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Optonica SA-5406

C

cyber104

Active Member
Hi All:
I see that this receiver has shown up in discussions here before - but I've exhausted the search feature and all threads seem to lead me nowhere. I see several threads that describe my issue exactly but there doesn't seem to be any follow-ups with regard to the fix.

I'm looking for a proper service manual/schematic.

The unit I have powers on but the speaker relay never clicks and it remains in "protection" mode.

I'd at least like to run thru the test points.

All I know at this point is that this is my first try at fixing something myself that isn't obvious (to me at least).

I sometimes see test points in pairs - and on this unit I see TP601 and TP602 immediately near the corresponding STK 0070 ii power amps.

TP601 shows 0.0 VDC and oscillates between (+) and (-) every 3 seconds or so. Positive probe of my digital multi-meter is on the TP and negative probe is on chassis ground. Rotating VR601 does nothing to TP601 readings.

TP602 shows a steady 47 VDC. Positive probe of my digital multi-meter is on the TP and negative probe is on chassis ground. Rotating VR602 does nothing to TP602 readings.

Thanks much!
 
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Did you replace the fusable resistors? This has been the problem on every Optonica I've worked on.

However it sounds like one of the packs is dead and putting out rail voltage.....
 
Thank you for the reply. I see the resistors you are talking about. Can those be tested while they are still soldered to the board or do I have to remove them to get an accurate reading?

I did order 2 new packs already since this problem is similar to one I had with my old Technics SA-400. The packs were inexpensive so I figured I didn't have much to lose.
 
cyber104 said:
Thank you for the reply. I see the resistors you are talking about. Can those be tested while they are still soldered to the board or do I have to remove them to get an accurate reading?

I did order 2 new packs already since this problem is similar to one I had with my old Technics SA-400. The packs were inexpensive so I figured I didn't have much to lose.
Click to expand...
Why test? Replace them!!!

If you got the packs from eBay know that they may or may not work, and if they do work they're not rated even close to the originals.
 
OK - can those resistors account for the problematic readings I'm seeing ?

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And if the eBay packs aren't any good - where can I find some good ones?
 
Voltages don't matter until you replace them, actually no other troubleshooting matters. Please just replace them.
You won't ask if you need an oil change if the motor doesn't even start.

An AK member sells discrete modules to replace them eBay. His username is delta9electronics, or if you just search STK-0070 they come up.
 
Hi All:

Just wanted to follow up on this issue. The unit is fixed. It was just one of the STK0070 IC's. I used a Chinese replacement. It works just fine and this Receiver sounds quite good!

I also picked up (4) OEM STK0080 II's and (2) 3082's from a reliable source. I'll keep them in storage just in case the Chinese STK0070 blows up. But at this point it seems fine and I don't push this unit very hard.
 
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