Memphis 16-MC1000D

seankane · 2024-03-27 11:53 pm

Hello all.

Can anyone tell me what the two large ic's are on this board behind the RCA jacks?

Perry Babin · 2024-03-28 2:35 am

mc14060
lm361
The circuit is very similar to the attached amp.

email me.
babin_perry@yahoo.com

seankane · 2024-03-28 3:15 am

Ok thank Perry.

The amp came in with shorted outputs, blown power supply, burned up pwm card, and vented rail caps.

I've replaced everything and the amp will power up and has relay engagement but only with that card uninstalled. All other cards and parts are in place. I'll have to think that on that card is the problem. I replaced all the transistors on that card just not the ic's or the a431 shunts.

Perry Babin · 2024-03-28 3:18 am

There is a transistors with its collector connected to pin 5 of the 494 on the PS board. Does your PS board have this transistors?

seankane · 2024-03-28 3:22 am

The MC14060 is obsolete but digikey says the CD4060BE is a sub, wanting to know your opinion?

Perry Babin · 2024-03-28 3:27 am

I think it's a good sub.

Do you have that transistor on the PS board?

seankane · 2024-03-28 3:36 am

Yes it does, I have replaced it with a BD139. Pin 5 of the 494 goes to the collector of Q41 and to a capacitor C17.

Perry Babin · 2024-03-28 3:39 am

Remove it. Does the amp power up with the audio PWM board installed with that transistor out of the circuit?

seankane · 2024-03-28 3:48 am

To be clear, you want me to remove that transistor from the power supply PWM card and reinstall the card I posted the photo of and see if the amp will power up?

Perry Babin · 2024-03-28 3:50 am

That's right.

seankane · 2024-03-28 3:54 am

With that transistor removed the amp powers up and idles fine with relay engagement and the audio PWM card installed. I must ask why?

Perry Babin · 2024-03-28 4:03 am

Honestly, I don't know. This has been a problem and amps that have the circuit for it, often omit these parts. They are part of the sync circuit that stops the amp from having a low-level whistling/whining (sounds like attached file).
https://www.bcae1.com/temp/cooleditmixedoscillator01.wav

seankane · 2024-03-28 4:07 am

Ok good to know. I'll put it back in the heat sink and check audio.

seankane · 2024-03-28 4:43 am

The amp works good, thanks again Perry.

Memphis 16-MC1000D

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