Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Whatever happened to that Hohner amp? 5e3 Build Content

Discussion in 'Shock Brother's DIY Amps' started by rocksmoot, Dec 4, 2017.

  1. rocksmoot

    rocksmoot Tele-Meister

    159
    May 6, 2012
    Rogers, Arkansas
    Yeah, I did a full build thread on aguitarforum.com, but I brought it over here to get the rough edges smoothed out. Your notion that there's crud on the terminal is one that occurred to me but I've probed that pin every which way I can imagine, and I've reflowed the solder joint and it looks really nice. I don't think it's a short in the tube unless both tubes have it.

    Both tubes are pretty hot. Once temps reach the "damn, that hurts!" stage I can't really tell the difference.

    I wish (for the hundredth time) I had an oscope. Had some nice ones in the service.
     
    Last edited: Dec 7, 2017 at 12:42 PM

  2. rocksmoot

    rocksmoot Tele-Meister

    159
    May 6, 2012
    Rogers, Arkansas
    Well, I fixed it. I replaced the rectifier socket. It was a cheap ceramic and all the other sockets were Belton sockets. After I did the swap I'm getting 378 volts on pin 3 of V3. Most likely it was a questionable solder joint, but there ya go. Thanks for chiming in on this issue, guys!

    Now I'm waiting on my zeners and VVR parts.
     

  3. jtcnj

    jtcnj Tele-Meister

    Age:
    53
    361
    Feb 2, 2015
    Brick, N.J. USA
    here is definitely the better place for this part of it.
    Ok so you swapped tubes and the problem stayed on the socket pin and did not move with the tube. Check.

    do you have unloaded B+ voltage at v3 socket pin 3 with the tube out?
    At the OT side of the plate resistor?
    Could the socket be burnt / carbon traces and be conducting somewhere else?

    The tube is warm, your cathode voltage is similar to v4, the amp sounds good.
    Something is misleading on this.

    If output tube is pretty hot I figure that as a general go / no go that the tube is conducting or not. I had a cool one and a failed open screen resistor was the culprit.

    I just read on an audio forum if the anode is open and voltage is present on the screen, it will destroy the tube.

    I'm not sure how but I am thinking the only + charge then becomes the screen and the current path is from the cathode through the screen. But wouldnt that still be limited by the screen resistor?
    Or is that the case where NO screen resistor is employed?
     

  4. jtcnj

    jtcnj Tele-Meister

    Age:
    53
    361
    Feb 2, 2015
    Brick, N.J. USA
    I am glad you got it sorted but I dont get that.
    B+ leaves the rectifier socket to the OT CT and comes out both ends to the plate resistors.

    If it were me I would keep rechecking that v3 pin3 reading while you are in the scaling the B+

    I just ordered some zeners for my 5e3 too.
     
    Last edited: Dec 7, 2017 at 2:41 PM

  5. rocksmoot

    rocksmoot Tele-Meister

    159
    May 6, 2012
    Rogers, Arkansas
    I don't get it either. It doesn't make sense to me since the voltages looked good at the B+ anyway. Unless of course things are breaking down under some kind of load but that doesn't make sense either because I measured it at idle. Maybe some smart guy will come along and explain to us how it's all very elementary.
     
    jtcnj likes this.

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