I am replacing all electrolytic caps in a C2200 and there are over 50 electrolytics in the signal path alone. Are the "Audio Grade" caps worth putting in? I was looking at the Elna SILIMIC II to replace the general purpose Rubycon YK series that are in there now.
The amplifier isn't mine. It belongs to a good friend of mine, he tells me that once in a while the right channel gets quiet and distorted. I have had the amp at my house hooked up to an oscillator and a loaded the output with 100k load (his power amps input Z) and I can't get it to misbehave. I have tried for 40 hours. Anyway he has had the amp for 10 years and might sell it soon so he wants to clean, retube, recap, and rebulb the amp.
The amplifier isn't mine. It belongs to a good friend of mine, he tells me that once in a while the right channel gets quiet and distorted. I have had the amp at my house hooked up to an oscillator and a loaded the output with 100k load (his power amps input Z) and I can't get it to misbehave. I have tried for 40 hours. Anyway he has had the amp for 10 years and might sell it soon so he wants to clean, retube, recap, and rebulb the amp.
I don't think it is the cable or the amplifier. My buddy said when it happens the meter needle drops for that channel (right) no matter what input source was selected. Just to be sure he tried reversing the left and right inputs, still same channel was dead. He also said he tried reversing output interconnects going to the amp left and right, sound would come from the right channel now and not left, so it is the preamp right channel for sure.
He doesn't really want to tinker with the design, just replace the caps with a finite life span that degrade over time. I saw several 85 degree 100uF lytics' up pretty close to the tube sockets. Figure if the problem is so intermittent just replace all things that age poorly, listen to it for a while and see if it cures it. Of course if the problem would just present itself for me to look at it I could track it down a lot easier. Pretty much just guessing at this one but also do a little "maintenance" at the same time.
He doesn't really want to tinker with the design, just replace the caps with a finite life span that degrade over time. I saw several 85 degree 100uF lytics' up pretty close to the tube sockets. Figure if the problem is so intermittent just replace all things that age poorly, listen to it for a while and see if it cures it. Of course if the problem would just present itself for me to look at it I could track it down a lot easier. Pretty much just guessing at this one but also do a little "maintenance" at the same time.
In proposing to just replace every cap, you are going about it the wrong way. You should FIRST identify excatly what the fault is, which part it is - no matter how hard that may be. It is all too easy to add additional faults by error if you just go replacing willy nilly. Many a good piece of electronics has been abandoned because of this, or given to a professional to fix at enormous cost.
In fact experience has long taught me that if someone comes to me with an amp, radio, or whatever that he has replaced every capacitor willy nilly, and it has a fault it didn't before, I usually refuse to help - it just chews up too much time.
With intermittent faults that the owner reports that you have yet to see, there are two main ways to sort it out:-
a) while playing a tone from an oscillator through the system, gently, with an insulating stick, move parts about and tap them. This will reveal PCB cracks, dry joints, and other mechanical faults.
b) Selectively squirt small amounts of freezer on parts untill you find the temperature sensitive one that brings on the fault. You can buy small pressure pack cans from electronic parts stores for just this purpose. This method works reallly well with solid state equipment but its good with tube equaipment as well. DO NOT allow freezer to get on tubes, and don't squirt transformers - it's pretty much a waste of time.
When the owner reports an intermittent fault that won't re-appear, its usually a mechanical fault. Vibration in transporting it tio you may temporarily make it come good.
Don't overlook that the fault may not be in the amp - it may be in cables or other gear that the owner used with it but didn't give you.
Faults such as you describe are often tubes, or grid coupling capacitors if the amp is very old. Professional techs build up experience that tells themn certain brands of cap never fail, and ceratin caps in certain amps nearly always fail.
I NEVER replace electros willy nilly in equipment made in the 1960's or later. Electros made in the 1960's and later, when made by reputable manuafctuers such as Philips, most USA makers, and the Japanese manufacturer Elna are very reliable. British brands such as Ducon are crap.
In fact experience has long taught me that if someone comes to me with an amp, radio, or whatever that he has replaced every capacitor willy nilly, and it has a fault it didn't before, I usually refuse to help - it just chews up too much time.
With intermittent faults that the owner reports that you have yet to see, there are two main ways to sort it out:-
a) while playing a tone from an oscillator through the system, gently, with an insulating stick, move parts about and tap them. This will reveal PCB cracks, dry joints, and other mechanical faults.
b) Selectively squirt small amounts of freezer on parts untill you find the temperature sensitive one that brings on the fault. You can buy small pressure pack cans from electronic parts stores for just this purpose. This method works reallly well with solid state equipment but its good with tube equaipment as well. DO NOT allow freezer to get on tubes, and don't squirt transformers - it's pretty much a waste of time.
When the owner reports an intermittent fault that won't re-appear, its usually a mechanical fault. Vibration in transporting it tio you may temporarily make it come good.
Don't overlook that the fault may not be in the amp - it may be in cables or other gear that the owner used with it but didn't give you.
Faults such as you describe are often tubes, or grid coupling capacitors if the amp is very old. Professional techs build up experience that tells themn certain brands of cap never fail, and ceratin caps in certain amps nearly always fail.
I NEVER replace electros willy nilly in equipment made in the 1960's or later. Electros made in the 1960's and later, when made by reputable manuafctuers such as Philips, most USA makers, and the Japanese manufacturer Elna are very reliable. British brands such as Ducon are crap.
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Hot electrolytics don't usually go intermittent, they go low in value and high in ESR.
Read post 4 very carefully. Follow its advice.
Read post 4 very carefully. Follow its advice.
I have been repairing electronic equipment for 50years and have never heard of the brand name Ducon. Sorry.
Sprague, Mullard, ITT, Daly etc. were always good makes. Ducilier were French.
Sprague, Mullard, ITT, Daly etc. were always good makes. Ducilier were French.
John, given that you are located in England, if you haven't heard of Ducon (in its later years a division of Plessey), you must have had a very sheltered life! They were very common in consumer equipment in the 1950's, 60's and early 70's. Perhaps you repaired professional grade equaipment.
Mullard is what Philips was known as in England, for historical reasons and out of respect for Stanley Mullard, who was on the Board for about 60 years. When Stan Mullard finally died, the Mullard name was dropped.
Dubilier was another barnd made in both USA and UK. The UK made Dubiliers for consumer equipment were even more crap than Ducon, but they also made capacitors to higher standards for professional equipment. Another British capacitor brand was Erie (ok but not as good as Mullard/Philips)
Mullard is what Philips was known as in England, for historical reasons and out of respect for Stanley Mullard, who was on the Board for about 60 years. When Stan Mullard finally died, the Mullard name was dropped.
Dubilier was another barnd made in both USA and UK. The UK made Dubiliers for consumer equipment were even more crap than Ducon, but they also made capacitors to higher standards for professional equipment. Another British capacitor brand was Erie (ok but not as good as Mullard/Philips)
Well I didn't think it was a bad idea to replace the electrolytic caps (unless I was really bad at working with PCB's) but oh well, I will hold off until I find the fault. A mutual friend loaned him a Soundcraftsman preamp so I can look at the Mcintosh longer.
I was told that the freeze spray was bad for components and to not use it by an old TV repair man😕 I will pick up a can and give it a try, obviously I won't be spraying the tubes
So I guess I was wrong about electrolytic capacitors, they can have a life span of 50 years without degrading, who knew😉
I was told that the freeze spray was bad for components and to not use it by an old TV repair man😕 I will pick up a can and give it a try, obviously I won't be spraying the tubes
So I guess I was wrong about electrolytic capacitors, they can have a life span of 50 years without degrading, who knew😉
Made a chilly run to RatShack and picked up some freeze spray. I had a good laugh at the register.......buying freeze spray on the coldest day in the last 6 years lol, as if it's not cold enough.
Anyway, I got to thinking, he has his preamp on the shelf directly above his tube power amp and heat rises. So now I placed a heating pad under the preamp hoping to heat up the faulty component. If I see a fault I will systematically freeze a component to see if the fault goes away.
Before posting I had already poked around looking for a bad connection/solder joint during the 40 hrs of bench testing. I will still do this under the now warmer environment.
If he sells it he isn't going to do the caps, just the repair. If he keeps it he might upgrade them down the road.
Anyway, I got to thinking, he has his preamp on the shelf directly above his tube power amp and heat rises. So now I placed a heating pad under the preamp hoping to heat up the faulty component. If I see a fault I will systematically freeze a component to see if the fault goes away.
Before posting I had already poked around looking for a bad connection/solder joint during the 40 hrs of bench testing. I will still do this under the now warmer environment.
If he sells it he isn't going to do the caps, just the repair. If he keeps it he might upgrade them down the road.
BTW, the troubleshooting described does not rule out bad cables between the preamp and power amplifier. You have to swap L and R cable ends first
at the back of the preamp for the first test, and then for the next test at the power amp inputs, to be sure. Or, just replace them with different cables
if problem is very intermittent.
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Just got a vital piece of information from the owner that I believe rules out the cables to the power amp. When the fault occurs, the output level meter for the right channel goes down on the C2200. Also all sources are effected, including the phono section.
I feel confident sooner or later if there is a problem it will reveal itself. Thank you all for helping me with the great advice, still no fault with the extra heat from the heating pad, but it's only been a little over an hour. I plan on leaving it on until I go to bed.
I feel confident sooner or later if there is a problem it will reveal itself. Thank you all for helping me with the great advice, still no fault with the extra heat from the heating pad, but it's only been a little over an hour. I plan on leaving it on until I go to bed.
The pros also look for intermittents sometimes with a heat gun - the sort used to shrink heatshrink plastic onto cables and connectors. Thse let you direct a small stream of air onto just one or two components. Use the lowest heat setting.
At a pinch, you can use a hair dryer with a home made tin-plate jet+heat reducer fitting to localise the air flow and reduce its temperature - the average hairdryer is way too hot.
This method needs a little more skill and judgement and has greater risk of damaging parts.
This idea of replacing all electros is an old story believed by those with little or no experience. In equipment made before the 1960's, electros did have a limitted life. Even so, you should always find the actual fault FIRST. Then, and only then, to improve reliability, replace electros one by one, testing each time.
Feeezer spray is indeed also bad for parts - if you over do it. So is soldering heat. I used to supervise a workshop. Young apprentices seemed to love squirting enough spray to produce ice around parts. That's obviously not good for the parts or the equipment, and it wastes and awful lot of spray. Reminds me - when I was a teenager starting out in TV repair, we used to squirt cockraoches (the shop was infested with big lazy brown ones about 40 mm long) - a tiny quirt on their back end - boy can they go fast then.
Another word of advice derived from much experince: Do not ignore, but do not absolutely rely, on the advice of the owner as to what he did and what effect it had. We all make mistakes. Non-qualified owners make more of them. Get his cables and repeat the tests yourself. Give each a good wriggle.
A true story for you: Whenh I worked in TV repair, our receptioniste was trained to ask callers a standard set of questions so that we could load the truck with a tailored range of parts, and not carry around all teh time all possible parts for all brands and models. The questions were:-
1) What brand is your TV?
2) In what year did you purchase it? New?
3) Is the picture affected?
4) Is the sound affected?
5) Is it crook on only one or two channels or are all affected?
An old lady phoned in and said her set had bad picture and bad sound on channel 2. Other channels were ok. The set was a 1961 HMV. As the tuners in these often went, causing just such a fault, I put a recon tuner in the truck and drove over to her. The set was completely dead - on all channels. Power transformer was u/s. Turns out she only ever watched channel 2. She said the other channels were ok because she didn't care about them.
I recall another case where a customer kept complaining that his stereo kept intermittently failing in one channel. We eventually figured out his 3 year old son kept turning the balance control hard over, trying to turn the set on.
I had another customer who kept complaining that his integrated stereo was intermittently failing on FM with bad sound quality. Actually it was his girlfriend switching it to AM to listen to a news station.
At a pinch, you can use a hair dryer with a home made tin-plate jet+heat reducer fitting to localise the air flow and reduce its temperature - the average hairdryer is way too hot.
This method needs a little more skill and judgement and has greater risk of damaging parts.
This idea of replacing all electros is an old story believed by those with little or no experience. In equipment made before the 1960's, electros did have a limitted life. Even so, you should always find the actual fault FIRST. Then, and only then, to improve reliability, replace electros one by one, testing each time.
Feeezer spray is indeed also bad for parts - if you over do it. So is soldering heat. I used to supervise a workshop. Young apprentices seemed to love squirting enough spray to produce ice around parts. That's obviously not good for the parts or the equipment, and it wastes and awful lot of spray. Reminds me - when I was a teenager starting out in TV repair, we used to squirt cockraoches (the shop was infested with big lazy brown ones about 40 mm long) - a tiny quirt on their back end - boy can they go fast then.
Another word of advice derived from much experince: Do not ignore, but do not absolutely rely, on the advice of the owner as to what he did and what effect it had. We all make mistakes. Non-qualified owners make more of them. Get his cables and repeat the tests yourself. Give each a good wriggle.
A true story for you: Whenh I worked in TV repair, our receptioniste was trained to ask callers a standard set of questions so that we could load the truck with a tailored range of parts, and not carry around all teh time all possible parts for all brands and models. The questions were:-
1) What brand is your TV?
2) In what year did you purchase it? New?
3) Is the picture affected?
4) Is the sound affected?
5) Is it crook on only one or two channels or are all affected?
An old lady phoned in and said her set had bad picture and bad sound on channel 2. Other channels were ok. The set was a 1961 HMV. As the tuners in these often went, causing just such a fault, I put a recon tuner in the truck and drove over to her. The set was completely dead - on all channels. Power transformer was u/s. Turns out she only ever watched channel 2. She said the other channels were ok because she didn't care about them.
I recall another case where a customer kept complaining that his stereo kept intermittently failing in one channel. We eventually figured out his 3 year old son kept turning the balance control hard over, trying to turn the set on.
I had another customer who kept complaining that his integrated stereo was intermittently failing on FM with bad sound quality. Actually it was his girlfriend switching it to AM to listen to a news station.
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Keit… same for the Computer Business.
When the world was young, and dinosaurs still were roadside pests, my little Berkeley company installed Personal Computers for the avid newcomers in the 1980s. Wild times.
Never will forget the lady who called, and said, "Its such a nice computer. I am however having problems with the disk drive. It doesn't want to read my disks." Trying to at least get a sense of what might have been up (it was an era where disk write-tracks could be in slightly different positions from manufacturer-to-manufacturer, and especially with age), i asked her to get the "standard disk we showed you to start with". She did. Inserted it, and it passed the basic tests.
Hmm… "my dear, is there anything else you can think of mentioning that might be related to the problem?" … "Oh yes. I have much more trouble getting my personal disks into the drive." (Hmmm… what?) "Ok. They're all pretty much the same … could you tell me anything else about this?" … "Certainly. I have found they fit ONLY if I fold them in half a certain way…" (I put her on mute, and literally plant my palm in my face. OH NOES.) The old "8 inch disks in a 5 inch drive" phenomenon.
I ended up buying her, on my nickel, a nice used 8 inch drive, and got it hooked to her computer. Rather amazingly, after we "unbent" her 8 inch media, a fair amount of it could be read without too many errors.
TRUST NOTHING THE CUSTOMER SAYS … COMPLETELY. Their memory for detail, and their attribution as to cause, are oft-as-not entirely fabrications and fictions inspired by a smarter-than-average, but still less-than-competent mind.
GoatGuy
When the world was young, and dinosaurs still were roadside pests, my little Berkeley company installed Personal Computers for the avid newcomers in the 1980s. Wild times.
Never will forget the lady who called, and said, "Its such a nice computer. I am however having problems with the disk drive. It doesn't want to read my disks." Trying to at least get a sense of what might have been up (it was an era where disk write-tracks could be in slightly different positions from manufacturer-to-manufacturer, and especially with age), i asked her to get the "standard disk we showed you to start with". She did. Inserted it, and it passed the basic tests.
Hmm… "my dear, is there anything else you can think of mentioning that might be related to the problem?" … "Oh yes. I have much more trouble getting my personal disks into the drive." (Hmmm… what?) "Ok. They're all pretty much the same … could you tell me anything else about this?" … "Certainly. I have found they fit ONLY if I fold them in half a certain way…" (I put her on mute, and literally plant my palm in my face. OH NOES.) The old "8 inch disks in a 5 inch drive" phenomenon.
I ended up buying her, on my nickel, a nice used 8 inch drive, and got it hooked to her computer. Rather amazingly, after we "unbent" her 8 inch media, a fair amount of it could be read without too many errors.
TRUST NOTHING THE CUSTOMER SAYS … COMPLETELY. Their memory for detail, and their attribution as to cause, are oft-as-not entirely fabrications and fictions inspired by a smarter-than-average, but still less-than-competent mind.
GoatGuy
It could be the "output muting" circuit, and it's just before the output meter connection.
See if the signal sustains prior to that point.
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UPDATE: Almost a month later and the problem has reared it's ugly head finally. I am scared to shut it off because then it might resolve itself again.
It seems to have something to do with the volume control. The right channel does not work UNTIL it reaches 64. Anything from 0-63 does not output sound from the right channel, as soon as you reach volume 64, it works😕
It seems to have something to do with the volume control. The right channel does not work UNTIL it reaches 64. Anything from 0-63 does not output sound from the right channel, as soon as you reach volume 64, it works😕
When it works, are the channels balanced as normal? Also, do you have a scope and the schematic so we can troubleshoot it?
Yes, balanced normally.
Yes I have a scope, and here is the service manual: http://akdatabase.org/AKview/albums/userpics/10004/C2200 Service.pdf
I switched the amp off and on really quickly and now it works perfectly again.
Ok, then you should scope points in the circuit until you've localized the problem. Like I said before,
the most likely place is the output muting circuit. Scope the U19 outputs, they probably won't cut in and out.
The control circuit for the relays following this is likely to be the problem. It's run by the microprocessor.
However, the micro likely controls both channels by the same output, so it's probably not the problem.
Could be a relay or a connection, for example.
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I guess what is stumping me is why with just a quick off and on cycle it resolves. When it messes up I have to turn it off to get it on my bench and hook my test equipment up, then it works and I can't troubleshoot it. I hate intermittent problems like this.
I have freeze sprayed, poked, and tapped, U4, Q9-Q16 and surrounding circuitry and I can't get it to mess up again. Firmware issue maybe?
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