Technics SC CA1080 Hifi amp

[blindboybenton]

Hello
Im hoping somebody can help me I have a Technics SC CA1080 hifi midi system in
Iv'e had these before, Normally a dj or two on the output chip,
This one had the same found a few djs , soldered them back up, and tested found still no sound. Headphone working ok as this comes from another chip

Found i had correct supply voltage and see audio in on the scope and can see nothing at the outputs

Replaced the chip ( IC501 RSN3403 and still the same.
Signal is present at the inputs
technics_se-ca1080.pdf
all the voltages at the chip are present and correct apart from
Pin 7= 0v
Pin 12= 0v at collector junction with
The chip i got new from ebay and UK firm had it shipped from china i have used them before but never for this item

Anybody have any idea's

Have a good Day

BBB

Forget the link below i attached the wrong one !!

[Enzo]

Disk Jockey?

What is a dj?

Q201,202 are muting transistors at the PA input. Are they turned on?

[blindboybenton]

Dj = dry joint I have finished for the day now I will check tomorrow. Thanks enzo

[blindboybenton]

I have finally got round to checking it again . I think myself the chip is faulty. Ebay seller ive used before has been good but has got some bad feedback for fault or cheap parts.
Pin 12 on schematic says its should have 12V- but has 0v
Pin 4 say it should have 4.5v- on but has zero

These chips are hard to find either get from the usa or china


pin out voltages are

Pin 1 0v
Pin 2 36v+
Pin 3 36v-
Pin 4 0v
Pin 5 14v-
Pin 6 0v
Pin 7 0v
Pin 8 14v-
Pin 9 0v
Pin 10 0v
Pin 11 signal good
Pin 12 0v
Pin 13 signal good ( seen on scope )
Pin 14 0v

Does anyone have any thoughts on using a different type of power output chip and wiring in. Any unforeseen issues

BBB

[Jazz P Bass]

Not too sure about pin 12 supposed to having -12.5v on it.
It's the 'sync' pin.
Usually it's grounded.

Pin #7 is a problem.
That is the 'mute' pin.
Unfortunately the voltage is supplied internally.
I would try replacing the cap on that pin.

[blindboybenton]

I have changed the cap if my memory serves me right. Not in the workshop now. Will check tomorrow

[blindboybenton]

As i thought i had changed the cap on that mute pin. 7. I did note that it was internal voltage when i checked it, so as it was a 0v i put 2+ 2 together and thought chips up the spout

Ive rigged up a -4v on the the mute and the whole thing seems to work ok. just running it on test.

BBB