Merlin's Standby

[Tage]

I want to inquire about a Standby method described in Merlins power supply book. It's the method were a high value resistor, 100k-470k, is placed across the standby switch. I was wondering if anyone has used this method on a high powered amp, say 100+ watts.

Does this method work? what are some of the draw backs? a customer asked to have a standby function on a current build, I don't usualy use them at all, but this seemed like a decent compromise.

Thanks for the feed back.
Tage

[tubeswell]

I've done this with a couple of amps and it works fine (I used 1W 150k in both instances). Its not a standby switch anymore though. Its more like a 'soft start' switch.

[Tage]

Yeah that's exactly my intention, just to let the bias get up and have things a little warm, although the amp will be running around 600 volts, so I think I'll keep the value low and use a very over rated resistor, ie 10Watt

[Gaz]

I've used 220k/2W in a 100W with good success. I used that value because it's also what I was using for balancing resistors across the series reservoir caps. It mutes the sound completely (even though a little voltage is leaking through), and is properly overrated. Only thing is it makes a really cute creaking/alien sound when it powers down. Might freak out a customer a little, but then again, it's better some of the scary sounds you hear when turn off a 'traditional' standby

[Tage]

Ok that's also encouraging. I've rarely used stand by's on amps other than maybe to mute things, and that is all this will be for as far as the customer is concerned. I'll tell him that the Magic smoke will come out of the amp if the standby is not used and things should be all good.

[trobbins]

I've used the standby switch bleed resistor on 3x 100W'ish amp restorations, where the heaters are on, and the standby powers the B+. My intent was to reduce the stress on the power path when switching over to ON, and partly precharge any signal caps. Often I'm space limited, as the resistor is positioned on the switch, so the resistor is a 2W PRO2 for a design worstcase dissipation of about 0.5W. The resistor needs to be voltage rated for the job, as it may have more than 250-350VAC on it if you aren't using a doubler.

I guess you could also use it as a form of protection - if the B+ doesn't rise to a certain voltage level via the bleed resistor then use an interlock relay to keep the secondary HT OFF.