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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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    too much of a good thing?

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    • Post n°1

    too much of a good thing? Empty too much of a good thing?

    Post by Guest Thu Jan 28, 2016 2:44 pm

    Would there be any advantage of using a time delay board after a thermistor in the St-35? I use a thermistor now at turn-on and then switch it out after a few minutes of warm-up with a make- before- break thingy I rigged up. With the multimeter hooked up to the bias pots, it's kinda' cool to see the voltage being delayed for a bit and then gradually increase. But I wonder if a delay board would also be beneficial, since the thermistor doesn't delay the high voltage. Overkill? I don't mind over engineering. Laughing
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    • Post n°2

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    Post by Guest Fri Jan 29, 2016 6:53 pm

    Thanks for all the replies so far! Laughing
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    peterh
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    • Post n°3

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    Post by peterh Fri Jan 29, 2016 7:13 pm

    Be my guest :-)
    I do not see any reason to delay B+

    What could be of use is an automatic delay that prevents start / restart until the delay has passed.
    20s should be enough .
    Why ? It would prevent dangerous current rush in case of main blinking and it would also
    protect against a user that flips power on and off. An automatic turn-on delay would achieve this.
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    Bob Latino
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    • Post n°4

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    Post by Bob Latino Fri Jan 29, 2016 8:17 pm

    Captain Coconut wrote:Would there be any advantage of using a time delay board after a thermistor in the St-35? I use a thermistor now at turn-on and then switch it out after a few minutes of warm-up with a make- before- break thingy I rigged up. With the multimeter hooked up to the bias pots, it's kinda' cool to see the voltage being  delayed for a bit and then gradually increase. But I wonder if a delay board would also be beneficial, since the thermistor doesn't delay the high voltage. Overkill? I don't mind over engineering. Laughing

    I don't really think you need a delay board in the Dynaco ST-35. Consider two facts ..

    1. Dynaco probably sold many thousands of the ST-35. I have opened up a number of the ST-35's - no delay in there -  just the two original diodes in there doing the rectification and they just "keep on ticking" (playing well)

    2. That amp runs a B+ of only 370 - 380 VDC noticeably below the 440 VDC B+ on the Dynaco ST-70. So the "high" voltage on the ST-35 isn't really all that high compared to most other tube amps.

    I have two ST-35's here and the both have the stock rectification and they both have played fine for a number of years. I had one in my workshop here that I used for background music for years. It still plays fine .. I have had to replace some tubes at times but the amp does not seem any worse for wear using solid state rectification which allows the high voltage to come up almost instantly ..

    Bob
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    • Post n°5

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    Post by Guest Sat Jan 30, 2016 9:20 am

    Thanks Bob. Smile
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