Vintage Receiver Pitches Hissy Fits

For my first foray into vintage audio, I recently picked up an Ampex ASR-100: a stylish little early Nineteen-Seventies receiver with some good old-fashioned current behind the low-ish 40 watt figure.
Yes, the audition went very well. I payed the craigslist seller a tiny sum and happily drove home with my sweet little receiver. The next day was different... I hooked my speakers up to the ASR-100 and the happy preview was a thing of the past!
Essentially, I found that my receiver puts out a very significant hiss - in the right channel only - at any volume level, including zero. The input source and signal type makes no difference whatsoever; Tape, FM, CD are all effected. I also switched the speakers to confirm that the hiss is in the right channel only.
So do I haul it into a repair shop and watch my investment multiply many many times over? Or do I learn "a few things" (more than the zero I know now) about audio repair and take it apart? I am not awash in cash; then again, I am just passable with a soldering iron. Your thoughts?

Check for hissing cockroaches first! (sorry poking fun at stereorob) If you're not comfortable with working on it yourself...find a shop the will work on it for a reasonable price. If you like it then it worth getting it fixed. No matter what you paid for it.

Caminokid said:

Check for hissing cockroaches first! (sorry poking fun at stereorob) If you're not comfortable with working on it yourself...find a shop the will work on it for a reasonable price. If you like it then it worth getting it fixed. No matter what you paid for it.

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the bug in your system !!!! HAHAHA.........

Justfurfun said:

For my first foray into vintage audio, I recently picked up an Ampex ASR-100: a stylish little early Nineteen-Seventies receiver with some good old-fashioned current behind the low-ish 40 watt figure.
Yes, the audition went very well. I payed the craigslist seller a tiny sum and happily drove home with my sweet little receiver. The next day was different... I hooked my speakers up to the ASR-100 and the happy preview was a thing of the past!
Essentially, I found that my receiver puts out a very significant hiss - in the right channel only - at any volume level, including zero. The input source and signal type makes no difference whatsoever; Tape, FM, CD are all effected. I also switched the speakers to confirm that the hiss is in the right channel only.
So do I haul it into a repair shop and watch my investment multiply many many times over? Or do I learn "a few things" (more than the zero I know now) about audio repair and take it apart? I am not awash in cash; then again, I am just passable with a soldering iron. Your thoughts?

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at any volume level, including zero

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problem is amp or power amp. what about the other channel???

As the hiss doesn't vary with volume, you've already determined that the problem is almost certainly in the power amp section of the receiver.

If it's a steady hiss, I might suspect a noisy input differential pair on the bad channel.

If it's more of a variable crackle, it could still be the input pair, or possibly a bad solder joint someplace.

An oscilloscope and signal generator, along with a schematic, should make pretty short work of this repair.

You can try buying a can of freeze spray and spraying each component in the amplifier section (it will be the board near the heat sink) with a small amount of freeze spray. Connect a set of speakers you don't care about to avoid damage to your good ones. When you find a component that causes the hiss to get worse or go away, that's the bad one. Transistors will be the ones with black plastic or metal cases. Spray those first.

Hey Dr. Audio, about that freeze spray. You have a wealth of experience over me, I'm not trying to call you out or start "one of those" discussions AT ALL, but the subject came up in one of my electronics classes at school the other night. Our teacher was talking about how he never uses freeze spray unless he is 100% prepared to replace whatever component he nails with it. He said that the sudden temperature drop puts a tremendous stress on parts, and can often cause premature failure. Maybe not right when you spray, but he has seen the lifespan of many components drastically shortened after using the stuff. Many of theses devices are incredibly sensitive to temperature (how many times have I walked up to a receiver while measuring bias, etc, only to have the slight breeze I created cause voltage fluctuations? I don't smell that bad!), and they were just not designed for sudden swings like this. Again, I've read many of your posts, and you obviously know your stuff, just wanted to bring it up for some discussion. If it helps, my teacher has been involved in anything and everything electronics (I think 30 years in A/V, among other things), and, like lots of folks here, seems to know his stuff.

Nothing like going back to school, believing you know everything at the age of 36, only to be constantly reminded you know a lot less than you think! Every night it seems, something I thought I understood gets shot down, but the satisfaction from really being able to wrap my head around a concept by the time class ends makes it worth it. If you're wondering, it was AK that made me want to go back to school so that I can become more proficient at keeping our beloved dinosaurs alive.

OP, sorry about the slight hijack. I say read, read, then read some more. If you got that thing cheap, I would say skip the tech and troubleshoot this problem to the death. I have learned the most from trying to sort out completely dumfounding audio mysteries using whatever resources I have available, and I can't remember the last time I didn't start with the knowledge of the folks here. If I can do it, you can do it. Trust me.

guys also used hot air guns on components as well. melting caps and over heating devices.

I knew a guy at corporate who claimed using a stethoscope he could hear a noisy transistor :scratch2:

kcvet said:

guys also used hot air guns on components as well. melting caps and over heating devices.

I knew a guy at corporate who claimed using a stethoscope he could hear a noisy transistor :scratch2:

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You can't hear an en zyme...

dspear99ca said:

As the hiss doesn't vary with volume, you've already determined that the problem is almost certainly in the power amp section of the receiver.

If it's a steady hiss, I might suspect a noisy input differential pair on the bad channel.

If it's more of a variable crackle, it could still be the input pair, or possibly a bad solder joint someplace.

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Hey, Thanks guys. Yeah, the hiss is like leaving the FM between stations; it's a steady hiss with no "added effects".
2 Questions: I am kind of concerned about my first foray into restoration involving freezing or overheating components. :worried: Is the repair you envision something a neophyte would even approach? If so, is there a thread pointing newbies to - say - a book or manual to get (me) up to speed on the basics?

One thing you could try - this is coming from someone else who would be classified as beginner at best - is try listening through headphones to see if the hiss is or isn't there. Probably won't do any good but then if it isn't in the phones that should confirm the amp stage diagnosis (I think - like I said, I don't know much about these things - the experts can feel free to weigh in if that's a mistaken hypothesis). Good luck getting to the bottom of the problem.

Ben

BenWaB3 said:

One thing you could try - this is coming from someone else who would be classified as beginner at best - is try listening through headphones to see if the hiss is or isn't there. Probably won't do any good but then if it isn't in the phones that should confirm the amp stage diagnosis (I think - like I said, I don't know much about these things - the experts can feel free to weigh in if that's a mistaken hypothesis). Good luck getting to the bottom of the problem.

Ben

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The headphone is a simple test, and I recommend it just because it's easy enough, takes no time, and can sometimes narrow it down:thmbsp:

Just to double check, the right channel has a definate hiss at any volume, is the left channel just fine?. I would suspect the power amp as well, I think.

I was pretty close to you with the vintage stuff when I first started repairing/restoring/collecting about a year ago. I did have a bunch of pretty basic electronics knowledge beforehand, just from 20 years of tinkering with audio and home theater stuff, but this kind of systematic component level troubleshooting felt very new... Just jump right in, man! I know others will disagree, but I really believe the best way to learn is by doing. That being said, there are some caveats:

1) BE SAFE. There are sometimes voltages and current in this equipment that can KILL you if you are not careful. If you don't know the dangers of electricity, I have no doubt you can find at least a few threads here discussing what you might face. I can't stress the safety issue enough. I like to think I'm pretty safe (I wear goggles when I solder, for example), and even I shock the **** out of myself every now and again. DON'T DIE.

2) BE SAFE. I'm probably gonna say it a few more times.

3) Search here not only for Ampex problems (wish I was more familiar), but do really general searches for the symptoms you are describing. ALWAYS use the Google search of the site, as it works much better than the standard search. For example, I was working on a Marantz 2238B that would crackle intermittently at low volume levels. I read a post about someone with the exact same issue in their Pioneer receiver, and it ended up being the speaker relay with fouled up contacts. Guess what? Same exact thing on the Marantz. I swapped out the speaker relay, problem solved. This will not always be the case, but at the very least it will open some avenues for troubleshooting, especially if you don't know where to begin.

4) DON'T KILL YOURSELF. See 1 and 2 above.

5) I think it helps to have a plan. Don't just go in and start poking around. Maybe at first, because you might see an obviously toasted part that needs replacing. And remember that any fried components might have well taken out some of their brethren, some of which might be destroyed with nothing visible to show it. If the eye test fails, again, find a thread with a solution to similar problems, and with that guidance you should be able to do some worthwhile, step-by-step troubleshooting. If that first thread doesn't help, look for another with a different solution, and another, etc, etc.

6) Go to Harbor Freight and buy a $4 meter for the above mentioned troubleshooting. You are going to have to measure voltage and stuff. Don't go nuts with a super nice Fluke or anything like that at first. You might hate this vintage crap. You might turn that meter into a molten pile of copper, plastic, and solder mask. At least you only spent $5 on it. Don't get me wrong! If in a few months the people you know start looking at you as if you are mentally disabled, your wife or whatever is complaining about the smells, or your 5 year-old daughter sticks a note on your stack of speakers that says, "NO MORE DADDY. YOU ALREADY HAVE 22.", you are good to go. Visit Ebay and buy a decent used Fluke from a few years back.

7) Don't be afraid to ask for help. But only after you have searched until your eyes bleed. If you really truly can't find a solution to your problem, post away. But if someone two threads down asked the same thing as you yesterday, or worse, had their issue solved, the AK ninjas will already be hiding in your front yard. Or in your closet.

7) Please don't get hurt or die. I'm serious.

I think any reasonably intelligent person (i.e. you can usually get Tab A into Slot B, or don't throw your hands up in frustration when faced with a polarized plug like my mom) could get going doing the above, which is basically what I have been doing for the past 10 months or so. And I feel I have learned a ton. Learn to spot the guys who really know what they are doing (Echowars and Mark come to mind), and defer to their experience. With some patience, you can learn to evaluate problems by thinking about other problems you have faced before the current one. It all starts to come together, as they say. And of course, have fun: that should always go without saying.

33&athird said:

The headphone is a simple test, and I recommend it just because it's easy enough, takes no time, and can sometimes narrow it down:thmbsp:

Just to double check, the right channel has a definate hiss at any volume, is the left channel just fine?. I would suspect the power amp as well, I think.

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Hi guys and thanks for this amazing level of response! Yes. Absolutely, positively, the right channel - and the right channel only - makes the hiss, at any volume setting, including "zero". The hiss is not subtle; you could package it as some sort of meditation sound on an overpriced c.d. set, and a bunch of nearly deaf New-Agers would send you great feedback about their achieving internal peace!

Also, being new and uneducated in this area; I can see myself running into a barrier. That is: I identify and remove the faulty part(s). Now what? Where do I get replacement parts for such an obscure piece of audio gear?

These are valid concerns, but in over 30 years of repairing audio equipment I have never seen a component fail from spraying it with freeze spray. You should only spray a small amount anyway, because otherwise you will affect other components, plus all it takes is a small amount to see a change.

le greque said:

Hey Dr. Audio, about that freeze spray. You have a wealth of experience over me, I'm not trying to call you out or start "one of those" discussions AT ALL, but the subject came up in one of my electronics classes at school the other night. Our teacher was talking about how he never uses freeze spray unless he is 100% prepared to replace whatever component he nails with it. He said that the sudden temperature drop puts a tremendous stress on parts, and can often cause premature failure. Maybe not right when you spray, but he has seen the lifespan of many components drastically shortened after using the stuff. Many of theses devices are incredibly sensitive to temperature (how many times have I walked up to a receiver while measuring bias, etc, only to have the slight breeze I created cause voltage fluctuations? I don't smell that bad!), and they were just not designed for sudden swings like this. Again, I've read many of your posts, and you obviously know your stuff, just wanted to bring it up for some discussion. If it helps, my teacher has been involved in anything and everything electronics (I think 30 years in A/V, among other things), and, like lots of folks here, seems to know his stuff.

Nothing like going back to school, believing you know everything at the age of 36, only to be constantly reminded you know a lot less than you think! Every night it seems, something I thought I understood gets shot down, but the satisfaction from really being able to wrap my head around a concept by the time class ends makes it worth it. If you're wondering, it was AK that made me want to go back to school so that I can become more proficient at keeping our beloved dinosaurs alive.

OP, sorry about the slight hijack. I say read, read, then read some more. If you got that thing cheap, I would say skip the tech and troubleshoot this problem to the death. I have learned the most from trying to sort out completely dumfounding audio mysteries using whatever resources I have available, and I can't remember the last time I didn't start with the knowledge of the folks here. If I can do it, you can do it. Trust me.

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