gsb wrote:Hi,
Here some pictures ,all SMD.Q1 transistor is marked with MX. I have played one more time -pedal works fine all controls are fine ,no led .I have check voltages on q1 . Measured voltage about 9,06v pin2 -S,8,6v on pin 3 -D and 9,06 on pin 1 G. Voltages are equal in off and on mode!! I think it must be Q1 ?
gsb
Or perhaps the connection to the switch.
Could you please trace the switching circuit?
hi,
I dont work usualy with SMD ,Friend need the drive ,i have disabled q1 and put bs250 in and shorted the legs .Now led is working .I hate fu....g SMD.Sorry i cant trace this build.Pedal is working very good .
thanks for help
gsb
gsb wrote:hi,
I dont work usualy with SMD ,Friend need the drive ,i have disabled q1 and put bs250 in and shorted the legs .Now led is working .I hate fu....g SMD.Sorry i cant trace this build.Pedal is working very good .
thanks for help
gsb
The main thing is, the LED is working again.
I agree with you in SMDs.
"The earliest OCDs used 2 x Mosfets plus 1 x Germanium diode, but very quickly these diodes became harder and harder to find, and they became expensive.
Recently I stumbled across a reasonably large stash of the right kind of Germanium diodes so I ponied-up and bought all of them. I then decided to do a small run of the ultimate OCD: a Custom Shop offering with a few circuit tweaks, 2 x Mosfets plus 2 x Germanium diodes...
The sound? Great definition, more tube-like feel, a bit wider dynamic range, more sustain, and a more focused single-note tone."
D4 is a schottky diode, 3v3, 5v6 or so. Must be much lower than supply voltage to operate correctly.
C19 together with R23 controls the speed of switching, I beleive, it's something in between 1n and 22n.
The whole point of this circuit is to smooth led switching (and possibly mitigate popping nose which is not the case here). Seems more like a remnant, than a feature.
Thanks. I found that schematic earlier in this thread.
It's not clear what the difference is between V2 and V2.01 other than the claim that V2.01 is "less compressed". The manual that came with my V2.01 is labeled V2 and dated 2017. The date could be wrong.
A friend gave me an Abominable Electronics Oppressive Cult Destroyer to fix. This is a clone of the OCD, tuned for bass, and with a boost circuit, footswitchable clipping diodes.
The problem was the pedal squealing as hell... my solution was to swamp the opamp with a LM358 and higher the cap between lugs 1 and 2 of the opamp from 220p to 330p/470p.
For all who are interested these are some guts of the Abominable Electronics Oppressive Cult Destroyer I had for repair last week. These are the pictures prior repair.
Top right under that spongy thing there is a charge pump to convert 9VDC to 18VDC (a classic one based on the MAX1044 or 7660/2).
Looking over all the schematics available, it seems like only a couple things really matter to the "tone" between versions V1.1-V1.7
The drive knob and tone knob values only affect the overall range of those controls. They usually affect the frequency response in a noticeable way. The 25k tone pot can hit all the same values as the 10k. They sound different with the knobs at noon, but the switch to 10k only limited the overall range.
And if you have a buffer after the pedal, the value of the volume knob is basically irrelevant too (since even a 1uF output cap is high enough that hardly any volume knob settings settings cut bass).
The 220k bias resistor adds less than 1dB of gain, hardly significant.
Obviously the 1N34 diode affects the dynamic response, and perhaps the tone in how it appears to allow through more bass because it clips less, but that's easy to stick on a toggle switch.
So what matters for the "tone" of the different versions? Seems like it's just three capacitors: the the tone knob cap and the two feedback caps. The tone cap has a major impact on the low mids, and the feedback caps have a big affect on the overall emphasis.
With a With a 1M drive knob and a 25k tone knob (for maximum range of each), you can get any of the sounds of V1.1 to V1.4 just by adding a couple switches for those capacitors (or a single 3PDT).
Maybe someone did this already, but I haven't seen it in this thread. I guess that's understandable, as folks seem to be using speculation rather than simulation software in the early posts.
someone asked about my last past, so here's a schematic. all versions of the pedal in one schematic. short the labeled pins to access the alternate versions. in the real world just sub 100pF for the ideal 110pF.
for the 3PDT pins, see the image below. 1 refers to the first row (leftmost SPDT), 2 refers to the second row, etc. the letter is the pin within each SPDT. or alternatively, you can use three spst switches, since all you need to do is short pins together.
EDIT: fixed value of R17
Last edited by smear on 08 Jan 2023, 00:23, edited 1 time in total.