Valve amp help please (blown/dead valve/s???)

[hearingisbelieving]

Lol Chris how do you get a goat from my avator? The actual pic is the album cover from Oceansize's Self Preserved While The Bodies Float Up album. To my mind it is a drawing of a headless female bust.

[hearingisbelieving]

Ordered a quad matched set of Sovtek EL84M/6BQ5 Military Spec from HotRoxUK yesterday. Selected budget delivery option but it appears they have been delivered today. Cant wait to get home, put them in and make sure that they solve this problem I have been having. Fingers crossed!

[hearingisbelieving]

Well thats fucked it! Got home all excited about getting my amp working again. Put all the new valves in and....
Nothings fucking changed!!!!
Same very worrying noise being emmitted from the speakers as the valves start to warm up....
So what is the likelihood that it is one of the 3 remaining ECC83 valves that i havent changed yet. They are all Full Music 12AX7's and look bloody expensive to replace like for like so maybe I should get some cheap ones to see if they are the problem? Or maybe I should just take it to a reputable service tech - anyone know anyone in the West Midlands?

[robin]

chris, when i blew my leak 20 up putting a cap in the wrong way round it was two of the 3 ecc83s that were damaged, so could be worth buying some cheap ones off ebay to make sure

[Valvebloke]

I don't think we have enough information to guess what the fault is I'm afraid. When you were looking at the output valves earlier you thought that the fault had followed a valve from one channel to the other. If you can be sure about that, i.e. that both channels have, at one time or another, exhibited this fault then it has to be something which is common to both channels (say the power supply ?) or it has to be something which you moved from one channel to the other (one or more EL84s, assuming you changed nothing else). It's now looking like the root cause is not the EL84s though. I guess the ECC83s are not common to both channels either so unless the same fault has appeared simultaneously in two of them then the root cause will be somewhere else. The '83s may or may not be damaged, as Robin's were, but that's not the root cause and it's that that you have to track down. It sounds like it's time to get a tech involved. He'll have access to the kit needed to isolate the fault which will be tough, and potentially expensive in unnecessary spares, if you try to do it from scratch.

VB

[hearingisbelieving]

thanks Robin and VB. Looks like its time to get a tech involved. If anyone knows a reputable one in west midlands please let me know.

[robin]

pm bigdur he will put you right

[hearingisbelieving]

pm bigdur he will put you right

already been in touch with Jack as I bought the amp from him. He is very busy with his Ming Da stuff at the mo and life in general so dont want to bother him too much. I have used good ol google and found a company/tech that looks very good and is very local:
http://www.amplabs.co.uk/
his profile and testimonials certainly are encouraging so will give him a buzz tomorrow and see what he can offer.
thanks

[Toe rag]

what is you avatar Chris? I find it rather disturbing - and thats coming from me!, is it half goat / half woman?

Funny enough I thought that aswell
Also I always thought that one should never have the speakers disconnected when turning on a valve amp

[hearingisbelieving]

Not disputing that Chris but why have a "pre-amp out" output if that is the case? I used the Oto as a Pre to my active speakers for several hours and it didnt seem to do it any harm(at the time that is...). Do other valve integrateds have pre-outs and if so what are you supposed to do if you want to use that function???

[i_should_coco]

It depends on the amp. But with any amp a dummy load it's a good idea if not using speakers

[hearingisbelieving]

It depends on the amp. But with any amp a dummy load it's a good idea if not using speakers

not being funny but you would think they would mention that in the manual.
Especially if they already go to the length of listing what the volume control does
When you say dummy load do you mean using some resistors? if so what value and rating would they have to be?

[i_should_coco]

As I said, it may not be a problem, depending on the topology. It's more of an issue with pentode our ultra-linear amps as the high impedance of the tube means you can get some very high voltages in the output transformer primary, causing it to be damaged. Triodes have a lower internal impedance, so it's less of an issue.

As a note, such damage is really only likely if you actually try and play music through it.

Ideally use 8 Ohms or so. Up to 20/30 ohms should be fine, it's not critical and 20W should be adequate as a rating.

As I said, it may but be necessary, but the dummy load won't hurt and better safe than sorry.

[hearingisbelieving]

As I said, it may not be a problem, depending on the topology. It's more of an issue with pentode our ultra-linear amps as the high impedance of the tube means you can get some very high voltages in the output transformer primary, causing it to be damaged. Triodes have a lower internal impedance, so it's less of an issue.

As a note, such damage is really only likely if you actually try and play music through it.

Ideally use 8 Ohms or so. Up to 20/30 ohms should be fine, it's not critical and 20W should be adequate as a rating.

As I said, it may but be necessary, but the dummy load won't hurt and better safe than sorry.

There's the rub - I was playing music through it when I had my actives connected to the pre-out...
Luckily I have found a competent tech so hopefully he will be able to get to the bottom of this and it wont be too expensive!

[i_should_coco]

I'm pretty sure it will be fine. If the output transformer was fried, you wouldn't get noises, you'd get silence!

[hearingisbelieving]

I'm pretty sure it will be fine. If the output transformer was fried, you wouldn't get noises, you'd get silence!

Wow thats a relief to know as I believe they are the most expensive component in a valve amp - especially AN! Will report back when the tech has inspected the damage...

[hearingisbelieving]

Just been informed by email that the Oto is now mended and ready for collection. Picking it up tomorrow night so will report back soon. It took a while for the guy to repair it but for a fixed fee of £90 you cant really complain! As well as the repair he also carried out a couple of small mods i had requested, and a couple he thought might be a good idea for no extra charge.
Cant wait to hear it sing with the new valves as well!

[Jazid]

Ignore my post

[adsa]

What was up with it then?

[Jazid]

For some inexplicable reason I only got 1st page of the thread. I thought that was all of it and offered some sterling advice about 6N14P valves, then when I clicked the reply button the post came up three pages later. I didn't have time to read them all and it seemed best to remove the post, and I was amazingly enough (probably) right. Not v. exciting