I got a Hall Express Today... And Broke It!

[JazzGuitarGimp]

I think the bottom plastic plate on the tube was all flat with no markings. I am not sure though and my pics dont show it. When I get home I will look at the bottom of the tube and see. Hopefully it will have a little slot where the key is supposed to be.

It's usually pretty obvious where the key was.

[Firestorm]

I think the bottom plastic plate on the tube was all flat with no markings. I am not sure though and my pics dont show it. When I get home I will look at the bottom of the tube and see. Hopefully it will have a little slot where the key is supposed to be.

It's usually pretty obvious where the key was.

If not, you can meter the pins: in an EL34, the only pins with continuity between them will be 2 and 7; 1 and 8 are between those and the key is between 1 and 8.

[Cantplay]

Take a small self tapping screw, #2 and screw it into the pin. Grab the screw head with pliers.

On some sockets the hole goes through and the broken piece can be pushed out from the back side.

John

[cap217]

I was going to order a set of backup EL34/6ca7's at the same millamp as the ones he included so I wouldnt have to rebias. But the ones I have read 29.2 and 30.1 and they asked at what voltage? I dont know and I have to find out but I am finding that these are pretty low readings for EL34's.

Can someone explain this?

[Reeltarded]

Oh dear. You have to measure the B+ to know and then you have to put the tubes in and measure the B+ while following the normal biasing procedure found on every page of every site on the internet to know what your bias vs your tubes should be.

It's like around 400v give or take 2-3%. It won't hurt if it hits you.. for long.

29.2 and 30.1mV are .9mV apart at some possibly arbitrary voltage. Are those from Dana's readings? He matched in your amp.

You are probably not ready for this.

[M Fowler]

Depends on plate voltage and % of max dissipation. If I'm at 415v on the plates and the amp sound good at 30mA it's a good safe setting for the tube's life expectancy. I think the TW Express Build guide shows 415v at 35mA but that is subjective.

Mark

[M Fowler]

I should call Richie's 24 hour Hotline and find out.

[cap217]

Oh dear. You have to measure the B+ to know and then you have to put the tubes in and measure the B+ while following the normal biasing procedure found on every page of every site on the internet to know what your bias vs your tubes should be.

It's like around 400v give or take 2-3%. It won't hurt if it hits you.. for long.

29.2 and 30.1mV are .9mV apart at some possibly arbitrary voltage. Are those from Dana's readings? He matched in your amp.

You are probably not ready for this.

Im not looking to bias anything. I just wanted to order a set of backup tubes so I had them. I told them the reading and they asked how it was measured. I have no idea and told them I would find out.

But after looking at EL34 mV I found that 29 and 30 were lower than what others had. That fine, Dana sent me these for my amp. I was just curious as to why they were that low and what I need for backup tubes.

[Reeltarded]

Again, you really don't understand.

The tubes don't rate anything until they have voltage applied. The -mV reading is based on what the B+ is.

If I had those tubes in one of my amps (423-456v B+) they would bias at near -40mV to -34mV. Unless you know your B+ you have no clue what the hell anything is.

This is why there are one-billion sites with biasing information and every good amp ever bought tells you to rebias when swapping output tubes.

I have 3 pairs that match closely enough to swap into my main amp in a pinch and those 3 pairs came from collecting close pairs for years, not calling an 800 number and asking.

Understand the frustration with your question. It's not how it's done. Stop asking that. Call Dana and ask him what your B+ was and ask him how much he left on the table. Are they biased 60%? 70%? He won't lnow what your local wall service provides. Is it 118VAC? Is it 122VAC?

Dood

[BIG Dave]

Thanks for making me feel better about this. Like I said, the tube is fine but I dont know pin #'s. What sucks is that these are supposed to be amazing NOS tubes (again, dont know the name). I would hate to have to use new production tubes bc I broke the plastic...

I'm pretty sure those are RFT (commonly referred to as "Siemens"). They are very good tubes, better than anything made today. They routinely sell for about $100 for NOS pairs.

[sunnydaze]

These work OK - should be able to match the keyway orientation with your other tube.

http://www.tubesandmore.com/products/P-STKY-1

Mike

[cap217]

Sorry I didnt respond last night. I had a long day... Anyways, there were no markings under the tube but you could see where the key broke off, where the slot was. I just lined it up and it all worked as it should.


Thanks for the help. If I was at home and saw the tube it would have been easy to see. But trying to "fix" it from work wasnt the best thing.