Amp guru advice required

[hoodoo]

G'day to all, Matt here. Just picked up an old peavey session 400 amp for pocket change, that has some issues. I've done some googling and the replacement of old electrolytics could be the answer. I know that amps can kill, and you need to discharge the  caps on tube amps, and i plan on learning how to do this, but i was curious if the same applies to solid state amps, i'm suspecting that this is the case. If this is needed, can anybody recommend a site/youtube or reference material that will teach me how to do this. I'm about to do a little research, but we all know there is a pile of misinformation out there. Any and all advice greatly appreciated, thanks.

[alanp]

Any big capacitor can hold a charge, and they can also develop "memories", IIRC.

http://ampmaker.com/discharging-capacitors-946-0.html

[alanp]

I'll also add that anything hooked up to mains voltage, it is a very good idea to get a licensed electrician to do the job, or if they do not know how, to get a proper technician to poke at it.

Mains voltage is VERY capable of killing. I have been told, when working on high voltage amps, to keep one hand in your pocket. (This stops electricity from flowing up one arm, across the chest (and heart), and down the other arm.)

[hoodoo]

Thanks for the link and advice Alan. I'm quite aware that mains voltage can kill, as mentioned in my initial post. The smart and safe thing would be to get a qualified technician to look at it, however in doing so, i'd learn nothing, which is the point of this DIY exercise. In that article it only refers to tube amps, so my question still remains, are there the same/additional hazards, when working on solid state devices.

[lincolnic]

As Alan said, any big capacitor can hold a charge. So yes, it's still dangerous, and you should still discharge the caps. Then double check voltages with your multimeter before you put your hands in there.

[hoodoo]

Thanks for the response, i've got it, that caps hold a charge that can kill and they should be discharged. However, all the youtube vids i can find are all to do with tube amps, and they all seem to have different ways to perform this procedure. From what i've seen online,  If a tube amp is let warm up properly before turning off, the caps discharge well anyway,(never assume so) but will a solid state amp without tubes do the same. Are there any things that you need to do differently, to safely discharge caps on a solid state amp than what is done on a tube amp, and is there a preferred method to use. The method that i thought looked the safest was, the alligator clips with a resistor in line, one end to ground on the amp chassis and the other end attached to the positive end of each capacitor for 30 secs or so. Am i right in thinking that this would suit my needs for a solid state amp.  Thanks, Matt.

[lincolnic]

As far as I know, that same method will still work, but don't just count to 30 and expect it to be done - use your meter to confirm.

[pryde]

I just repaired a PV session 400 (steel guitar amp) for a customer 2 weeks ago. These are loud and powerful amps for sure and sound great once they are sorted. As a starting point, replace ALL electrolytics on the power and preamp boards. The little 2uf coupling caps on the preamp board should be converted to 2.2uf film caps when changing all of them.

There are some common issues these amps have and I would be glad to help you through them if need be but get all those caps changed first.

[hoodoo]

Thanks gents, advice greatly appreciated. Pryde, from the research i have done, this is exactly what was recommended, good to have confirmation that this info was correct. I'll give it a go, thanks, Matt.