Pultec Eqp-1A Build

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paulisher

New member
Joined
Dec 14, 2017
Messages
4
I am new to this forum and new to DIY electronic builds and I have built a Pultec EQP1a with a Vintage Windings complete filter unit, Sowter transformers and Cinemag. The Pulec sounds amazing and is as quiet as I would expect from a tube equalizer but the bypass switch has very low volume in bypass mode (unusable as a bypass switch) and the LF boost and LF atten are also very low volume when turned counter clockwise. At about level 2 of both the LF boost and atten pots the volume drops off to almost nothing.  All my pots are  the correct value and taper mostly Ohmite with one Allan Bradley. The switches are Chinese if that makes a difference. I have retraced my wiring many times and believe that it is wired liks the diagrams that I used to build it. I used the top half of Martin Zobel's hand drawn diagram and the bottom half of Chris's Vintage Windings diagram for wiring the pots and switches. I also contacted Brian Sowter to get how the pins on the Triad HS-56 and HS-29 relate to the corresponding Sowter transformers. Does anyone have any idea what could be wrong given my discription or have advice for troubleshooting this?
 
You've probably already seen this schematic, but here's the gyraf one http://www.gyraf.dk/gy_pd/pultec/pultech.gif

Bypass switch is easily legible here. No idea what you're problem is. Maybe post a couple pictures and somebody might spot something?

I had a problem at one point (long time ago, hard to remember) that seems like it had similar symptoms to yours. Turned out I had accidentally swapped the filter input and output. Still partly worked going through the filter backwards, but things were definitely off and not immediately obvious what was going on.
 
Thanks JW.  I'll retrace the filter unit. I purchased a complete filter unit from Chris at Vintage Windings and all the wires are labeled. I have never looked inside it assuming that all the wires are correctly labeled. I have tried to include a picture but it keeps getting rejected and it's only 309 kb. 
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I guess I'll contact the administrator.
 
Can anyone tell me if I'm using the right switch? I installed a Switchcraft leaf switch DPDT and its behavior is different than a switch that I am use to. It doesn't make connections from one side of the switch to the other. The Leaf switch I have makes no connections when it's switched up, the IN position. When switched down to bypass it connects 1 and 2 , 3 and 5. Could this be my problem?


Carling DPDT
toggle switch          Switchcraft Leaf Switch

        ^                                                          ^
      In                                                        In
    1    2                                                    1    2
    |    |
    3    4                                                    3    4

    5    6                                                    5    6



    1    2                                                    1--2
             
    3    4                                                    3    4
    |    |                                                      |
    5    6                                                    5    6
    Out                                                    Out
      Y                                                          Y
 
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