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defex
Joined: Jun 27, 2008 Posts: 36 Location: Toronto, canada
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Posted: Tue Sep 20, 2011 7:14 pm Post subject:
20 Stage/Tau questions and comments |
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a nice pair:) the transistors are ebay CA3046 from the US "blue dot", supposedly tested somewhere, they seem to work anyways. capacitors in the stages are 5%, vishay BFC237042153 from digikey, and they accidentally sent me 100 extra, hmm what to do with them?
Just bench tested my first one. the only difference from stock, is a slightly slower capacitor for the LFO, and replace the 1u electrolytics in the signal driver with 1u film caps (because i had them, not because of any hi fi freakery)
temporary pots just for testing.
It sounds great! and thats just with a function generator.
I am building both of them behind a 2u MOTM synth modular panel, and what i want to do is use an extra pot to feed the output of one side in to the other. my guess is that i can just use another resistor at the junction of r2 and r4 and connect it the same way as the input or feedback pots. does that seem correct?
also, here is how i made a MOTM connector for it, in case anyone is interested.
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sonicwarrior
Joined: Dec 22, 2005 Posts: 266 Location: Cologne, Germany
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Posted: Wed Sep 21, 2011 12:11 pm Post subject:
Re: 20 Stage/Tau questions and comments |
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Nice idea with the MOTM connector. I think I'll copy that although I already soldered the resistors in.
Which capacitor did you choose for the LFO? |
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defex
Joined: Jun 27, 2008 Posts: 36 Location: Toronto, canada
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Posted: Wed Sep 21, 2011 12:38 pm Post subject:
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It is a 0.68u with 500k pot, i might try something even larger, or even 2 with a switch
I just tested the second one and it has a strange problem. even though the resistance from power to ground on the non working and working boards are very close, on the second one, the 10 ohm resistor on the positive side gets very hot and i do not get any output.
never mind, it is fixed. stupid error!
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defex
Joined: Jun 27, 2008 Posts: 36 Location: Toronto, canada
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Posted: Mon Sep 26, 2011 10:40 am Post subject:
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They are both working perfectly now, and panelized, just waiting for some supplies to do the graphics.
i really like this module, thanks for the great design! |
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mig27
Joined: Mar 09, 2011 Posts: 21 Location: Berlin
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Posted: Sun Feb 26, 2012 1:10 pm Post subject:
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defex wrote: |
I just tested the second one and it has a strange problem. even though the resistance from power to ground on the non working and working boards are very close, on the second one, the 10 ohm resistor on the positive side gets very hot and i do not get any output.
never mind, it is fixed. stupid error!
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Funnily I have the same problem.
One of the 10 ohm resisistors gets really hot.
As a matter of fact, I got magic smoke, so I didn't even test my board any further.
Would you like to share what "stupid error" you debugged?
Probably the same here..
Thanks a ton!
Michael |
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defex
Joined: Jun 27, 2008 Posts: 36 Location: Toronto, canada
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Posted: Sun Feb 26, 2012 1:30 pm Post subject:
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I had put an IC in backwards! |
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mig27
Joined: Mar 09, 2011 Posts: 21 Location: Berlin
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Posted: Mon Feb 27, 2012 9:17 am Post subject:
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Thanks for your quick reply!
Unfortunately, my ICs are not the culprit - all properly mounted.
But it indeed seems that there's an issue with my power rails.
Now I'm wondering if JH's +/-15V implementation is all that good.
I followed the instructions mentioned on his site:
However I have the impression most folks did it à la Bill & Will:
Any thoughts?
Thanks!
Michael |
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defex
Joined: Jun 27, 2008 Posts: 36 Location: Toronto, canada
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Posted: Mon Feb 27, 2012 9:34 am Post subject:
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you can see in my pic, that i didn't do the power the recommended way at all, but the result should be the same, as long as you have +15v and -15v (i measured on the legs of the 10 ohm resistors) i doubt that is the problem.
if the resistors get hot then something is shorting in the part of the circuit that is powered after them.
if you used sockets, try taking the ICs out and checking to see if the resistors still overheat. then put them back in one by one, and see which one is related to the problem.
it doesnt meant that IC is bad though, it could be something around it.
if it still overheats after you remove the ICs, maybe there is a short somewhere, possibly the SMD capacitors? check the resistance to ground from the positive and negative supplies (after the 10 ohm resistors) |
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mig27
Joined: Mar 09, 2011 Posts: 21 Location: Berlin
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Posted: Mon Feb 27, 2012 9:42 am Post subject:
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Yup I've seen that.
Will probably try out this alternative +/-15V wiring.
A used some older surplus lytics near my burned 10 ohm resistor.
The 22uF ones seen here:
Maybe I should replace these too.
Well, at least I saw the two LEDs flashing during the 3 seconds I had my tau board fired up (pun intended) - so a little something working already
Will keep you guys posted. |
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marvkaye
Joined: Mar 14, 2011 Posts: 225 Location: Fla
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