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5E7 build please help

Discussion in 'Shock Brother's DIY Amps' started by Doctormo4, Mar 12, 2018.

  1. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    I have rebuilt so to speak a 5E7 clone which was eating tubes and in doing so have I been turned onto the voltage issues and the 90 ma choke . I have a new 200 ma choke classic tone transformers. My voltages are really close the the original fender schematic voltages, but my amp sounds weak and weird and when I plug into the bright channel the regular channel needs also turned up to achieve any sound same for the normal channel bright needs turned up for the normal to make any sound. When doing the pop test I get a huge pop on pin 7 grid of v3 and I get zero pop on the pin 2 of v3. I have really good correct transformers and I cant find a wiring mistake and I have new Dijon caps . I tested the resistors and they look ok on the meter now the 1 meg reads 1 meg out of circuit and 136 k in the circuit. It seems like way to much voltage is coming into 7 v3 and I have no voltage in 2pin 2 of v3. I joined this forum out of desperation . The huge pop on 7 on v3 is where that 1 meg resister resides next to 1500 K Thank you in advance to all of you helpers I should note the bias of out put tubes is at 35 ma on my allesandro bias probe and plates on 6l6's at 428 volt each schematic says 410
     

  2. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

    Jan 2, 2007
    Virginia, USA
    I am not good enough to troubleshoot your issues... However, I can tell you that your 428 volts is well within the 20% tolerance of the schematics.

    Have you ever heard of Rob Robinette's web page about amp building stuff? He has a great amp start up procedure that really helps narrow down some issues like these: Rob's amp start up page

    Welcome aboard, more knowledgeable folks will be along any minute now. I bet they can get you on your way without too much work. Just have a little patience.
     

  3. dan40

    dan40 Tele-Holic

    924
    Aug 19, 2015
    Richmond Va
    Does it stay true to the original schematic or did you make changes? We will need some clear pics of all of the wiring and we will also need a full set of voltages at all tube pins so that we can see what's going on.
     
    D'tar likes this.

  4. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    Thank you I used the original fender wiring schematic except the heaters are on pins 4,5 and 9 where as the original fender has grounds on preamp tubes on 9. In other words modern heater set up wiring My chassis has the treble and bass pot positions exactly like an original 5E7 not switched around like the weber. Voltages 6l6 pin 3 428 6l6 pin 3 428 (410 on schematic)
    100uf/25 volt -44 (-40 schematic)
    1 st 16 uf 448(415)
    2 nd 16 uf 436 (410)
    3 rd 16 uf 350 (332)
    between 56k and 1500 k off of pin 3 PI 1.78 volt (1.7 volt)
    between 56 k 1 meg and 1500 k 64 volt (53.3)
    PI tube pin 8 at .1 uf 65 (55)
    PI tube pin 6 at .1 285 (270)
    junction of 220 r resisters -44 (-40)
    pi TUBE PIN 1 AT .O2 UF 236(213)
    PIN 6 V2 AT 8 UF ELECTROLYTIC 293 (220)
    PIN 1 V2 177 (140)
    V2 CATHODE PIN3 AT 25UF/25 VOLT 1.65 VOLT (2.2)
    PIN 6 V1 140 VOLT (140)
    pin 1 v1 140 (140)
    pin 8 v1 2.39 ( 2.2)

    I am sorry I forgot to measure v2 pin 8 at the .1 uf cap and 100 k res I will do so tonight and try to fire off picture I want to thank you all.
     

  5. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    Also the amp has no mods or changes other than I used a big ass 200 ma 5 H choke. I biased the output tubes according to the allesandro bias probe giving 35 ma I had to use a 78 K resistor in the bias section instead of the 56 K on schematic .
     

  6. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    also the amp has a new speaker jack new transformers excellent grounding soldered to the chassis only the volume pots and prescence pots are grounded via the pot casing . There is sound the speakers have been checked speaker cables You can hear the guitar signal speakers just very weak and aided by turning up the other volume pot . The original builder has the brass plate in the amp as grounding for the pots and jacks. I have the original jacks in the amp which look very good. I wonder if the grounding in those pots are ok ?? any way this is my albatross I have successfully put together 2 amps so I am no expert nd I don't have an oscilloscope etc. I used the plate grid pop test descending from power tubes to preamp tubes and the grid 7 pin off off v3 made a really loud pop so much so I really could not measure voltage and the grid on the other side of the v3 tube at pin2 had nothing
     

  7. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Doc, a voltage chart needs to be more understandable. Tube by tube...
    Ex:
    V1...12AY7
    P1– voltage
    P2–voltage
    P3–voltage
    And so on.
    When done in this manner, one can easily have an idea as to what voltages are present throughout the circuit.

    As for the pop test, as I learned it one would test the plate voltages starting with the power tubes and working back through the circuit. The pops should increase in volume as one works toward the input.

    It is also advantageous to provide the schematic, ime, so that it can be referenced in the thread. Although this has nothing to do with your problem, I would be using a different cap in that bias circuit....100mfd/100v does the job.
     
    King Fan likes this.

  8. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    scematic
     

    Attached Files:


  9. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    voltages recorded are based on fender schematic
     

  10. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    What are the actual voltages in the amp? If presented in an orderly manner, those figures are more accessible and usable. In this thread....
    http://www.tdpri.com/threads/no-b-voltage-drop-after-output-tube.798542/#post-8136652
    You will find an example of a voltage chart that I suggested to strider77...post #8. In his response, he gave us a really nice chart built up in a computer program....post #9.
     

  11. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    I made this one in xls. Makes it easy to give before and after voltages. Had to convert to pdf to upload the file.
     

    Attached Files:


  12. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    D’tar, would it not be much more useful to have the tube listed on the left?? Some circuits have more than one tube functioning off of a single power supply node. I have never seen a tube voltage chart that did not have the type of tube info there.

    Fwiw and imho, any kit should include a blank voltage chart and a schematic.
     

  13. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    Ha! Maybe I'm just Bassackwards. I've redone it both ways and that's the way my brain likes to see it.

    I write the valve location at the top, the tube type just beneath it, and the voltages vertically. The node readings to the left.

    100% agree with the chart and schematics.

    my "example" of a 5e3 not actual

    upload_2018-3-13_11-47-33.png
     
    Last edited: Mar 13, 2018

  14. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Okay, I get it now. I didn't take note of the "V" for tubes on the top horizontal line. my bad....
    IMho, having the AC source voltage and the power rail voltages is important, but I have never seen them put on a voltage chart before. Perhaps if they were given above and separately from the chart, I would not have gotten confused about things. The way it is drawn there is an association between the info on the left with the pins.
     

  15. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    Thanks I printed out the blank chart and will try to make things more presentable and will send in photos
     
    Wally likes this.

  16. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    Here is the voltage chart. Note high voltage pin 7 v3
     

    Attached Files:


  17. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.
    trying to post photos
     

    Attached Files:


  18. Doctormo4

    Doctormo4 TDPRI Member

    Age:
    61
    11
    Mar 12, 2018
    Pittsburgh Pa.

  19. Viejo

    Viejo Tele-Holic

    845
    Feb 12, 2011
    Southern IL
    You could try connecting the OT centertap before the choke instead of after. Gerald Weber talked about this in one of his books. His claim was running all the current through the choke causes the amp to sound " tight and constipated"
     

  20. screamin eagle

    screamin eagle Poster Extraordinaire

    Oct 9, 2008
    S. CA
    Im not really knowledgeable to comment, but I do remember seeing something about the choke in the 5e7 bandmaster was positioned and wired differently than a typical fender choke. Also the reason why it’s 200ma vs 90ma.

    Is there a chance you have the 200ma choke wired like the 90ma might be in other fender amps? I think even some booteeq builders use the 90ma choke cause it’s how fender did it with later amps.
     

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