Help with Crate CA-125 Acoustic Amp

[Tejaus]

I picked up a Crate CA-125 Acoustic amp that has a Le Son TLX-1 tweeter in it.
I'm not sure that the highpass section of the amp is working properly as there was only a very slight hiss coming out of the tweeter. It's showing around 21VDC across the output. I'm not sure if the tweeter was blown or not but it also has something loose rattling around in it so I figured I need to replace it anyway and they pretty cheap.

:: Le Son ::
These tweeters have a tuning coil and transformer built in to raise the output so they're not a standard issue piezo. They're used in SWR, Ampeg and other amps too. They need power to boost the output but I think it's AC not DC.

Here's the patent that shows how they work:
Piezoelectric Transducer And Transformer Circuit - Patent 4845776

I did replace diodes D9 and D10 because they measured funny in the circuit. They measured ok out once out but I put new ones in anyway. What I don't understand is why is the Vs+ and Vs- connected to pin 4 Output of the TDA2050 in the first place.

Still learning for sure. I do have all four schemos too.

I'm also looking for a reverb pan for the amp too. An Accutronics 1BB2C1A, 8BB2C1A or 8BB3C1A will work if you have one for sale.

Thanks

[52 Bill]

Your high frequency power amp is shorted, there should not be any voltage on the output line. The two diodes to the power supply rails are reverse biased and are there to center the output.

If you compare the low section (which I assume is working) with the high section you should find that the output to the woofers is at near 0vDC.

[Tejaus]

I pulled the TDA2050 and there is only 8 ohms between 3 and 4 so it's cooked. It looks like the heat sink grease was too sparse on that end of the rail so that may be why it failed.

Thanks for the help!

[RussG]

I do have all four schemos too.

I have schematics of three of the boards (courtesy Jazz P Bass) but not of the power amp board. That partial diagram you posted is the only one I've seen here.
Sure would like to have the whole thing if you have it in pdf or some other format, or if you could scan it.

[Jazz P Bass]

Crate CA60 Schematic

I simply reposted a copy of the original post schematic.
Yes, it is indeed missing a page or 2.
I would start a new post, requesting one. (it may get more attention)
In the mean time, I have uploaded the Crate CA60 schematic.
It may get you closer.

[RussG]

Thank you, it's interesting to see how the CA60 is designed, and there is a lot of family resemblance.

I also contacted "Enzo" by email and he sent me a schematic for a CA125 Power Board which looks like a match to the amp I was servicing.

[Jazz P Bass]

Can you be so kind as to post it?

[Enzo]

Sorry, I should have done so myself.

[Jazz P Bass]

Thanks, Enzo.