• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Optonica SM3205 no output.

Richs_Trains

Richs_Trains

Well-Known Member
Okay, so I have a ton of Marantz stuff, I love it, but every now and then I stray. This tine it is an Optonica SM 3205 amp. Optonica was Sharp's attempt to compete with the big boys in the 70's. I have a 4646 and it is built like a tank with three power supplies (one for each amp and one for the pre-amp), so I thought I would take a chance on this one I only spent $37.50 for it, so if it's a fail, that's okay. I hooked it up on a DBT just to be safe and it passes, but there is no audio from any source. This is probably beyond me, but I thought somone might have worked on these before and would like to see if it will run again. Any help or info (can't find an SM for this one either) Thanks as always Rich

sm3205_4.jpg sm3205_2.jpg sm3205_3.jpg sm3205_1.jpg
 
Register to hide this ad
You want to check for blown fuses first.
There are 2 speaker protect fuses near the output IC's. Check that they are good. You should have another power supply fuse, maybe on the board where the main Filter caps is mounted, or possibly on another board. You could also have a line fuse either as a screw in on the back panel, or mountes somwhere inside. The 1515 has a total of 4 fuses, but not sure of yours.

Are you getting light on the dim bulb initially? If so, then the line fuse is OK.
 
All fuses good, re-capped main board, passes DBT. Have very low volume, but some audio. Have check DC at speaker terminals ... Left channel 13.1mv / right channel 10.5mv. Went ahead and re-capped because it was so accessible I now have very low volume on both channels. I have de-oxit all controls and switches and the headphone jack. Someone suggested I run the input to the output of tape 1, this also produces very low volume. Thanks Rich
 
Oh, and I found a hard copy SM, but it won't be here till next week, $20. Rich I'll scan it and put it on HiFiengine.
 
Here a few things you can try.

Test #1 Feed an audio source (2 channel) into AUX.input. Could be anything including a hand held mp3 player
Confirm that tape monitor is off, and any possible audio mute switch is off
See if you get audio.
Test #2 If not, leave the existing audio feeds in, and put a pair a audio patch cords from the "Tape out" connectors on the Optonica to the "Tape in" on a different unit than where you are feeding the original audio from. On this second unit put the tape monitor on. Listen to this second unit you put the tape monitor on.
Do you get audio?

If you get audio during the first test, then the problem is before the driver/power amps.
If you don't get audio on the first test but get it using tape monitor for the second test, you may have 2 bad power amp modules (very hard to find ( Sanken S-60W's).

If you don't get audio during the first test, and don't get audo on on the second test, I would look for cracks on the circuit board, especially near the controls up front, or broken solder connections where the controls and switches connect to the main circuit board in front. Also check connections by the power supply for overheated areas and bad connections.

When you post the SM let me know, and I can look closer.
 
Get very faint audio when inputting on either Aux, or tape 1 out. I get clear audio with the tape 1 out (Optonica) routed to the tape 1 in on my 1060 and a 112 tuner connected to the aux, the audio is there whether the Optonica is powered on of off. Think it is probably the outputs, have order some on eBay from a company in NJ, lets hope they are real. Thanks Rich
 
There's much more to it... power supply to front end/tone control circuit... I don't find it to be the case for output modules considering that both fuses haven't blown or appear to be meddled with.... is check. Signed feed voltages for the +/-1.2v (pins 2 and 6) and contiguity over the emitter resistor array (3-4 4-7).... the power supply feeding the front end often feeds the muting/protect circuit(easy to affect both channels)
 
Hi guys.

Proud Optonica 4646 owner here. Mine went poof yesterday out of the blue. When I power it on, I can hear the transformers starting to buzz (it's loud enough that changing the case isolation was on my list) but nothing else happens. Normally the protection light would switch on (red) and after 5 seconds turn to green (all systems 'go'). I've done the regular poking and prodding and found a 125ma fuse on the left amplifier channel that doesn't pass the tests, otherwise at first glance I can't detect any obvious issues.

Reading the detailed service manual, it seems the area with the blown fuse is the main entry for the small transformer (there are three in this system) to the amplifier board. In this track there are two diodes and one capacitor. The second wire goes to a track just beside it which branches off into two sides; one track uses capacitor c618 to bridge into another track, which in turn has a capacitor that bridges onto the fuse track (c617). Capacitor C618 was changed by me some time ago (Nichicon Muse) because the old capacitor was broken and had leaked considerably. The resistors next to it are fine and undamaged. I haven't had the time to recap the rest of the board, other machines were in need of greater overhauls and the build quality is superb.

Obviously I'd zoom in on the capacitor i've changed but it checks out fine.

What do you think? I feel that i'm missing something completely obvious here.

Regards,

Bert
 
Bert,

Welcome to AK. It would be best for you to start your own separate thread so that the issues get resolved separately. This will nelp others out more in the future as your issue is probably different from the OP's.
 
Richs_Trains said:
Oh, and I found a hard copy SM, but it won't be here till next week, $20. Rich I'll scan it and put it on HiFiengine.
Click to expand...
Hi, I have a line on a broken SM-3205 I would like to fix. I checked online for a SM but had no luck on Hifiengine.com Any chance the one mentioned here got uploaded somewhere?

Thanks, James
 
jmccanna said:
Any chance the one mentioned here got uploaded somewhere?
Click to expand...
I don't remember if I ever uploaded it. I will try to find it and scan it when I can. It is a nice sounding and well built amp. I have an extra pair of outputs if you end up needing them. Rich
 
Thanks Rich. I was a tad slow in getting back to the seller and it is gone off of CL. Oh well. Those that wait lose.

James
 
You must log in or register to reply here.
Back
Top Bottom