Dammit, another preamp tube smoked --help?

[Gainfreak]

bump for Olaf

Quit fucking around already and fix it

Hey can we use your kitchen table? My bench is kinda full.

Sure! I cleaned off all the excess crap that was on it!! We are ready to rock!

 

[tweed]

Sure! I cleaned off all the excess crap that was on it!! We are ready to rock!

Excellent! I'll be right over

 

[duesentrieb]

Hi Randy,

please repeat the measurements. For the heaters set DMM to AC (!) 20V. Red to PIN 4, black to PIN 9.

 

[tweed]

Hi Randy,

please repeat the measurements. For the heaters set DMM to AC (!) 20V. Red to PIN 4, black to PIN 9.

Ok Olaf will do. May be a while before I get back to you with the measurements. Im at work right now and inlaws are in for the weekend.

 

[duesentrieb]

I don't think its your heaters voltage though (tube white = oxidation = lost vaccum = fucked manufacturing), but it might be useful to know how to do it. And as you know from James' Peter's some types can't handle cathode followers conditions.

I'm off to France tomorrow morning and it takes until sunday evening (my time) to reply.

Nice weekend over there !

Olaf

 

[MOAAH]

Most of the tubes in my amp are from the 50s and 60s and last forever and sound good.

Oh my, don't say that!?! You may get paraphrased for eternity

 

[MOAAH]

Crap I gotta find something else.

Have you tested for normal voltage and resistance in the V1 circuit?

Sad to hear that several new tube brands are seemingly having bad runs.
Glad I have good stock on old and older runs:

Oh you bastard!

I've been called worse

 

[MOAAH]

It happens man, in my experience it usually happens with preamp tubes from tension at the pins.

+1, for sure.

I used to say how lucky we were today with such a wide selection of new inexpensive tubes. Now, with the falling Greenback and poor production runs, I'm not so sure. I have received two major price increases lately, right from the manufacturer. Tube prices have pretty much doubled in the last year or so, soon I'm sure, to be evident at a dealer near you

 

[tweed]

Hi Randy,

please repeat the measurements. For the heaters set DMM to AC (!) 20V. Red to PIN 4, black to PIN 9.

Olaf, I redid the readings.

Pins 1/6 = 37 (1000DC)
Pins 4/5-9 = 2.55 (20V AC)

 

[MOAAH]

Pins 1/6 = 37 (1000DC)
Pins 4/5-9 = 2.55 (20V AC)

When you check pins 1&6(anode, AKA plate) you need to connect the black lead to ground and do them separately, reading should be ~100 to 300VDC; looks to me like you checked the difference between 1 and 6. If the Bogan uses 6VAC heaters you should get a reading ~6.3VAC from pin 4 to 9 or 5 to 9.

 

[tweed]

Pins 1/6 = 37 (1000DC)
Pins 4/5-9 = 2.55 (20V AC)

When you check pins 1&6(anode, AKA plate) you need to connect the black lead to ground and do them separately, reading should be ~100 to 300VDC; looks to me like you checked the difference between 1 and 6. If the Bogan uses 6VAC heaters you should get a reading ~6.3VAC from pin 4 to 9 or 5 to 9.

Here are the readings after putting the black to ground and measuring each pin individually with the amp in run mode, not standby.

1 -164 6 202
next 12ax7
1 -182 6 297
final 12ax7
1 -251 6 262

 

[tweed]

well I stopped playing with the bogen and started messing with the Lafayette 55. Before I had no signal nothing.

Today I got things working and actually wired an input jack and ran a guitar thru it. It was very clean sounding and dull which was to be expected. Im looking inside and it has a TON of components and the chassis is only 1" deep. Very hard to get around in there to do anything.

I'm wondering if this Lafayette would be a good base to build say a Champ circuit in to mess with. Or should I just sell it off and find something else?


Suggestions?

 

[tweed]

sunday mornin bump

 

[tweed]

el bumpo

 

[MOAAH]

well I stopped playing with the bogen...

I'm wondering if this Lafayette...Suggestions?

Those B+ readings on the Bogen are well within the norm.

As for the Lafayette, really just depends on your ability! You could use the extra circuitry to mod it to more of a guitar amp. If I remember and it's the same amp we talked about before, there is at least 1x12ax7 and a pentode before the 12ax7 drive/PI and OP stage. The first 12ax7 and the pentode preamp tube could combine to make one heck of a preamp, again, depending on your ability.

If you have a schematic, I could use it to outline a possible higher gained AC15 circuit, or you could skip the pentode in the preamp, and just do more of a champ/delux circiut.

Or, you could just use a pedal EQ to boost the front end!!!

Im looking inside and it has a TON of components and the chassis is only 1" deep.

Bet it looks like a rats nest, some PTP does, LOL.

Very hard to get around in there to do anything.

Kinda hard to see your way around?

 

[MOAAH]

FWIW -
Krank stopped using EH 12AX7s and switched to Ruby because of a high failure rate.

Update, FWIW.
I just received a new batch of EH 12ax7s. So far they don't even fit into my high rise(with sliding sleeve for full coverage after tube is inserted) American made NOS sockets:

They must have changed how they do the glass, or somethin'

New one on the left.

Old one to the right.