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
What do I do if it has adjustable bias?
Man
To measure the bias voltage, the black probe should be connected to pin 1 (grid). The red probe should be connected to chassis ground.
Do this without the tubes installed.
What are the other tubes in the amplifier?
Do this without the tubes installed.
What are the other tubes in the amplifier?
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.
Thank you very much for the information.
So does that mean the two factors that determine which tube to use are the grid DC Voltage and output transformer impedance?
I am pretty sure the output transformer impedance is 7k. If it is 7k, is it for 845 or 211?
So does that mean the two factors that determine which tube to use are the grid DC Voltage and output transformer impedance?
I am pretty sure the output transformer impedance is 7k. If it is 7k, is it for 845 or 211?
I have a Fluke 87 V. It can probably read higher than 1KV.
So I need to measure the plate voltage with the tube installed?
So I need to measure the plate voltage with the tube installed?
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.
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.
I have a Fluke 87 V. It can probably read higher than 1KV.
only goes to '1000'
Fluke 87V digital multimeter (DMM) for maximum industrial productivity
So I need to measure the plate voltage with the tube installed?
start the amp with a varible transformer.
and slowly bring the voltage up .
not more than 100 input volts, as thats what the power transfomer is made for.
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Frank,
That is a good question. There are 3 small tubes sockets. Each with 8 pin holes. Any suggestion on how to figure which tubes to use. There is another amp that is similar to mine which uses 211 tubes with 12BH7A and 5751.
That is a good question. There are 3 small tubes sockets. Each with 8 pin holes. Any suggestion on how to figure which tubes to use. There is another amp that is similar to mine which uses 211 tubes with 12BH7A and 5751.
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?
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
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