Palomar 250A blowing fuses

[flapineagle]

Have owned this amp for more than 15 yrs. but hasnot been inline for at least 10 yrs, lost interest but resently got the amp out opened the case and cleaned out the dust from sitting on the bench. Decided to just turn the power on and let the filiments warm up for a while. Plugged it up and made sure nothing was on turned the power switch on saw that the meter lite glowed for a second and was a hum from the transformer and the fuse (15 amp) blew. The one on the transformer did not blow also a 15 amp. Have looked it over and only thing I can see is the big caps on the bottom look as if they have leaked. Know that this is an old amp and that caps don't last forever. Question is (is this a good place to start or am I overlooking anything?) Thanks Also took some pictures and could post them.

 

[TonyV225]

Im willing to bet that not only the big filter caps are bad but the others may also be failing or are on the verge. This sounds like the common symptoms of a bridge rectifier failure aswell so it could be one thing or several

Look at Ebay some of the sellers and their stores sell complete rebuild / replacement part kits for certain amplifiers to solve this problem or to simply upgrade them someone here may also know of someone that has these kits aswell.

 

[mackmobile43]

I bet you doubty can answer this question.

 

[flapineagle]

Well for me this was my bad as it was late atnite when I posted then as I was thinking back realized that the amp is a 300A which makes no difference with the problem. As I gather from the replies that maybe my problem lies with the big caps and the rectifier board. I sure would like to get the amp back working again so any help from those that work in amps would be appreciated. Art

 

[Beetle]

Well for me this was my bad as it was late atnite when I posted then as I was thinking back realized that the amp is a 300A which makes no difference with the problem. As I gather from the replies that maybe my problem lies with the big caps and the rectifier board. I sure would like to get the amp back working again so any help from those that work in amps would be appreciated. Art

You're going to have to check out the power supply down to the component level. For this you're going to need a good multimeter, soldering equipment, various pliers and cutters, and a schematic of the power supply.

You'll want to check the filter capacitors and the rectifier stack or bridge (among other things). If you find they're bad, you'll have to replace them.

 

[flapineagle]

Palomar blowing fuses

I have the amp on the bench and checking the schematic I do not see the rectifier stack on the board with the big caps. any idea where they are? Am sending a few pic of the amp.

 

[flapineagle]

palomar amp

Found the rectifiers all tucked under the big caps. Getting things ready to send an order to start work on the amp. If I can find all the parts to rebuild it. Have been practicing on my soldering and wish I had a little better steady hand but all that goes with age so will make the best of it. Also found a better pic of the bottom of the amp.

 

[MisterFatty]

Haven't done a close read of this thread but be careful poking around in there, probably not enough in there to be considered deadly, but definitely enough voltage present to wake you up....

Discharge the caps, work with one hand, no jewelry, and all the happy stuff you probably already know about...

 

[flapineagle]

250 Palomar really a 300A

Got home today and the UPS had a package so have my parts for the amp so tomorrow will get busy and install some parts. Will keep posting.

 

[flapineagle]

300A blowing fuses

I got the big caps and the rectifiers all replaced rechecked all my work and reasembled and turned the power on and was sure relieved that all went well and the power came on and the filiments all lit so stopped there and let the tubes get used to the power for about six hours then tuned and loaded the amp using the low power at first to just check and see if all went well. Had a dead key on the radio of two watts and the amp tuned somewhere around 100 watts, tryed the high side and it would modulate about 400 so am happy as I know it will do better with a good tuning later. Thanks to all for the help getting me in the right direction and with some good advice that there is some danger in an amateur getting into one of these. Did notice that I have a relay intermitten on the preamp so will be taking the plug in board out and giving that a check and replacing some of the components on the board as I also got the two transistors for that board and will also replace the electrolitics there also. Was fun for an old man.