New and innovative ways for a valve to die and take out your amp!

[anthonyTD]

I think what we are trying to establish now is what damage has the valves in question caused to the amp, which is what i am most concerned with at the moment.

[AlexM]

Hi Anthony,

The amp has a main fuse, and a plate fuse (internal) per side. Helpfully, there is an indicator LED that illuminates if the plate fuse is blown. Neither the left or right channel plate fuses are illuminated.

The situation is somewhat confusing as the faulty tube shown above appears to be on the right channel, but the noise is from the left. The valve numbering is somewhat unhelpful as the KT120 output valves n the left channel are numbered V2 ,4,6 & 8 and those i. The right are v, 7,9 & 11. V1 is the 12AU7 phase splitter and V2 and v3 are the left and right channel 6n30pi drivers.

V9 is the faulty valve with the loose bits from the right channel, but the noise was from the left speaker. So my quandary is having replaced V9 with a spare, and then putting them into the left, I still have no sound. I haven't swapped left to right as there may be a faulty valve there too. I'm not sure I now have eight good output tubes, so I am loathe to cause any potential further damage.

I have put the four output tubes from the right channel into the left. Heater supply is up as all of them appear to be glowing, but it could be an HT rail down - does each channel ypically run it's own HT supply?.

Thanks in advance for any advice.

Alex

[anthonyTD]

Hi Alex,
Does sound like the main HT supply has gone down, do you have a circuit schematic, if not, i will try and find one, i really need to look at that before i can give you any more pointers.

Hi Anthony,

The amp has a main fuse, and a plate fuse (internal) per side. Helpfully, there is an indicator LED that illuminates if the plate fuse is blown. Neither the left or right channel plate fuses are illuminated.

The situation is somewhat confusing as the faulty tube shown above appears to be on the right channel, but the noise is from the left. The valve numbering is somewhat unhelpful as the KT120 output valves n the left channel are numbered V2 ,4,6 & 8 and those i. The right are v, 7,9 & 11. V1 is the 12AU7 phase splitter and V2 and v3 are the left and right channel 6n30pi drivers.

V9 is the faulty valve with the loose bits from the right channel, but the noise was from the left speaker. So my quandary is having replaced V9 with a spare, and then putting them into the left, I still have no sound. I haven't swapped left to right as there may be a faulty valve there too. I'm not sure I now have eight good output tubes, so I am loathe to cause any potential further damage.

I have put the four output tubes from the right channel into the left. Heater supply is up as all of them appear to be glowing, but it could be an HT rail down - does each channel ypically run it's own HT supply?.

Thanks in advance for any advice.

Alex

[Spectral Morn]

God, I hope not. The output transformers on this thing are massive very high quality items, and they are guaranteed to be very pricey!. Hopefully it is something less drastic. Will have to get my meter to test resistance side to side.

Regards,
Alex

If its the CJ then sadly I don't see a new transformer being cheap, but fear not it may just be a resistor blown under the valve base. Go get it checked out it may not be as bad as it appears.

Edit I see plenty of advice from Anthony - should have read full thread first lol


Regards Neil

[AlexM]

It's under warranty, happily. Should have it back early next week.. I'll update once I've got a report back