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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    GZ34 Soft Start Synchronizer

    t8ter
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    t8ter


    Posts : 11
    Join date : 2010-01-03
    Location : Calgary, Alberta
    • Post n°1

    GZ34 Soft Start Synchronizer Empty GZ34 Soft Start Synchronizer

    Post by t8ter Mon Feb 06, 2012 12:10 am


    Hi all, I recently came across a product on ebay that I was wondering if anyone had used.

    Welcome to SIGTOMICS!
    This item is used with a tube rectifier to delay application of B+ in the amplifier or radio. It does this through a timing circuit, delaying turn-on for an additional 15-30 seconds beyond the tubes normal characteristics. For a typical 5U4 that amounts to 20-30 seconds or a 5AR4/GZ34 about 30-45 seconds before the tube begins applying high voltage.
    Based on a DYNACO Mark III with 6550 tubes, the tubes are warmed up enough to prevent the spike in high voltage and it settles down safely under the rating of the filter capacitor, not shooting up to 600 Volts, well beyond the Mark III's capacitor rating of 525 Volts. This item should be a welcome addition where tube are used
    In addition, 1000Volt PIV silicon protection diodes are built in, providing a measure of safety to the rectifier tube and amplifier circuit.
    Use this synchronizer to prevent any likelihood of amplifier tube cathode stripping. Because the output tubes are functioning normally and the voltage is at operating level, no inadvertent damage should occur.
    This add-on will increase the overall height of the rectifier tube installation by one inch. Please check your cage clearance or space above (below) to ensure there is room available.
    Flat rate shipping, No additional shipping charges beyond the quantity one order
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°2

    GZ34 Soft Start Synchronizer Empty Re: GZ34 Soft Start Synchronizer

    Post by Bob Latino Mon Feb 06, 2012 6:14 am

    If you use a tube rectifier you don't really need any delay device. The tube rectifier itself is a "delay device". A GZ34 has an indirectly heated filament that takes time to warm up to the point where the GZ34 will allow current flow. A 5U4 is directly heated but still takes a few seconds before it will completely warm up. You only really need a delay device (IMHO) if you use a solid state rectifier.

    Bob
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    t8ter
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    t8ter


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    • Post n°3

    GZ34 Soft Start Synchronizer Empty Re: GZ34 Soft Start Synchronizer

    Post by t8ter Mon Feb 06, 2012 10:13 pm

    Thanks Bob, Kind of what I thought from reading yours and everyone else's thoughts about rectifiers. You had said in the past and few times that a tube rectifier like a GZ34 had a slow enough warm up time to allow power tubes to warm up.Only the SS rectifier (Weber copper cap type), although they do emulate a tube rectifier but allow a 1-2 second warm up before the in rush of power. And I think,if I read correctly a tube is 7-9 seconds. Please feel free to correct me if my understanding is incorrect.
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    Bob Latino
    Bob Latino
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    • Post n°4

    GZ34 Soft Start Synchronizer Empty Re: GZ34 Soft Start Synchronizer

    Post by Bob Latino Mon Feb 06, 2012 10:37 pm

    The Weber WZ68 and WZ34 take maybe 3 to 4 second before full high voltage is applied. The 3 to 4 seconds on the Weber rectifiers has proven (at least to me) to be enough of a delay to not cause a problem. A GZ34 tube rectifier with an indirectly heated filament is more like 15 to 20 seconds before the high voltage comes up completely. I have said this before on other posts - Dynaco themselves used solid state rectifiers on their own SCA-35 and ST-35 amps. These two amps had NO delay and there are thousands of these amps still out there working fine which leads me to believe that the "danger" of using a solid state rectifier with no delay may be overstated.

    If you want to use a solid state rectifier in your Dynaco amp and the thought of no delay is a concern of yours, then contact Roy or myself and pick up a VTA TDR (Time Delay Relay)($35 + $5 shipping). The TDR will give a 17 second delay before high voltage is applied. It is also a great protector of amps in the case of power failures or a quick ON/OFF/ON situation which can take out a rectifier. If the power is interrupted even for a fraction of a second then the TDR resets itself for another 17 second delay sequence. Below is a TDR installed into an ST-70. The TDR replaces lugs 5, 6 and 7 on the 7 lug terminal strip on a stock ST-70 OR it replaces the three lug terminal strip completely on a VTA amp kit.

    Bob

    GZ34 Soft Start Synchronizer VTA-TDBinstalledcropped


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    burnedfingers
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    burnedfingers


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    • Post n°5

    GZ34 Soft Start Synchronizer Empty Re: GZ34 Soft Start Synchronizer

    Post by burnedfingers Fri Feb 17, 2012 8:09 am

    There has been a lot of discussion on the other audio tube boards concerning delayed B+ turn on,

    First, there will be no cathode stripping at the voltages we are concerned with on the Dynaco products.

    Secondly, a hell of a lot of amps were produced NOT using a 5AR4 rectifier tube but just a straight 5U4. A classic example

    of this is in a common Wurlitzer 6420 mono block produced in the 40's. I have 4) of them with original tubes and guess

    what? They still work and work fine. Put a CL60, or CL70 in series with the filament voltage and the rectifier tube will


    slow start and it won't cost $40 to do it.
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    GP49
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    GP49


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    GZ34 Soft Start Synchronizer Empty Re: GZ34 Soft Start Synchronizer

    Post by GP49 Fri Feb 17, 2012 1:27 pm

    burnedfingers wrote:There has been a lot of discussion on the other audio tube boards concerning delayed B+ turn on,

    First, there will be no cathode stripping at the voltages we are concerned with on the Dynaco products.

    Secondly, a hell of a lot of amps were produced NOT using a 5AR4 rectifier tube but just a straight 5U4. A classic example
    of this is in a common Wurlitzer 6420 mono block produced in the 40's. I have 4) of them with original tubes and guess
    what? They still work and work fine.

    Another example, of direct interest on this board: the Dynaco Mark II, a pair of which (highly modified) are my daily-driver amplifier
    with exemplary tube life. They have had the same original Mullard EL34s in them for fifteen years.

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