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We don't talk much about repairing or upgrading solid state gear such as the Marantz 2270 and the Pioneer SX-850 and other solid state gear of a similar nature..Believe it or not,they have similar problems that their tube cousins have and that is, capacitors whether they be coupling or bypass.
The biggest culprits in solid state gear are the 1 uf and the 2.2uf, and the 4.7uf, and the 16uf, and the 47uf caps..If you have weak volume in one channel or the other whether it be the phono stage or line stage,chances are its a cap of one of those values causing the problem..The 1uf caps are typically input couplers and they open or get severely leaky and can cause weak output.
It helps to have a schematic and having an oscilloscope is an added plus.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Edits: 01/09/15Follow Ups:
Never really paid attention to specific values before, but I've been refurbishing a bunch of 70s and 80s gear lately and those are the values that are shot.
I mean ESRs 10-100X what would be reasonable, to the point of so high I can't measure, and little to no signal getting through (which of course makes them easy to find).
Don't forget 10 and 22μF, and even up to 100 or 220 which are sometimes used for discrete stage inter-coupling. But yeah, I get the point, it's the smaller ones that really seem to get unusably bad.
I've found 70s SS receivers to be more complex with many more switches that get dirty and fail.
I recently fixed a bad right channel on a SX-838 by cleaning the switches. I think this unit had sliders, toggles and rotary switches and 5 or 6 pots for tone, volume, balance.
looking for some jazz and a little libations - joe strummer
I've found 70s SS receivers to be more complex with many more switches that get dirty and fail.
That happens as well..I was referring mostly to low volume in one channel and many times that turns out to be a small electrolytic used in coupling or emitter bypass,
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
I had a SAE pre with about 20 bad electrolytic caps. The caps were so bad the protection relays would start to cycle.
looking for some jazz and a little libations - joe strummer
I hear you..THe Sansui 9090DB I had worked on a few years ago would go into shut down and I had recapped the driver boards and that cured it..The ESR meter was a lifesaver.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
Replacing power supply caps are a must. I use Elna Silmic II to replace the old coupling caps for superior sound. SS amps equipped with the older op-amps will perform better with newer op-amps.
I do find tube gear easier to service due to more room under the chassis, no stacked circuit boards, lots of interconnect cables and at times less components overall.
I truly believe that it was built with NO intent towards repairing the unit.
I had one with a simple channel out problem. I knew where the problem was. But was actually unable to get to the board withou dis-assembly about 90% of the unit. Rendering it - unfixable.
A lot of the Japanese equipment seems to be designed as a puzzle box. Yamahas can be difficult to get apart too. Contrast that to Hafler, which is built like military gear. It is very easy to work on.
Dave
Hi Mike,
Now you talking the bulk of what I have. I would add that cold solder joints also are a common problem. I am trying to teach myself how to work on this stuff.
It turns out that my RatShack volt/ohm meter that I bought years ago to measure the throttle positioning sensor on my 86 5 liter Mustang, also has a capacitance meter. Would this be useful in checking these capacitors?
Of course it would be best to replace them with film, but usually there is not enough room, so an electrolytic is required. What electrolytic capacitors do you use to replace them?
TIA,
Dave
No, you need an ESR meter to check the small 'lytics. Your VOM will only tell you if the capacitance is correct. Bad caps usually read the same capacitance but have a high ESR.
I knew it was time to pony up the money for an EST meter. Fortunately the are not very expensive.
Dave
Dave, not the go off topic too much but what is a good and inexpensive ESR meter?
I'm assuming my Heathkit CT-1 isn't very useful.
looking for some jazz and a little libations - joe strummer
Hopefully an inmate with more experience them me will chime in. I do repair, but it is pretty basic stuff. Actually, I suspect that as long a the Heathkit is functioning properly, it will do. I don't think it has to be that accurate to see that a capacitor is out of commission.
The Blue looks interesting but I don't really know if it is good (see link). I to have a vintage tube ESR meter that was given to me by a retired TV repair man, but I need to bring it up to spec. He thought it was still usable!
Dave
Back in the day, when I had an interest in learning how to fix 70's gear, I found out that very same fact.
I would recap all the entire entire unit and find that the balance would return. As well as bass, clarity, etc...
But I still came back to tubes in the end.
charles
The Recklinghausen byline is the finest truth I know in Audio. Thanks for the ss tips Michael.
The Mind has No Firewall~ U.S. Army War College.
Edits: 01/08/15
Your welcome Ken.
"If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you have measured the wrong thing."
- Daniel R. von Recklinghausen
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