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Optonica SA-5605 Help

Ok. The one bad one that doesn't make sense is R649. All the others are on the power amp board around the driver transistors. And looks like both L & R channels. Which is odd.
Test the voltage at test points K709 & K708 (POS and neg from the big caps)
Might be a good idea to check the output transistors and all the driver transistors on that board ... starting with the differential pair Q501 & Q502. Those regulate the DC offset. The 5606 was upgraded with an adjustment for it.
 
Fusable resistors tend to drift on essentially every unit they are in ....Sansui, Yamaha.. Replace them all and I bet you got sound again.
 
ttbccw said:
Ok. The one bad one that doesn't make sense is R649. All the others are on the power amp board around the driver transistors. And looks like both L & R channels. Which is odd.
Test the voltage at test points K709 & K708 (POS and neg from the big caps)
Might be a good idea to check the output transistors and all the driver transistors on that board ... starting with the differential pair Q501 & Q502. Those regulate the DC offset. The 5606 was upgraded with an adjustment for it.
Click to expand...

Readings:
K708 +53.1V
K709 -53.0V

You want readings on Q501 & Q502, or want me to remove them to test them out? (sorry I am rusty).
 
Question:
I was able to find/order all fusible resistors from Mouser except for these four:
R537 270 OHMS 1/4W <<<BAD
R538 270 OHMS 1/4W <<<BAD
R543 270 OHMS 1/4W <<<BAD
R544 270 OHMS 1/4W <<<BAD

I ordered the above four from eBay. Mouser parts should be arriving on Saturday, but the eBay parts who knows when (as per eBay: Estimated delivery should be Thu, Sep 2 - Wed, Sep 8). But the vendor has not posted a tracking number, so...

Just in case, I'm getting from Mouser four Metal Film Resistors - Through Hole 1/4 WATT 270 OHM 2% (Mouser # 660-MF1/4LCT52R271G). These are NOT labeled as fusible resistors. Would it be ok to use them until the eBay parts arrive? Or should I just wait?
 
Juan-Jose said:
Question:
I was able to find/order all fusible resistors from Mouser except for these four:
R537 270 OHMS 1/4W <<<BAD
R538 270 OHMS 1/4W <<<BAD
R543 270 OHMS 1/4W <<<BAD
R544 270 OHMS 1/4W <<<BAD

I ordered the above four from eBay. Mouser parts should be arriving on Saturday, but the eBay parts who knows when (as per eBay: Estimated delivery Thu, Sep 2 - Wed, Sep 8). But the vendor has not posted a tracking number, so...

Just in case, I'm getting from Mouser four Metal Film Resistors - Through Hole 1/4 WATT 270 OHM 2% (Mouser # 660-MF1/4LCT52R271G). These are NOT labeled as fusible resistors. Would it be ok to use them until the eBay parts arrive? Or should I wait?
Click to expand...
Use em. Check the datasheet on them, many times they have a firecoating on them. Good rule is to not go bigger in wattage for these. They offer fuse like protection so they need to be weak to 'pop' if required. Probably why they drift ....
 
Take them out and test both sides of the 501 &502
I just think it's strange that they would all be bad on both channels in the positions they are in.
I agree with
The Fuxtor said:
IF the unit comes out of protection the DC offset is probably good. I would think if you had a shorted output the protection would engage as well?
Click to expand...
Hard to tell bc the 53+ and 53- from the power supply looks good. It's all the resistors between the DC offset pair and the output pairs. Just strange.
 
thought I would add this so others that might be able to help troubleshoot. The R355 & R356 are between the AUX input board and the phono pre-amp, both fed from the 23.3v+ and 23.3v- power section. R649 feeds the tone amp board from the same power supply. including Q603. The amp voltage of 53.3v+ & 53.3v- as you tested is as it should be. It's very possible that these resistors did drift and replacing them could solve the issue...but just in case somebody might catch something I'm missing.
 

Attachments

Still testing all functionality. The only issues I've noticed so far:
  • some scratchiness on the pots
  • a bit more power thru one channel
So, I guess DeoxIt cleaning and DC Offset check is next
 
cademan said:
And the problem was..............
Click to expand...
A bunch of open fusible resistors:

R531 100 OHMS 1/4W <<<BAD
R532 100 OHMS 1/4W <<<BAD
R523 100 OHMS 1/4W <<<BAD
R524 100 OHMS 1/4W <<<BAD
R525 100 OHMS 1/4W <<<BAD
R526 100 OHMS 1/4W <<<BAD
R527 100 OHMS 1/4W <<<BAD
R528 100 OHMS 1/4W <<<BAD
R545 100 OHMS 1/4W <<<BAD
R546 100 OHMS 1/4W <<<BAD
R547 100 OHMS 1/4W <<<BAD
R548 100 OHMS 1/4W <<<BAD
R649 100 OHMS 1/4W <<<BAD
R355 100 OHMS 1/4W <<<BAD
R356 100 OHMS 1/4W <<<BAD
R537 270 OHMS 1/4W <<<BAD
R538 270 OHMS 1/4W <<<BAD
R543 270 OHMS 1/4W <<<BAD
R544 270 OHMS 1/4W <<<BAD

It is working perfectly now!

Scratchiness went away after cleaning all pots and switches ...and there was no balance issue, rookie mistake: the Balance knob was not properly aligned with the pot. LOL just needed to be re-inserted.
 
Just had a look over at Hifiengine. They don't have the manual for the 5605 but they do have one for the 5606 and those two units look to be almost the same. Not sure what the difference is. Might be worth it to download and take a look.

Also I see a 5606 on sale on the Bay. Same exact issue. Comes out of protection but no sound. How good is it that someone here knew exactly how to do the repair...

 
I had a factory service manual when I fixed one. I never thought to scan it and returned the service manual to the owner.

I found a lot of fusible resistors blown. I replaced them and the open frame trimmers. the trimmers were pretty intermittent.

I thought it was pretty easy to work on and fix.
 
And with anything this old, check for prior work. I found some fusible resistors replaced with 2w or higher watt resistors. my guess this is what the last guy had in his parts bin. I'd suggest replacing with 1/4 watt resistors.

This is the only pic I could find. you get the idea
1739584948266.png
 
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