Help me troubleshoot. Blowing tubes and fuses

[Banzini]

Double post

[Banzini]

Triple post

[Banzini]

Quad post

[tubeswell]

tubeswell, I posted the voltages. If there are others that I need to check please tell me how because I'm not following the lingo. Newbie here.

g2 = shorthand for "screen grid" (g1 = control/signal grid, g3 = suppressor grid, k = cathode, a = plate/anode)

You posted the cathode and plate voltages earlier but not the screen voltage IIRC.

If your winged C's had something wrong with them and they (say) took out the screen grids with a voltage spike when you had the amp dimed, you may have affected one of the other components. The bias voltage on g1 looks okay

[lgehrig4]

In regards to the flash why are we ruling out that it was the tubes in that case? Would the voltages look good if a component was bad in the power supply? This is what I'm not following. I posted my measurement and they are pretty much in line with what others have gotten. So why would the tubes behave differently?

[M Fowler]

Under the filter cap board did you wire that correctly? Did you use the two other filter caps under the board?

[tubeswell]

Have you measured the OT Pr:Sec VAC ratio yet? (for both sides of the primary)

[lgehrig4]

Well, not much more to say other than you've got a bad component somewhere in your power supply. Bypass the cap at the node that feeds the screens w/ an equivalent cap and see what that does for you.

Thanks for the suggestion. I'll check that out

[lgehrig4]

tubeswell, I posted the voltages. If there are others that I need to check please tell me how because I'm not following the lingo. Newbie here.

g2 = shorthand for "screen grid" (g1 = control/signal grid, g3 = suppressor grid, k = cathode, a = plate/anode)

You posted the cathode and plate voltages earlier but not the screen voltage IIRC.

If your winged C's had something wrong with them and they (say) took out the screen grids with a voltage spike when you had the amp dimed, you may have affected one of the other components. The bias voltage on g1 looks okay

Ok, where do i measure the screens? I just followed someone else's Asteroid voltage chart.

Thanks for clearing up the symbols. Helps a lot.

[lgehrig4]

Under the filter cap board did you wire that correctly? Did you use the two other filter caps under the board?

Yes. You had sent me the board layouts a couple months ago and I followed them to a T. Only difference is that I replaced one of the 80uf caps with a 220uf per Concorde spec. The two 80uf caps are wired under the board in series with the 80/220uf caps on the top.

[lgehrig4]

Have you measured the OT Pr:Sec VAC ratio yet? (for both sides of the primary)

Please tell me how to do this and I'll test it tonight. Not sure what you mean by ratio, but I did measure the secondaries at pins3 of V4 & V5 and got 487V

[M Fowler]

Here is the Asteroid 60 and Concorde voltage chart.

[lgehrig4]

I think that's the one I went off of. Since mine is a hybrid I'm going off the K60 chart because that how my preamp section is wired. You can see that my voltages are pretty much on.

[M Fowler]

Is the bias in good range, I've had amps where the bias was too hot and take out a tube.

By the way you did a very good job building this amp hope you or someone can identify the problem so you can enjoy.

[tubeswell]

Have you measured the OT Pr:Sec VAC ratio yet? (for both sides of the primary)

Please tell me how to do this and I'll test it tonight. Not sure what you mean by ratio, but I did measure the secondaries at pins3 of V4 & V5 and got 487V

See attachment. Transformers have a Pr:Sec VAC ratio, which (in absolute number terms) is the same as the Pr:Sec turns ratio of the respective windings (i.e.; a Pri:Sec turns ratio of 2:1 will produce a Pri:Sec VAC ratio of 2:1). The only way you can accurately measure the VAC ratio is to supply one of the windings with a VAC source, and then measure the resulting VAC on the other winding. For your run-of-the-mill guitar amp OT, the VAC ratio test usually works more accurately if you supply a low VAC to the secondary and measure the resulting VAC across the primary (and for a PP OT you need to measure both sides of the primary winding). You need to measure accurately the VAC on all the windings to get the VAC ratio as accurately as you can, because you have to square the result to get the OT's impedance ratio. Yes. that's right, the Pr:Sec impedance ratio is the square of the Pri:Sec VAC ratio. (It is the impedance ratio of the OT that determines the reflected load that the OT provides at the primary when a speaker of a particular impedance is connected to the secondary.)

If the OT is buggered it will usually give you the wrong VAC ratio (and often in the case of a PP OT, an unbalanced VAC ratio on each side of the primary winding).