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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS65 Tube VCA - need help troubleshooting
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hottlungs



Joined: Feb 16, 2011
Posts: 11
Location: long beach, ca

PostPosted: Mon Feb 21, 2011 1:20 pm    Post subject: CGS65 Tube VCA - need help troubleshooting Reply with quote  Mark this post and the followings unread

I am supplying power from a Synthesizers.com QPS1 Power supply(+15, Gnd, -15). When power is supplied to module, no module in system will produce an output (including the Tube VCA). Both LED's light but I am unable to test the circuit further or calibrate. When module is removed from the power supply, the other modules in the system function normally. I have questions about the ferrite bead I selected(Having 4 legs, large size compared to the smaller axial ferrite beads i've seen online) and also the value of the 330k resistor(my local electronics supply only had 331k 1%)

I am not new to electronic projects or a soldering iron but I do have a very unsuccessful background in troubleshooting them if they don't work. I have triple checked the back of the pcb to make sure that there are no shorts. I also triple checked the wiring of the pots and jacks. Does anyone have any advice?

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My Parts List
Caps
47pf x 4
100n x 3
220n x2
10uf 25v x 2

Resistors
330r 1% x1
1k5 1% x2
2k2 1% x1
8.25k 1% x1
10k 1% x1
100k 1%x12
220k 1% x2
331k 1% x1

100k trim pot x 1
100k linear pot x 2
100k logarithmic pot x 2

Semis
1N4148 x2
3mm LED x2
LM358 x1
TL072 x1

Misc
1J24B x1
6pin MTA m connector x1
Ferrite Beads x2
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hottlungs



Joined: Feb 16, 2011
Posts: 11
Location: long beach, ca

PostPosted: Wed Feb 23, 2011 11:26 am    Post subject: Reply with quote  Mark this post and the followings unread

I replaced the tube and double checked the component values. LED's light, but again no sound from any module. I'm wondering if i should try replacing the ferrite beads with 10r resistors.
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andrewF



Joined: Dec 29, 2006
Posts: 1174
Location: australia
Audio files: 4

PostPosted: Wed Feb 23, 2011 4:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

You are missing a link, 2nd picture down, just below the 100k, to the right of the 'SN' hole. This link provides -V to the TL072.

One of the first things to do when debugging a circuit is to check all the chips are getting power on their power pins.

I use 10 Ohm rather than ferrite so that if there is something wrong the 10 Ohm resistors start to smoke, it is a good way to find out.
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hottlungs



Joined: Feb 16, 2011
Posts: 11
Location: long beach, ca

PostPosted: Wed Feb 23, 2011 7:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is this the link?
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hottlungs



Joined: Feb 16, 2011
Posts: 11
Location: long beach, ca

PostPosted: Wed Feb 23, 2011 7:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

low and behold... the missing link. consider this thread troubleshot.
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