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Optonica SM 4545

A

atomic drftr

New Member
Hi Everyone,

I just got an Optonica SM 4545 amp from GW that I like really well. I have a couple of questions:

1. Does anyone have a users manual? I have the service manual.
2. I cannot get a signal from either phono outputs. Does this unit require a pre-amp to run the phono or could something be burned out?
3. When I turn on the system on the relay is slow to close, but is consistent and always turns on. Is this normal?
4. Where can I gat a bulb replacement for the single light it has?

Thanks....Great forum.

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atomic drftr said:
I cannot get a signal from either phono outputs. Does this unit require a pre-amp to run the phono or could something be burned out?/QUOTE]
I assume you meant to say phono inputs. This model has a whopping +120VDC power supply rail dedicated to the phono preamp section. Somebody clearly went after phono preamp dynamic range issues with real vengeance. Fuse F801 protects that circuit exclusively, so if you're lucky, a new 150mA fuse in that position will bring joy.
Click to expand...
 
Thanks Binary Mike!

I checked the F801 fuse and it was blown. Both F801 and F802 are supposed to be 150 mA fuses. I pulled out 2-100 mA fuses. I could not find any replacements here in Portland so I ended up replacing them with 125 mA fuses. I switched them out and turned the amp on but can not still get phono. The trouble shooting guide says it could be a defective equalizer amp?

Thanks

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This failure is likely power supply related, because you're reporting both channels out, right? The EQ section gets two power supply voltages. In addition to +120V at the power supply ends of R329 and R330, you should have +13.8V at R339 and R340 on the EQ board.

It is a possibility that both Q309 and Q310 have failed, so if you confirm correct supply voltages, then check collector voltages on both of these devices. They should be sitting near +60V. If they're wildly different, e.g. near +120V, then I would change 'em out. No guarantee, but it's a fair bet.

DigiKey has 150mA fuses in .25 x 1.25 inch and 5x20 mm sizes.
 
Yes, both channels are out.

Thanks, I'll check. To verify:
1. Check supply and collector voltages on Q309 and Q310 on the EQ board. They should be around +60v.

Thanks

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