I built this up and it's not quite right. The knobs all do what they should but there's crazy loud background squealing going on. I'm a complete bozo with schematics but I looked it over and found a few things. I think the 10k resistor on the right should be 100k. Also I think the Tranny is backwards. Has anyone else tried this yet?
Gave the rest of the schematic a good look over, but can't find anything else. The 10k's are all correct - one to bias the collector of the tranny and the other two 10ks are to create a voltage divider for 4.5v+
Hey Chris - no, you're spot on - that signal needs to pass in series through a 1k before coupling out via that 1uf capacitor - which would explain the funky gain control and white noise.
The unfortunately I think Chris was right to point out that R16, C12 mix up in the schematic. You can get pretty creative with components in parallel, but as the schematic is now you have two components in series swapped - I really think that 1k resistor needs to be in series on front of the coupling cap. That's gonna require a bit of shuffling components around - I don't see a quick way as it is now.
Okay - if you can stomach one more go, I'm pretty confident this will fix it. Add cut O12 or 13. Remove 1uf at L17,M17. Move 1k at Q15,L15 to M15, O15. Place positive leg of 1uf at O19, negative a Q19.
I built this up and it's not quite right. The knobs all do what they should but there's crazy loud background squealing going on. I'm a complete bozo with schematics but I looked it over and found a few things. I think the 10k resistor on the right should be 100k. Also I think the Tranny is backwards. Has anyone else tried this yet?
ReplyDeleteTranny is definitely backwards - 220r should connect emitter to ground.
DeleteGave the rest of the schematic a good look over, but can't find anything else. The 10k's are all correct - one to bias the collector of the tranny and the other two 10ks are to create a voltage divider for 4.5v+
DeleteOh and I'm counting 12 links
ReplyDeleteAnd only 20cuts unless I've missed onw
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ReplyDeleteThe tranny is backwards and the 1u at P11 is the wrong polarity according to the schematic.
ReplyDeleteI flipped the Tranny and the 1u cap and have the same result. A working circuit with crazy loud white noise
DeleteRest the schematic checks out against the layout. You flipped that capacitor too? Check with bridges and signal probe time if so...
DeleteOnly thing different is after gain 1 it should be the 1k then 1u (it's 1u then 1k here) but I don't think that would make a difference.
Hey Chris - no, you're spot on - that signal needs to pass in series through a 1k before coupling out via that 1uf capacitor - which would explain the funky gain control and white noise.
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ReplyDeleteNevermind - found c9 in the 3rd revision - it is indeed a decoupling cap for 4.5v
ReplyDeleteQuick test if you can - move gain 1 wire in-board to m11 or m12 - if this fixes your issue we know what's causing it
ReplyDeleteI just moved it to m11, and it didn't fix the issue.
DeleteThe unfortunately I think Chris was right to point out that R16, C12 mix up in the schematic. You can get pretty creative with components in parallel, but as the schematic is now you have two components in series swapped - I really think that 1k resistor needs to be in series on front of the coupling cap. That's gonna require a bit of shuffling components around - I don't see a quick way as it is now.
DeleteOkay - if you can stomach one more go, I'm pretty confident this will fix it. Add cut O12 or 13. Remove 1uf at L17,M17. Move 1k at Q15,L15 to M15, O15. Place positive leg of 1uf at O19, negative a Q19.
DeleteI just added the cut and moved the two components, no luck. My vero is getting super messy. I'm pretty close to scrapping it and starting over.
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