Hello
I am wondering when would be the best time to recap my vintage solid state Kenwood amp. When opened the casing, and looked at the caps, they are not bulging or leaking anything that.
But when powering on, the sound is a bit crackling and popping for about 5 minutes, and it seems OK for the rest of the day.
The amp is from late 70s or early 80s, and has original parts. Would it be best just recapping now, or wait until further degrade of sound or function, and physical signs - bulging and leaking caps?
Thanks for your advice and info. cheers.
I am wondering when would be the best time to recap my vintage solid state Kenwood amp. When opened the casing, and looked at the caps, they are not bulging or leaking anything that.
But when powering on, the sound is a bit crackling and popping for about 5 minutes, and it seems OK for the rest of the day.
The amp is from late 70s or early 80s, and has original parts. Would it be best just recapping now, or wait until further degrade of sound or function, and physical signs - bulging and leaking caps?
Thanks for your advice and info. cheers.
I think that "crackling and popping" sounds are not caused by electrolitic capacitors.
I suspect transistors or diodes.
Old elco's are not bulging, only newer types develop this rather recent desease.
I myself never change capacitors if there is no real problem.
As such, I do not believe in "recapping".
If there are not obvious problems, keep the item original!
I suspect transistors or diodes.
Old elco's are not bulging, only newer types develop this rather recent desease.
I myself never change capacitors if there is no real problem.
As such, I do not believe in "recapping".
If there are not obvious problems, keep the item original!
The amp has been put away for a few weeks for the purpose of having a look inside again. I took it out, connected, have tried powering on again this morning.
It was not crackling and popping this morning, but the sound on one channel is very weak, and puffy for a while (say 2 -3 minutes), and then settles down. It is OK after that.
It was not crackling and popping this morning, but the sound on one channel is very weak, and puffy for a while (say 2 -3 minutes), and then settles down. It is OK after that.
If the switches and pots need cleaning then that should be fairly obvious as the crackling will come and go as the switch/pot is moved.
If the crackling happens with the volume control turned down then its more than likely a faulty component in the power amp.
Remember that these kind of faults can suddenly become permanent putting a large DC offset across the speaker blowing that and the amp.
If the crackling happens with the volume control turned down then its more than likely a faulty component in the power amp.
Remember that these kind of faults can suddenly become permanent putting a large DC offset across the speaker blowing that and the amp.
This happens first time when it is powered on in the day.
When volume is turned up and down, sound from one channel appears and disappears like kind of fading.
After about 10 minutes powering up and playing music, from then on, it is OK for the rest of the day.
When volume is turned down, it is absolutely quiet all time.
When volume is turned up and down, sound from one channel appears and disappears like kind of fading.
After about 10 minutes powering up and playing music, from then on, it is OK for the rest of the day.
When volume is turned down, it is absolutely quiet all time.
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I would certainly replace every electrolytic capacitor in the amplifier. After 30+ years, it's certain that they have dried out.
The silicon grease (heat sink compound) under the power transistors is probably dry too.
You should remove all transistors which are mounted on the heat sink (one by one), scrape the old silicon compound from the transistors, mica insulators and the heat sink(s). Apply new silicon compound and re-mount the transistors.
This will take some time. If you value the amplifier, it's time well spent.
After doing the above, if you are still having issues with the amplifier, you should be able to trace the noise using 'freeze spray' to localize the problem.
Have fun ... and take your time!
The silicon grease (heat sink compound) under the power transistors is probably dry too.
You should remove all transistors which are mounted on the heat sink (one by one), scrape the old silicon compound from the transistors, mica insulators and the heat sink(s). Apply new silicon compound and re-mount the transistors.
This will take some time. If you value the amplifier, it's time well spent.
After doing the above, if you are still having issues with the amplifier, you should be able to trace the noise using 'freeze spray' to localize the problem.
Have fun ... and take your time!
If its quiet with the volume turned down then it sounds like the problem is in the preamp section... which could be switches and pots needing a clean. Small signal stuff is low powered and usually pretty reliable. Does it matter what input is selected ?
You need to make a start and see what you find.
You need to make a start and see what you find.
Oh man, this is when I despair at DIY audio. Some silly comments, but the first ones were perfect.
Ignore RNMarsh and Frank Berry completely. Listen to the other people here who are trying to give you real advice and help. Replacing all the caps without knowing the actual source of the fault is retarded. It may be a cap, but MUCH more likely transistor/dry joint. Look for signs of a hot resistor and what it would be running next to, post pictures if you can, listen to the advice given by the others... we can solve this by thinking
Ignore RNMarsh and Frank Berry completely. Listen to the other people here who are trying to give you real advice and help. Replacing all the caps without knowing the actual source of the fault is retarded. It may be a cap, but MUCH more likely transistor/dry joint. Look for signs of a hot resistor and what it would be running next to, post pictures if you can, listen to the advice given by the others... we can solve this by thinking
Thanks. Great info.
It was interesting because I got conflicting answers - from 986driver - he would keep the amp as original as possible, no recapping - this is a bit different from what I used read and hear in the past.
I was only using one input CD via AUX, as I do not have any other source. (waiting for a Garrard deck coming soon)
Just now I am playing a CD, and the amp has been on all day. Now it is playing great as if there is no problem at all. Tomorrow morning, when it is powered on, it will be different matter.
Maybe I should take it off, and start doing service on it?
It was interesting because I got conflicting answers - from 986driver - he would keep the amp as original as possible, no recapping - this is a bit different from what I used read and hear in the past.
I was only using one input CD via AUX, as I do not have any other source. (waiting for a Garrard deck coming soon)
Just now I am playing a CD, and the amp has been on all day. Now it is playing great as if there is no problem at all. Tomorrow morning, when it is powered on, it will be different matter.
Maybe I should take it off, and start doing service on it?
Oh man, this is when I despair at DIY audio. Some silly comments, but the first ones were perfect.
Ignore RNMarsh and Frank Berry completely. Listen to the other people here who are trying to give you real advice and help. Replacing all the caps without knowing the actual source of the fault is retarded. It may be a cap, but MUCH more likely transistor/dry joint. Look for signs of a hot resistor and what it would be running next to, post pictures if you can, listen to the advice given by the others... we can solve this by thinking
OK - I will try to get some photos soon - it was covered in thick dust, and I cleaned it up.
OK I had this issue not on a home amp but a classic commercial peavey power amp. Some of the solder joints looked very dull. I found nothing to be loose but I reheated them anyway. The crackling has now disappeared. Also in all my years of repairing both commercial and home audio I have brought more units than I can count back to life by reworking the solder joints in the power supply voltage regulator section as the heat generated there tends to weaken or destroy the solder joints on the board. As crazy as it sounds if you see any charring or discoloration on the circuit board rework those solder joints even if they look ok as that is a sign of lots of heat generated by that part. If that part is not designed to generate lots of heat during NORMAL operation that is a good sign that something else is going on. Another area to look for
bad solder joints is at and around large or heavy duty resisters. Best of luck.
Adam
bad solder joints is at and around large or heavy duty resisters. Best of luck.
Adam
Best not to use it until repaired, I've seen amps in similar condition go pop... then a $2 repair becomes a $80 repair and a royal pain in the ***.
Just to clarify, it's very trendy to replace capacitors at the moment in diy audio. Ten years ago it wasn't.
Of all the amplifiers I've repaired, a lot being vintage, the only time I've ever had to replace a capacitor was when it was close to a hot resistor and spec'd as 85 degree instead of 105. Replacing capacitors to repair an unidentified fault is a pointless exercise, likely to take a lot of time and effort and highly unlikely to repair the fault.
Of all the amplifiers I've repaired, a lot being vintage, the only time I've ever had to replace a capacitor was when it was close to a hot resistor and spec'd as 85 degree instead of 105. Replacing capacitors to repair an unidentified fault is a pointless exercise, likely to take a lot of time and effort and highly unlikely to repair the fault.
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