The bias probe is here (some help)

[Joeytpg]

ok guys the bias probe thing I bought from tube-town is here. now I have two questions:

-How in the blue hell do I "strip down" the Vh4? how do I take it out of the headshell

-Where do I connect the black and red leads that came attached to the bias probe? when where do I connect the leads of my multimeter? (so far my logic tells me I gotta "touch both leads" the red lead from the probe to the red lead of the multimeter and black with black........am I correct?)

here's a pic of the probe and the black/red leads I'm talking about.

 

[duesentrieb]

Unhook rear grille
unhook 4 screws (bottom of amp)

set DMM to 200mV DC
black to black, red to red

pull tube
put adaptor in (watch orientation)
pull tube into adaptor

switch amp on
read millivolts (=milliamperes cause you are reading across 1Ohm)

set bias until you read 33mA (=mV here).

 

[Joeytpg]

alright, so I'm not gonna use the lead that came with my multimeter, I'll use the ones attached to the probe, correct?


I'll set the multimeter to 200m as I did with my einstein

 

[Joeytpg]

actually my multimeter has a DCA section (direct current Amperes) right? but it also has a DCV (direc current Volts)

When I rebiased my Einstein it was in the DCA section (200m)

 

[steppenwolf3080]

Yes, but you'll need to set the dmm to dcv with the adapter

 

[duesentrieb]

Joey, when reading Einsteins current you are doing that at the plates, directly with a DMM by taken the fuse out. Thats why the DMM has to be set to current. You are reading plate current.

The adaptor has a 1Ohm resistor soldered into it. You are converting this way cathode current into "cathode volts", thats why it is set to Volts (DC), not Ampêres.

 

[Joeytpg]

oh ok....DCV section then

 

[duesentrieb]

 

[Joeytpg]

man this is hard hehe (can I touch the "metal" part of the vh4 while taking it out of the headshell?

because I have to turn it upside down.

by the way, olaf....show I just test the current on the tube BEFORE turning it upside down? and then after that take all the power tubess out and turn it upside down and set the bias with the trimmer?

Do I need to take the fuses out?

 

[duesentrieb]

VH4: (!) leave fuses where they are !

put transformers (amp flipped) onto two books - huge books.

 

[Joeytpg]

set bias until you read 33mA (=mV here).

33? hmmm but aren't I supposed to set the current of a pair of tubes? or just read the current of the tubes and match it with the bias trimmer?

 

[duesentrieb]

One adaptor = one tube, Joey.

Set it to 33mA=mV.

 

[Joeytpg]

DONE!

hehehe ufff...that was hard (getting the amp out of the headshell!)


olaf I only tested one tube and set the current to 33mA and done....right? no need to do it with other tubes or anything else.


sounds great! I can hear some of the 6L6 bigness and the crunch of the EL34, wow, great sounding tubes......

also changed the V2 preamp tube, and the amp is no longer doing the crackling thing

thank you all VERY much!



and most importantly, I'M ALIVE!!

 

[duesentrieb]

Congrats !!!!!

(one is enough - the others would read the same)

 

[duesentrieb]

btw: readjust/reread after 1/2 hours of useage (serious). Probably you don't need to take it out then . ..

 

[Joeytpg]

I can read it again without taking it out of the headshell, but if I gotta rebias it (in case it's nor reading 33mA this time) I gotta take it out! the damn bias trimmer is on the bottom....


peter should start making the vh4 with external bias pots!

by the way.....there was no 6L6 - EL34 switch like the tech corner on the Diezel website says Olaf..... is it ok?

 

[duesentrieb]

Sure. The trimmer has a wider range than before and can do both, Joey.

When I had a VH4 I've installed one myself to its back and labelled it "sound"

 

[Joeytpg]

you DIY nerds that's make life SOOO much easier!

 

[Joeytpg]

I read the current again and it's at 34.......... nice!