• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Which tube does my amp use? 845 or 211

HP8903B

Member
2010-06-06 8:17 pm
I don't know who makes the amp. I attached some pictures.
 

Attachments

  • Tango 845 Amp.jpg
    Tango 845 Amp.jpg
    34.6 KB · Views: 543
  • Tango 845 Amp (bottom).jpg
    Tango 845 Amp (bottom).jpg
    64.2 KB · Views: 525

HP8903B

Member
2010-06-06 8:17 pm
To measure the grid voltage, do I put the RED probe on the Pin 1 (Grid) and the BLACK probe on the Pin 2 (Filament)? Do I do this with the tube installed? If so, which tube should I installed? I do notice that the 211 and 845 have very different DC grid voltage, 211 is -61V and 845 is -145V at 1000V plate voltage.

What do I do if it has adjustable bias?

Man
 
Put the black probe on the chassis ground and measure the grid voltage without the tubes. Don't try measuring the plate voltage. Most digital meters top out at 1KV and unloaded the supply will read much higher. Judging by the pics the amp looks homemade but well built. If the bias has enough range then you could run either tube depending on the transformer impedance.
 

HP8903B

Member
2010-06-06 8:17 pm
I over looked Frank's reply.
The two replies contradict with each other.

If I put the BLACK probe on Pin 1 (grid) and RED on the chassis, will I get a negative reading?

If I put the RED probe on Pin 1 (grid) and BLACK on the chassis, will I get a positive reading?

I noticed that the specs data for grid voltage is negative. I guess it doesn't matter whether it is positive or negative reading.
 
Last edited:

HP8903B

Member
2010-06-06 8:17 pm
Thank you for the information on the Fluke. If it is over 1000V, the Fluke will just state "max" right? It will not get damaged?

So do I measure the plate voltage with the tube installed or without?

To measure plate voltage, do I put the RED probe on the plate and BLACK on the chassis?
 
....

To measure plate voltage, do I put the RED probe on the plate and BLACK on the chassis?

asking this sort of question and messing with 1KV amp is big no-no , at least in my book


there must be drawn a line what's for beginners and what isn't .

find someone experienced who will help you and teach you in vivo .

your life worth more than that amp .
 
Thank you for the information on the Fluke. If it is over 1000V, the Fluke will just state "max" right? It will not get damaged?

i do not know for shure.

so -

i would NOT try this.

So do I measure the plate voltage with the tube installed or without?

tube installed.

but not with an underated meter.

To measure plate voltage, do I put the RED probe on the plate and BLACK on the chassis?


will not matter on a digital meter.

the electrons are only going to go one way through the tube.

really though, start this amp with a varible transformer.

110