Can someone suggest a simple B+ delay circuit for tube power amp with full-wave diode-rectified B+ around 450VDC?
I found some circuits for solid-state amps, none for tube amps -- except many references to why tube rectifiers are superior, etc.
The idea would be... Turn power switch on, heater supply turns on immediately, ten seconds later the B+ gets switched on.
Thanks.
I found some circuits for solid-state amps, none for tube amps -- except many references to why tube rectifiers are superior, etc.
The idea would be... Turn power switch on, heater supply turns on immediately, ten seconds later the B+ gets switched on.
Thanks.
I prefer to have separate power and plate supply switches. This is simplest.
Then you can also put the amplifier to stand-by mode.
Then you can also put the amplifier to stand-by mode.
Just for fun link:
http://www.diyaudio.com/forums/tubes-valves/126239-b-time-delay-circuit-your-comments.html
Regards
M. Gregg
what about making a 555 circuit that has a low output at turn on and a hi output after say 30 seconds. the output can be to a transistor that activates a relay. if theres enough current available you could rectify the heater supply.
I think what you're looking for can be found here: tubes4hifi amplifier KITs page I don't own one, but it looks like a simple 555 and relay based circuit that will meet your requirements.
There' no harm in putting in delay or standby switch arrangements (except for more possible points of failure), but they're really not necessary with 'low voltage' tube circuits (B+ V<750v).
Kevin O'Connor at LondonPower has commented on this, others also.
But more switches and lights are always fun!
Kevin O'Connor at LondonPower has commented on this, others also.
But more switches and lights are always fun!
Hi
That's right! Indirectly heated tube rectifiers, especially TV dampers as those mentioned are the easiest and most convenient way to get a delayed B+ and gentle rise of the voltage. And sounds better too 😉
Thomas
That's right! Indirectly heated tube rectifiers, especially TV dampers as those mentioned are the easiest and most convenient way to get a delayed B+ and gentle rise of the voltage. And sounds better too 😉
Thomas
There is a mod to the RC delay circuits some of you may want to consider. If you wish to have a shorter discharge time so that the circuit restarts the delay during power drop-outs (not brown-outs), place a reverse biased diode (of the proper voltage rating) in series with a resistor. Place this in parallel with the charge resistor (R23 in the case of bigpandahk's design). Set the new resistor value to control the discharge time in the event that power drops low long enough to be concerned but not so short that momentary dropouts (half cycle etc) cause resets.
If you want to use an amperite delay.......
Check out post #36 of this thread:
http://www.diyaudio.com/forums/tubes-valves/161702-opus-5-0-modern-mullard.html
Check out post #36 of this thread:
http://www.diyaudio.com/forums/tubes-valves/161702-opus-5-0-modern-mullard.html
I've thought about such a B+ delay circuit for some time.
My present thinking is about using a tube rectifier with an indirectly heated cathode for the delay.
A relay with a d.c. coil (and series resistor) between the cathode of the rectifier and common ground would pull when the rectifier tube conducts.
Contacts on the relay would bypass the tube rectifier with the appropriate solid state diodes.
A small electrolytic capacitor across the relay coil would prevent relay chatter.
My present thinking is about using a tube rectifier with an indirectly heated cathode for the delay.
A relay with a d.c. coil (and series resistor) between the cathode of the rectifier and common ground would pull when the rectifier tube conducts.
Contacts on the relay would bypass the tube rectifier with the appropriate solid state diodes.
A small electrolytic capacitor across the relay coil would prevent relay chatter.
The most chicken Sh*t way of a slow on for a diode bridged b+ supply is to put a damper diode tube in series between the first and second cap in the B+. I use a cap stack to take the higher B+ until the amp comes on line. The voltage to the amp has the delayed B+ rise, about 20 seconds as the damper tube starts to conduct. The voltage on the amp rises to 440V DC without the 500V spike settling down to the 440V. That is a little easier on the caps on the PCB.
6CG3's are still cheap and need the 12pin compactron socket.. I only loose 10V in the supply voltage at 225ma current. The cathode to heater voltage is over 700V, 6.3 volt heater, what else is there to want?? Oh and it sounds great!!
6CG3's are still cheap and need the 12pin compactron socket.. I only loose 10V in the supply voltage at 225ma current. The cathode to heater voltage is over 700V, 6.3 volt heater, what else is there to want?? Oh and it sounds great!!
This is my idea. Since the tube rectifier is only powering the relay coil, a 6X4 can provide more than enough current.
A nice mains cycle counter based timer... You can adapt it to run
off 6.3V, instead of directly from the mains in the original schematic.
The timing chart is based on 50Hz. For 60Hz, the timing increments will be in 4.25 seconds instead of 5.1
off 6.3V, instead of directly from the mains in the original schematic.
The timing chart is based on 50Hz. For 60Hz, the timing increments will be in 4.25 seconds instead of 5.1
An externally hosted image should be here but it was not working when we last tested it.
Or why not use a good old AMPERITE Thermal Delay Relay ? They are still available,very reliable and give a nice "vintage touch" to your project. (most looks like an electron tube and can be socketed). Probably the simplest and most effective way. (one part count, just compare to the schematic posted above)
Amperite Thermal Delay Relays at RF Parts Company
Slow warm-up big color TV damper diodes (6CL3,6CK3,6CM3,6DW4, etc...) are very robust and dirt cheap but are not available in dual plate (full wave) versions and you'll need a pair for full wave rectification. For safety reasons, better to avoid the versions with Cathode caps.
Amperite Thermal Delay Relays at RF Parts Company
Slow warm-up big color TV damper diodes (6CL3,6CK3,6CM3,6DW4, etc...) are very robust and dirt cheap but are not available in dual plate (full wave) versions and you'll need a pair for full wave rectification. For safety reasons, better to avoid the versions with Cathode caps.
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It is a stabilized voltage regulator that waits for tubes to warm up and start draw current, then it increases speed of smooth raise of output voltage.
There are a number of circuits available ready-built and cheap enough to where it doesn't make sense to reinvent the wheel.
However, if you choose a relay-based unit, you generally can't put it in the B+ line because the relay isn't rated for high voltage DC. You must be able to put it in the primary.
I've used the Rubli board and it works fine, no mechanical relay, works at high voltage DC and is a 2-wire connection with almost zero disruption/modification of an existing amp.
However, if you choose a relay-based unit, you generally can't put it in the B+ line because the relay isn't rated for high voltage DC. You must be able to put it in the primary.
I've used the Rubli board and it works fine, no mechanical relay, works at high voltage DC and is a 2-wire connection with almost zero disruption/modification of an existing amp.
The problem with relay is, it switch on abruptly. Since coupling capacitors are discharged it causes large current impulse through output tubes and transformers. It is real danger, unlike questionable belief about harm to cathodes when B+ is applied when cathodes are cold.