Hi all,

I know it it good to delay the b+ to mercury tubes
Q1: does it have to be delayed?
Q2: Would edison delay relay tubes work? I have 4, 2 with 6.3 volt (heater) 60 sec delay contacts:150vdc 250ac 3A, and 2 117v (heater) 75 sec, contact:150vdc/250vac 3A
these will be switching 375vac
Q3 Mercury tubes cant handle large input capacitors, If I place a large (10hny) choke from the filament to a 40mfd cap can the tube handle that?

This is going to an audio amp, not a transmitter.

Thanks for any help,
Ian

:Hi all,
:
:I know it it good to delay the b+ to mercury tubes
:Q1: does it have to be delayed?
:Q2: Would edison delay relay tubes work? I have 4, 2 with 6.3 volt (heater) 60 sec delay contacts:150vdc 250ac 3A, and 2 117v (heater) 75 sec, contact:150vdc/250vac 3A
:these will be switching 375vac
:Q3 Mercury tubes cant handle large input capacitors, If I place a large (10hny) choke from the filament to a 40mfd cap can the tube handle that?
:
:This is going to an audio amp, not a transmitter.
:
:Thanks for any help,
:Ian

Answer 1
The mercury needs to be vaporized before applying the
high Voltage.

Answer 2
Now, I don't know, the only 866s I was around were in a factory built RCA broadcast transmitter,where they were bias rectifiers, and all the mercury tubes had a 60 second time delay before AC was applied to them.

Answer 3
Again, I am not sure, as I said earlier, my 866s were not under much load, and didn't have much filtering.
Hope I helped a little.

::Hi all,
::
::I know it it good to delay the b+ to mercury tubes
::Q1: does it have to be delayed?
::Q2: Would edison delay relay tubes work? I have 4, 2 with 6.3 volt (heater) 60 sec delay contacts:150vdc 250ac 3A, and 2 117v (heater) 75 sec, contact:150vdc/250vac 3A
::these will be switching 375vac
::Q3 Mercury tubes cant handle large input capacitors, If I place a large (10hny) choke from the filament to a 40mfd cap can the tube handle that?
::
::This is going to an audio amp, not a transmitter.
::
::Thanks for any help,
::Ian
:
:
:Answer 1
:The mercury needs to be vaporized before applying the
:high Voltage.
Q:1.1 Ive done some tests with a tube tester, filament and b+ turned on at same time, and i did not get any arcing.
:
:Answer 2
:Now, I don't know, the only 866s I was around were in a factory built RCA broadcast transmitter,where they were bias rectifiers, and all the mercury tubes had a 60 second time delay before AC was applied to them.
Q:2.1
I was mainly concerned about the ratings of the relays. they say 250vac and I will be applying 375vac. I have some that are 450v but have 27.5 150sec heaters
:
:Answer 3
:Again, I am not sure, as I said earlier, my 866s were not under much load, and didn't have much filtering.
Q:3.3 The data sheet says max input filter is 4.1 mf, and min input choke is 2.1hny. I think that if there is a choke first, the caps can be any value because the datasheet says nothing about it?
:Hope I helped a little.
:Lewis
:
:
:
:

Good Grief, what are you building? If you are using a pair of 866's to rectify 350 volts, why not use a 555 timer and a relay to delay the center tap of the B+ winding to the ground? Plenty of info on the net about this That's how I do it to allow filaments to warm up in tube amps using silicon diodes. I have enough to atone for, lest I add cathode stripping.

Or are you building a space heater. Winter is coming.

:Hi all,
:
:I know it it good to delay the b+ to mercury tubes
:Q1: does it have to be delayed?
:Q2: Would edison delay relay tubes work? I have 4, 2 with 6.3 volt (heater) 60 sec delay contacts:150vdc 250ac 3A, and 2 117v (heater) 75 sec, contact:150vdc/250vac 3A
:these will be switching 375vac
:Q3 Mercury tubes cant handle large input capacitors, If I place a large (10hny) choke from the filament to a 40mfd cap can the tube handle that?
:
:This is going to an audio amp, not a transmitter.
:
:Thanks for any help,
:Ian
:

First off they are not 866's , they are 866JR (no cap). Essentially they are 1/2 a 5u4 (2.5U2?)Im using them in a later project, eventually, what I am currently trying to do is replace a 5u4 for the reasons: Because I can, and they glow.

I never thought of the center tap thing. It is zero volts right? Can I use the relay tubes for this?

DO I REALLY HAVE TO PREHEAT THEM?!?!? They start just fine in the tester.

Ian

:Good Grief, what are you building? If you are using a pair of 866's to rectify 350 volts, why not use a 555 timer and a relay to delay the center tap of the B+ winding to the ground? Plenty of info on the net about this That's how I do it to allow filaments to warm up in tube amps using silicon diodes. I have enough to atone for, lest I add cathode stripping.
:
:Or are you building a space heater. Winter is coming.
:
::Hi all,
::
::I know it it good to delay the b+ to mercury tubes
::Q1: does it have to be delayed?
::Q2: Would edison delay relay tubes work? I have 4, 2 with 6.3 volt (heater) 60 sec delay contacts:150vdc 250ac 3A, and 2 117v (heater) 75 sec, contact:150vdc/250vac 3A
::these will be switching 375vac
::Q3 Mercury tubes cant handle large input capacitors, If I place a large (10hny) choke from the filament to a 40mfd cap can the tube handle that?
::
::This is going to an audio amp, not a transmitter.
::
::Thanks for any help,
::Ian
::
:

In a tester they are not subjected to the same current. Your amplifier probably draws more current to begin with, and having to charge the filter caps adds strain.

If the B supply and A supply are fed from separate transformers, the delay relay tube with 150VAC contacts should work fine. Use this to switch the primary of the B transformer. This way the points will be handling 120VAC RMS.

The rectifier filament supply must not be part of the B supply, as you want the filament to be warm before you energize the B circuit. Best to use a 6.3/5.0 volt filament transformer with separate windings and adequate current supply. Use this to also power the heater of the delay relay tube if its heater requires 6.3 volts.

T.