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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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    triode-electronics st70

    corporalspiffy
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    Post by corporalspiffy Thu Apr 23, 2015 8:12 pm

    i plugged in the SS rectifier and i think it damaged the filter caps because now there is a pronounced hum coming from the speakers.
    i started rolling tubes and i thought that the JJs didnt hum while the shuguang did but now it seems the amp hums with the JJs too.

    i guess i have to replace the filter caps.

    i kept the SS rectifier for back up in the event of the GZ 34 failing but now i dont think i will ever use it again.

    can someone recommend a seller of capacitors that accepts paypal payments?
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    Post by Guest Thu Apr 23, 2015 8:49 pm

    are you talking about the Weber Copper top SS rectifier?
    Those things are SOLID as, and I would be VERY surprised if the Weber did do any damage to your amp.
    Your problem may lay somewhere else. I would check ALL ground connections first in the amp before blaming the Weber rectifier....
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    Post by corporalspiffy Thu Apr 23, 2015 9:20 pm

    MontanaWay wrote:are you talking about the Weber Copper top SS rectifier?
    Those things are SOLID as, and I would be VERY surprised if the Weber did do any damage to your amp.
    Your problem may lay somewhere else. I would check ALL ground connections first in the amp before blaming the Weber rectifier....

    no it's the t-ssr01 rectifier.

    ill check the ground connections.

    you dont think the filter caps may have been damaged?

    thanks
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    Post by Guest Thu Apr 23, 2015 9:42 pm

    .


    Last edited by PeterCapo on Thu Dec 03, 2020 4:23 pm; edited 1 time in total
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    Post by corporalspiffy Thu Apr 23, 2015 10:12 pm

    PeterCapo wrote:It's not a Weber.  It's just a straight solid state diode replacement for the 5AR4.  I have two of them.  The internal voltages ran too high with the T-SSR01 in use and might have damaged the capacitors.  If you can do so safely, it might be good to check the internal voltages, first.  Suggest checking all the connections at the rectifier socket, too, as sometimes rolling an octal base in/out can disturb the connections at the socket lugs.

    Do you have a quad cap or a cap board?  If a cap board, is it the original Sheldon Stokes board or the current Triode USA "upgrade" cap board?  If it's this one m/st70capupgrade.html you can download the manual and parts list.  Capacitors may be available from Triode USA (if they ever answer their phone or e-mail) or possibly Mouser or Digikey or maybe Newark.

    yes. that's the board i have.

    im waiting for triode USA to answer my email. are they not responding to calls or emails?
    i have all the part numbers for the caps, im hoping to find a seller who accepts PayPal.

    ill get a weber copper top. is there no risk using these? i installed CL 90 current limiter but i guess that didnt protect the caps.
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    Post by Guest Thu Apr 23, 2015 10:34 pm

    .


    Last edited by PeterCapo on Thu Dec 03, 2020 4:24 pm; edited 1 time in total
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    Post by corporalspiffy Thu Apr 23, 2015 10:40 pm



    oh boy!! i hope triode writes back.

    ill check the voltages.

    thanks for the feedback.
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    Post by Guest Thu Apr 23, 2015 10:59 pm

    .


    Last edited by PeterCapo on Thu Dec 03, 2020 4:24 pm; edited 1 time in total
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    Post by corporalspiffy Thu Apr 23, 2015 11:10 pm

    they dont accept paypal. i think i sent them personal checks before.
    what a hassle.

    i have the push/pull miniblok and the SET amps that i built. ill guess ill just listen to those until they fail.

    when you get older electronic devices dont seem to last as long
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    Post by Guest Fri Apr 24, 2015 9:36 am

    .


    Last edited by PeterCapo on Thu Dec 03, 2020 4:25 pm; edited 1 time in total
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    • Post n°11

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    Post by Bob Latino Fri Apr 24, 2015 10:34 am

    corporalspiffy wrote:when you get older electronic devices dont seem to last as long

    oh boy!! i hope triode writes back.

    Some of the Dynaco ST-70's are now 50 - 55 years old and you are correct .. With gear that old, you do run into problems now and then. If Triode Electronics has not contacted Peter in 2 to 3 weeks, you chances of being contacted are probably pretty slim ...

    See if you can post a photo of your amp's internal wiring here on the Forum. Check the sticky above on how to post a photo on the Forum. One of us with more familiarity with the amp may be able to see an issue that may not be readily apparent to you ...

    Is the hum on both channels at equal volume levels OR is it just on ONE channel? Equal volume level hum on both channels does usually indicate a power supply problem - BUT - it could be some other issue ?

    Bob
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    Post by corporalspiffy Fri Apr 24, 2015 12:30 pm

    i checked all the pinouts and the voltages seem good and it did operate well until i plugged in the t-ssr01 unit. these measurements were taken with the gz34 rectifier.
    the plate voltages with the SS rectifier are only 10 volts higher.
    one of the filter capacitors is slightly damaged and dented.

    1. 1.05 v
    2.-7. 6.8v AC
    3. 416v
    4. 419v
    5. 32
    6. 32
    8. 1 v

    triode-electronics st70 <a href=triode-electronics st70 SAM_0974_zps9ripqure" />
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    Post by Bob Latino Fri Apr 24, 2015 2:35 pm

    With the amp OFF > You should check the cap values of those 8 power caps on the Triode board .. If you do not have a capacitor tester, you should get one OR a multimeter which has a capacitor range. You may have to pull the Triode cap board to do this. There is no sense in replacing the caps on that board if they test as they are marked.

    Bob
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    Post by corporalspiffy Fri Apr 24, 2015 6:55 pm

    I ordered one from china so it will take a while.
    i assume i will have to take the caps out of the circuit?
    thanks again for your help.
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    Post by Bob Latino Fri Apr 24, 2015 7:10 pm

    corporalspiffy wrote:I ordered one from china so it will take a while.
    i assume i will have to take the caps out of the circuit?
    thanks again for your help.

    You can test those caps "in circuit". Those 8 caps are actually 4 sections of two caps each in series. When you place caps in series like that the voltage rating doubles and the capacitance is cut in half. See below. C1 and C2 are in series which gives you in effect 41 uF @ 800 volts. The thing that I don't like about the Triode/SDS cap board is that the last 3 sections contain 250 volt caps in series giving you and effective voltage rating of 500 volts. At turn on, the voltage surge can easily go over 500 volts. Dynaco knew this and used a 525 volt quad cap ... The Triode board has more capacitance than the original Dynaco quad cap but the voltage rating on the last 3 sections are (IMHO) too low. Triode should have used 300 to 400 volt rated caps on the last 3 sections giving an effective voltage rating of 600 - 800 volts. Using a solid state rectifier as you did with no time delay makes the power surge issue even worse. Using a tube rectifier with a slower warm up is easier on the cap board ..

    C1 = 82uF 400V Snap in Capacitor
    C2 = 82uF 400V Snap in Capacitor
    C3 = 390uF 250V Snap in Capacitor
    C4 = 390uF 250V Snap in Capacitor
    C5 = 270uF 250V Snap in Capacitor
    C6 = 270uF 250V Snap in Capacitor
    C7 = 270uF 250V Snap in Capacitor
    C8 = 270uF 250V Snap in Capacitor

    Bob
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    Post by corporalspiffy Fri Apr 24, 2015 7:35 pm

    very interesting information
    i have a USB oscilloscope, is it useful?
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    Post by GlacierJohn Mon Apr 27, 2015 11:40 am

    Bob Latino wrote:
    corporalspiffy wrote:I ordered one from china so it will take a while.
    i assume i will have to take the caps out of the circuit?
    thanks again for your help.

    You can test those caps "in circuit". Those 8 caps are actually 4 sections of two caps each in series. When you place caps in series like that the voltage rating doubles and the capacitance is cut in half. See below. C1 and C2 are in series which gives you in effect 41 uF @ 800 volts. The thing that I don't like about the Triode/SDS cap board is that the last 3 sections contain 250 volt caps in series giving you and effective voltage rating of 500 volts. At turn on, the voltage surge can easily go over 500 volts. Dynaco knew this and used a 525 volt quad cap ... The Triode board has more capacitance than the original Dynaco quad cap but the voltage rating on the last 3 sections are (IMHO) too low. Triode should have used 300 to 400 volt rated caps on the last 3 sections giving an effective voltage rating of 600 - 800 volts. Using a solid state rectifier as you did with no time delay makes the power surge issue even worse. Using a tube rectifier with a slower warm up is easier on the cap board ..

    C1 = 82uF 400V Snap in Capacitor
    C2 = 82uF 400V Snap in Capacitor
    C3 = 390uF 250V Snap in Capacitor
    C4 = 390uF 250V Snap in Capacitor
    C5 = 270uF 250V Snap in Capacitor
    C6 = 270uF 250V Snap in Capacitor
    C7 = 270uF 250V Snap in Capacitor
    C8 = 270uF 250V Snap in Capacitor

    Bob

    Thanks Bob, that is a great explanation. I wish I had discovered this forum before I went with the SDS cap board last year on my MK IIIs, but I didn't. They seem to be working fine, but now I'm wanting to upgrade the rest of my amps, including new driver boards with tubes4hifi components, but I'm worried about the new driver board fitting with my SDS board which overhangs the driver board.
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