Fender Passport 500 Pro SMPS question

[JP-Stereo]

You, how will you do that ?
Are you using an auto transformer or else ?
The test is done, direct in a plug through an ampmeter, JA2 still disconnected.

A single 2 sec 1 amp surge at power on then about no draw.
Only the green POWER LED and the REVERB button and Led on the front panel.
No Protect or else.

I will study the mixer circuits...

[x-pro]

I have such a power supply B5-50. It has an output voltage of +300V and a current of max 0.3A. If this is not enough, then I also use a lamp.
If it is not enough and everything in the circuit is working properly, then I change the lamp power.
But for idle operation, without a signal and without a load, a power supply with a power of up to 500W usually starts normally from B5-50.
True, sometimes you have to bypass all sorts of protections so that the PWM starts normally.
I don’t remember how this smps should behave with a lamp. But we had to fix them.

[x-pro]

I rarely use Variac for other purposes.
We have a 220V network. But there are devices with an input voltage of 110/120V.

[x-pro]

A single 2 sec 1 amp surge at power on then about no draw.
.

In this case, what supply voltages are available on the secondary winding? Are all items connected to the U605?

[JP-Stereo]

OK, i look at the +/- 15vdc rails while the mixer is connected:
+ 14.5vdc and - 5.47 vdc...

JA1 and JA3 disconnected:
+ 14.5 vdc and - 15.6 vdc.

This time something in the mixer is loading the negative rail.

[x-pro]

I will study the mixer circuits...

If the problem was in the low-current power supply and the main power supply was not initially damaged, everything will probably turn on. The starting current of 1A is the charge of the capacitors at the +-50V output. The total capacitance of one arm is almost 10000uF.
If these voltages are present when JA2 is disconnected, then the whole power supply is working. When connecting JA2 to the amplifier, don't forget to discharge the capacitors.

[x-pro]

This time something in the mixer is loading the negative rail.

Oh, yes.
C617 replaced?
See the DC voltages at the outputs of the U801 and U802 master line chips. Page 10 of the schematic. There should be zero on all outputs. Pins 1 and 7 of each chip.

[JP-Stereo]

Wow following JA1 from the MSPS lead to JB5 on the INPUT BOARD.

Do we have to crack the case open, in order to reach that board or it can be pull out by the rear ?

Oups...
You're right, i didn't replace C617 yet...

[x-pro]

See the DC voltages at the outputs of the U801 and U802 master line chips. Page 10 of the schematic. There should be zero on all outputs. Pins 1 and 7 of each chip.

We're forgetting about that for now.
The reason could be something else

[JP-Stereo]

Ok C617 replaced, +14.5vdc / -15.5 vdc with the mixer plugged, very clean.
So the 15v rails on JA1 are OK.

But the front panel is not alive...
Only the Power Led and the Reverb.

To reach the Mixer board is it necessary to desassemble the case or we can pull it by the backdoor ?

[x-pro]

To reach the Mixer board is it necessary to desassemble the case or we can pull it by the backdoor ?

I'm not going to fantasize. I don't remember. Or I've never dismantled it to that level.

[JP-Stereo]

No problem, i will find...

At this point, knowing that these lines were the most weared out.
The following components on the stream are these ones, pretty much as suspects as the previous ones to me.



I have to get this Input & Mixer board out...

[JP-Stereo]

There is a real puzzle in this casing.
A few try than i proceed on something else...

Since one of the biggest remaining problem was in fact C616 & C617, i replaced all other capacitor at that level on the other voltage lines
All the first caps after EC28; C633, C648, C646 and just to be safe C636, C683, C631, C651, C647.
Looking around U603, i also find out that C680 was out of specs and replaced it.

The mixer and the amp are plugged, now i have more life on the mixer but the front PROTECT led is ON...
The +/-50v is fine, as for the +/-15v, there is also a +/-5vdc that feed the amp that is hard to reach while the amp is in.
I am trying to find a way to verify these.

Otherwise, the SD, the MUTE and DCP will need attention.
I don't understand yet the function of GS and GHS lines ?

[x-pro]

It is necessary to check the voltages on the board "PROTECT LED CONTROL" page 3 of the service manual.
Voltages on cathodes D724, D725. When the "Protect" LED is on, it should be around 4.5V, and need the SD value.
The main thing is that if the main problem was in the power supply, you probably need to check other supply voltages on all nodes of the input part and especially the power amplifiers (there are two of them).
I didn't find GS and GHS lines on the diagram.

[JP-Stereo]

Hi, back in the shop after a few days break.

I've found something unstable around U601 and U602 when everything is plugged.
So i replaced the regional caps; C235, C235, C62, C637 and C642.
Now i have more stable waveforms before D616 and D617, but the tension is 3vdc after D616 on the positive rail.
Since D619 is only a protection, i replace D616 with the removed D619 without improvement.

Lines Before the diodes;_____________________________________________and After;



D619 may have been damaged too because it's a protection device, so i ordered them and a new 5v regulator.
I will try that as soon as possible.

If this +5v line is back alive and the Protect still on, i will jump to D724 and D725, SD and so.

The GS and GHS lines are on page 2 top center but are not apearing anywhere else ?