fuse blowing on peavey 6505+112

[guitarplay3r]

hi all,
not sure if it's the right section to post it, but here's my problem. My friend gave me his peavey 6505+112 because the internal fuse melted over and over. so i cheched in it, i tried new power valves, and i checked for damaged resistors that could overdrain current, but i found nothing. I also checked for short circuit, but i found nothing. Just to say the valve heaters still works, and led toon but no sound come off the amp.

here's the amp schematic : http://www.prowessamplifiers.com/schema ... 505112.pdf

the fuse is F2.

any ideas?

regards

[Groovenut]

F2 is the fuse for the high voltage supply. If you have cleaned the power tube sockets and checked for arching, I would check each screen resistor. These amps have had issues with blowing screen resistors. That would certainly cause this. Just as a further check, try powering up the amp without the power tubes in it. If the fuse blows the problem is further down the chain in the preamp, if it doesnt the issue is in the power amp section.

[guitarplay3r]

well, actualy, the amp still blow with no any tube on it. when you say the screen resistors, you're talking about R97 end 1R98 right?

[blackbunny]

If F2 blows when you switch from Standby to On, check power supply filter capacitors C33 (100uF 550v) and C73 (22uF 450v) with a DMM to see if either is shorted out.
If F2 blows when mains is switched on, but still on Standby, then check rectifier diodes D6-9 and filter capacitor C32 (100uF 550v) to see if any are shorted out.

[ppluis0]

well, actualy, the amp still blow with no any tube on it.

Hi guitarplay3r,

Try to make an adaptor with a series lamp, similar to this image:


If you connect the alligator clips to the male prongs of the plug of your amp and use an incandescent lamp of, say, 150 watts, you can test what is wrong inside the unit, while the lamp glow more or less but avoid any new fuse blown.

Good luck,
Jose