Böhm- Trickverzerrer  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Manfred
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Post by Manfred »

BTW, Manfred: perhaps you must check the connection of DISKANT potentiometer in your board, according to this new diagram ?
I have this original circuit diagram already for a long time this was attached with the purchase of my trick distortion.
The circuit of the treble control is shown incorrectly in this.
The circuit redrawn by me have found by tracing my layout.
Also TWSpedals came by tracing his trick distortion to the same circuit of the Diskant control.
TWSpedalsTrickverzerrer.jpg
See also the pictures from this link from the post above.
https://drive.google.com/drive/folders/ ... sp=sharing

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Manfred
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Post by Manfred »

I have changed the layout and schematic in the posts above because the value of R5 was wrong, it is 39k instead of 47k.

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Post by Manfred »

The PCB is repaired the oxidized conductor path was broken as suspected.
The transistors were all replaced with the SC207 type.
The T3 (F16 C-1) was obviously also original, the measured Hfe value of this is 89@5mA and was replaced with a SC207 with the same Hfe value.
Here the schematic with the measured voltage and Hfe values:
BoehmTrickverzerrerSchematic.JPG

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Manfred
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Post by Manfred »

Here are some signal traces with different input voltages and potentiometer settings and the frequency response,
the values and settings can be found in the pictures:
Trickverzerrer frequency response.png
Trickverzerrer frequency response.png (7.35 KiB) Viewed 2860 times
MeasurementTrickverzerrer #1-#9.jpg
MeasurementTrickverzerrer #10-#18.jpg
MeasurementTrickverzerrer #19-#27.jpg
MeasurementTrickverzerrer #28-#30.jpg
The redrawn complete schematic:
BoehmTrickverzerrerSchematic.JPG
PCB layout PDF-files:
BoehmTrickverzerrerPCB_ComponentsSide.pdf
(17.53 KiB) Downloaded 138 times
BoehmTrickverzerrerPCB_SolderSide.pdf
(10.28 KiB) Downloaded 142 times
SprintLayout6 file:
BoehmTrickverzerrer.zip
(25.32 KiB) Downloaded 138 times

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Levi8000
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Post by Levi8000 »

I'm having trouble reading the Vermona schematic. What do the fractions mean for the capacitors and for R6 why is it an X? Also what is the ladder type thing between the in and output? I'm trying to clone the circuit for a pedal.

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Post by Manfred »

Levi8000 wrote: 06 Feb 2021, 01:29 I'm having trouble reading the Vermona schematic. What do the fractions mean for the capacitors and for R6 why is it an X? Also what is the ladder type thing between the in and output? I'm trying to clone the circuit for a pedal.
The value of R6 is used to adjust the range of the operating point setting of T3 depending on its currently selected type or its current properties.
For example, in my device this value is 15 kiloohms in the device from TWSpedals 22 kiloohms.
The ladder type thing between the in and output is a switch with four changeover-contacts.
I will draw a circuit schematic for a clone.
This has a true bypass and the switching on of the supply voltage via the input jack as it is usual.
The "Diskant" control is wrong in the Vermona schematic, follow the redrawn schematic.

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Post by Manfred »

BoehmTrickverzerrerSchematic with jack plugs.JPG

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Post by Levi8000 »

I don't understand, for the in and out why are there multiple connections I thought there was only hot, ground, and negative for stereo? Also what is the point of having a four way switch as opposed to an on off stomp switch?

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Post by Manfred »

Levi8000 wrote: 06 Feb 2021, 18:29 I don't understand, for the in and out why are there multiple connections I thought there was only hot, ground, and negative for stereo? Also what is the point of having a four way switch as opposed to an on off stomp switch?
This device was designed for the Böhm organs, so I think that this is related to a special socket assignment of the organ.
According the pin assignment to the DIN standard, the output pin would be connected to the input pin, which makes no sense.

Furthermore, it should be mentioned that the input is very sensitive and the maximum output signal is already reached with a few millivolts.
Also the input resistance is very low with about 10 Kiloohm.
This means that in this form the trick distortion is not suitable for guitar.
An emitter follower as input buffer with a potentiometer with a value of 1 Megohm in front of it would be a possibility for adaptation.

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