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Mitsubishi DA-L70 - NO Sound - Help needed please.

Paulluap

Feb 25, 2023
3
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Feb 25, 2023
Messages
3
Hi
I have a DA-L70 stereo unit that I have had for years. I brought it from a secondhand shop. Never had a problem with it. I don't have speakers plugged into it, just use RCA outputs to another amp.

One day I went to show it off and it wouldn't turn on. Found the F901 fuse had blown. Replaced fuse and the system started up again.
I thought fixed, replaced some belts on the tape deck while it was open, all good to go. But I never tested the RCA output until I recently replaced my amp I am using.
That's when I worked out I have no output from the speaker terminals, RCAs or the head phone jack on the DA-L70.
Found drawing and pretty sure the protection relay is not turning on. No click and 34vDC on each side of coil.
Not that good with testing transistors etc.
Am I right thinking that Q953 should turn on grounding negative side on coil??
Testing R951 has 34v on one side and only 0.7v on the other side and it should be 13.1v I think?

Any help would be appreciated. A few drawings attached.
 

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kellys_eye

Jun 25, 2010
6,498
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6,498
I'd say the main output (speaker) driver chip(s) have gone dud - STK4151.

What's the voltage at the base of Q952?
 

Paulluap

Feb 25, 2023
3
Joined
Feb 25, 2023
Messages
3
Hi Thanks for the reply.
Q952 is -0.7v Attached is the voltages on all the STK4151 Pins
Cheers
 

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Paulluap

Feb 25, 2023
3
Joined
Feb 25, 2023
Messages
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I have installed a new STK4151 amp but the unit is still not working. The voltages have changed though on pins 1 to 18 as shown in red on the attached. What do I look for now? Thanks
 

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