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My V55HD no longer seems to function. Turned it on, in standby, it went pop. The power light went out and now the amp has no life at all. Any ideas what the most likely thing to have gone wrong before I lug it down to an amp tech?

I haven't a clue about amps but first step is replace the fuse in the plug!

Dave wrote:I haven't a clue about amps but first step is replace the fuse in the plug!

Yeah, first thing I tested. The plug is fine.....

If the amp will not power on, the first thing to check is a blown fuse. There is probably a HT (High Tension) fuse inside for one or both power tubes. When a power tube fails, it blows this fuse to protect the rest of the amp. Make sure you replace the fuse with exactly the specified value and note weather it is slow blow or fast blow.

Replace the fuse and power the amp on without power tubes, if it works, you probably have blown a power tube. It's not always easy to tell if you have blown a tube, but if it's vacuum has been compromised, you will see the silver getter shit has oxidized and turned white.



^bad tube / vacuum seal has been breached causing oxidization of getter (it should be shiny like silver)



I have the schematic for this amp on hand and will try to see if there are any other fuses. I would imagine there are.

If you could take the chassis out and post a good hi res gut shot, that might be helpful if you need assistance locating the fuses

Just had a quick look at the valves, they look ok on quick inspection, but it's beer o'clock so will take em out tomorrow when I have picked up a new fuse. Think it's a TA1H 250V looking at the back of the amp. Cheers for the info, will post findings tomorrow.

Ok, had 10 minutes to kill befor the pub, took the chassis out, only obviousness fues is located on the back next to the power socket. Guess this is the first thing to replace. Valves themselves look ok.

Rayjaysonic wrote:Ok, had 10 minutes to kill befor the pub, took the chassis out, only obviousness fues is located on the back next to the power socket. Guess this is the first thing to replace. Valves themselves look ok.

yes.
if you can't actually see if the fuse is blown, you can check across them with a multimeter. diode test function, if it's a short, it's good. if you got nothing, its bad!

make sure you turn on the amp without the power tubes first to take them out of the equation.

Ok, fused changed, power valves taken out. We have life! I have put the stock 6l6's back in for now and everything seems hunky dory! The JJs look fine, and I have read a few postings the the V55 can blow a fuse for no real reason, but I will order some new valves just to be on the safe side. Thanks for the advice. Saved me the cost and hassle of taking it to a repair shop, for now at least (not that I'm a pessimist but it is a Bugera after all).