Need advice: broken Electro-Harmonix Qtron+

[patrickbrose]

Something is definitely not right there. You are showing 18v at ground. Can you test voltage on the ground plane. You should get:
Top Pin 18V
Middle Pin 0v
Bottom Pin 24v
Somethings not right...
-P

[guile]

Something is definitely not right there. You are showing 18v at ground. Can you test voltage on the ground plane. You should get:
Top Pin 18V
Middle Pin 0v
Bottom Pin 24v
Somethings not right...
-P

My mistake, I'm not ranked a 'Diode destroyer' for nothing
Your voltages are excatly what I measure now.

Is the constant led a clue?

[guile]

I also notice that the overload led is also reacting when the effect is bypassed.
So the on-of led and overload are both always on...

Mysterie still not solved 

[electricstorm]

My bad on the assumption of a 78L05 regulator. Didn't think it would be something else, but couldn't see what was printed on it.

The LED's could be a clue, just not sure what that might be at the moment. What voltages are you getting at the IC's (pins four and eight)? Are they 18 volts also? To possibly rule out the regulator (78L18) measure the voltage at the regulator when you first turn it on, then when you have signal loss check the voltage again. Are they the same? If they are the same, then the problem may lie elsewhere. You should still have the same voltages you measured earlier (24v, 0v, 18v) if the regulator is good. If the voltages are not the same, then either the regulator is bad or something is pulling the voltage down.

If you adjust the pots, or the switches, does it make any difference? Is there still a loss of signal no matter where the controls are set? Do you have an audio probe? This would help in tracking down where the signal is being lost at.

Jim

[Scruffie]

It's a power LED, not a status LED, that's why it's always on.

You're gunna have to post voltages of all the ICs.

And you're sure that your regulator is consistent with the above voltages, even when going in to failure? Does it or D3 get hot.

[guile]

It's a power LED, not a status LED, that's why it's always on.

You're gunna have to post voltages of all the ICs.

And you're sure that your regulator is consistent with the above voltages, even when going in to failure? Does it or D3 get hot.

Thanks for the info!
I will do another test tonight and will report back.

I appreciate everyone's input very much.

[guile]

Finally got some time to do some research again.
I tightened some screws and bolts here and there and guess what, the stupid thinks works and sounds great...
That may be great, but I cant trust it on stage...

The only question that remains is the 'status led'. I askes a friend of mine who has a similar generation EHX Qtron+ to verify if the led is always on (status led) and according to him it's only on when engaged...

[Scruffie]

Finally got some time to do some research again.
I fastened some screws and bolts here and there and gues what, the stupid thinks works and sounds great...
That may be great but I cant trust it on stage.

The only question that remains is the 'status led'. I askes a friend of mine who has a similar generation EHX Qtron+ to verify if the led is always on (status led) and according to him it's only on when engaged...

I have the schematic, you have an early model which did have the Power LED (it's on the schem, no status shown) they later moved to 3PDT (and some relay bypass I think) true bypass which would have meant an status LED. You can tell cause you only have a SPDT switch.

Tightening may have been just a loose ground.

[guile]

Thanks for the info.
So there's nothing wrong 

Thanks all for your input. If it fails on me again I'll be back!

G♫S

[guile]

Finally got some time to do some research again.
I fastened some screws and bolts here and there and gues what, the stupid thinks works and sounds great...
That may be great but I cant trust it on stage.

The only question that remains is the 'status led'. I askes a friend of mine who has a similar generation EHX Qtron+ to verify if the led is always on (status led) and according to him it's only on when engaged...

I have the schematic, you have an early model which did have the Power LED (it's on the schem, no status shown) they later moved to 3PDT (and some relay bypass I think) true bypass which would have meant an status LED. You can tell cause you only have a SPDT switch.

Tightening may have been just a loose ground.

Can I change it to a status led?