Crate CA30D No Output Help

[misterc57]

I have a CA30D with no output. The speaker pops when turning ON so I think the output side may be okay.

I started checking the input path and noticed something odd (to me) about the TL074s in the path. The + and - 15V supplies are opposite the schematic and TL074 pinouts. I am seeing -15 VDC at pins 4 and +15 VDC at pins 11.

Schematic shows otherwise. However there is continuity to D1 and D2 that supports the readings I am seeing. So I am confused...

The TL072 further down the path has correct power supply polarities.

Attaching schematic.

Thank you! MarkO



crate_ca30d_07s287_sch.pdf

[g1]

How about at D15 cathode and D16 anode?
And I hate to ask, but no chance probes got plugged into wrong ports?

edit: also, 072 has opposite of 074 on pin4.

[Jon Snell]

Read anti clockwise from the top;

[misterc57]

How about at D15 cathode and D16 anode?
And I hate to ask, but no chance probes got plugged into wrong ports?

edit: also, 072 has opposite of 074 on pin4.

TL072 pin 4, - 16 VDC
TL072 pin 8, + 16 VDC

D15 cathode, + 16 VDC
D16 anode, - 16 VDC

I hear you... My probes are in the right place and are never removed from the meter.

[misterc57]

Read anti clockwise from the top;

Argh.... I had it backward. Sorry guys. VDC are correct.

Okay, back to my no output mystery....

[misterc57]

ok. I have signal up to R10. C13 may be a problem as I see nothing after that.

C13 re-soldered. Amp is working!!!

[J M Fahey]

You were drowning in a glass of water

[misterc57]

You were drowning in a glass of water

Yes I was.