestions you might offer; if you don't help me, my wife is going to slip it into her next yard sale or or toss in the dumpster -- and neither of us want that on our conscience. Thanks, Gerry

A: Hello Gerry,

Put your conscience to rest. Although your description of the problem is vague, 99% of the non-cosmetic parts are readily available for that model from many sources.


Q: I recently acquired a Marantz 2270 to take over for my Pioneer sx-636 which I’ve had for many years. I became unhappy with the Pioneer’s tuner and spent a lot of money to have it brought up to snuff but it was to no avail. I was told by the collector who I bought the 2270 from that it was recently serviced but I plan on having it aligned soon anyway.
My question is, I have the opportunity to buy a Marantz 2100 tuner (I’m also considering an st-400 but have not located one), would I achieve better AM reception running the 2100 into the 2270 or does the 2270 already have a superior tuner? I realize the 2100 was not one of Marantz best efforts.
Any guidance you can give me would be greatly appreciated. I will thank you in advance for your reply.


A: Hello Scott,

Please don't shoot the messenger. I would not rate any of the tuners in the units you mention as anything but average. Marantz did not do all that great with tuners, compared to Pioneer and Sansui. The 2270 will probably be the best of the lot, but you'll have to find someone with experience to align it. By all means, avoid the ST-400. If you want a great tuner from Marantz, look for the later top of the line receivers (1974 - 1976) and look for the top of the line separates. I owned a 2130 which was quite impressive.


Q: Looking to buy a receiver that will power more than 4 speakers. Would like to have speakers inside and outside, at least 6 maybe eight. The only thing that I would be playing is XM radio and I really do not have a clue as to what I need to do this. Thanks for any help.

A: Hello Michael,

There are many options. You can buy a "multi zone" receiver, you could cascade amplifiers from a common control preamp, or you could by an FM transmitter for your XM and place boom boxes or stereos wherever you want.


Q: Hi,

Do you feel the SX850 at 65 wpc would be a bit more mellow sounding than an SX1050 at 120 wpc? I play guitar and the 50 watt Marshall heads always sounded a bit smoother and not quite as harsh as the 100 watt head; or is this just a tube thing?

Another question I have is with caps. Are all receivers, amps, etc. that are like 30 years old going to have caps that have either dried up or are in some state of drying out? If so, wouldn't this diminish some of the original sound quality to a certain degree? When testing vintage gear can a piece of equipment still fall within specs even though the caps have somewhat dried up - meaning even though the unit appears healthy on the testing equipment it may not have all of its original sound quality?

I read all of the questions in the "ask the tech" section for something similar and although I didn't find my answer there, I did think the question about the urine soaked receiver was a refreshing change from the norm. I think that guy should come clean and rather than blame some poor animal, admit that it was actually him who peed on his own receiver during a drunken frenzy! Oh yea, I forgot about that other psycho who wanted to mount the Sansui G-9700 in his car!

Thanks again,

A: Bob,

I agree with your theory of the urine soaked receiver!
I do not think you can compare instrument amplifiers with home audio. They're designed for completely different applications. I would expect the difference you may hear between 65 and 120 watts to be in bass definition, and that would vary greatly depending on the speakers.

There is much talk about capacitors and vintage gear, but no compelling truths. Some people insist that all electrolytic capacitors be replaced after "X" amount of time. None of them have ever produced any empirical data showing any difference in performance. In fact, none of them even run basic tests before and after such extensive modifications. I consider that approach ridiculous. Caps do age and will dry out under certain conditions over varying periods of time. In my experience a bad cap will show up during testing as distortion or frequency response problems, and sometimes just as a catastrophic failure. I believe that any electrolytic capacitor has the potential to last indefinitely. What usually kills them is a random failure, excessive heat or excessive voltage. The expense involved in blindly replacing every capacitor in a receiver would cause the selling price to be unreasonable. I do support replacing caps in known problem areas and will do that when appropriate.

As far as whether "unseen" problems can reduce sonic quality, who knows? The most popular audio equipment on the planet has terrible technical specs. I refer, of course, to tube based equipment.



Q: Hi, I just bought a Yamaha K-17 cassette deck & manual off ebay. When I try to play a tape it goes very fast (almost like fast forward but not quite) and no sound comes out via the headphone jack or the amp. Everything seems to function properly (rewind, fast forward, etc) but I can't make the cassette stop racing on play back. I've tried different tapes and different tape selections (Norm / Metals, etc) but it makes no difference. Have I bought a dud? The seller didn't mention this problem. This tape deck has Play/Stop/Rew and FF all on different sides of the same button, so I'm wondering if maybe the button has developed a defect of some kind. Any thoughts?
Many thanks

A: Hello Robert,

Sounds like the pinch roller is not contacting the capstan. With no tape in the unit, get it into play mode and make sure the pinch roller is turning.

R: Many thanks for this. I've since found that the heads don't come up at all
on Play or Record and the pinch roller isn't turning, so you were right.
I'll have a look inside when I have more time and hopefully it'll be
something simple.

Thanks very much again for your assistance.



Q: I am looking at acquiring a vintage receiver from the Carver corporation, and was interested in getting an opinion about which one might be the most useful to me. I understand that the power output of these boxes ranges from 90W to 200W, and that they use some sort of Carver electronic wizardry called "Magnetic Field Amplification" I also have an old NAD 7080 receiver that has 90W per channel with a dynamic headroom of about 2.5-3.0 db. My questions are:

1) What is "Magnetic Field Amplification", and how does it compare to the amplifier section of my NAD?

2) If I purchase the Carver Receiver 900, could I potentially bridge the outputs, and use each unit as a mono amp? Would they have similar sonic properties? If I purchase a different unit with say 150 or 200 WPC, would this disparity in power make mono bridging imposible and/or inadvisable?

3) Is any of this line considered to be a higher quality piece of equipment than the others, i.e. better sonic characteristics, better build quality or repair track record? Is there one of these that I should shoot for over the others?


A: Hello Allen,

The Carver "Magnetic Field Amplification" is a system that provides power "on demand" by regulating the power supply with an SCR. Depending on the music content more or less current is available to the amp section. This design eliminates the need for giant power transformers and filter caps. It also prevents the amp from producing it's rated output for more than a few seconds. Personally, I think they sound terrible.
(Ed. for a good technical description of this design and others go here:

You cannot bridge the outputs of ANY amplifier unless it is specifically designed to do so.

I really don't have any recommendations regarding the different products in the Carver line.


Q: I recently obtained a Pioneer SX-980 and have fallen in love with the quality of its fm stereo sound. One problem however is that the right side stereo sound intermittently disappears. At first I could remedy this by simply switching to mono and then back to stereo. When that no longer worked, I switched out of loudness on to loudness off and back again. Later I had to switch from tone-on to tone-off to to regain the right channel. Eventually it was pressing in the am button which brought back right channel. Most recently a good hard slap to the right side of the receiver reinstated the right channel. I have a rubber mallet ready now as my next possible fix for this problem. Do you have any suggestions for first aid.

Many thanks

A: Hello,

Avoid the rubber mallet. That sort of behavior leads to harder things, like a hammer. Have all of the switches, controls and relays cleaned.


Q: I have a HK A401 that I have been keeping alive pretty well. I have a dc offset prob, now. Left channel 48mv, right channel 11mv. Not a big deal, really but I would like to keep this amp running as long as possible. I use it with my turntable and it suits me just fine. I have the service manual, and can do most r&r needed. I believe that I probably have some bad caps in there, as this thing is 30 or so years old. They're ELNA electrolytics. Decent stuff i'm guessing.
Also, I installed new trim pots last year. So-so but would like to find some 40 turn sealed in the 1K ohm flavor. Ideas? Perhaps better quality trimmers would help with the dc offset? I just put in Radio Shack's pots, because at the time I couldn't get anything else. Perhaps that's the problem?


A: Hello Doug,

DC offset is caused by an imbalance in the "push-pull" designed amplifier section. New adjustment pots will not likely fix the condition. Many things can cause the condition such as leaky output devices, leaky driver devices, leaky input devices, leaky coupling capacitors, leaky bypass capacitors, power supply imbalances, resistive imbalances in the driver section and even bad juju from the preamp section. In short, it can be a real pain. Start by checking the outputs for leakage and work your way back. Keep notes of the voltages in each stage compared with the one that is working better. You're looking for clues here, akin to CSI.


Q: Say what you will about the Kenwood KR 9600, but there are two basic cases here. Those that have them and those that wish they did! Those IC's you refer to are really 2 Darlington transistors encased in one enlongated can. They will take as much punishment, or more than your typical power output transistor. The power supply in this unit is a true dual supply feeding each channel. I have owned and abused one for 30 years now without even a light bulb failure! I have used the unit in a bi-amp setup to power 2 15-inch subwoofers from the power amp and my mains through a second receiver using the preamp through an electronic crossover for the last 10 years. The subs were designed to reproduce pipe organ music and have considerable output, as verified by a test signal, down to 13 Hz! If anyone can get their hands on one of these, they are truly blessed! Just my real world experience, not opinion!


A: Hello Greg,

I appreciate your real world experience, and certainly those output ICs may last forever. But, my real world experience is that those types of ICs may not last forever. When they first were introduced they were by far the most common failure mode, when a failure occurred, in any brand or model. There is a lot more inside some of those ICs than just Darlington pairs, such as pre-drivers and input stages. A discrete input/driver/output stage can be repaired indefinitely. When one of your ICs goes, it's pretty much over. Perhaps someday someone will make a replacement.


Q: I have a Zenith stereo with a radio in a walnut cabinet that is approx 40 years old. It plays 78/45. It is in very good condition. I am curious what I should ask for this antique. Please advise.
Thank you
Pete Colella

A: Hello Peter,

Hard to say. The market for those console units is pretty much unknown. A lot of people gut them for the components, especially if they've got tubes. Check with this site:


Q: I am the original owner of a Sansui Seven. A few years ago a friend tipped over his beer into it and now it has no power. I kept it because it has sentimental value despite being a great unit. Is there any hope of fixing it?


A: Hello,

Depends. Was it cheap swill or a microbrew? Were pretzels involved? Was it a bottle, can or glass? But seriously, beverage spills can be fatal. You should first inspect the damage and look for any obvious residue. At the very least, you'll probably have to do a complete teardown and cleaning.


Q: I have read with interest your advice on classic gear - thanks for the great information.

My question involves output IC's. You recommend avoiding purchasing receivers that use due to the lack of parts avaiability, thus making such receivers practically impossible to repair.

I noticed several references to Kenwood KR-9600's, which you state use these output IC's. I recently purchased a Kenwood KR 4070 receiver from Ebay and I am wondering if you know whether it has these output IC's or not? The receiver was described as working well, but who knows what that means on Ebay. It only cost me $13.45, so I guess I am not risking too much should it turn out to be a lemon.

I do not have the receiver yet, since I just bought it a few days ago. If you don't know if it uses IC's, can you tell me what I should look for inside the receiver to find out for myself once it arrives? I am a newbie, so I really don't have any idea what to look for, so I don't know how to tell if there are discrete transistors or ICs. Are they computer-like flat chips?

Perhaps a description of how to identify these ICs would help us out when evaluating a receiver in person for possible purchase, since I doubt there is a list available anywhere that we could go by that identifies receivers that use ICs.

I know this is probably a dumb question, but I am guessing that others who have little experience in this field (but who also enjoy the look and sound of vintage equipment) are wondering the same thing.


Mark H.

A: Hello Mark,

I don't know if the 4070 uses output ICs or not. Most models that did were made in the late seventies. The only way to tell for sure is to inspect the inside of the unit. The ICs are attached to large heatsinks and are rectangular, about the size of a pack of cigarettes but much thinner.


Q: Hi,
I recently purchased a vintage receiver, Pioneer SX-1980 on Ebay. The receiver was in working condition when I bought it, except that when the VU meters reached 35 watts the relay (I am not sure about this though)would just shut the music on and off. I took it to a local technician who, after having the receiver in the store for a month, said he could not repair it. A couple of weeks later I took it to another technician who said the supply power had major problems and he had to replace a lot of components. When he was done fixing it I took it home just to learn that the receiver had a very noticeable hum regardless of what section (AM, FM, AUX, et) was selected. I took it back to the technician, but he said that he had never seen something like that and he could not fix it. All sections of the receiver seem to be in good working order, except for this really annoying hum. Any idea what's causing this loud hum ??
Thank you very much for your time,

A: Hello Mark,

That type of hum is generally an indication of a problem in the power supply section. You need to locate a competent technician, check here: (San Diego) (Virginia) (Connecticut) (Connecticut)


Q: Just picked up an adcom GFA-535 amp. Heard that changing the power and rail fuses to ceramic will improve the soundstage of the amp. Is this true? How do I change the fuses and where are they?


A: Hello Barry,

If changing the fuses changes the sonic performance of an amplifier you either have an amp with a very bizarre problem, or you need to adjust your meds. Sorry, I don't know where the fuses are on that model.


Q: Hi, I have a 2270 marantz receiver that i just got via ebay, everthing seems to work just fine sofar except one thing. I have to push the left mono in button in to get the right speaker to work. Sounds great but what could be the problem? Also the pointer on the radio dial does not line up with the station I am listening to. Is that a easy fix? thanks, Randy

A: Hello Randy,

You bought a bare bones, non serviced, edition of a great receiver. Your unit needs to be serviced, as most all vintage equipment does after several decades of use. Performing that service properly requires a competent hand. There is not really much that you can do yourself.


Q: I have a Marantz 2230 receiver, and like many, I am somewhat addicted to the "loudness" button even though I keep the tone controls pretty neutral.

I have always thought that the loudness circuit was designed to lose it's effect as volume increases, even when the button remains depressed. Can you verify if this is true, or does the loudness function continue to boost the extreme lows and highs even at higher volume settings?

I have searched both the owners manual and service manual where I thought I had read this, but in fact cannot see where it says what I thought. I'm concerned about over-stressing irreplaceable old drivers.


A: Ed

Hello Ed,

The loudness "contour" is designed to diminish as the volume is increased. At around the 12 o'clock position of the volume control the contour is essentially disabled.


Q: Exactly 3 years ago I bought a Marantz "Professional" audio CD recorder model CDR-500. Now when I place a blank disk in it for recording, it feezes up with an error message "No disk Found". Several service places in Texas, as well as Marantz themselves told me only their Superscope service center can work on my component. Superscope tells me that parts are no longer made for that model. Did I just spend $1,100 on a paperweight.

A: Bummer. In my experience the "pro" label on consumer brands such as Marantz is often nothing more than "goo" from the marketing department. If Marantz say's your toast, you probably are. You may be able to find the parts yourself by buying another troubled unit, with a different problem, at a discount.


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