• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

need help with short

shovel52

Member
2016-02-15 1:03 am
This amp is short circuited some where..Here are the symptoms..I have included two sections of the schematic and outlined in red the components and wires that are frying..I have also included a link to the full schematic..
At first it blew a fuse and may still blow the fuse if I were to leave it on long enough.I have tested all tubes with a tube tester for shorts and quality..I do have a variac, and am using a 100 watt bulb to monitor. I do have quite a bit of experience with electronics. but am better with transistors.. the symptoms listed are with the rectifier tube in only......

I have tested the power transformer with my ohms meter and according to the schematic all readings are normal.....I get no short with all tubes removed,but when I insert the rectifier,
tube, the red out lined areas are shorted..(smoke) I have tested the following component
all components connected to the red lines which are resistors and capacitors.
I am stumped at this point and just need some experience..I know you need more information
just tell me what might be happening and what to check or expect..thanks schematic
is below..


a.jpg b.jpg



99-D schematic
 

shovel52

Member
2016-02-15 1:03 am
Wow,, I didn't expect all this help this fast..I just came back in side from the shop, and found that if i disconnect the 375 volt supply at 160 ohm resistor, it relieves it.. I don't know why I am frying
on schematic a but there has to be something shorted near the output..give me a day to go over all this advise and i will be back thanks
 

shovel52

Member
2016-02-15 1:03 am
I found the problem...the output transformer.....when i disconnected the center tap it freed the amp up...I could hear the arcing with a stethoscope...Does anyone know of a general purpose 22 watt
or similar transformer that would work..that won't break the pocket book?