70s Ampeg V4B Blows Fuses

[ca7922303]

Did you find out why R28 is burning? (see second part of post #214). Did you get all the power tube heaters running yet?
There are several problems with your amp and they need to be dealt with, if you have done so, let us know. If not, tackle them before moving on to other issues.

V4 pin#3 and #8(0.8mv) without V201 installed, 0.4mv with V201 installed.

[ca7922303]

Did you find out why R28 is burning? (see second part of post #214). Did you get all the power tube heaters running yet?
There are several problems with your amp and they need to be dealt with, if you have done so, let us know. If not, tackle them before moving on to other issues.

Anything look wrong about any of these readings in relation to power tube heaters?

[g1]

Oh, come on g1, we're only at 224 posts on this one amp. There's plenty of space on the server.

How much of that do you figure is due to misguided attempts to 'blueprint' the amp rather than just get the darn thing working (and I'm not talking about the OP) ?

[g1]

V4 pin#3 and #8(0.8mv) without V201 installed, 0.4mv with V201 installed.

And does R28 still measure 1.5K ? V4 heaters are lit?
With those voltages V4 is not working, so you would not hear anything if you connected signal to 'ext.amp' jack. Is that the case?

[ca7922303]

And does R28 still measure 1.5K ? V4 heaters are lit?
With those voltages V4 is not working, so you would not hear anything if you connected signal to 'ext.amp' jack. Is that the case?

R28 is still 1.5k and getting signal thru ext. Amp jack, but not preamp out.

[Pixel]

Have you considered filling in your profile? Maybe there is someone nearby who can take a quick look at your amp.

[g1]

V4 pin#3 and #8(0.8mv)

R28 is still 1.5k and getting signal thru ext. Amp jack, but not preamp

Those 2 things can't both be true at the same time.
If you can get sound by going in the 'ext.amp' jack, then V4 is working. If V4 is working, those voltages would be what is shown on schematic.
Your measurements are not reliable or they are taken under the wrong conditions.

Measure DC volts at V4, pins 1,3,6, and 8. (with 120VAC from wall (or variac) and amp on in 'play' mode).
Keep trying til you get consistent readings that match what it shows on schematic for V4. Dig your probes in and you may even need to sharpen them so they make better contact.
Until you can get consistent reliable readings you will not be able to do any more with this amp.

[vintagekiki]

Your measurements are not reliable ...

[vintagekiki]

Until you can get consistent reliable readings ...

Show must go on.

[Leo_Gnardo]

Have you considered filling in your profile? Maybe there is someone nearby who can take a quick look at your amp.

Good idea. I hope it's not me (put cringe smiley thing here.)

[ca7922303]

Those 2 things can't both be true at the same time.
If you can get sound by going in the 'ext.amp' jack, then V4 is working. If V4 is working, those voltages would be what is shown on schematic.
Your measurements are not reliable or they are taken under the wrong conditions.

Measure DC volts at V4, pins 1,3,6, and 8. (with 120VAC from wall (or variac) and amp on in 'play' mode).
Keep trying til you get consistent readings that match what it shows on schematic for V4. Dig your probes in and you may even need to sharpen them so they make better contact.
Until you can get consistent reliable readings you will not be able to do any more with this amp.

V4 pin#1(542v), #3(10.4v), #6(541v), #8(10.4v). Tested with V6 & V8 installed. Able to hear signal thru ext. Amp jack. When V5 &V7 installed pin#3 &#8 go to 0mv and no signal thru ext amp jack.

[g1]

Show must go on.

You are not being helpful. Many of your posts in this thread have just made it worse. Maybe reconsider your contributions.
What would be very helpful would be for you to learn the official language of the forum and abandon the 'translation machine'.
You do not need to know the language if the only things you post are links or attachments. If you want to participate in discussions, being able to understand the language is essential.

[DrGonz78]

V4 pin#1(542v), #3(10.4v), #6(541v), #8(10.4v). Tested with V6 & V8 installed. Able to hear signal thru ext. Amp jack. When V5 &V7 installed pin#3 &#8 go to 0mv and no signal thru ext amp jack.

What’s the voltage reading at R28 when v6 & v8 are installed. Also check voltage at r28 when v5 & v7 are installed. I am curious to see if there is a difference at r28 between those two conditions. We know that r28 burnt up earlier.

[vintagekiki]

You are not being helpful. Many of your posts in this thread have just made it worse. Maybe reconsider your contributions.
What would be very helpful would be for you to learn the official language of the forum and abandon the 'translation machine'.
You do not need to know the language if the only things you post are links or attachments. If you want to participate in discussions, being able to understand the language is essential.

Dear friend you're right.
I did all to understand you ...
Not a problem in understanding the language, the 'translation machine' is quite sufficient to understand what it is about, the problem is in the diversity of language syntaxes, which the other side want or not want understand.
Possibility for individual learn the official language it is incomparably greater than the possibilities that 80% of forum participants learn the basics of electronics.
But if you say ...

[ca7922303]

What’s the voltage reading at R28 when v6 & v8 are installed. Also check voltage at r28 when v5 & v7 are installed. I am curious to see if there is a difference at r28 between those two conditions. We know that r28 burnt up earlier.

I can get readings this evening when I get off work. I've got a 10k resustor @ R28. Any reason to believe thats an issue?

[ca7922303]

What’s the voltage reading at R28 when v6 & v8 are installed. Also check voltage at r28 when v5 & v7 are installed. I am curious to see if there is a difference at r28 between those two conditions. We know that r28 burnt up earlier.

R28 with V6/V8 installed(10.6v/0mv), R28 with V5/V7 installed(10 6v/0mv).For some reason now all four power tubes pin #1(245v),pin#3(10.5v), pin#6(246v), pin#8(10.5v), and able to hear signal thru ext. Amp jack. Something is intermittent here it seems to me. Still no signal thru input front of amp.