VH4. Bit confused over the fault indicators

[Ailean]

Hi all

Loving my VH4 Only had it a month, but it rocks!

However, looks like I've been hit with a faulty power tube. I had a loud POP through the speakers the other night, everything seemed ok so I thought nothing of it. However I noticed today that indicator lights 1 and 2 were lit. Fuse 2 has blown big style, and fuse 1 has fizzled out.

Now I thought that the power tubes were paired up as 1 with 4, and 2 with 3, so if I've lost a fuse from each pair then wouldn't I have lost both pairs and have no sound?

Could it be that tube 2 has gone and has just taken out the fuse of tube 1?

What's my most likely case here?

I've ordered some spare fuses, but I can't test until they turn up.

Also as a side note, I tested the bias with a biasrite (I'm thinking of dropping in a set of NOS Phillips 6L6's), and tube 3 is at 50ma and 4 is at 60ma, now I'm not too fussed that they are out by 10 to each other, but I thought 6550's were supposed to be biased to between 80-100ma?

 

[Hey_bert_whtcha_doin_bert]

When you read with a bias probe you are reading for 1 tube. So it should be 50 mA. 100 is for a pair of tubes.

 

[Ailean]

Ahh.. makes sense

Although that means I have (had) 1 pair running at 120ma which isn't so good.

 

[steve_k]

Ahh.. makes sense

Although that means I have (had) 1 pair running at 120ma which isn't so good.

POW!!!!!!

VH4 is not paired. Matched quad. With a bias rite, read each tube, although there is only one bias adjustment for the lot, which is why a matched quad is important. Get a set of 6550's and don't look back!


Steve

 

[Ailean]

POW!!!!!!

VH4 is not paired. Matched quad. With a bias rite, read each tube, although there is only one bias adjustment for the lot, which is why a matched quad is important. Get a set of 6550's and don't look back!
Steve

It's only a month old, came with 6550's from the factory, and I assume they were a matched quad.

 

[steve_k]

POW!!!!!!

VH4 is not paired. Matched quad. With a bias rite, read each tube, although there is only one bias adjustment for the lot, which is why a matched quad is important. Get a set of 6550's and don't look back!
Steve

It's only a month old, came with 6550's from the factory, and I assume they were a matched quad.

Oh shit. If you haven't touched the bias, PM one of the Diezel guys. That shouldn't have happened.

steve