Sansui 331 Blowing fuses

[vmedia]

Hello -
I just acquired a ($20) 331 that was known to blow a fuse.
Upon inspection, F604 was blown. I replaced and it failed dim bulb test.
I then replaced C603 and C609 on questionable visual inspection - it seemed to pass DBT (albeit the bulb flickered in a strange way)
So, I brought it up slowly on Variac and F605 blew at around 90 Volts (F604 survived)
I assume the next step is to measure some voltages. I did check the leads on F605 fuse holder (Under DBT) and see 99.3 VAC on the side that connects to TM6 and 4.4 VAC on the side that connects to the BRN lead from the Voltage Transformer. Next steps? Thanks

 

[vmedia]

Update: Pulled BRN connection from board and tested (DBT) reads 1.4 VAC

 

[avionic]

Looks like a bad STK

 

[avionic]

I then replaced C603 and C609 on questionable visual inspection

Did you get the new ones installed correctly ?

 

[avionic]

Check for solder bridging around your work.

 

[vmedia]

Double checked and they match photos I took and printing on board.
Is there an easy way to check the STK or do I need to desolder and see if it passes DBT without STK installed?

I've noticed when comparing with photos of other 331 - I do not seem to have a red wire coming from the transformer (?) Is this normal?

 

[avionic]

Whats your geographic location ? Mains voltage ? Red wire is and 100VAC tap for Japan.

 

[avionic]

need to desolder and see if it passes DBT without STK installed?

Ideally. Yes. First. Unplug the unit. With your multimeter - connect the black lead to metal chassis ground. Measure the resistance at pin 8 of one of the STK's.with your red test probe. Post results.

 

[vmedia]

I'm in US.
I'm noticing that it appears someone else has worked on this (groan) Attaching photos of some numbered stickers and the pins of the STK014 - notice the broken trace and repair.

Assuming that pin 1 is on the end with the white dot - I am seeing continuity to chassis ground on Pin8 - in fact quite a few of the pins are grounded to the chassis

 

[avionic]

I'm in US.
I'm noticing that it appears someone else has worked on this (groan) Attaching photos of some numbered stickers and the pins of the STK014 - notice the broken trace and repair.

Assuming that pin 1 is on the end with the white dot - I am seeing continuity to chassis ground on Pin8 - in fact quite a few of the pins are grounded to the chassis

Less than 1000 Ω ?

 

[avionic]

- in fact quite a few of the pins are grounded to the chassis

Regroup...There are a few points on that chip that are tied to ground.

 

[vmedia]

Sorry - I did not read your request fully.

I get .8ohms on Pin 8

 

[avionic]

Sorry - I did not read your request fully.

I get .8ohms on Pin 8

Me thinks one or both of the STK's are toast.

 

[avionic]

Sorry - I did not read your request fully.

I get .8ohms on Pin 8

Remove F604 fuse and recheck pin 8.

 

[avionic]

Remove F604 fuse and recheck pin 8.

Skip it... You have bad STK(s).

 

[avionic]

Both STK pin 8's are tied together. If one is shorted in circuit they both will read shorted in circuit.

 

[vmedia]

I'll try to track down an STK - thanks.
Is there a procedure to follow once I install the new one?

 

[Tom B]

That STK014 is a 2 channel Stereo amp. Only one needed. I suggest you get the ECG replacement available on the auction site, as other STK014 can be questionable
ECG1252 STK014 ECG1252 Stereo Audio Power Amplifier Module 15W per Channel NOS