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Old 18th October 2007, 12:34 AM   #1
dre7 is offline dre7  United States
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Default Standby Switch

I seem to recall somewhere seeing a way of setting up your filament and HT standby switch so that it's basically impossible to get the sequencing wrong...I have searched but can't find it! Could someone post a link, please?

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Old 18th October 2007, 01:02 AM   #2
kmtang is offline kmtang  Canada
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The filament supply should be connect to the mains switch. Once the mains is on, the filament will be ON. The HT standby switch should be between the CT of the HT's secondary winding and ground.

Simple, right? The worst case is that you switch on the mains (with filament) and the HT at the same time.

In case you want to avoid such kind of issue, you should employ a delay timer in the HT standy circuit.

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Old 18th October 2007, 01:26 AM   #3
kevinkr is offline kevinkr  United States
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There is another circuit that requires two switches to be flipped, but the order does not matter, filaments always come on first.

Get two dpst or spdt switches wire one set of contacts in parallel - these go to the filament transformer. Wire the other set of contacts in series - these go to the plate transformer or alternately the B+ center tap on your secondary.

This incidentally works fine as a standby switch as well, just flip either one to off.

It's even cooler if the rectifier tube filament is fed from a winding on the plate transformer..
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 18th October 2007, 05:01 AM   #4
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I use an Amperex delay tube (10 seconds). When triggered by switching on, the filaments are heated for 10 seconds. When the Amperex switches, it triggers an Omron relay, which simultaneously switches on the B+, while switching off the Amperex (preserving its lifespan).

This seems pretty foolproof and is further refined by using a Belkin power conditioner which switches on my power-amp (solid-state) after 15 seconds ie. five seonds after B+ comes on in my preamp. I can send you the wiring diagram for the Amperex / relay system.

In spite of the hum problems with my preamp, I can safely sleep knowing that at least the switch-on sequence is foolproof, even if the preamp ground wiring isn't

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Old 18th October 2007, 05:58 AM   #5
first is offline first  China
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some one told me

If you live 110 voltage Country purchase Transformers with 110v and 220v AC input.

110v for normal listening mode
220v half power for standby mode
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Old 18th October 2007, 08:07 AM   #6
dre7 is offline dre7  United States
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Thanks, that's the one I was thinking of. Pretty elegant. I see how it works with DPST, just can't wrap my head around how you'd do it with the SPDT switches.

The 300b amp on your web page is really nice looking. Is that chassis 260 brass? What thickness sheet did you use?

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Old 18th October 2007, 08:07 AM   #7
dre7 is offline dre7  United States
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Oops, I see now it's copper!
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