Rectifier with slow start up?

Original Burnedfingers · 29th June 2008, 11:48 PM

Is there any way to easily make a rectifier that would be like a Copper Cap but have a longer delay before reaching full B+?
The Copper Cap has a 1 sec delay I believe.

Tweeker · 30th June 2008, 03:21 AM

Damper diodes give some of the slowest warm up times, and are among the lowest resistance vacuum diodes. Warm up one the order of 15 seconds. Filament supply for them may be an issue.

To emulate copper cap youd probably get close with a pair of diodes, a thermistor and a resistor.

ray_moth · 30th June 2008, 08:58 AM

Dampers vary. I like the 6D22S from Svetlana, which has about 25 secs warm-up time. It's no problem feeding its 6.3v heater, which is very well insulated from the cathode, hence the slow warm-up. It can tolerate 600v between heater and cathode, which means it can share the heater circuit of the other tubes.

kevinkr · 30th June 2008, 04:32 PM

Surprised that no one has mentioned the venerable 5AR4/GZ34, currently available from at least 3 sources this tube has relatively long warm up times of up to 30 seconds or so.. Vf is typically 25V or less compared to some of the better dampers at 15V - 20V.

Original Burnedfingers · 30th June 2008, 09:17 PM

Quote:

Surprised that no one has mentioned the venerable 5AR4/GZ34, currently available from at least 3 sources this tube has relatively long warm up times of up to 30 seconds or so.. Vf is typically 25V or less compared to some of the better dampers at 15V -

The 5AR4/GZ34 is what I am trying to replace.

kevinkr · 30th June 2008, 09:37 PM

Quote:

Originally posted by burnedfingers

The 5AR4/GZ34 is what I am trying to replace.

Hi burnedfingers,
Any particular reason why you want to move away from the 5AR4? Might give us some sense of what you want to accomplish by so doing, and hence we could fine tune our recommendations, or provide possible reasons for reconsidering the decision..

Original Burnedfingers · 30th June 2008, 11:48 PM

Sure, it probably would help if I did give my reason for wanting something else. I just finished putting in my 3rd 5AR4 in my modified Dynaco stereo 70 amplifier. It toasted 2 in less than 6 months.

The power supply board is a SDS and has a first capacitor value of 40mfd. Well within the limit for this rectifier.

THe heater draw is 2.4A per side as I am running 6BG6GA's for output tubes. I am running 1) 6SJ7 and 1) 6SL7 per channel for the front end.

The 6GA6's are biased at 50mA per tube.

I shouldn't be going thru rectifier tubes this fast. Thus the reason I would like to come up with something that will give me a slow start up for the B+ and a life longer than what I have experienced so far.

You would think this combination would be easier on things since the current draw for a channel (stock) is 3.45A.

audiowize · 1st July 2008, 12:20 AM

Have you tried adding and inrush limiter?

nodiak · 1st July 2008, 12:21 AM

Which 5AR4's? Some such problems with JJ's and Sovteks have been mentioned.

Original Burnedfingers · 1st July 2008, 12:28 AM

I haven't tried an inrush limiter. I didn't think I needed one because of the fact the tube has a slow warm up. At this point I am ready to try about anything except for a high dollar Mullard.

I have had both the Sovtek and the JJ in the amp. The last tube was a JJ.

I am thinking about putting diodes before the 5AR4 in hopes of making it last longer.

I'm up for about anything

29th June 2008, 11:48 PM	#1
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Rectifier with slow start up? Is there any way to easily make a rectifier that would be like a Copper Cap but have a longer delay before reaching full B+? The Copper Cap has a 1 sec delay I believe.

30th June 2008, 03:21 AM	#2
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Damper diodes give some of the slowest warm up times, and are among the lowest resistance vacuum diodes. Warm up one the order of 15 seconds. Filament supply for them may be an issue. To emulate copper cap youd probably get close with a pair of diodes, a thermistor and a resistor. __________________ Be sure your foil hat has a good low impedance ground.

30th June 2008, 04:32 PM	#4
kevinkr diyAudio Moderator Join Date: Sep 2004 Location: Boston, Massachusetts Blog Entries: 6	Surprised that no one has mentioned the venerable 5AR4/GZ34, currently available from at least 3 sources this tube has relatively long warm up times of up to 30 seconds or so.. Vf is typically 25V or less compared to some of the better dampers at 15V - 20V. __________________ www.kta-hifi.net

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30th June 2008, 08:58 AM	#3
ray_moth diyAudio Moderator Emeritus Join Date: Jan 2004 Location: Jakarta	Dampers vary. I like the 6D22S from Svetlana, which has about 25 secs warm-up time. It's no problem feeding its 6.3v heater, which is very well insulated from the cathode, hence the slow warm-up. It can tolerate 600v between heater and cathode, which means it can share the heater circuit of the other tubes.

30th June 2008, 11:48 PM	#7
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Sure, it probably would help if I did give my reason for wanting something else. I just finished putting in my 3rd 5AR4 in my modified Dynaco stereo 70 amplifier. It toasted 2 in less than 6 months. The power supply board is a SDS and has a first capacitor value of 40mfd. Well within the limit for this rectifier. THe heater draw is 2.4A per side as I am running 6BG6GA's for output tubes. I am running 1) 6SJ7 and 1) 6SL7 per channel for the front end. The 6GA6's are biased at 50mA per tube. I shouldn't be going thru rectifier tubes this fast. Thus the reason I would like to come up with something that will give me a slow start up for the B+ and a life longer than what I have experienced so far. You would think this combination would be easier on things since the current draw for a channel (stock) is 3.45A.

1st July 2008, 12:20 AM	#8
audiowize diyAudio Member Join Date: Aug 2005	Have you tried adding and inrush limiter?

1st July 2008, 12:21 AM	#9
nodiak diyAudio Member Join Date: Nov 2004 Location: really northern cal. coast	Which 5AR4's? Some such problems with JJ's and Sovteks have been mentioned.

1st July 2008, 12:28 AM	#10
Original Burnedfingers diyAudio Member Join Date: Nov 2002	I haven't tried an inrush limiter. I didn't think I needed one because of the fact the tube has a slow warm up. At this point I am ready to try about anything except for a high dollar Mullard. I have had both the Sovtek and the JJ in the amp. The last tube was a JJ. I am thinking about putting diodes before the 5AR4 in hopes of making it last longer. I'm up for about anything

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