Can share the link here to the thread? Because I can't seem to find it. Is that part a must replace?
I still need 2x 1uF/50V (C11/C12) WIMA cap for the tone control, I didn't consider this board but just the main one 😢
Luckily, I still had some WIMA 10uF 50V available, time to go to my local electronic supply store.
Hey but apart for this good news!
I just finished replacing 99% of the electrolytic capacitors inside this amp!
I am pretty happy now the amp sounds so much better, the sound is more precise and full, I could already see the difference on the VU-Meters with the same test song that I used in the beginning when I found it 🙂
I noticed that some electrolytic capacitors had leaked on the board, they were so light.
The old filter caps were 8000uF/50V had 3 pins, one of them was for physical support for the mounting, I replaced them with 2x 10'000uF/50V caps.
These are the replacements for the capacitors (unfortunately, I forgot to take a photo of the filter capacitor):
Man the improvements of tecnology always surprise me, look at the size difference!
Here I had alternatives depending on the space used on the PCB. (80V of capacitor because Mouser had finished everything)
the 10uF from WIMA is massive for the capacity
One of the not polarized caps
here the size difference is massive (it is like the filter cap smaller and also bigger)
The other not polarized capacitor
This was small, so I said why not
For caps smaller than 10uF, if space wasn't a limit on the board, I used WIMA polyester caps (MKS2/MKP2 series), instead for all the other I used the Nichicon caps audio series UFG/UKZ/UKA/LKS, I am a bit sad that the audio series of caps of this company is in end of life 🙁I considered using polypropylene caps, but they were too big, mainly they were 3x times the size compared to the polyester equivalents (space was a constraint)
I also cleaned all the boards with 99% alcohol and now the PCB is so much better. Now I can see colors 🤣
Luckily, I still had some WIMA 10uF 50V available, time to go to my local electronic supply store.
Hey but apart for this good news!
I just finished replacing 99% of the electrolytic capacitors inside this amp!
I am pretty happy now the amp sounds so much better, the sound is more precise and full, I could already see the difference on the VU-Meters with the same test song that I used in the beginning when I found it 🙂
I noticed that some electrolytic capacitors had leaked on the board, they were so light.
The old filter caps were 8000uF/50V had 3 pins, one of them was for physical support for the mounting, I replaced them with 2x 10'000uF/50V caps.
These are the replacements for the capacitors (unfortunately, I forgot to take a photo of the filter capacitor):
Man the improvements of tecnology always surprise me, look at the size difference!
Here I had alternatives depending on the space used on the PCB. (80V of capacitor because Mouser had finished everything)
the 10uF from WIMA is massive for the capacity
One of the not polarized caps
here the size difference is massive (it is like the filter cap smaller and also bigger)
The other not polarized capacitor
This was small, so I said why not
For caps smaller than 10uF, if space wasn't a limit on the board, I used WIMA polyester caps (MKS2/MKP2 series), instead for all the other I used the Nichicon caps audio series UFG/UKZ/UKA/LKS, I am a bit sad that the audio series of caps of this company is in end of life 🙁I considered using polypropylene caps, but they were too big, mainly they were 3x times the size compared to the polyester equivalents (space was a constraint)
I also cleaned all the boards with 99% alcohol and now the PCB is so much better. Now I can see colors 🤣
Attachments
The editor didn't let me upload any other images, so I published some of them on Imgur
Images of the amp & workstation:
Short video of the amplifier after the work was done (first test):
Images of the amp & workstation:
Short video of the amplifier after the work was done (first test):
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Look from the side, here you can see another problem that I found later (some audio inputs didn't work for this, read below)
The multiconductor flat cable that transports some inputs cracked when I was moving the cable to replace the caps, leaving the metal part of the cable visible...
(you can see it a bit better at the end of the YouTube video)
Do you know which cables could I use to replace these two cables? Something not flat would be better I think because you would see better the board without having to move the whole input section
Currently, the tuner inputs still work, so I'm OK!
Presently, just the 1-6 section cable appears damaged, the other one is a bit hard but still fine at this moment.
Another low-priority thing to do in the future is to make some small adjustments to the idle current and for the VU-Meters
(and also changing the lights of the vu-meters)
It is really nice that you have the instructions about how to make maintenance for the amp 🙂
Woah, what a ride, I worked 3 days for this 😀
Yes, believe me, I noticed that that thing was glue, I could feel it during the replacement of the capacitors xD
Man so, much, glue in those filter caps, even for the 220uF 50V. I had to bend a bit the board during the replacements.
The leaking happened in some smaller capacitors like the 470uF 16V or 100uF 25V if I recall correctly, I had to clean the PCB afterward because of the residue.
Well now at least both channels work great!
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I too have found precision & repeatability of sound increased after replacing 40 year old electrolytic caps wholesale. Particularly the .22 uf, .47 uf, .68 uf, 1 uf electrolytics used in the RF portions of Japanese radios. I've turned a couple of seventies fuzz boxes into good performing FM tuners just by changing these tiny caps without realighnment. More stable than the **** craig radio I bought new in 2021. The craig has to be retuned 6 times an hour to kill the fuzz.
I disagree with post #2 and #13. Metalized paper cap is a 1959 technology, now limited to musical instrument amps where the exorbitant price of paper reproduces the sound of historic gear. If adason intended to say metalized polyprophylene caps, there I can agree. However a 250 v polyprophylene cap from partsexpress is like putting earthmover tires on a sports car. They don't fit. 250 v polypro caps are for crossovers in >100 watt speakers, where there is plenty of room.
#13 fear of ceramic caps, well certainly if you can buy CPO ceramic caps that improves linearity. If you can't get CPO and need to fit in something smaller than a WIMA MKP, using a 50 v or 100v x7r ceramic on a 1 volt signal minimizes the non-linear effects. I've done it and really preferred the sound of ceramic to the fuzz and drift of dried up old electrolytics.
I disagree with post #2 and #13. Metalized paper cap is a 1959 technology, now limited to musical instrument amps where the exorbitant price of paper reproduces the sound of historic gear. If adason intended to say metalized polyprophylene caps, there I can agree. However a 250 v polyprophylene cap from partsexpress is like putting earthmover tires on a sports car. They don't fit. 250 v polypro caps are for crossovers in >100 watt speakers, where there is plenty of room.
#13 fear of ceramic caps, well certainly if you can buy CPO ceramic caps that improves linearity. If you can't get CPO and need to fit in something smaller than a WIMA MKP, using a 50 v or 100v x7r ceramic on a 1 volt signal minimizes the non-linear effects. I've done it and really preferred the sound of ceramic to the fuzz and drift of dried up old electrolytics.
When you are cleaning the boards with 99% alcohol,just clean the surface,or use cold wind blow it after your clean work,or it might hurt the components.
I tried at first blowing air and using a brush, but it was still not enough 😢
Some dust was still stuck on the components, so for that reason, I used alcohol, do you know a better chemical to use on this occasion?
Would you like to check if you can buy "Contact cleaner Falcon 530 spray 550ml" from AliExpress or Amazon. The price won't be too much,in China,it is around $1-$2/pcs.
Little update:
I've finally changed the two 1uF 50v with 2x WIMA caps:
Noted, they are a bit bigger than usual because the shop only had the 100V versions.
When I did this last replacement, I noticed that I missed a 10uF 50v electrolytic capacitor on the front of the amp,
it was a bit difficult to replace because I didn't have any space on the bottom enclosure of the case, and so I had to disassemble the front of the amp completely (shame that I don't have the photo of the part, just of the part replaced).
(this little one, with a bit of lever I could replace it)
(don't worry, I have cut the leads of the capacitor, it was an old photo during the process this one)
a
The position wasn't really ideal at the beginning, but then once found the right one was fine.
It could be placebo I think, but afterward I could hear less of EMI interference I think on the sound of the amp.
Then I also replaced the broken flat cable, but I don't know if it was really a 100% fix rate because now:
I've finally changed the two 1uF 50v with 2x WIMA caps:
Noted, they are a bit bigger than usual because the shop only had the 100V versions.
When I did this last replacement, I noticed that I missed a 10uF 50v electrolytic capacitor on the front of the amp,
it was a bit difficult to replace because I didn't have any space on the bottom enclosure of the case, and so I had to disassemble the front of the amp completely (shame that I don't have the photo of the part, just of the part replaced).
(this little one, with a bit of lever I could replace it)
(don't worry, I have cut the leads of the capacitor, it was an old photo during the process this one)
The position wasn't really ideal at the beginning, but then once found the right one was fine.
It could be placebo I think, but afterward I could hear less of EMI interference I think on the sound of the amp.
Then I also replaced the broken flat cable, but I don't know if it was really a 100% fix rate because now:
- the Aux input work again
- the Phono input has got a 50hz sound already at half volume (but 1-4 is fine), maybe because there is no input there, I can't really test it right now because my turntable is broken 😢
- The Tuner input doesn't work, and before it did work, I reviewed the schematic, but I still can't figure out which cables are the problematic ones.
It would probably be easy with a signal generator and an oscilloscope to resolve this problem but I don't have them, but I need a bit more debug
Currently, the amp runs really well on my desk, the bass and highs are really great, I think there was also an improvement made on the tone control with the replacement of the two old capacitors.
I have to say, with the 3.5 mm jack of the PC I had EMI interferences, I could hear the mouse while moving it and graphic cards during the load, so I bought a little external DAC for it, and now it is dead silent, really great result.
Now it is bearable also when you listen to the headphones on it (Grado SR80).
Yes, there is just a little bit of ground noise, but not as the level of a telephone line, so is fine 😆
I have to say, with the 3.5 mm jack of the PC I had EMI interferences, I could hear the mouse while moving it and graphic cards during the load, so I bought a little external DAC for it, and now it is dead silent, really great result.
Now it is bearable also when you listen to the headphones on it (Grado SR80).
Yes, there is just a little bit of ground noise, but not as the level of a telephone line, so is fine 😆
In the future, I need to look at the bias of the power transistors, maybe change the voltage regulators while am there and also look if there are some black leads transistor to change potentially 🙂)
Thx vintageaudioaddict to exist, I learned alot
Thx vintageaudioaddict to exist, I learned alot