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October 05, 2022, 03:58:56 AM

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Fender 112 Deluxe Plus

Started by FenderDeluxe112Plus, April 12, 2022, 04:39:01 PM

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FenderDeluxe112Plus

Apologies .0002 ohms for both readings.

g1

That's good.  Now measure DC voltage at CR39 anode and cathode.

FenderDeluxe112Plus

With com clipped to chassis.
C39 cathodeYou cannot view this attachment.

You cannot view this attachment. 

FenderDeluxe112Plus

Cr39 anodeYou cannot view this attachment.
You cannot view this attachment. 

g1

That is really strange.  There is no where for that extra couple volts on Q8 collector to come from. 
If it were a solder bridge, it's unlikely the same exact thing would show up on the negative side (Q9).
So I would guess it's either an oscillation that the meter is interpreting as DC, or it's just a ghost reading and irrelevant.

Do Q8 and Q9 check out ok with diode check in circuit?

FenderDeluxe112Plus

Diode check Q8

Pos to collector com to base 1
Com to collector pos to base .6489

Pos to base com to emitter .6536
Com to emitter pos to base 1.0033

Pos to collector com to emitter 1
Pos to emitter com to collector 1.0390

FenderDeluxe112Plus

Q9
Pos to collector Com to base .6760
Com to collector poss to base 1

Com to emitter pos to base 1.0018
Pos to emitter com to base.6780

Pos to emitter com to collector 1
Pos to collector com to emitter .8232

g1

Quote from: FenderDeluxe112Plus on May 28, 2022, 04:53:24 PMQ9
Pos to collector com to emitter .8232
That seems a bit suspect.  Have Q8 and Q9 been replaced?
I would remove them and re-check them out of circuit.

Also, have CR5 thru CR12 and CR39 thru CR42 been checked in circuit?  Just looking for proper .4 to .7V readings forward biased, and no shorts.

FenderDeluxe112Plus

#83
Thanks g1,

Cr9-12 and cr39-42 read between 0.6 and 0.7 with a reading of 1 with leads reversed.

Cr5 -8 are within the heatsink so I can't read them at the moment - I did pull them to test when I changed the output transistors and they were good.

Agree about q9. I have a few 2n4403s so I will replace it next time I pull the board.



FenderDeluxe112Plus

Cr13 and 14 have a forward voltage of 0.5 which seems ok.

Reversed they read 1.9020 and 1.8064
Does that check out ok?

g1

Quote from: FenderDeluxe112Plus on May 29, 2022, 03:18:32 AMCr13 and 14 have a forward voltage of 0.5 which seems ok.

Reversed they read 1.9020 and 1.8064
Does that check out ok?
Yes that seems right.
In post #41 sound file, is that the sound it makes with no signal, or is that with a tone at the input?

FenderDeluxe112Plus

Yes, that is the sound at switch on with nothing plugged in.


g1

So that sounds like oscillation to me.
Try jumpering CR3 anode (or CR4 cathode) to ground and check if the oscillation sound is still there.

FenderDeluxe112Plus

With a jumper to ground at cr3 anode the buzz is there but quieter.

FenderDeluxe112Plus

Similar to plugging guitar into power amp in.