TM5 range and offset

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robboten
 
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TM5 range and offset

Post by robboten »

Hi. Recently finished my first x0x from willzyx and all went pretty well (except some minor problems with the jumper cables). I tuned it while building and that went fine. After finishing I decided to tweak some components:

R97 - 2k trimpot + 8.2k resistor for resonance boost
C20/C21 - 0.1uF for fuller bass in VCF
R120 - 100k trimpot for getting a boost for the resonance volume
Q11 - tried different c945 and c536 and went with a c945 that to my ears sounded best.

After this I went on to program some patterns and noticed that they sounded of. I then checked the tuning and it was to narrow. I tried to turn the TM5 and TM4 to tune it (the front pots 50% at first but tried different settings) but the with is just too narrow, I can't get a full octave in it's range. Also I noticed that TM5 not only change the with, it moves both ends up and down while turing, which makes it quite hard to get it right. I'm rather confused in this. I could replace the original components but aren't they in the filter? How could that change this pot? Any suggestions how I should proceed?

(At CV out I get 1.85V for the lower C and 2.67V at C2 these don't change when turning TM4/TM5)

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antto
 
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Re: TM5 range and offset

Post by antto »

check your 5.333V line, see if it's really 5.333 or not
if it's gone off - retune it using TM6

robboten
 
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Re: TM5 range and offset

Post by robboten »

Yes. I have checked that and it's 5.3V.

Found the eagle voltage reference board here in a thread. What I as different in my measurements starts at the 174 where pin 2 is 4.71V instead of 5.33V. At pin 3 it shows 4.99V. Out of R90 is 1.83V (for C). By D30/31 I get the same voltage instead of 5.26V. At R106 I read 5.20V on one side and at the other 2.44V - 1.85V at max/min. J6 pin 1 is also 1.85V.

robboten
 
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Re: TM5 range and offset

Post by robboten »

Is 5.98V in to gate of 74174 and 4.7-4.6V out normal? I also get about 0.17V on the outputs when input is off at 0.01V. Have tried to swap to another ic but with the same result.
Last edited by robboten on Sun Jul 07, 2013 8:03 am, edited 1 time in total.

robboten
 
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Re: TM5 range and offset

Post by robboten »

I have now also changed all resistors around ic9. Still 1.85V at C2 (at CV out or J6 pin 1). C1 gives however 1V. But then 2V is D2 and 3V is E3.

C1= 1.01V
C2= 1.85V
C3= 2.68V
C4= 3.55V
C5= 4.42V

Anyone have any ideas?

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mmm
 
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Re: TM5 range and offset

Post by mmm »

Please measure (unpowered) the resistance between the 5.33 power rail and IC9 pin 2, 5, 7, 10, 15, 12 and report the results.

robboten
 
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Re: TM5 range and offset

Post by robboten »

With IC 9 in socket (in kohm):
2 - 400
5 - 595
7 - 766
10 - 838
12 - 685
15 - 499

Without IC 9:
2- 400
5 - 601
7 - 802
10 - 902
12 - 701
15 - 501

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mmm
 
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Re: TM5 range and offset

Post by mmm »

robboten wrote:With IC 9 in socket (in kohm):
2 - 400
5 - 595
7 - 766
10 - 838
12 - 685
15 - 499

Without IC 9:
2- 400
5 - 601
7 - 802
10 - 902
12 - 701
15 - 501
Two things are obvious here:

1. The resistor values are ok without IC9. Which means they all are ok.
2. The resistor values are no longer ok with IC9 installed.

This leads me to the conclusion that this problem is related to either IC9 or its soldering points. Since you mentioned you already swapped the IC it might be useful to check if there are any solder bridges or copper bridges between IC legs and ground or other IC legs.

robboten
 
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Re: TM5 range and offset

Post by robboten »

Thank you for tour suggestion. I'll try to desolder the ic holder. But shouldn't the reading show this even if the if is removed since I measured at the ic holders pins?

robboten
 
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Re: TM5 range and offset

Post by robboten »

Desoldered the socket, cleaned and changed for new one. No difference. :-(

robboten
 
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Re: TM5 range and offset

Post by robboten »

Can also add that both ic9 is sn74ls174 from the same series (17axy4m e4). James from willzyx did a test on his part and those where OK.

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mmm
 
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Re: TM5 range and offset

Post by mmm »

robboten wrote:Thank you for tour suggestion. I'll try to desolder the ic holder. But shouldn't the reading show this even if the if is removed since I measured at the ic holders pins?
That's hard to pinpoint. I don't think the IC is at fault. In my opinion it is more likely that one of the other IC pins (not 2, 5, 7, 10, 12, 15) has an irregular connection which makes the system malfunction once the IC is installed.
I'm not home right now and hence can only do this from the schematic.
Sometimes the PCB has hairline copper bridges between a pad and for example the ground plane.

robboten
 
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Re: TM5 range and offset

Post by robboten »

I have tried to look for any but can't see any. Tried to clean the flux with some cotton swabs but became even more sticky. I hope the pics are OK anyway. Some scratches from desoldering woes. The ugly trimpot at r106 is for trying to test this resistance.

https://www.dropbox.com/sc/oixvtwfrho93o66/HD149nNaoc

robboten
 
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Re: TM5 range and offset

Post by robboten »

Problem solved by changing the supplied 74LS174 IC9 for a 74HC174. James saw this and sent me a replacement. Excellent service from Willzyx! Thanks to all who helped me out.

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