Egnater Tweaker 15 Troubleshooting Question

[funkmasterron]

I am troubleshooting an Egnater Tweaker 15 guitar amp head, that has no output.

I am tracing the circuit using this schematic: (https://el34world.com/charts/Schematics/files/Egnater/Egnater_tweaker_15.pdf)

R27 (1k 5W resistor) was measuring an open circuit impedance. I am measuring 406VDC at the C26 side of R27, then 0V at the other side of R27. I performed a continuity test and resistance value test of all of the resistors in that power supply circuit and everything checks out. C26 is measuring an infinite impedance when in the circuit which seems odd, so I will replace it. All 4x of the filter caps (C28, C29, C30, C33) are measuring an impedance in the circuit so don't appear to be shorted.

I removed the QC2 - QC5 jumpers connecting the output of the power supply to isolate the issue to the power supply circuit or its load (aka other circuitry).
With the QC2 - QC5 jumpers removed, I replaced R27 with the same resistance/power rating part, and in about 2 seconds, that resistor visibly gets hot and blows again.
I need to purchase some more 1k 5W resistors to run more tests, so I'm typing this post out to get some ideas of what to try next.

My thought is that the problem appears to be in the power supply circuit. My next test would be to remove each "leg" of the R27 output (R28 and R30) to see which "leg" is causing the issue.

Or think this is a problem with the power transformer (ground connections, perhaps)?

Any other thoughts?

TIA!

 

[BmwE30]

I am working on the same amp ur working on with possibly similar issues. The one I’m working on, the PT failed, but all the fuses are good! The only info I got from the owner is that there’s no power, and when I tested the PT, it’s bad! I unplugged the secondary of the original PT and connected one of my PT of similar spec (280-0-280, 3.15-0-3.15); HV to QC8, QC9, CT to QC10, then filament to QC20, QC23, and CT to QC3. Now the indicator lights work but the issue I am running into is very low volume, barely hear guitar signal at max master volume and max gain. I’m still trying to figure it out. Traced the whole schematic and everything seems to be good.