Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 66Strat on March 06, 2020, 01:14:00 pm

Title: Toggle Switch for PT secondaries
Post by: 66Strat on March 06, 2020, 01:14:00 pm: I have a power transformer with 275-0-275 and 325-0-325 secondaries. I want to place a switch between the transformer secondaries and the rectifier. I would prefer an On-On (break before make) switch but an On-Off-On switch would suffice. Will the Lamb ST switch that Doug in his catalog work?
Title: Re: Toggle Switch for PT secondaries
Post by: sluckey on March 06, 2020, 01:21:15 pm: Yes, it will work just fine. I'd rather have a DPDT ON-OFF-ON. Center would be standby.
Title: Re: Toggle Switch for PT secondaries
Post by: 66Strat on March 06, 2020, 01:25:51 pm: Thank you! :thumbsup: Is Doug's switch a 3 position switch?
Title: Re: Toggle Switch for PT secondaries
Post by: sluckey on March 06, 2020, 01:29:37 pm: Quote from: 66Strat on March 06, 2020, 01:25:51 pm
Thank you! :thumbsup: Is Doug's switch a 3 position switch?
Doesn't so it is so I would assume NO. A pm to Doug would confirm.
Title: Re: Toggle Switch for PT secondaries
Post by: pdf64 on March 06, 2020, 01:39:29 pm: If using a tube rectifier, that would be a ‘less than ideal’ method of arranging standby (as it’s hot switching).
Title: Re: Toggle Switch for PT secondaries
Post by: sluckey on March 06, 2020, 01:59:33 pm: Quote from: pdf64 on March 06, 2020, 01:39:29 pm
If using a tube rectifier, that would be a ‘less than ideal’ method of arranging standby (as it’s hot switching).
I disagree.
Title: Re: Toggle Switch for PT secondaries
Post by: 66Strat on March 06, 2020, 02:06:27 pm: Quote from: sluckey on March 06, 2020, 01:29:37 pm
Quote from: 66Strat on March 06, 2020, 01:25:51 pm
Thank you! :thumbsup: Is Doug's switch a 3 position switch?
Doesn't so it is so I would assume NO. A pm to Doug would confirm.

Thanks. PM sent.

Quote from: pdf64 on March 06, 2020, 01:39:29 pm
If using a tube rectifier, that would be a ‘less than ideal’ method of arranging standby (as it’s hot switching).

I agree that hot switching is not a good thing with tube rectifiers. But I don't know if it makes that much difference if the AC is switched going into the rectifier or the DC coming out. IME, if the filter caps have enough time to drain, it would stress the rectifier in either situation, if the tubes are still hot. My goal is to switch between two AC voltages.
Title: Re: Toggle Switch for PT secondaries
Post by: pdf64 on March 07, 2020, 10:35:04 am: Quote from: 66Strat on March 06, 2020, 02:06:27 pm
...I don't know if it makes that much difference if the AC is switched going into the rectifier or the DC coming out. IME, if the filter caps have enough time to drain, it would stress the rectifier in either situation, if the tubes are still hot. My goal is to switch between two AC voltages.
I don't think it makes any difference whether the switch is on the plate or cathode side of the rectifier, the exact same current is being switched, hot switching a discharged reservoir cap will result in high peak surge currents through the rectifier either way.
To switch between the 2 HT winding voltages, I suggest it's best to do so when the amp is off.

Quote from: sluckey on March 06, 2020, 01:59:33 pm
Quote from: pdf64 on March 06, 2020, 01:39:29 pm
If using a tube rectifier, that would be a ‘less than ideal’ method of arranging standby (as it’s hot switching).
I disagree.
I'd appreciate it if could you expand on that :w2: