I strayed, maybe someone can help.

[Steven Tate]

Ok, the manual came today and it is for the wrong model , so now I have to argue with the seller. Hopefully the right one will be here soon!

Grrrrrrr. Waiting on the mail for something so you can move forward with your project, and then getting the wrong thing......frustrating.

 

[airtime]

What model did he send you. Was it the SM-1515H. I that is the nearest model I can find on line.

 

[Richs_Trains]

It was for a tuner the ST-4205, so no help. He is sending out the correct one, probably be here next week. Thanks Rich

 

[Richs_Trains]

Update: Since I was unable to repair the Optonica, I sent it to my expert tech and this is the outcome:

Hi Rich. Just finished the Optonica SM-3205. Found that the muting circuit was always on. Q403,404 were forward biased, thus sending the audio to ground at the input to the power amplifier stage. Q401 had around +15 volts at all 3 terminals. This was caused by R701 being open, located on the circuit board mounted on the big filter capacitor. May have been caused by bad capacitors. Unit works great, output IC’s are fine. Less than 10mv dc offset on either channel. 40wpc at less than .04% thd at rated output. Nice amp. Brad

Thought it was the muting circuit when I got the SM, but I had no idea how to troubleshoot it, Thank you to Brad at Precision (Previd) Rich

 

[airtime]

That was why I recommended you trace the signal until it drops out. From there - ahhhh ya gotta have the schematic.

So is it working?????

 

[Richs_Trains]

I have not gotten it back as the tech I trust with vintage stuff is in Idaho, but he, not familiar with Optonica, was duly impressed with it performance and build quality. Should be here by early next week as he also has my Mode 24 Pre-amp/Tuner. I let you know when I hook it up. Rich