Fender Passport 500 Pro SMPS question

[JP-Stereo]

Still the same with new U601, D616 and D619.
No DC after U601, a stable -5vdc after U602.

I have removed the amplifier board to unload the lines and have +19.9 and -19.9 vdc after the diodes.
And + 4.77 and -5.1 vdc after the regulators, so the amplifier board is loading this + 5vdc line.

[JP-Stereo]

There is 2 zeners (Z711 and Z713) that protect the positive supply of both U705 and U706 that are short.
Once these diodes removed the +5vdc line is at about 1k ohm from the ground, is it unloaded enough or something else is still broken ?

These 5vdc lines are only feeding these 2 OpAmp (U705 and U706) and the Over Temp Protection Circuits (Q712 and Q721).

[x-pro]

Is it possible to read the meter from desoldered zener diodes Z711 & Z713?
The 5V line also powers the U700. What is the condition of R700B?

[JP-Stereo]

In diode test mode both (Z711 and Z713) read 0.043 foward and 0.044 v reverse.
Looking to replace these diodes.

R700 is a twin ? First time i see this on a drawing...
Both test 5.06 k ohm.

[x-pro]

R700B in the positive supply circuit of U700

[JP-Stereo]

Positive "Input" (U700 pin 3) or positive "Supply" (U700 pin 8) ?

Lot of expectation on these diode replacement...

[JP-Stereo]

It's a very poor identification pratice...
I just locate the odd R700B at pin 8 of U700-C, now i understand...

So once Z711 and Z713 are replaced, the +/- 5 vdc is back and very clean with everything plugged.
The front panel is fully responding (leds) but the Protect led is still ON.

The voltage at D724 cathode is +24.7 vdc and D725 cathode is at +14.8 vdc.
I took the GND on JA1 pin 3.

SD is at 0 vdc at D740 cathode.

[x-pro]

The voltage at D724 cathode is +24.7 vdc and D725 cathode is at +14.8 vdc.
I took the GND on JA1 pin 3.

It is the same point. There can't be different values unless it's in a cliff.

Check D742, Q720, Q719, R718B

SD is at 0 vdc at D740 cathode.

Check the operation of "Pop noise circuit" node in SMPS.
The output of R662 should be about 8V.

[JP-Stereo]

Hi a typo, so these reading are from the anodes of D725 (+24.7vdc) and D725 (+14.4vdc)...

R718B test at 46.8k.
R721A test at 8.16k.
The cathode of D742 jump to over 5vdc for a few seconds at powerup and power down.
The cathode of D743 Stay at 0vdc.

The Protect follow D742 at 5vdc and the Protect led turn on when the protect get back at 0vdc.
So Q720 & Q719 seem to work ok.

[x-pro]

The Protect follow R742 at 5vd

where is he?

[JP-Stereo]

Another typo, i must slow down a little...

The cathode of D742 jump to over 5vdc for a few seconds at powerup and power down.
The Protect line follow D742 up to 5vdc for a second than the protect line get back down to 0vdc and the Protect led turn on.

[x-pro]

Check Q722, Q721, Z701, Q705, Q706, Q716.
Is +5V supplied to Z701

[JP-Stereo]

Q721, Q722, Z701, Q705, Q706 and Q716 are passing the diode test "on board".

But Q707 test open on the board, will mesure off board but this shouln't change anything...
I have this MMBT551 on the shelf !
Replacing it right away !

Not measure the voltage yet at Z701.

[JP-Stereo]

The voltages at Z701 are now; Cathode = 4.77vdc, Anode = 1.99vdc.

After replacing Q707, no more Protect led.
The unit seem to be fully fonctionnal, when connected to the line out from a CD player.

I am reassembling it for further testing.

[JP-Stereo]

Confirmed, the last Protect problem was Q707, (MMBT5551).
I let it play loud for over 30 minutes and the fan started as it should.

The time will tell...