Marshall VS265 one side dead

[Captngeetch]

Hoping some one can point me in the general area i should be looking at for my issue. Only one speaker is working. I swapped the wires and ruled out a blown speaker. The left ext speaker jack is dead as well, but when i plug in head phones both sides work. Could it be a couple blown diodes. I opened her up and the diodes in D6 and D7 appear to be cracked and there is some residue on the board in that area.


Any help appreciated

[Enzo]

I don't see any cracks, and the flux residue is al over that area, and not a problem. The diodes are shorted or not, check with a meter, but they look normal.

One of your power amps is not working.

[Jazz P Bass]

It appears that the Left Ext jack may be bad (abused?).

Try to measure the Left Black wire to chassis ground.

If there is no continuity I would suspect that Ext jack.

marshall_vs265r_2x65w.zip

I see nothing wrong with the diodes.
That sgunge is glue.

[Captngeetch]

Sorry, it's the right side that is dead. There is zero continuity thru the speaker wires on the right, and excellent continuity thru the left. Checked both at the board and thru the wires. If this helps any. The diodes have continuity thru them, so they are good I assume

[Jazz P Bass]

Put a plug in the Right Ext Spkr jack.

You should have continuity from the Blue speaker wire to the tip of the plug.

The ring should have continuity to chassis ground.

If this is true, jumpering the tip to the ring should make the circuit & the speaker should work.

Which indicates a faulty Right Ext jack.

If no sound, then the amp may be at fault or the headphone jack.

marshall_vs265r_Right Spkr.pdf

[Captngeetch]

Put a plug in the Right Ext Spkr jack.

You should have continuity from the Blue speaker wire to the tip of the plug.

The ring should have continuity to chassis ground.

If this is true, jumpering the tip to the ring should make the circuit & the speaker should work.

Which indicates a faulty Right Ext jack.

If no sound, then the amp may be at fault or the headphone jack.

[ATTACH]38398[/ATTACH]

The right ext jack has red and black wires. I have continuity from the black wire to the tip, and zero continuity from the ring to the red or the chassis ground. On the left side the continuity is good on both.

So does this mean I have a bad ext jack causing the issue ? Is there a work around other than swapping out the jack ? I appreciate all your help

[Jazz P Bass]

Insert a plug in the Ext jack & jumper the Tip to the Sleeve.
(which is what the jack is supposed to do with nothing inserted)
marshall_vs265r_Ext Spkr.pdf

If the amp now works, there you go.

One of the Ext jack contacts is sprung.

Replace the jack.

[52 Bill]

So does this mean I have a bad ext jack causing the issue ? Is there a work around other than swapping out the jack ?

Have you tried to clean the jack with some DeoxIt spray? Often all it takes is a little spray and few flexes of the contacts to fix a bad jack.

I spray a little DeoxIt on the closed contact points and then insert and remove a plug a few times to make the contacts open and close. Then I retest the jack.

Of course this all assumes that the jack is properly soldered in the pc board or to the connecting wires.

[Captngeetch]

Insert a plug in the Ext jack & jumper the Tip to the Sleeve.
(which is what the jack is supposed to do with nothing inserted)
[ATTACH]38409[/ATTACH]

If the amp now works, there you go.

One of the Ext jack contacts is sprung.

Replace the jack.

No luck with that, still dead. But the red wire now shows continuity when grounded to the chassis, the black wire zero.

[Jazz P Bass]

The Black wire, if hooked up to the speaker, should now read 'the speaker coil resistance' through the Red wire to ground.
If the speaker is not hooked up, that explains that.

If it is, check the speaker, as it may be open circuit.

[Captngeetch]

The Black wire, if hooked up to the speaker, should now read 'the speaker coil resistance' through the Red wire to ground.
If the speaker is not hooked up, that explains that.

If it is, check the speaker, as it may be open circuit.

That was with the speaker not hooked up

[Jazz P Bass]

So with the speaker hooked up, does the amp work?

You found a major issue.

The Ext jack is bad. (which would prevent the Right speaker from working)

Jumper the Right Ext jack as in the test & try the amp.

[oc disorder]

Here's a simplified picture not pdf.

[Captngeetch]

So with the speaker hooked up, does the amp work?

You found a major issue.

The Ext jack is bad. (which would prevent the Right speaker from working)

Jumper the Right Ext jack as in the test & try the amp.

No, doesn't work...not even a crackle. Oddly with the soeakers hooked up, if I check continuity from the dead sides speaker to the chassis ground, both wires show negative numbers, where as the working side shows negative on the (-) and good on the (+) side
Tried jumping the jack from the internal contacts and same result..no sound at all.

Have you tried to clean the jack with some DeoxIt spray? Often all it takes is a little spray and few flexes of the contacts to fix a bad jack.

I spray a little DeoxIt on the closed contact points and then insert and remove a plug a few times to make the contacts open and close. Then I retest the jack.

Of course this all assumes that the jack is properly soldered in the pc board or to the connecting wires.

I tried that first of course..lol. Did all and the pots as well. The jack is the original.

[oc disorder]

The negative numbers can be ignored , you are looking for continuity , I would suspect as the amp had no load on that side some of the caps are still charged up and affecting your readings.

Just for clarifications sake you have done the test Jazz suggested and there is no problem with that jack?

The attached makes complete sense?

If Yes time to check the headphone socket.