Cave dweller II dub edition

[PMowdes]

Hi all

Finished this over the weekend

http://tagboardeffects.blogspot.co.uk/2014/04/madbean-cave-dweller-ii-dub-edition.html

and although it kinda works it seems to get stuck in a feedback loop which builds to white noise which makes it unusable.

I measured the voltages as follows:

Pt2399
1 4.90                     16 2.45
2 2.44                     15 2.45
3 0                         14 2.45
4 0                         13 2.45
5 3.06                    12 2.45
6 2.43                    11 2.45
7 3.9~ (Variable)    10 2.45
8 3.9~ (Variable)     9 2.45

The voltage at pin 7 and 8 changes with the pot position (sorry cant be more specific than that)

Just about the same voltages on both chips.

Voltage regulator :
I 8.22
G 0
O 4.89

Q1
E 0.24
O 0
C 2.42

Q2
E 0.24
O 0
C 2.43

I've checked the layout a bunch of times and I'm pretty sure that the components are in the right places.  






Thanks in advance

[induction]

Your PT2399 voltages look ok, and you're getting repeats, so the PT2399's are working. I can't find a schematic for this circuit (the link in the version 1 layout page is dead), but the symptoms you're describing are mentioned in the dub edition layout page:

"Additionally, the dark repeats have been limited to non-oscillating by using a larger value for R12 . If you do implement the Mix mod, you can lower the value of this resistor from 750k to a value between 470k and 560k to re-introduce oscillation. This is not recommended when not using the Mix mod."

Without the schematic I can't be definitive, but you should first verify that the 750k resistor is, in fact, 750k. If it is, try increasing it. Maybe temporarily replace it with a 1Meg pot set up as a variable resitor, dial it in to non-oscillation, read the value from the pot with a DMM, and replace with the appropriate resistor.

This should probably work, but I make no guarantees without a schematic.

[PMowdes]

quote author="induction">
Your PT2399 voltages look ok, and you're getting repeats, so the PT2399's are working. I can't find a schematic for this circuit (the link in the version 1 layout page is dead), but the symptoms you're describing are mentioned in the dub edition layout page:

"Additionally, the dark repeats have been limited to non-oscillating by using a larger value for R12 . If you do implement the Mix mod, you can lower the value of this resistor from 750k to a value between 470k and 560k to re-introduce oscillation. This is not recommended when not using the Mix mod."

Without the schematic I can't be definitive, but you should first verify that the 750k resistor is, in fact, 750k. If it is, try increasing it. Maybe temporarily replace it with a 1Meg pot set up as a variable resitor, dial it in to non-oscillation, read the value from the pot with a DMM, and replace with the appropriate resistor.

This should probably work, but I make no guarantees without a schematic.




Thanks, I did read that but it might as well have been in Chinese,  looking at it I may have put a 150K instead of 750K, I'm pretty sure that I tested everything before mounting but maybe I misread it,  I am soo bad with resistor colours.<

[PMowdes]

induction wrote

Your PT2399 voltages look ok, and you're getting repeats, so the PT2399's are working. I can't find a schematic for this circuit (the link in the version 1 layout page is dead), but the symptoms you're describing are mentioned in the dub edition layout page:

"Additionally, the dark repeats have been limited to non-oscillating by using a larger value for R12 . If you do implement the Mix mod, you can lower the value of this resistor from 750k to a value between 470k and 560k to re-introduce oscillation. This is not recommended when not using the Mix mod."

Without the schematic I can't be definitive, but you should first verify that the 750k resistor is, in fact, 750k. If it is, try increasing it. Maybe temporarily replace it with a 1Meg pot set up as a variable resitor, dial it in to non-oscillation, read the value from the pot with a DMM, and replace with the appropriate resistor.

This should probably work, but I make no guarantees without a schematic.

I removed and checked the resistor and it is 750K, i put a 1M pot in and whilst it made some difference there was still a load of feedback once the mix was about a quarter turn and it was worse when the dwell was turn up.  i socketed the resistor and went up to 10M, which again made the problem slightly better but even a small amount of dwell seemed to send it into horrible endless feedback.

[induction]

Sounds like you have a build problem then. I can't diagnose much more without a schematic, so we'll have to see if we can find a build error by comparing against the layout.

[PMowdes]

induction wrote

Sounds like you have a build problem then. I can't diagnose much more without a schematic, so we'll have to see if we can find a build error by comparing against the layout.

No worries.  I might scrap this one and re-purpose the IC's for something else.  perhaps the deep blue or something.

I've been over the layout about a dozen times and can't see anything wrong.  perhaps there is a duff component???  Although I did check all the resistors, trannies and caps before putting them on

[induction]

Oscillating repeats in a delay doesn't sound like a bad component, though it's not impossible. It sounds more like a build error somewhere in the feedback loop. Unfortunately, without a schematic I can't say where the feedback loop is in the layout, so I can't recommend where to start looking.

Higher resolution photos would help. The ones you posted are too pixelated for me to do very much with.