SA-7700 / SA-706 Recap/Restore
- Thread starter xlbee
- Start date
This is an important one boys and girls!!! It helps to reinforce why it's so important to PAY CLOSE ATTENTION when you are recapping.
The first two caps I pulled from this unit (C105 and C106) have the board silkscreen showing the incorrect orientation. I verified with the schematic that the component layout diagram is correct. Put them in wrong and you could get fireworks!
The picture below shows the incorrect silkscreen:
The image below is the compnent layout diagram (normally foil side view) that has been flipped so it is the same orientation as the component side.
The first two caps I pulled from this unit (C105 and C106) have the board silkscreen showing the incorrect orientation. I verified with the schematic that the component layout diagram is correct. Put them in wrong and you could get fireworks!
The picture below shows the incorrect silkscreen:
The image below is the compnent layout diagram (normally foil side view) that has been flipped so it is the same orientation as the component side.
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Ah, good times! More fun stuff!
Recap, Deoxit & Faderlube is done. No explosions so far.
This unit had an issue before I started. When switched to Phono, the left channel would sizzle and pop intermittantly. Still had the issue after cleaning & recapping. I found that Q3 (2SC1919) was bad. Replaced it with KSC1845. All good.
Just now I realized that in the area of the board that is heat stressed, someone replaced Q26 (2SD712) with a 2SC1398. Looking at the specs leads me to believe this is not a very good sub. It runs HOT along with the two 75 ohm resistors beside it. Not good. Going to replace it with an MJE15032.
Thoughts? Comments? Chime in...
Recap, Deoxit & Faderlube is done. No explosions so far.
This unit had an issue before I started. When switched to Phono, the left channel would sizzle and pop intermittantly. Still had the issue after cleaning & recapping. I found that Q3 (2SC1919) was bad. Replaced it with KSC1845. All good.
Just now I realized that in the area of the board that is heat stressed, someone replaced Q26 (2SD712) with a 2SC1398. Looking at the specs leads me to believe this is not a very good sub. It runs HOT along with the two 75 ohm resistors beside it. Not good. Going to replace it with an MJE15032.
Thoughts? Comments? Chime in...
petehall347
the brandy coffee man
bigger heat-sink
:scratch2:
:scratch2:
Ok, all done. Been running full out for 2 hours and all seems well.
Standard disclaimer: The attached parts list represents a snapshot in time. It's the right list for my unit, yours may be slightly different. Mouser part numbers change and they run out of stock so you may need to make some substitutions. The list should also be inspected by one of the AK gurus (you know who you are) to ensure it meets with their approval. The mods are more than welcome to publish it in the AK recap database if approved by one of the AK gurus.
Standard disclaimer: The attached parts list represents a snapshot in time. It's the right list for my unit, yours may be slightly different. Mouser part numbers change and they run out of stock so you may need to make some substitutions. The list should also be inspected by one of the AK gurus (you know who you are) to ensure it meets with their approval. The mods are more than welcome to publish it in the AK recap database if approved by one of the AK gurus.
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bigger heat-sink
I cut a "T" shaped piece of aluminum from a leftover piece of capet edge cover plate, drilled a hole and fastened it to the back of the original heatsink with the same screw that fastens the transistor to the heatsink.
romaxmaniax
New Member
C319 c320 ???
Hello xlbee,
I recap my SA-706 successfully thanks to your list but I have a doubt about C319, C320.
Indeed, on the silkscreen and on diagram they are supposed to be polar caps however the original caps are bi-polar.
Why did you choose stacked film cap (667-ECQ-V1H224JL) to replace those where other poeple use Low Leakage Electrolytic Cap (647-UKL1HR22KDDANA).
Did you mix something with C301-C302 in the list?
Anyway my SA-706 is working great.
Thank you very much for this list :ntwrthy:
Hello xlbee,
I recap my SA-706 successfully thanks to your list but I have a doubt about C319, C320.
Indeed, on the silkscreen and on diagram they are supposed to be polar caps however the original caps are bi-polar.
Why did you choose stacked film cap (667-ECQ-V1H224JL) to replace those where other poeple use Low Leakage Electrolytic Cap (647-UKL1HR22KDDANA).
Did you mix something with C301-C302 in the list?
Anyway my SA-706 is working great.
Thank you very much for this list :ntwrthy:
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Hello xlbee,
I recap my SA-706 successfully thanks to your list but I have a doubt about C319, C320.
Indeed, on the silkscreen and on diagram they are supposed to be polar caps however the caps are bi-polar.
Why did you choose stacked film cap (667-ECQ-V1H224JL) to replace those where others use Low Leakage Electrolytic Cap (647-UKL1HR22KDDANA).
Did you mix something with C301-C302 in the list?
Anyway my SA-706 is working great.
Thank you very much for this list :ntwrthy:
Electrolytic caps will fail over time (which is why we are doing this exercise). Any electrolytic caps that are less that 1uf (bipolar or not) can be replaced by stacked film without size issues and they will last forever. Standard practice for a lot of techs and casual recappers here on AK.
