Dropping String Problems

[passfan]

I can't get much response out of resistor changes to my string in my 124. I started with
440
285
284
278

I've changed the 22k out to 27k and now to 44k. I added 200k to ground at B5 and now have changed the 2.2k out to 8.2k and the best I got was
440
285
272
250

I've swapped out tubes with no change. What's the trick to loading down my B+?

[ToneMerc]

I'm not clear on what you are trying to do, off the top of my head I think 272 and 250 is pretty low. Under load, what were the actual voltages at V1 thru V3 as orginally built?

TM

[passfan]

The main B+ is 440. The rest are the plates at V3 , V2 , and V1. Sorry for the confusion.

[M Fowler]

The dropping resistors are only going to change V3- V1.

The B+1 can only be dropped by using a large zener of whatever voltage value you want it to drop connected to HT center tap. Reverse Zener bolted to chassis is what I use.

I would not want to lower that 440v anyway.

Mark

[ToneMerc]

The main B+ is 440. The rest are the plates at V3 , V2 , and V1. Sorry for the confusion.

I concluded that, but what are end goals in changing the dropping string? Are you trying to drop V1 thru V3 lower than normal or you are to trying to lower the B+ of 440 down?

TM

[ToneMerc]

The dropping resistors are only going to change V3- V1.

The B+1 can only be dropped by using a large zener of whatever voltage value you want it to drop connected to HT center tap. Reverse Zener bolted to chassis is what I use.

I would not want to lower that 440v anyway.

Mark

A 25W 100-150 ohm aluminum cased power resistor from the HT center tap to ground will do it as well.

TM

[passfan]

From what I've read the ideal plate voltage for V1 is around 190 volts and V2 is around 200. Is this incorrect ? I'm 50 to 70 volts above that.

[M Fowler]

The only source I have for voltages is of a Dlite.

[ToneMerc]

From what I've read the ideal plate voltage for V1 is around 190 volts and V2 is around 200. Is this incorrect ? I'm 50 to 70 volts above that.

That's at the plates of the tubes, not at the B+ nodes. You should be checking voltages at pins 1 & 6 of V1 & V2.

TM

[passfan]

Those are my plate voltages, not my B+ nodes. My B+ nodes are
440
418
413
375

[ToneMerc]

Refer to this diagram of #183 which has voltages; it has the B+ nodes, the plate and cathode voltages listed.

You can you use any of these methods to log voltages.

https://tubeamparchive.com/viewtopic.php?t=16913

TM

[M Fowler]

loaded or unloaded values?

In other words with tubes in or out?

[M Fowler]

Too funny I have looked at that layout of 183 so many times and forgot the voltages where noted.

[ToneMerc]

Those are my plate voltages, not my B+ nodes. My B+ nodes are
440
418
413
375

ok the devil is in the details, so verify that both V1 & V2 cathodes are grounded and this is with tubes installed correct?

TM

[passfan]

Yes , cathodes are grounded. V1 is 1.9 and 2.03 , V2 is 1.9 and 1.9 . Amp is playing. I have a switching problem with mid boost and rock/jazz being st instead of dt. preamp boost switch throws the amp into an over the top gain and fizz monster that just got me yelled at. Could be due to my switch problems.
Tubes are installed and the circuit is loaded.