filter cap issue with a hot rod deville...

[freakshow__]

hey all.... I did this tube rec. simulator mod to my fender hot rod deville and I am wondering why my filter caps have made a crackling/popcorn noise when I play.....also I opened up the amp and noticed that the 2 100uf 350 volt caps look like they are about to explode...ie...the rubber end caps to the capacitors look like they are about to burst/explode from the capacitor body! anyone think I should just replace the caps and return the circuit back to it's normal spec??help!!!!
many thanks!

http://www.youtube.com/watch?v=fYkblefwEWo

[The Tone God]

Might be a good idea. Be careful when working with HV.

Andrew

[geertjacobs]

Crackle and pop issues with a Hot Rod Deville:
http://studentweb.eku.edu/justin_holton/

[GibsonGM]

Holton's site is awesome...I did most of the mods on there to my HRDx, it is a totally new (improved) amp!  I didn't do the last one, with the FET, however.  The problem you're having with the caps seems like it could be related to a short somewhere -- or could the new rect mod have exceeded their voltage rating for some odd reason??  A short across the switch that's sending full voltage to the caps?  Maybe a measurement at the + side of the caps is in order.   As Tone God said, BE CAREFUL IN THERE!!!!  Read about draining the caps, one-hand probing with a non-conductive object etc etc.  Sorry if you already know this, it has to be said, there are fatal voltages present     

Check it out, recheck your work; easiest route might be to go back to stock, yup!  Something is probably over-voltaged due to a short.  That mod scared me a little, being so away from stock, so I avoided it.   

Things like that can happen if there's a short to the chassis, also (I've seen blue smoke from not removing a shorting jumper before powering up to test, LOL).    Please let us know what happens, I own your amp's brother and could learn something from your results!  Good luck.

[freakshow__]

I just replaced the 2 larger filter caps....the 350 volt 100uf ones...like I said before mine looked like they were about to explode! When I removed them from the board (they're glued to the board) they both vented and made the "pfft" noise. I replaced them with sprague atom caps of the same value. I might add that the sprague ones are twice the size of the stock ones....you will have to carefuly fit them inside your amp without shorting them on soemthing....I insulated the leads so they would never short out on anything over time etc... I think the stock caps are junk.....the sprague ones are clearly more "heavy duty". I also need to add that I removed the tube rectifier simulator that is on justin holton's site. I dunno if that mod was the cause of my caps going bad or not...but I definately did it exactly as he shows and 2 weeks later my caps are junk...so I went the safe route and got rid of the power resistor. I cannot reccommend to anyone that you try this mod yourself because it could potentially ruin your amp in a hurry.

[GibsonGM]

Good call on putting it back to stock...the other mods are working out great in mine, but they're mostly in the tone stack, low voltage stuff.   Your experience concerns me...same symptoms as caps either exceeding max voltage or shorting.  Hopefully the new ones will end that problem for ya! 

[Paul Marossy]

If they were bulging like that, it sounds like they were exposed to an overvoltage, but didn't make it to explosionville...