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As per comments on this forum that anyone with a vintage unit should replace capacitors, I plan to replace those in my 70's era amp.
I have searched the forum for advice on replacement, but haven't really found what I'm looking for.
So, where to start? And how to tell which ones need to be replaced? All of them? Or are there some that are more likely to need replacement?
Also there have been conflicting bits of advice as to re-soldering components. What does one look for to decide if that should be done?
The amp is a Denon DRA-1025R, if that helps at all.
Thanks in advance.
Ron
Follow Ups:
If you have electrolytic caps that serve as coupling caps, make sure you replace them with electrolytic caps of the same value (capacitance and voltage) and make sure the replacements are intended for coupling cap usage.
I have used Nichicon FGs for audio coupling use and they have done well.
Ed
We don't shush around here!
Life is analog...digital is just samples thereof
Most have recommended that you replace them with caps of matching dimensions and uf Value, and possibly higher voltage rating.I'd suggest looking into getting quieter diodes - Schottkys - IF they will fit, and go with the highest voltage rating AND uf caps that will fit the available space.
? better diodes will be quieter, both in the audio band and above it which can help if it's a wide bandwidth circuit.
? Higher voltage ratings will increase the life of the caps.
? And, high storage PSUs make power amps sound more relaxed at LOUD, IMO&E. Bass will be better, too.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 12/01/16
I would replace all electrolytics.
It's important to choose decent parts; I'd go Elna Silmic II or Nichicon kZ for small values, and something like Panasonic low-ESR for the big PSU caps
beware of non-polar electrolytics, those should be replaced with non-polar as well!
Finally, once you're done, don't be too quick in judging the new sound: it will most likely sound very disappointing for the first 100 hours, the more so if you've chose Elna Silmic II capacitors. They really need to burn in. They will open up and sound great but in the beginning you'll think you've broken something (been there with my preamp) ;)
I would replace the power supply caps with caps of like capacitance and similar physical size, and a voltage rating equal to, but preferably higher than, the original rating.
If there are any other electrolytics on the board, same as above.
If the coupling caps are electrolytics, same as above, but if they are film caps, I would not bother as the sound may change, and not to your liking.
Absolutely, do not mess with the FM board unless it is acting up, as pointed out above, you would probably need a realignment which would not be good value in the context of the overall value of the piece, but if there are sentimental reasons for redoing the tuner, absolutely, just realize that the water is a bit deeper.
Inspect all resistors, particularly power resistors, for burn marks and replace as needed. Also check diodes as they can get very hot and not only burn, or discolor, the board, but can age as well.
Clean and degrease all potentiometers, and inspect the power cord for fraying or damage.
You should be good for another fifteen years!
Thanks for your advice. I've been going over the schematic to identify coupling caps - the power caps are obvious. For the moment the plan is to replace power and coupling caps, then go over the boards checking solder joints. We'll see how it goes from there
From my reading it is the electrolytics which are prone to fail or change value as they age. Some say after 10 years, some say after 15, I don't know. I would begin with sony6060's advice, but add all other electrolytics, just to be safe, along with replacing any others which show obvious damage.
A service manual/circuit diagram would be essential for me. That should list the types of capacitors to identify the electrolytics, their values, and locations. Then comes the question of de-soldering and soldering; do you have experience? If not, I'd suggest finding a junk board to practice on, avoiding too much heat.
Anyone who actually knows about electronics is welcome to correct any bad suggestions here.
"The piano ain't got no wrong notes." Thelonious Monk
I would replace all electrolytics of that age. They are cheap. Order them from Digi-Key or Mouser. Once the unit is open and apart, there is no reason not to do it all at once. Stay with the original value and voltage. You can go up in voltage with no problem, but dont go below if you dont know the voltage that is on it.
I would agree with sony6060 that the power supply would be the place to start.
" And how to tell which ones need to be replaced? All of them? "
The only reliable way to know which caps need replacement, other than obvious ones that might be bulging or leaking, is to use an ESR meter. I've had good luck with my Blue ESR meter, but whether it's worth the investment for the average hobbyist is questionable.
So, without actually being able to test the caps, the only truly safe way would be to replace all of them, which can be a pain.
Be advised that although you called your Denon an "amp", a search revealed to me that it is actually a receiver, meaning it has an FM tuner in it. If the capacitors in the tuner section are replaced, the unit will likely require realignment.
As to the re-soldering question, I'd suggest looking at a lot of youtube videos on soldering. You should get a good idea from those as to what a quality joint should look like. Then re-solder any that don't look that way.
Good luck with it.
Replace both power supply electrolytic and audio coupling caps
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