70s Ampeg V4B Blows Fuses

[Dave H]

So*

Replace D6. Orientation of C16 doesn't matter. I'd fit it with the numbers visible.

[vintagekiki]

So*

What so.
What answer do you expect from the previous post you posted less than 1 minute ago.

[SoulFetish]

remember that you will not get bias voltage until you switch it out of standby. So, there will be an initial surge where the tubes will pull heavy current until the bias voltage develops and settles.
The other thing to consider is that D5 is in series with the ground return on these amps, so make sure that you have continuity between the cathode of D5 and one side of the standby switch

[ca7922303]

So* was posted to correct the word do in a previous post. It was a spelling error which comlecompl changed the dynamic of the sentence contained in the post.

[ca7922303]

Removed D6, reads 0.875 k resistance with leads reversed both ways. Is that a bad diode?

[Dave H]

Removed D6, reads 0.875 k resistance with leads reversed both ways. Is that a bad diode?

Yes, it's toast replace it already!

[ca7922303]

Ok, new D6, C16(61vac & 124vac),(28vdc & 153vdc), D6(28v/-36v), C15(-36v/-0.1mv+), C23(-36v/-0.1mv+)

[vintagekiki]

And ... ...

[ca7922303]

Pin#5 on 4 power tubes(-36v)

[Dave H]

Pin#5 on 4 power tubes(-36v)

Is that with the variac at 60V or 120V?

[ca7922303]

Variac @ 60v

[Dave H]

Variac @ 60v

Looks like it's working then. Turn it up to 120V and check the voltage on pin 5 of the power tubes.

[ca7922303]

Pin#5 all power tubes (-60vdc) @ 100v on variac.

[ca7922303]

No power tubes installed.

[Dave H]

No power tubes installed.

It's looking good. Install the power tubes and turn up the variac from 60V to 120V checking for red plating.