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    Dynaco MK3 Low output!!!!

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    arledgsc

    Posts : 459
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Dynaco MK3 Low output!!!!

    Post by arledgsc on Wed Jun 21, 2017 9:13 pm

    Pin 3 is the anode and pin 4 the screen grid. You should see close to 500v DC on the anode and a high voltage as well on the screen grid. Is your meter still set to AC voltage when measuring these pins? I assume bias sets up OK so may be a measurement error.
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Wed Jun 21, 2017 10:07 pm

    arledgsc wrote:Pin 3 is the anode and pin 4 the screen grid.  You should see close to 500v DC on the anode and a high voltage as well on the screen grid.  Is your meter still set to AC voltage when measuring these pins?  I assume bias sets up OK so may be a measurement error.

    It might have. I ill check tomorrow to confirm. I should note that the bias is set to 1.4v dc I used a 10 ohm 2% 10w resistor on the bias. The tubes in both amps light up and get hot equally. Both pass sound because i tested it with one and then the other and still got sound both times.

    Could the low output be just the preamp tube and the kt88's doing nothing?
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    pichacker

    Posts : 26
    Join date : 2016-08-01
    Age : 53
    Location : Near to London - UK

    Re: Dynaco MK3 Low output!!!!

    Post by pichacker on Thu Jun 22, 2017 2:13 am

    Bob, can you post a good quality photograph of the faulty amplifier? A picture paints a thousand words.
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Thu Jun 22, 2017 7:08 am

    Yes I can I'll do that tonight
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    Bob Latino
    Admin

    Posts : 2554
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Dynaco MK3 Low output!!!!

    Post by Bob Latino on Thu Jun 22, 2017 7:43 am

    BobtheBuilder wrote:Yes I can I'll do that tonight

    Since Bob is a new member, he will not be able to post a photo or link until this coming Sunday June 25. Bob, on Sunday the forum software will allow you to post photos or a link to a gallery of photos of your amp. This is done so that a "member" cannot join and immediately post spam or porno links on our forum. Believe me, this has happened before. Note > The forum software here cannot "host" a photo. You must host the photo somewhere else on the internet and then link to it. Read the sticky above on how to post a photo.

    Bob
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Thu Jun 22, 2017 8:07 am

    Okay fair enough.
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Thu Jun 22, 2017 9:11 pm

    All reference is to ground pin 3 is 471v dc pin 4 is 475v dc pin 5 is -52v dc pin 6 is -52v dc pin 7 is 3.8v dc pin 2 is 3.9v dc. It is the same with both kt88s.
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Thu Jun 22, 2017 9:21 pm

    Great news it's fixed! Thanks you to everyone who helped it was a resistor on the transformer output was burned up. It was new but I hit it with the soldering iron and destroyed it I thing.

    BNR_1

    Posts : 84
    Join date : 2013-06-11

    Re: Dynaco MK3 Low output!!!!

    Post by BNR_1 on Thu Jun 22, 2017 11:24 pm

    I am glad you figured out the problem. But I am a bit disappointed. This post was like a suspense tv program....waiting for The Who did it. Now it is all over.
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    arledgsc

    Posts : 459
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Dynaco MK3 Low output!!!!

    Post by arledgsc on Fri Jun 23, 2017 12:57 am

    Congrats and good job!
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    PeppaPig

    Posts : 24
    Join date : 2017-06-18
    Location : West Dakota

    Re: Dynaco MK3 Low output!!!!

    Post by PeppaPig on Fri Jun 23, 2017 8:51 pm

    Yah I know. Even  I was hoping for something better, like the amp was cursed by a pirate and I was damned to sail the seven seas or the metal they made it from was radioactive and I was turning into the hulk.

    Lesson hear is be careful where you poke it.

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