XOX(BOX) Trouble shooting

Re: XOX(BOX) Trouble shooting

Postby guest » Wed May 06, 2015 5:02 pm

ok, set it to the 200mV range when doing the 100k resistor measurement.
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Re: XOX(BOX) Trouble shooting

Postby spotta » Sun May 10, 2015 5:45 am

Lwr octave lwr C - 0mV
Middle octave lwr C - 0mV
High octave lwr C - 0.5mV
Higher octave lwr C - 23.7mV
Higher octave high C - out of range

I also now have two spare 2SK30AO's now ready to fit, but haven't ordered another 2SC1583 yet.
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Re: XOX(BOX) Trouble shooting

Postby guest » Sun May 10, 2015 12:24 pm

were those with the capacitor removed? if so, then its sounding like the 2sc1583 is the problem. what were the voltages on it for 2 different CVs?
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Re: XOX(BOX) Trouble shooting

Postby spotta » Tue May 12, 2015 6:39 am

I hadn't removed C33 - I must have missed that bit, however I now have and everything's the same.
voltages across 100k resistor in Q25 on mV scale are
middle low C = .000
higher low C = .5
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Re: XOX(BOX) Trouble shooting

Postby guest » Wed May 13, 2015 1:32 pm

so i went back and looked at some of the earlier debugging info you posted, and realized that i made a mistake. there is something wrong with the scaling. this could be Q26, or the resistors (most likely Q26). can you use your multimeter to double check the resistance of R100, R106, and R118 (make sure power is off). they wont read exactly right, as they are in-circuit, but they should be somewhat close.
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Re: XOX(BOX) Trouble shooting

Postby spotta » Wed May 13, 2015 1:54 pm

Q28 is still unpopulated and the resistor is still in Q25
but I get

R100 .493 for both R100A & R100B
R106 2.39
R118 13.33
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Re: XOX(BOX) Trouble shooting

Postby guest » Wed May 13, 2015 5:34 pm

it looks like r106 might be bad. desolder one leg, and measure the resistance again out of the circuit. it should be 27k. it could be reading low becuase its in the circuit, or it could be bad. do the same for R118 (that should read 100k).
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Re: XOX(BOX) Trouble shooting

Postby spotta » Thu May 14, 2015 3:46 am

Yep R106 is bad. The build manual states this should be 24k rather than 27k, which would you recommend replacing it with?
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Re: XOX(BOX) Trouble shooting

Postby guest » Thu May 14, 2015 12:15 pm

yes, use the 24k.

and my most sincere apologies for not catching this earlier. i feel really bad about having you rip apart half of the VCO, and order new parts and all. im not sure why i messed up my calculations the first time.
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Re: XOX(BOX) Trouble shooting

Postby spotta » Thu May 14, 2015 12:38 pm

Dude, you have been helping me out on this for three weeks. you have no reason to feel bad at all. I am so grateful to have someone who knows the x0x so well helping me out :)
Do you think i should repopulate C33 and Q25 after R106 is replaced and try it?
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