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RE: New Build- 1625 SE Triode Strapped - Misty

137.200.1.109

Mr_Steady

A

In Reply to: RE: New Build- 1625 SE Triode Strapped - Misty posted by rcollege on May 02, 2017 at 12:33:42

Kudos. A very nice build.
I've never seen anybody use a relay tube. I take it allows the heaters to warm up first before the HV hits? Cool. I wonder if that would work well for DHT direct coupled amps?
Man you're right, those anode caps aren't going anywhere! :)

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Big speakers and little amps blew my mind!

Edits: 05/02/17

Follow Ups:

RE: Delay relay Tubes - gusser 13:44:27 05/02/17 (6)
Yes, they do work well and a perfect complement to a vintage design.

Can be a bit hard to find though.
- Thank you gusser (NT) - Mr_Steady 16:30:43 05/02/17 (5)
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  Big speakers and little amps blew my mind!
  - RE: Thank you gusser (NT) - rcollege 17:16:44 05/02/17 (4)
    Thanks Mr Steady,
    
    They work well, easy to wire and look nice. I was lucky to run into a couple. I've also seen some on sale at tube suppliers...the main manufacturer is Amperite.
    
    They come in different heater voltages...the one I'm using here is 115V heater.
    
    Normality frightens me- its what they use to lure you into the cookie cutter.
    Roger
    - Delay Relays - Triode_Kingdom 21:14:51 05/02/17 (3)
      One potential issue with delay relays has to do with the relatively small contacts. For longest life, it's a good idea to use a larger relay to turn on the HV transformer. I'm getting ready to add delays to my own SETs, and have decided to go even a step further. The delay relay will power a main relay, and that one will be wired so it latches electrically. In addition, one set of contacts will be wired to disconnect the delay relay. So, once the amplifier is fully operational, the delay relay will power down and cool off. Not only will its contacts only need to pass a few mA to activate the HV, its heater will only be used for a minute or so each time the amplifier is turned on.
      
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      Buy Chinese. Bury freedom.
      - Re: Disconnecting Relay sound like over-kill - Johno 03:24:55 05/03/17 (2)
        
        In Reply to: RE: Delay Relays posted by Triode_Kingdom on May 02, 2017 at 21:14:51
        
        You said
        "One potential issue with delay relays has to do with the relatively small contacts"
        
        Correct that also includes SS time delay relays.
        
        You said
        "The delay relay will power a main relay, and that one will be wired so it latches electrically. In addition, one set of contacts will be wired to disconnect the delay relay. So, once the amplifier is fully operational, the delay relay will power down and cool off. Not only will its contacts only need to pass a few mA to activate the HV, its heater will only be used for a minute or so each time the amplifier is turned on"
        
        The disconnection of the delay relay is simply overkill I've run a similar scenario using 24V/30A relay activated from SS delay mains relay / timer for 10 yrs without fault. You can safely derate the DC current rating by 50% into a inductive load ie transformer and still be well under the DC rating. Relay coil DCR for 12-24V are under 1k ohm so the current requirement are small. But install a diode - reverse biased across relay coil to absorb back EMF on turn on / off. Seriously this configuration has been used in cross bar / step by step electro-mechanical telco exchanges for generations....bullet proof.
        
        Johno
        
        Re: Disconnecting Relay sound like over-kill - Tom Bavis 07:35:06 05/03/17 (1)
        
        In Reply to: Re: Disconnecting Relay sound like over-kill posted by Johno on May 03, 2017 at 03:24:55
        
        Disconnecting the relay heater after it closes has the additional advantage of resetting the timer. This means that the timing cycle will occur on a brief power interruption as well as cold turn-on.
        
        Re: Disconnecting Relay sound like over-kill - Triode_Kingdom 08:32:06 05/03/17 (0)
        
        In Reply to: Re: Disconnecting Relay sound like over-kill posted by Tom Bavis on May 03, 2017 at 07:35:06
        
        "...the timing cycle will occur on a brief power interruption as well as cold turn-on."
        
        Exactly right. The main relay will drop out instantly in the event of a power failure, then the delay relay cycles again. This is necessary in order to be sure the DHT filaments are always at full temperature when HV is applied.
        
        About Johno's comments, none of the glass delay relays in my stash have contacts rated anywhere near 30A. Most are probably 3A, and that's probably a non-inductive rating, perhaps DC. I've also noticed costs rising for these parts, and I wonder if replacements will be easy to find in 10 or 20 years. Call it overkill if you want, but all things considered, I don't regret taking the necessary steps to see that these last as long as possible.
        
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        Buy Chinese. Bury freedom.

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