SX-626 TURN ON THUMP Wrong Cap and other Questions

[markthefixer]

The big cap was changed. I used a 6800 63V in its place based on other threads.
I am reading 57.3 volts at the cap.

Ah HAH...

You went from 3300 to 6800...

try changing the C21? C18? timing cap (100uf) with something larger. Add another 100uf in parallel or a larger cap (470uf) and see what happens to the thump.

 

[moondogtn]

I have both so will try it this afternoon/evening and post up findings. Is one more preferable?

Also, would I be better off installing old large cap or getting 3300?

Bill

 

[leesonic]

I've never had an issue with using a 6800uF main cap.

Lee.

 

[larryderouin]

Try both and use the one that gives you the least thump.

 

[merlynski]

try changing the C21? C18? timing cap (100uf) with something larger. Add another 100uf in parallel or a larger cap (470uf) and see what happens to the thump.

Which cap? Where in schematic?

(BTW FWIW Elektrotanya has a better SM scan than Hifiengine)

 

[markthefixer]

Which cap? Where in schematic?

(BTW FWIW Elektrotanya has a better SM scan than Hifiengine)

@Q13, base lead to timing cap. Different names in different schematic scans, and on different pages.

 

[merlynski]

@Q13, base lead to timing cap. Different names in different schematic scans, and on different pages.

Thanks Mark, I see it now. It controls the delay of the power up of the VAS and bias sections of the Power Amp Assys., so the power supplies can stabilize first. Just trying to learn how it works . . .
EDIT: I was looking at the 1973 SM, then found that the 1971 SM has the circuit function on page 11

 

[moondogtn]

It’s C21 on my model. I swapped it out to a 330uf and oddly it seems to have eliminated the thump when speakers A are selected. If I try to use B then it seems to do it. This is for a bedroom and I have other projects waiting. If I do dig into it again, I’ll keep the progress updated. Thanks for all the advice.

Bill