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  1. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Q3 drain and Q5 emitter would have continuity both being connected to VCC they'll have continuity with everything connected to VCC The shop pcb image shows some traces Check Q5 base and emitter pins don't have continuity is it definitely 2N3906 you're using You shouldn't have continuity...
  2. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Q5 left to right is emitter base collector Did you check audio from Q5 collector through C5 to Q3 gate I'm assuming Q5 collector is 0.33, the same as Q3 gate, emitter 9 and base (middle pin) 7v?
  3. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    That would definitely lower the level as @giovanni pointed out it's part of the feedback network of a basic op amp set up Probe from Q5 collector through each component to Q3 gate and see if level drops at any component or fails to get through
  4. Mcknib

    Paragon Problems

    Very quick glance C10 looks the wrong way round It is hard to make out though
  5. Mcknib

    Parenthesis Octave LED

    Try reflowing your K cathode solder joint and the black and white wire joints on the pcb and 3PDT lug
  6. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    I knew it was a basic op amp set up could see the collector feeding the gates but just wasn't sure if source would output audio coz my head hurts! I've kinda lost track That explains it nicely cheers @giovanni
  7. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    You shouldn't get audio on anything coming directly from a voltage source ie power section you will sometimes get what I call bleed through audio, although I don't know what it is or why, it's usually very distorted Pin 8 of your op amp for example I learnt this from another debug too my great...
  8. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    R3 should have audio on the non grounded side Q5 and 6 are BJTs pins are C B E collector, base middle and emitter with the arrow Q5 and 6 should have audio on base and collector pins You will hear differences depending on whether it's going through an amplification stage (louder) or a tone...
  9. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Go that man I was just gonna say did you take resistances with no power to the circuit It'll jump around with caps discharging etc unless you let it drain for a few minutes once you disconnect power Anyway good to hear you've got a bit of action
  10. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Yeah you learn a lot and remember some of the stuff you've long forgotten You've just got to use a systematic approach always a visual check first then voltages A quick resistance check between Q3 source and ground will tell you if it's not connected you should expect R6 4K7 value as mentioned...
  11. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    One side should have continuity with ground the other Q1 and 3 source Reflow Q3 solder joints they don't look great @giovanni may have directed you to hopefully your only problem
  12. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    That set up is a long tailed or differential pair Q1, 3 and 5 and Q2, 4 and 6 work together like a basic op amp This isn't your usual kinda stuff you've also got gyrators making an appearance with Q7 so far from your normal frequently used pedal circuitry Your 2nd posted op amp voltages look...
  13. Mcknib

    Rat doesn't work

    A man of your ability and you've used non conductive fencing wire? Always check for continuity or you ain't going to Boomtown
  14. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    I agree it was a saga but you learn a lot from your mistakes and keep passing it on People like yourself @giovanni @zgrav @BuddytheReow @carlinb17 and many more keep this place one of the best forums passing on your knowledge and staying with it Jeff's now armed with how to use a probe and...
  15. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    As soon as you said things were getting hot apart from your brow I thought dead short but you placing your probes correctly ie + to + and - to - on the lugs and getting +9v as you would threw me especially when you didn't get -9v on the board Anyway hopefully because you never kept it plugged...
  16. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Normally you'd know right away it's inverted with negative voltage readings, but I'm not reading through it all again to see if there are any! Dare I say it.......hopefully You @giovanni deserve a medal for your continued patience fortunately @Jeff C is a good humoured chap too
  17. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Description for the DC jack says short lug is for the centre pin do you have that soldered to the + power pad making it centre positive Continuity check which lug the centre pin is attached to You want centre negative unless you're using a centre positive adaptor that is If you're using a...
  18. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Post a well lit pic of the component side so we can see all components clearly it's hard to get a good look with the images posted You can check and re check and still miss something Link where you got your DC jack Again it's hard to see it clearly
  19. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    I've just realised I should have told you to snip one side of D100 before jumpering it I was going on the path of least resistance but maybe it being soldered to the board it hasn't bypassed it What I'd do is snip D100 out completely on the component side of the pcb and solder a jumper in place...
  20. Mcknib

    SOLVED Cobalt Drive problems…..SOLVED……..FINALLY!

    Sure does that's not directly connected to VCC just check each point labelled VCC to ground only I'm saying dead short because you say the IC and C100 get hot so it's drawing more current than it should But from what you described earlier 9v one side and 1.2v the other side of D100 that'd be...
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