Help needed: Shiva lights up but no sound!

[Classic]

At a gig last night I all but completed a 45 minute set but then the amp cut out. I've check and it's not instrument, speaker or power cables causing the problem and it's not the guitar, which only leaves the amp.

All tubes are lighting up but there's still no sound.

Two things I've not tried yet are power tubes and the slow burn fuse. Could it be either of these or is it something more sinister?

 

[psche378]

If the power tubes are all lighting up I don't think it is the slo blo fuse they almost always blow when you first start up the amp when something is not right with the tubes but there could have been some sort of power surge so it is still worth checking out just because of how easy it is to see if the fuse has been blown. If the power tubes are still lit though it doesn't make sense that it is the fuse as they should be out. I had something similar happen to my mark v when I first bought it from a guy it got shaken while moving it. Have you checked the preamp tubes? I would change the phase inverter tube as that takes the sound from the preamp to the power amp the problem with my mark v was that tube was actually shattered so there was no link to the power section. Maybe also change the preamp tube responsible for your fx loop buffer as it could do a similar thing. Those are the first things I would do before going to a tech. Hope this helps

 

[glip22]

A preamp tube and or your HT fuse. I would check the HT fuse first.

 

[Classic]

I had a look at the HT fuse and it looks to be all in one piece with no visible burn marks. I've ordered some new HT fuses for future use and can check the HT fuse when they arrive.

All preamp and power amp tubes are lighting up (no red playing either) but I've not had he opportunity to try replacing any of the tubes yet. That will happen tonight.

 

[psche378]

I still think its one of your preamp tubes let us know what happens when you replace them. In the meantime you could just move some around and see if that fixes the problem also you should check the wiring in your speaker cabinet it could have come loose on the way to the gig and the vibration from playing halfway through the gig could have been the final straw I had a mesa vertical 2x12 and was playing with just the one top speaker for about a month before I realized

 

[psche378]

thats horrible for most amps depending on the wiring in your cab also you probably did so already but I would check the continuity of your speaker cable just to make sure there isn't a break

 

[glip22]

I had a look at the HT fuse and it looks to be all in one piece with no visible burn marks. I've ordered some new HT fuses for future use and can check the HT fuse when they arrive.

All preamp and power amp tubes are lighting up (no red playing either) but I've not had he opportunity to try replacing any of the tubes yet. That will happen tonight.

You need to test the fuse for continuity on a meter or replace it. The HT fuse in that amp is only .500 amp. It is not always noticeable. Bet you thats it

 

[Classic]

Things have taken a step backwards. The HT fuse, main and output tubes have been replaced (but not biased) and now there's no power at all. No lights at all. Now I'm worried.

 

[glip22]

Things have taken a step backwards. The HT fuse, main and output tubes have been replaced (but not biased) and now there's no power at all. No lights at all. Now I'm worried.

If the tubes were bias to hot they probably blew the fuses. Replace the fuses and bias correctly. You should aalways check the bias are you could be asking for trouble.

 

[Classic]

Power within the amp is required to bias the tubes and at present there isn't any, which is why I didn't/couldn't bias them.

 

[glip22]

Power within the amp is required to bias the tubes and at present there isn't any, which is why I didn't/couldn't bias them.

Did you replace the fuses again to see if it powers up?

 

[Classic]

I replaced both fuses before and after the tube swap with no joy.