Sansui 9090 re-cap gone bad

[Dougi]

My Sansui 9090 (non DB) would not come out of protection mode, so I did some research on this site and from the help of past posts it wisely lead me to look at the F2436 driver circuit board. At location R30 I found a bad/open fusible resistor, so I replaced it along with 11 other resistors, 4 capacitors, and 4 transistors that were included in the kit I bought online from Vintage Stereos LLC (qrxrestore.com).

My Sansui was working again and sounding GREAT !!! I was so happy my first circuit board re-cap job was a great success. So I decided to order a complete stereo re-cap kit from the same outfit.

With the parts included in the kit I re-capped the following Circuit boards:
F2542 Accessory Switch
F2546 Power Supply
F2547 Protection
F2541 Equalizer
F2431 Power Supply
F2549 FM-AM Tuner
F2545 Filter and Muting
F2544 Tone Control
F2543 Tone Control
and upgraded Main Filter Caps to 80v 12,000uf.

I power up my beloved Sansui 9090 for the first time since the complete re-cap and I heard a hum for a split second then the fuses blew at f03 and f04 on F2546 power supply circuit board. I pulled The F2436 Driver Board and replaced the fuses and powered it up again and POW the fuses blew immediately.

Does anyone have any suggestions where I should start to look for trouble? Keep in mid this is my first recap job. I carefully pulled and replaced each cap one at a time, took pictures watched polarity on the boards, not sure where I could have gone wrong. All suggestions are more than welcome.

Please help bring my Sansui back from the grave

 

[Hipocrates]

Man that will be hard... But let's see the work done (Pics)and maybe I can assist you.
What amp rating fuses are you using?
Do you have a DBT?
Did you did all the recap at once?

 

[The Fuxtor]

The filter caps installed correctly??

 

[tnsilver]

Verify the 8 output transistors at the back of the unit, make sure none are shorting or shot, replace if needed. Replace the blown fuses, pull out the F2436 driver amp and fire it up on a DBT.
What's the bulb doing? Out of protection? Don't get off DBT yet.

 

[Ultimatt]

There is a 3 part video of a 9090 rebuild that may be of some help...start here -

 

[Dougi]

Thank you for the replies,
Hipocrates, here are some picks of f2431 power supply, more to follow

The fuses that blew on f03 and f04 on board f2546 are rated at 10 amps.

I don't have a dim bulb tester.

I was able to verify the unit still worked by plugging in head phones after I re-capped boards,
F2436 Driver
F2541 Equalizer
F2546 Power Supply
F2544 Tone control
Then after that I no longer verified.

 

[Dougi]

F2541 Equalizer board

 

[Dougi]

F2546 Power Supply board

 

[Dougi]

F2543 Tone Control

 

[Dougi]

F2544 Tone control

 

[Dougi]

F2542 Accessary Switch Board

 

[Dougi]

F2549 FM AM Tuner Board

 

[Bob]

the caps should be replaced by it's original polarity, not by PCB stenciling, check your photos
of the before against what you have now. skip the non-electrolytics, bi-polars, and focus
on only those that are polarized.

if only one is reversed - can destroy one or more caps and cause fuses to blow.

 

[tnsilver]

I don't have a dim bulb tester.

build one. It costs peanuts (if you don't already got the materials at home), takes 20 minutes to make and is a lifesaver, that's unless you want to keep blowing fuses and frying transistors.

 

[Dougi]

The filter caps installed correctly??[/QUOT

I just double checked polarity on the filter caps, they are correct.

 

[Bob]

if you have a VOM/DMM, you can check resistance in the power supply section with the
power off and caps discharged. you might see a short in the bridge or a cap that's
shorted or damaged, and anything from rail to ground, etc.

polarity check - before pictures with after pictures. don't go by PCB markings.
since you have the boards out, trace the positives to ensure they are similar,
and then the negatives. one reversed makes for a bad day.

 

[Robisme]

Did you pull the outputs and reinstall them? If so, check to see that they are in the correct locations.

Rob

 

[Dougi]

the caps should be replaced by it's original polarity, not by PCB stenciling, check your photos
of the before against what you have now. skip the non-electrolytics, bi-polars, and focus
on only those that are polarized.

if only one is reversed - can destroy one or more caps and cause fuses to blow.

Thanks Bob, I did install the caps one by one however, I did rely on the printed circuit board for polarity, I will double check.

 

[Dougi]

Verify the 8 output transistors at the back of the unit, make sure none are shorting or shot, replace if needed. Replace the blown fuses, pull out the F2436 driver amp and fire it up on a DBT.
What's the bulb doing? Out of protection? Don't get off DBT yet.

I pulled my output Transistors and all 8 test similar to the pictures enclosed about 0.5xx. Could you verify I tested this correctly by my picture, Multi meter is in diode mode , I believe they are ok.

 

[Dougi]

I pulled my output Transistors and all 8 test similar to the pictures enclosed about 0.5xx. Could you verify I tested this correctly by my picture, Multi meter is in diode mode , I believe they are ok.

They were carefully pulled one by one so they weren't mistakenly put in out of place.