Palomar90a Just up and shorted out

#366290

I have a Palomar 90a that has served well for years. It's a little amp as far as power goes but a good amp all the same.
Earlier this evening I smelled what only could be described as burning insulation from a wire then, a power flicker when the amp blew a fuse. The amp was only powered on and not
on line. After a quick disconnect I popped the lid and one of the tubes ( 6KD6 as opposed to the 6LF6) tubes was literally sucked inward on its one side. I can only guess a power supply issue at the moment
but wanted to ask if anyone else had a similar issue.

Thanks
117
CWK

#366291

My guess is that you had an internal short in the tube that overheated it.

Try another tube after checking for any burnt wiring or other overheated components.

#366294

Nope. it was not a tube. I pulled them out and still have a short somewhere. filter caps look ok so far. Something looks and feels like 3inone oil.

#366295

Nope. No tubes in and still a short. Looking at the rectifier. I think it might be there.

#366327

You need to check the diodes in the hv supply an the bias circuit....it may have just been a tube but it may also of been loss or change of voltage on the tube to cause the melt down.....Capacitors all need checked also one could go bad in the bias circuit an the voltage would drop down an yes it would have a melt down just sitting their being on.....Anyway good luck .....be safe

#366329

If you found something that resembles 3 in 1 oil. Check caps. One somewhere let go. They can be had inexpensively. I would replace the caps in HV supply just to be safe. Then check the rectifiers.

#366478

I had a similar problem with a mobile amp back in the 80's. I only had it about a week and one of the micro screws backed its way out of a toggle switch and bounced around the inside of the box. the first red Flag was everyone told me I sounded bad then I popped the lid off and out came the smell. there the screw was laying loose on the board. ended up throwing it in the trash because the sellers idea of repair was to put in a new toggle switch and send me on my way. to add insult to the injury, when I bought the amp he charged sells tax.

back then it was a dollar per watt so I lost 200 bucks plus the sales tax that shouldn't have been added on. live and learn.

#367160

Sorry for taking so long to get back. I had to put it on the side. Thank all of you for the replies and I'll update as soon as I can.

Thanks!!
117 on the Stone looking 'round.

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