Re: Need schematic for Radio Shack Optimus SSM-1750 Mixer

[legg]

On Sat, 29 May 2021 22:38:19 -0500, Unlisted <unli...@nomail.com>
wrote:

>SSM-1750

Replacing the transformer should be pretty simple, as
it only has to supply one audio board.

Check for regulators on the board. Commonly +-15V 3term.

A 27V or 30V centertapped winding (2x13V5 or 2x15V)
should provide +/- 18V to 21V after the rectifiers, to
feed those. You could temporarily substitute a bench
supply, to see if there was a major supply problem.

The aux lamp connector seems to expect 12Vdc.

Once it's running, you'd know if it actually needs more
in-depth repair.

RL

[Peter Schneider]

Am 30.05.2021 um 05:38 schrieb Unlisted:
> I have a Radio Shack SSM-1750 mixer. The primary winding of the power
> transformer is open. The secondary has two windings. One is blue-black
> blue (centertap). That feeds power thru a bridge rectifier to the whole
> unit. The other windings are two brown wires that go to a diode and cap.
> All that does is feed power for an optional panel light.
>
> But I cant find any schematics online. I spent hours looking. Just
> owners manuals that are pretty useless.
>
>
> So I dont know what voltaqe transformer is needed for the main CT
> secondary. (The light one I can live without)
>
> A sticker on the trans reads. 059-154.
>
> Its a nice mixer. Id like to fix it. Can anyone help?
>
> WHATEVER HAPPENED TO ALL THE RADIO SHACK ONLINE MANUALS? ARENT THEY
> ARCHIVED SOMEWHERE?
>
>
>


many (but not your one) are here:

https://archive.org/details/manuals_radioshack?&sort=-week&page=6

[Miguel Giménez]

El 04/06/2021 a las 0:45, Unlisted escribió:

> Thanks for the advice. Yes, two 7815 regulators on board.
>
> What had me puzzled was the fact that if I hit the ON/OFF switch 50
> times I got a split second of light from the ON LED once out of those
> 50. An open winding would not do that.....
>
> Thanks to several YouTube videos about transformers, I found that this
> transformer had a built in thermal fuse. I sure dont know why... Heck
> the old transformers that had a lot more voltage and current on tube
> gear never had thermal fuses.
>
> Anyhow, I removed several layers of tape and insulation from the
> windings and found that thermal fuse. I removed it, soldered the wires,
> and reinsulated it with tape and epoxy glue.
>
> Transformer works again, and the whole mixer works great.
>
> Im not worried about the lack of a thermal fuse. The mixer has a half
> amp fuse on the power line. And if you ask me, those thermal fuses are
> only put there to sell costly replacement transformers. They may be good
> in a coffee maker or hair dryer, but seem useless on a low current small
> transformer.
>
> I'd still like to find a schematic for this SSM-1750 Radio Shack mixer
> in case anyone finds one online..... Or I'll pay postage and copying
> fees for a printed paper photocopy. I intend to keep and use this mixer.
>
>

Just in case other user needs them in a near future you can measure
secondary voltages and post them here.

--
Saludos
Miguel Giménez

[Michael Terrell]

> > I'm not worried about the lack of a thermal fuse. The mixer has a half

> > amp fuse on the power line. And if you ask me, those thermal fuses are
> > only put there to sell costly replacement transformers. They may be good
> > in a coffee maker or hair dryer, but seem useless on a low current small
> > transformer.

You've never seen a fire started by a cheap transformer without a fuse. I have. A 'service company' replaced 100 bad transformers in some old Jerrold JSX-3 and JRX-3 cable TV boxes back in the '80s instead of using the proper transformer from Jerrold. They were coming back to our office with belted cases, and in one case, the plastic case had caught fire. Withinn six months, every one of them had failed. The original transformers were both fused and had stell end bells to prevent a fire.