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

Tweedle Mod done Problem

Discussion in 'Shock Brother's DIY Amps' started by SacDAve, Jan 11, 2019 at 10:10 PM.

  1. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    I just finished my Tweedle Dee mod, have it fired up but am having a problem. The amp has very little volume and sound like a bad transistor radio. It seems the longer it’s on the volume even goes down more. Doing a voltage check it calls for a GC34 rectifier tube so the voltages are much higher than a 5Y3. B1 420, B2 384, B3 310. I put a 5Y3 in the B+’s dropped 40 volts. on V2 pin 8 I’m getting 5.3VDC I should be in the 50 to 60 Volt range looking at other 5E3’s. Also, when I went to move the chassis in the cradle, I got shocked. I’m guessing something is shorting out. Is there a way to test if the chassis is hot without touching it? I really haven’t been able to spend any time figuring out what’s going on, I did chopstick the wiring found nothing can’t see anything obvious. I did check all the resistors before I used them. At this point I’m thinking something grounding out. Any other suggestions? I might have some time late tomorrow to work on it. I put some picks The layout is the way I do the 5E3’s one of the pics shows Jumpers . BTW no Variac or light bulb limiter are not being used they were for start up.
     

    Attached Files:

  2. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    More pics
     

    Attached Files:

  3. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    V5 GZ34

    P-2&8 420

    P-4&6 357 VAC


    V-4 & 3 6L6

    P-3 408

    P-4 382

    P-6 384

    P-8 24.3


    V2 12AX7

    P-1 206

    P-3 1.5

    P-6 305

    P-8 5.3


    V1 12AX7

    P-1 182

    P-3&8 1.5

    P-6 175
     
  4. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    Do you have an insulator under the board?
     
  5. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    It's raised up and insulator between chassis and board.
     
  6. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    Bump anyone especially about getting shocked.
     
  7. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    Power off caps drained

    Can you ohm v2 p8 to ground. Is it what you expect. I cant read the values on my phone.

    Check from power nodes to chassis also.

    Some photos look "in progress" hows your preamp grounded

    Check your power cable and confirm the wires go to the proper terminal at the plug which goes into the wall
     
    King Fan and sds1 like this.
  8. sds1

    sds1 Tele-Holic

    Age:
    42
    809
    May 4, 2017
    Orlando, FL, USA
    Light bulb limiter would confirm the short but the shock is a pretty good indicator too I reckon!

    Go thru the schematic and measure resistance to chassis at every node in the circuit ?

    At first glance V2B cathode looks high but it is the phase inverter so that tube is not configured in the same way as a typical preamp stage.
     
    King Fan likes this.
  9. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Don’t have any great ideas, but is there a way to use a DMM to test for a hot chassis? If you run a length of (green!) Romex wire between your COM mini-gripper and the ground socket on a *tested* ground outlet then look for voltage on the meter? Or maybe better, I’d assume it was charged until we find out why you got shocked.

    Again, no brilliant insight, more like random questions I guess, but what did your lightbulb do when you fired up? Go all the way dim? What happens when you continuity test all the socket pins, B+ jumpers, etc. that *shouldn’t* be continuous to the chassis? What do you get when you ohmmeter test all socket pins against the schematic? Is there something like a solder bridge or wire strand somewhere? What do the pros think about those voltages? Is it something around V2? Have you tested voltages with no tubes, rectifier only, etc?


    Sent from my iPad using Tapatalk
     
    sds1 likes this.
  10. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Heh, @clintj , @sds1 , you type faster and say more with less than I do!!!
     
    Last edited: Jan 12, 2019 at 10:54 AM
    sds1 likes this.
  11. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    5E3-4 copy.jpg This shows the grounding pattern. Dose not show the fuse block or RFI cap. This is how the Amp was wired before I did the TD Mod. I've used this pattern in a couple amps.
     
  12. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    More pics, will be gone for a couple hours Thanks for replies
     

    Attached Files:

  13. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    The first thing to fix is the amp chassis ground. If you got shocked then the chassis isn't connected to ground. Check continuity from the chassis to the power cord's ground prong. Then check chassis to where the ground safety wire is connected to the chassis.

    If you don't find a problem check your wall receptacle, the ground may not actually be connected.

    Does your amp have a death cap?

    On a side note, the power cord hot black wire should connect to the fuse center terminal to prevent shock when changing the fuse.
     
    King Fan likes this.
  14. sds1

    sds1 Tele-Holic

    Age:
    42
    809
    May 4, 2017
    Orlando, FL, USA
    Chassis has paint on it -- could this be the problem?
     
    King Fan and Nickfl like this.
  15. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    You're forming a ground loop by connecting the preamp ground to the power transformer bolt unless you're using insulated input jacks.
     
  16. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Yes, that could be the cause. The paint needs to be scraped away at all the chassis ground points.
     
    Nickfl and sds1 like this.
  17. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    So, from what I gather... This was a functioning amp without issue prior to the mods.

    Captain Obvious might suggest this is a result of recent work:)

    I know you've built a few amps and will no doubt get to the bottom of this... Be careful and methodical!
     
    King Fan likes this.
  18. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    The low output and nasty tone is most likely an above human hearing oscillation but I wouldn't worry about this until the chassis ground is fixed. The two problems may be related since the ungrounded chassis isn't providing an RFI shield.
     
    sds1 likes this.
  19. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    I just got back not sure if I'll have time to mess with it today. I was going to mention pots and inputs have isolation washer. I did look at the amp no paint at cord ground. Rob will move hot to inner ring of fuse Thanks.
     
    robrob likes this.
  20. SacDAve

    SacDAve Poster Extraordinaire

    Age:
    67
    Dec 23, 2009
    Rocklin Ca.
    Today I redid the fuse connection. I did fire it up swiped the chassis with the back of my hand no shock. Wondering when I moved the chassis in the cradle if Didn't tag the hot or neutral on the RFI cap. I looked at everything blew it out with the compressor, found nothing. I also looked at my pic. of the underboard jumpers and compared them with the old board they look correct. I also disconnected one leg of the RFI cap and the 3.3M resistor & 2.2nf cap to pins 6 & 7 V2 did not solve the problem. Tomorrow I’ll recheck all the wires to the sockets. I’m even thinking of rewiring them along with the heater wires. I have feeling it’s something simple I’m just not seeing yet. The 12AX7 are new might try some others I have got a bad tube out of the box before.
     

    Attached Files:

    robrob likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.