INFANEM the driving notion clone

[goroth]

I think it's ibarakishi's and that EYG has it.

Maybe??

[crochambeau]

Based on this post in this thread it appears as if the actives have been measured:

viewtopic.php?f=151&t=63296&start=92

I would ASSume that if there were PNP devices that would have been realized at this point. I have not seen any reference of pinout, but it would be groovy if that was recorded somewhere.

I think it's ibarakishi's and that EYG has it.

Maybe??

Yeah, I think the original plan was EYG was going to re-house and return to ibarakishi, but the 2020 timehole appears to have delayed that. Here's hoping EYG is doing well, just busy, and can return to illuminate us.

[goroth]

Yeah he’s good peeps.
2020 was not good peeps.

[Schlatte]

Based on this post in this thread it appears as if the actives have been measured:

viewtopic.php?f=151&t=63296&start=92

I would ASSume that if there were PNP devices that would have been realized at this point. I have not seen any reference of pinout, but it would be groovy if that was recorded somewhere.

I think it's ibarakishi's and that EYG has it.

Maybe??

Yeah, I think the original plan was EYG was going to re-house and return to ibarakishi, but the 2020 timehole appears to have delayed that. Here's hoping EYG is doing well, just busy, and can return to illuminate us.

True... maybe there was a mistake? The DCA55 that was apparently used has autodetection maybe there was a misreading of PNP or NPN either by the device or by human?
The thing is, that all SOT23 Parts follow a standardized Pinout, where the collector is always at pin 3. There is just no possibility how there could be such a device with the emitter at pin 3, so the only thing that could somehow make sense is that it is a PNP... either used in some really funky configuration or something is off with the trace.
Another option is, that it is in fact a NPN, but intentionally used wrong? If we assume the standard SOT23 NPN Pinout and that the device is flipped upside down, the collector and emitter would swap places and the base would stay where it is... so basically you would use the NPN in reverse... idk why, but could be another option.

EDIT: this could actually be NPNs operated in reverse mode... they would have much less gain this way, and it would have to be some transistor type with enough reverse VBE Breakdown voltage... but would still work.

[mcatano]

Ok, I have pulled the pedal apart - build quality seems totally fine to me tbqh? Not sure what the issues are but anyway... it’s all SMD and half the board is obscured by the pots so I’m not sure how helpful I can be.

I’ll put some photos up in a sec - let me know if there’s anything in particular that you want to see.

[mcatano]

Big photos on imgur: https://imgur.com/a/eB6Bvqw

[crochambeau]

Oh hey, we've got differences between yours and ibarakishi's.

I note two components unpopulated, and the J201 in SMD.

Do we know which two components those are in relation to the schematic?

Oh, wait, those appear to be new footprints. There also appears to be a third hiding behind the pot legs.

[imJonWain]

PNP testing came up with nothing helpfull.

I'll test out the reverse NPN theory tomorrow for fun. Perhaps MPSA18?

Works in falstad for what that's worth.
https://tinyurl.com/yxd84w29

[BetterOffShred]

Just to chime in, during my go at this I made the following adaptations, to get the oscillations and sputtery madness down:

All the troubles I found were in the "Hi EQ" Path or Treble path or whatever you wanna call it. The schematic on EYGs website seems to be offline, so I can't show all the mods, but basically I did all this:

-) Added a 10M Resistor to +9V from the J201 Gate (causes a slight bias shift)
-) changed the strange 170k/17k biasing on the "Hi" BJT to 220k/22k
-) added the 47k Resistor to GND on the BJT after the 7n5 cap (as previously discussed in this thread)
-) changed the collector resistor on that BJT from 100k to 10k -> AC Gain is anyway given by the 10u Emittor Resistor bypass cap, reducing the DC Gain helps to reduce the sputterness
-) changed the biasing resistors on the next BJT stage to 470k/47k
-) also reduced the Collector Resistor to 10k on that one
-) reduced the 100n cap in series with the soft clipping diode to 10n
-) to get some gain symmetry, I also reduced the 47k Collector resistor on the BJT Stage in the "Bass" or "Low" Path to 10k, but that isn't strictly necessary I think.

As mentioned by goroth, it doesn't sound true to the original with those mods, but thats how I got it to work.

Yeah all my early troubleshooting back 8 pages or whatever also concluded the high EQ side is fucked and after the 7.5n

I tried a bunch of stuff and swapping 5089s around and all that and it always just has gnarly decay.

I can't bear to look at it anymore so I hid it in a drawer

[oldangelmidnight]

Ok, I have pulled the pedal apart - build quality seems totally fine to me tbqh? Not sure what the issues are but anyway...

The major build quality issues were with the jacks. They were kind of modified to fit into the enclosures and would just randomly fall apart.

[mcatano]

I guess they're "modified" in that the solder lugs are bent, but they're made of thin stamped sheet metal and I can't really see a single 90° bend causing any kind of problem in real world terms. Who knows though, stuff breaks.

[ibarakishi]

stuff breaks.

mine did

[DannDubbleEwe]

The jacks were modified by sanding off a large corner of them to fit in the enclosure. I never saw one completely fall apart, but on the handful I replaced the tip connection in the jack would eventually pull up while removing the plug and get worse over time until you could no longer fully insert a plug, and/ or twist so badly you would have to forcefully yank a patch cable out.

[imJonWain]

So swapping the Collector and emitter on Q6 and Q7 stops the "sputtery" sound and seems to solve most of the issues. Based on the images It's fair to say that's what is going on in the original. My test setup is janky but it's a solid distortion pedal now with alot of available gain and volume. Does that sound right?

I didn't use all the correct/assumed cap values since I didn't have them so mine is probably a little "off" I am gonna go back through and play with those next. I also used a 20k in volume pot and a 50k linear mix pot.

It will still break into oscillation with the "in" volume maxed, high control maxed, and mix set to the high side 100% for me though. This could just be my setup?

2n5088 works and so does MPSA18 but the MPS is a little more "unhinged" sounding in my setup to me.

From wikipedia...
"By reversing the biasing conditions of the forward-active region, a bipolar transistor goes into reverse-active mode. In this mode, the emitter and collector regions switch roles. Because most BJTs are designed to maximize current gain in forward-active mode, the βF in inverted mode is several times smaller (2–3 times for the ordinary germanium transistor). This transistor mode is seldom used, usually being considered only for failsafe conditions and some types of bipolar logic. The reverse bias breakdown voltage to the base may be an order of magnitude lower in this region."

more info...
https://electronics.stackexchange.com/q ... -operation

falstad sim:
https://tinyurl.com/y2kbotfv

[Schlatte]

Nice! I knew that there were some applications where BJTs are used in reverse, but never thought anyone would actually do that
So for all the people having problems with the PCB or stripboard builds, try flipping the BJTs around!