Yamaha Stagepas 300 no left channel

[nosaj]

When you replaced the cap, did it change the input voltage to the regulator?

Also, some of those Yamaha powered mixers need to be assembled to run, or else ground wires clipped in for testing. The preamp to power amp section ground is carried by a foil that is connected by screws when assembled. I'm not sure if this is one of those.

It brought it up to 15v. I had everything running with it all splayed out on the bench. So I would say it is not. Played bass through it at reasonable volume.

Thanks,
Jason

[The Dude]

Regulator input =15V or regulator output =15V?

[nickb]

Replaced the cap Fires up and plays both left and right channels. put it back in the case power supply and outputs screwed in Preamp still loose not screwed in . Symptom comes back. It was dropped pretty hard is what I was told. Solder joints all looked good. I'm wondering if I could be looking at a pcb problem since it is working out of the shell but not in it.

thanks,
nosaj

I hate it when that happens...

[nosaj]

Regulator input =15V or regulator output =15V?

16.5 in 15.15 out..

Everything works fine outside of the plastic shell and metal frame. But when it is mounted in the metal frame it errors out turns on then off. I even tried backing off the screws a little. But where the output modules are the metal shell does not extend out that far so you can see the board flex a little and then it won't work. This looks like it will always be a problem .

nosaj

[g1]

16.5V into a 15V regulator is still seems too low.
On the minus side there is there more than -16.5V into the -15V regulator?
The working out of the case thing may just be a lucky coincidence.

[nickb]

16.5V into a 15V regulator is still seems too low.
On the minus side there is there more than -16.5V into the -15V regulator?
The working out of the case thing may just be a lucky coincidence.

Agreed. I'd want the see 18V see post 26. The data sheet minimum is 17.5V. Are the 38V rails OK?. Have you checked to see if the relay across the input surge prevention thermistor TH802 is closing?

[nosaj]

Agreed. I'd want the see 18V see post 26. The data sheet minimum is 17.5V. Are the 38V rails OK?. Have you checked to see if the relay across the input surge prevention thermistor TH802 is closing?

Sorry to drop off on this. Just found out I've 30 days to move so that one's going to be put back for a while.
I really appreciate all your help.

nosaj

[g1]

Sounds like it was a surprise, that sucks. Good luck with the move.

[Cordwangle]

Hi all - just my 6-pennyworth...might be of use to someone.
I had Stagepas300 in for repair: fault - unit shutting down after switch-on.
Removed both power amp modules then tried each one on it's own; system worked fine on one module (in both slots) but other module not so...!
Visual checks revealed 1 x blown 0R56 & resistance checks on one mosfet (P14NF12P) read zero Ohms.
Sourced a couple of mosfets (had to fit insulation-pads/spacers tho') & resistors & replaced these - bit of a tricky job due to layout etc. but it solved the problem.
Cheers, Paul

[nosaj]

Hi all - just my 6-pennyworth...might be of use to someone.
I had Stagepas300 in for repair: fault - unit shutting down after switch-on.
Removed both power amp modules then tried each one on it's own; system worked fine on one module (in both slots) but other module not so...!
Visual checks revealed 1 x blown 0R56 & resistance checks on one mosfet (P14NF12P) read zero Ohms.
Sourced a couple of mosfets (had to fit insulation-pads/spacers tho') & resistors & replaced these - bit of a tricky job due to layout etc. but it solved the problem.
Cheers, Paul

This one both modules worked in either slot outside of the case. put it in the case and only 1 module installed in either slot it would work. But not both installed.

nosaj

[vistaleon]

Thank you very much for the information provided, I told you how I could solve this problem, which I had in the same error. I replace R860 and R861 with 180k ohms. I clarify that in the tests it had a starting load of 5.6 volts at the output for 2 seconds, with the 2 amplification modules. which activates the protection circuit. In this way it deceived the protection system and then the boot was correct. Likewise, the original failure of the equipment was replacement of IC804/top249Y and replacement of IC801/kia7815. voltage measurement pin 1-2 19.64Volts and output 15.34Volts between 2 and 3, after replacing the parts, C137/10uf50v, C142/10uf50v, C242/10uf50v and C237/10uf50v were replaced for safety. In the amplification modules, all the electrolytic filters were replaced. Also attached schematic of the Yamaha amplification module