The saga continues....1965 Gibson GA15-RVT New Conundrum

[widget2640]

Hi again fellas,

Thanks for all the help in sourcing the power transformer for my Gibson GARVT. I ended up going with the Mercury GA15-P. (The original PT was definitely toast. The caps were replaced as well.)

The Mercury GA15-P was installed (easily and I hope correctly) and wired up by the tech working on this for me. Sadly, then only 1 output tube lights up and it blows the fuse at about 50v when tested. (The original issue that caused me to bring it someone in the first place was blown fuses.)

He's going to do some "tracing" to see what the issue might be now.....

Any theories? Sorry if that's vague. No other symptoms.

Man this is becoming my Moby Dick - it will work again! ;-)

[Bloomfield]

When you say the fuse blows at 50 volts, do you mean you are running it through a variac at that voltage? If so it would draw over twice the current that it would at line voltage. Also the filament voltage would be very low which could explain the tube not lighting up.

Try again at line voltage (with a light-bulb limiter if possible,) it may be fine.

[mozz]

I would have all tubes out, meter on the filaments, meter on the plate, variac up slowly, if something doesn't look right find the problem before trying with tubes. By "caps" do you mean just filter caps or all electrolytic caps, cathode caps as well? Diodes are right there, check them, then even check the interstage trans for short to ground.

[nosaj]

Hi again fellas,

Thanks for all the help in sourcing the power transformer for my Gibson GARVT. I ended up going with the Mercury GA15-P. (The original PT was definitely toast. The caps were replaced as well.)

The Mercury GA15-P was installed (easily and I hope correctly) and wired up by the tech working on this for me. Sadly, then only 1 output tube lights up and it blows the fuse at about 50v when tested. (The original issue that caused me to bring it someone in the first place was blown fuses.)

He's going to do some "tracing" to see what the issue might be now.....

Any theories? Sorry if that's vague. No other symptoms.

Man this is becoming my Moby Dick - it will work again! ;-)

Well all I can say is if this is the original tech I hope he's paying you for the learning experience. After changing the PT voltages SHOULD be checked before putting in tubes.

Maybe The tech should be commenting maybe there is something we're not getting relayed.

nosaj

[Leo_Gnardo]

Man this is becoming my Moby Dick

With Captain Ahab manning the soldering iron, scope & variac? Dig deep darlin' I see another brand new xxxpensive Mercury PT in your future.

[olddawg]

Was the old transformer blowing fuses with the secondaries floating?

[loudthud]

Is this the right schematic ?

https://el34world.com/charts/Schemat...on_ga15rvt.pdf

[widget2640]

I'll be cutting and pasting your comment directly to the tech - I am only offering the result of what he did which was likely installing the PT then I assume firing the amp up. I'll confirm along with these questions.

Thanks Bloomfield !