Variac after cap upgrade

Kevin McCready · 20th November 2002, 05:26 PM

I wonder if anyone can tell me if I should bring my Bryston 4B to life, after a power supply cap upgrade, with a variac. I know it is suggested for tube amps but is it a good idea with solid state. I have heard the arguments for using the variac as allowing the caps to form to the applied voltage slowly when exposed to voltage for the first time. Also how fast should I ramp up the voltage on turn on? Kevin McCready

Nelson Pass · 20th November 2002, 06:58 PM

Variacs are some of the best spent mony in audio.

Highly recommended for initial fire-up, and be certain to
monitor the current when you do it.

Kevin McCready · 20th November 2002, 09:07 PM

Thanks for the response Nelson. The best thing about this variac is that it was free. I spotted it in the trash where I was formerly employed.I do have a question about how long I should spend on the turn-on voltage ramp time. There are some guitar amp rebuilders who suggest that you increase the voltage in increments of 10 volts per hour. This seems excesive because I am sure the cap will charge to 95-99% of applied voltage in 5 time constants.I am also conserned about the amp not liking low voltage for an extended amount of time, similar to a brown out. I am thinking 2-3 minutes would be fine. I may be wrong. Kevin McCready

MRehorst · 20th November 2002, 09:39 PM

If you put new caps in the amp, you don't need to worry about ramping up the voltage. If you put old caps in, then ...

MR

Kevin McCready · 20th November 2002, 09:50 PM

Say What? Did you have a stroke in mid sentence? Hello are you still with us?

Jocko Homo · 21st November 2002, 05:07 AM

If you have a variac, then by all means use it. If not, they are a good investment if you do a lot of work.

Jocko

20th November 2002, 05:26 PM	#1
Kevin McCready diyAudio Member Join Date: Sep 2002 Location: Cleveland,Ohio	Variac after cap upgrade I wonder if anyone can tell me if I should bring my Bryston 4B to life, after a power supply cap upgrade, with a variac. I know it is suggested for tube amps but is it a good idea with solid state. I have heard the arguments for using the variac as allowing the caps to form to the applied voltage slowly when exposed to voltage for the first time. Also how fast should I ramp up the voltage on turn on? Kevin McCready

20th November 2002, 09:07 PM	#3
Kevin McCready diyAudio Member Join Date: Sep 2002 Location: Cleveland,Ohio	Variac Thanks for the response Nelson. The best thing about this variac is that it was free. I spotted it in the trash where I was formerly employed.I do have a question about how long I should spend on the turn-on voltage ramp time. There are some guitar amp rebuilders who suggest that you increase the voltage in increments of 10 volts per hour. This seems excesive because I am sure the cap will charge to 95-99% of applied voltage in 5 time constants.I am also conserned about the amp not liking low voltage for an extended amount of time, similar to a brown out. I am thinking 2-3 minutes would be fine. I may be wrong. Kevin McCready

20th November 2002, 09:50 PM	#5
Kevin McCready diyAudio Member Join Date: Sep 2002 Location: Cleveland,Ohio	come again Say What? Did you have a stroke in mid sentence? Hello are you still with us?

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20th November 2002, 06:58 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Variacs are some of the best spent mony in audio. Highly recommended for initial fire-up, and be certain to monitor the current when you do it.

20th November 2002, 09:39 PM	#4
MRehorst diyAudio Member Join Date: May 2002	If you put new caps in the amp, you don't need to worry about ramping up the voltage. If you put old caps in, then ... MR

21st November 2002, 05:07 AM	#6
Jocko Homo Banned Join Date: Feb 2002 Location: As far from the NOSsers as possible	If you have a variac, then by all means use it. If not, they are a good investment if you do a lot of work. Jocko

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