preamp tube burnout

[dukes1986]

Help! I have a TSL 122 and have a problem. The first tube in the preamp burned out the other day and I replaced all three of them per someone's recommendation. Once I fired it up, (after proper warm-up) it burned the first 12AX7 tube up again. Any ideas before I take it to the shop? Thanks!

 

[MartyStrat54]

A TSL has "four" preamp tubes. V1 is located under a metal RF can. You twist the can and it comes off.

V1-Primary gain stages
V2-Secondary gain stages
V3-Tone Stack/Cathode Follower
V4-Phase Inverter

Someone gave you some bad advice if he thought there were only three tubes.

 

[dukes1986]

Thanks for the heads-up. My fault thinking there was only three preamp tubes. I didn't know there was one under the can. I am new at this. I changed out the real V1 also now and I am still getting V2 burnout. It comes on a little, then fades a few times and dies completely. How can you see if V1 is lit or not? Is it safe to turn it on with the can off? Just being cautious. Thanks for the help.

 

[chuckharmonjr]

Rather than keep feeding tubes to the fire, literally, Id say its time to admit you have a serious issue and take her to a tech for evaluation.

 

[MM54]

I had a 1962 Mullard shatter in V1 once, now that was exciting.

Does the tube itself get damaged, or when you move that tube to another position does it work correctly?

We need to determine if the problem is actually burning up the tube or if the socket just has a bad connection somewhere. One of the smart guys can help you from there

Oh, and yeah you can run it without the can on V1, it's just to keep noise down.

 

[Lane Sparber]

As Matt said above, we need to determine if the intermittent lighting up you allude to is the heater itself or if the tube is red-plating and destroying itself.

As only V2 seems to be affected and if the heater is in fact the problem with that position, at least we can rule out the heater string's bridge rectifier and filter caps. If they were failing, more than just V2 would be affected.

Also as Matt said, take a tube that has failed in that socket and try it in another amp. If it works, I'd suspect an intermittent heater connection somewhere on v2's socket. If the tube truly is blown, then you have a substantially more serious issue that would require a tech.

Let's at least clean out the socket. With the amp off, take a NON-LUBRICATING contact cleaner and spray a liberal dose of it directly into that socket and then quickly insert and remove the tube a few times to shake loose any stray dirt. Then try a known good tube there and see if that makes any difference in the amp's performance.

I hope this helps you!

-Lane

 

[dukes1986]

Thanks to all. It is now working. I learned a lot. Thanks again.

 

[chuckharmonjr]

Well DUkes....spill it dude....what did ya do to get it working?

 

[diesect20022000]

Well DUkes....spill it dude....what did ya do to get it working?

I'm guessing replacing V1.

 

[chuckharmonjr]

Now how could replacing V1 stop the burning up of anything in the V2 slot...and magically make the amp work...without blowing a fuse or something?.We aint heard the whole story line here. I feel like I am talking to some production supervisor mofo ....lol...cried wolf to maintenance and engineering pitching a fit about something it turns out was something they actually fucked up and did....just saying....got the overall feel

 

[chuckharmonjr]

Lol..Paul...you're what...late 20's early 30's?...I would venture to say Ive been in the Engineering and Construction business damned near if not more years than yoiu've been alive....that shit is rampant.....and you oughta see 'em crawfish and bullshit in senior staff meetings when ya call 'em on it...lol

 

[TradAmpGuy]

Well DUkes....spill it dude....what did ya do to get it working?

+1

 

[impetus maximus]

+2

 

[jcmjmp]

Thanks for the heads-up. My fault thinking there was only three preamp tubes. I didn't know there was one under the can. I am new at this. I changed out the real V1 also now and I am still getting V2 burnout. It comes on a little, then fades a few times and dies completely. How can you see if V1 is lit or not? Is it safe to turn it on with the can off? Just being cautious. Thanks for the help.

Well, it IS three preamp 12ax7 tubes. The 4th 12ax7 is part of the power amp circuit and its the phase inverter.