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Vintage Selmer Vanguard reverb issues

Discussion in 'Amp Tech Center' started by Acobberson1, Jul 15, 2017.

  1. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    Hi all, I'm hoping someone could help me out here.
    I've got a Selmer Vanguard amplifier that I'm trying to resurrect. Since I've had it, the reverb has never worked correctly. When I engage the reverb circuit I get a tiny bit of verb, then if I turn it up it starts oscillating and humming.

    I've tried the normal stuff:
    - flipping the tank 180 degrees
    - isolating the springs
    - replaced both the reverb driver tube and the ECC83 recovery tube

    Finally I suspect the reverb transformer to be the issue. With the amp on I'm measuring only about 2V on the primary, so it looks like that's the problem.

    So here is my question. The schematic has no information on the transformer other than its marked "T-215" The actual transformer in the amp is marked "T-188".

    Does anyone know what I can use as a replacement? Unfortunately since it is not working properly I can't get accurate measurements on it.

    Here is a link to the schematic
    http://www.vintagehofner.co.uk/britamps/selmer/schematic/vang.html

    Any help at all is appreciated.
     

  2. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    I should also mention that I've asked Mercury Magnetics and they have no replacement for it, however he did offer to either make a clone or rewind the original.
     

  3. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    2V DC across a small transformer primary is plausible. The DC resistance is very low compared to the AC impedance. I wouldn't replace that transformer just yet.
     

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  5. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    Really? 2V seems really low. I think the Deluxe Reverb is around the 400V range, right? Maybe I'm reading the schematic wrong.
    I should probably mention that I did the reading on pin 6 of the reverb driver tube (where the primary is wired in).
     

  6. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    You didn't specify the points for the 2V and I would have measured the voltage drop across the primary if it were my amp, so I thought that is what you meant.

    What is the DC resistance of the primary with the tube pulled and the power supply drained?
     

  7. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    Yeah, sorry. I should have mentioned that from the start.

    So here is the funny thing.

    I unplugged the amp, drained the caps and took the verb tube out.

    The primary measured right at 12V.

    I put the tube back in and fired it up. Now I'm measuring 260V on pin 6, which is much closer to what I would expect. But the reverb is still messed up.

    I do get the reverb "crash" when I knock on the cab, which should mean that the driver circuit is functioning, right?

    What should next steps be? Maybe hand it off to someone more experienced, haha. I've just heard bad stories of amp "techs" here in Germany.
     
    Last edited: Jul 16, 2017 at 9:25 AM

  8. telemnemonics

    telemnemonics Poster Extraordinaire

    Age:
    57
    Mar 2, 2010
    Maine
    Fender amps use a reverb section OT that's the same as a Champ OT, so if the spec of the Selmer reverb pan is the same as for a Fender, that might get you closer to the right OT if indeed that's the problem.

    AFAIK vintage British reverb sucks in general though...
     

  9. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    @robrob thanks for the link!

    -I've changed tubes with no luck.
    -Reverb crashes, so Springs and transducer seem to be functioning
    -The reverb wires are actually hardwired, no RCA cables. I wonder if someone at some point rewired them incorrectly?

    How "isolated" should the tank be? Maybe I'll try to do more to isolate it.

    @telemnemonics thanks for the info. I'll try to get more details on the tank. Unfortunately there is not much documentation for this amp other than the schematic I posted. Maybe the tank will have some codes on it.
    And you're right, I'm not expecting anything special, just want it to be fully functioning. I'm not even sure if I'll be keeping the amp. It does have a great "deluxe-ish" tone though.
     

  10. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    12V on a completely drained amp aside, going from 2V to 260V by removing and re-inserting the tube suggests a mechanical problem with the socket or a soldering problem.

    The "crash" means that the recovery circuit is working and tells you nothing about the driver circuit.

    Bad amp techs are not particular to Germany.
     

  11. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    How do you delete a post? I hit some super secret combination of keys that turned the entire post into a link to robrob's profile.
     
    Last edited: Jul 16, 2017 at 11:32 PM

  12. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    Do you mean that the wires are hardwired into the amp with phono connectors at the tank?

    If you measure the DC resistance of the tank input and output while disconnected from the amp and post the readings here, they can probably give you a good guess about what tank you have.
     

  13. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    @Ten Over regarding the reverb wiring, there are no connectors used at all. The tank's send and return are simply soldered to the circuit board. Here are a couple photos.
    DSC_0894.JPG DSC_0895.JPG
    The top wire snakes around and then is soldered to the reverb driver tube at pin 1. The other is soldered to the reverb transformer.

    I'll get those DC resistance measurements and better photos later, I just snapped these before leaving for work.

    Thanks everyone for your help!
     

  14. viking

    viking Friend of Leo's

    Age:
    51
    Jan 23, 2007
    Denmark
    I got one from a mate in a homemade head cab. It was the first amp I ever got into. Reverb works , but its not great. Starts to feedback rather early.
    I installed it in a dead Line 6 combo , but never got it reliable enough to use.
    The on/off switch for the reverb was put on the face of the amp , I presume it was originally a pedal ?
     

  15. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    Yes, the reverb switch is a originally a pedal. You can see in the first photo that I posted above, the black cable coming in from above the amp chassis is where the pedal is connected.

    The amp itself honestly sounds great. I am really impressed with the tone. Compared to other Selmer amps I have seen, however, I believe the Vanguard was meant to be more of a budget line amplifier. Instead of turretboard it has the PCB in there, and the way it is wired and constructed makes it a bit difficult to work on. You've got to be really careful when removing the PCB from the control section of the chassis because some of the circuit (tone caps and such) are wired directly from the PCB to the pots.

    That's really why I am trying to get this thing back to fully functioning. The amp sounds wonderful, and I have always wanted a Selmer, but at this stage I can't rely on it outside of just playing it at home.

    We'll see how long I can be patient before I track down an amp tech in the area to go over it... or just offload it and move on :)
     

  16. viking

    viking Friend of Leo's

    Age:
    51
    Jan 23, 2007
    Denmark
    Mine sounds really good. I believe they were the first Selmers with pcb construction. The traces on the pcb keeps lifting on mine , which gives all kinds of weird noises , LOL
     

  17. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    Lucky for me the PCB is in really good condition, so the only issues I am having are with the reverb. It has the original Brimar/Mullard tubes and Goodmans speaker in it too!
     

  18. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    I desoldered the tank's input and output leads and took resistance readings.

    Input DC resistance: 1.7 ohm (that doesn't seem right)
    Output DC resistance: 880 ohm

    When I resoldered the input and output I did them backwards (wired the input to the verb tube and the output to the transformer) to test the input transducer. I did the crash test, and sure enough, there was a crash. It was quieter, but definitely there. So it seems that both input and output transducers are working.

    I did find some markings on the tank. It was made in Japan, and had E8 stamped on the inside.
    It looks alot like one I saw in an old Kay reverb unit.

    Also, just for the heck of it, I wired in a 2n2 bypass cap on the verb tube's grid. I read that Fender stated adding this on the Deluxe to help control some reverb feedback. No help here. It's still howlin' like a mad dog with the reverb around 3.

    Anyway, I'm sort of at a loss at this point. I've tested everything I know to test. It might be time to seek professional help unless anyone has any ideas for me.
     

  19. Ten Over

    Ten Over Tele-Meister

    139
    May 13, 2015
    Central California
    1.7 ohms is right in there for an input impedance of 8 ohms. 880 ohms is typical for an output impedance of 10K. 8 ohm input is what you would expect for a transformer driven tank. 10K output is hard to find these days. The 10K output will typically put out 15mV while the readily available 2250 ohm output will typically produce 6.5mV.
     

  20. Acobberson1

    Acobberson1 TDPRI Member

    13
    Jul 27, 2015
    Efringen-Kirchen
    @Ten Over Thanks for your wisdom!

    So if the resistance readings seem good, and both transducers are working I can rule out the tank as the issue, right?

    Exchanging tubes didn't solve the problem.

    Input and output are wired correctly.

    Does that point back to the transformer as the problem?
     

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