Great day guys, this amp keeps blowing out the rail caps mainly the negative side, what could be the issue why it’s doing that, power on ok, then even with low volume it’s just pops the caps, I’ve change them but there seems to be an issue otherwise.
Low-side drivers and possibly a board that's become conductive.
If you look at the negative rail voltage, you will see the voltage become 2-3x what it should be when driving a speaker.
Do you have a Q124 and Q125 on the driver board?
If you look at the negative rail voltage, you will see the voltage become 2-3x what it should be when driving a speaker.
Do you have a Q124 and Q125 on the driver board?
I’m not seeing those numbers on the silkscreen, I’ve remove the board and sensing so you can point out further.
See attached. Q35 and Q36.
If you have the tutorial, ctrl-f on the Type 2 page:
Q124
or
Q35
And you will see a lot of references to these transistors.
If you have the tutorial, ctrl-f on the Type 2 page:
Q124
or
Q35
And you will see a lot of references to these transistors.
Yes Mr Perry, one of the transistor (MPSA42) was reading across the collector-emitter. The cap covering seems warped 10uf 25v, the resistor was scorched (10k) tho read good just replacing them for good measure
The card was repaired, problem I’m having now is I’m getting 8v on the input pin loopin thru the master/slave switch (coming from the input circuit somewhere) amp is on protect but when push to slave setting or remove the configuration switch module it’s power good all drive wave is good low and high. Infact if I add the audio straight to the input pin it plays but without processing (full range no gain control). Where do I check next opamp or bad caps?
Which of the op-amps on the main board have more than a fraction of a volt of DC on their output pins?
With reference to speaker ground (black probe) voltages was checked as diagram pins 1 and pin 7.
Hand drawn diagram with respect to actual picture layout.
Hand drawn diagram with respect to actual picture layout.
Do the front panel switches make a difference in the op-amps with high DC offset?
If not, post the DCV on all terminals of U10. Copy and paste:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
If not, post the DCV on all terminals of U10. Copy and paste:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
No changes from switch (will go to protect if the master/slave switch is in master position) but voltages only cycle as amp tries to power on.
Pin 1: 0.00
Pin 2: 0.00
Pin 3: 0.00
Pin 4: -14.97
Pin 5: 0.433
Pin 6: 0.401
Pin 7: 14.58
Pin 8: 14.82
Pin 1: 0.00
Pin 2: 0.00
Pin 3: 0.00
Pin 4: -14.97
Pin 5: 0.433
Pin 6: 0.401
Pin 7: 14.58
Pin 8: 14.82
I would think that U10 could be defective if the 14v was present on the op-amp's output with the switch board out of the circuit. This would be especially true if the DCV on pins 5 and 6 don't match with the board out of the circuit.
I’ve changed one of the opamp previously that leads to the the input of the driver board but still got the 8vdc so I just replace the U10 with the one I remove and still the same 14vdc on the output pin, I’ll get all them new and change all of them at once and see. It’s just 5 chips
I'm working from the best diagram I have.
Is there a 10k resistor connected between those pins? Its designation?
Is there a 10k resistor connected between those pins? Its designation?
Understood Mr Babin, those pins (6 & 7) of U10 is not connected to anything nor themselves, individual NC they are. I haven’t installed the new OPAmps as yet, thinking on Monday as I can’t find my spares now. When I installed them I’ll update you further.