MUFF WIGGLER Forum Index
 FAQ & Terms of UseFAQ & Terms Of Use   Wiggler RadioMW Radio   Muff Wiggler TwitterTwitter   Support the site @ PatreonPatreon 
 SearchSearch   RegisterSign up   Log inLog in 
WIGGLING 'LITE' IN GUEST MODE

ADSR/VCA Problem
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author ADSR/VCA Problem
Scorchi
Confidence was riding high after 1st time success with 2nd osc & mixer, but it crashed with ADSR.

At the point of testing testing 123 (in builders guide)

No smoke, no hot chips (in fact not even warm)

The LED is yet to flash, and I seem to be getting 13.79 volts from VCA & ADSR out. Trimming gain seems to have no effect.

Ive Checked for shorts, Checked Chips and swapped a couple out, and am currently checking rest of component values (I may be some time).

Should I be getting continuity across all four pins of S-R header? Also is socketing the THAT2180LC a bad move?

I've uploaded a pic in case its something glaringly obvious I'm yet to spot.



Thnx in advance.
Synthbuilder
Scorchi wrote:
The LED is yet to flash, and I seem to be getting 13.79 volts from VCA & ADSR out. Trimming gain seems to have no effect.

Presumably the LED is permanently on. The EG core is ramped to the positive rail. Check that pin 4 on the TL072s are all at -15V. Check that R23 and R24 are actually 390K. They don't look right on your photo.

Scorchi wrote:
Should I be getting continuity across all four pins of S-R header?

Only when all the pots are set to their minimum. Stick them at high and see if the resistance changes.

Scorchi wrote:
Also is socketing the THAT2180LC a bad move?

It should be no problem at all.

Tony
Scorchi
Thanks for reply Tony.

Sorry, by that I meant the LED is yet to turn on, its permanently off.

Will re check values tonight.

Phil
Scorchi
OK I have -15v on pin 4 of all 3 TL072.

Fortunately I have Krisp-1 versions of this module at work, so I brought one home and that works fine.

R23 & R24 are definately 390k 1% same as Krisp-1 (or, wht, blk, or, brn).

As you said I loose continuity and resistance goes up on S-R header when pots increased.

What I have noticed are some different chips.......

My Chips

U2 = CD4052BE
U7 = LM13700N

Krisp-1 Chips

U2 = HEF4052BP
U7 = 13700D

All other chips the same numbers different manufacturers.
thebot
ADSR/VCA was one of my first builds, and first with the SOCK4 board. If I remember correctly I had symptoms like yours and it turned out the problem was with the jumper to the sock4 board - it was back to front on one of the sockets.

Sorry if this seems really obvious - just trying to chip in with my early build issues experience! You may not be as daft as I am! If you're not sure if you post a picture of the jumper I can let you know one way or the other.
Scorchi
Thanks for your input thebot, I did check that early on & I just swapped my jumper with the krisp-1 jumper to make sure, but not the fix in this case.

Just to make extra sure I popped the SOCK4 board off and checked from solder side of headers on both boards to check header joints but all good there too.

Thanks again.

I swapped out C7 C11 & C16 (to match Krisp-1 2.5mm NPO) It seems to be working in normal mode now with 5v output but still no LED flashing and still no looping mode.

Getting there but also getting late. I think I've narrowed it down to two things now.

1: I've done something really odd
2: I've done something really dumb

d'oh!
Synthbuilder
Scorchi wrote:
I swapped out C7 C11 & C16 (to match Krisp-1 2.5mm NPO) It seems to be working in normal mode now with 5v output but still no LED flashing and still no looping mode.


The lead spacing on those capacitors should not have made a difference. So long as the value is fine the circuit should work. However, you may have inadvertently fixed a different problem by taking the older caps out.

Try swapping the LED's leads around and see if that gets it lit. That should be an easy thing to do with that MTA socket. If it doesn't work do check the wires going into the MTA socket have been properly inserted. It may be worthwhile using the tool on each one again.

No looping could mean that the output of the core doesn't fall low enough. If you are getting 5V from the ADSR output when triggered in normal mode, what is it when it is not triggered? It should be only a few mV.

In loop mode turning Sustain up will cause the ADSR output to be fixed at a set voltage. With S at 100% it should be around 5V. With S at 50% is should be 2.5V. Is this happening?

Tony
Scorchi
Thanks for your help Tony

Yes I realise about lead spacing, I thought I'd wandered from NPO ect in my attempt to source 5mm caps and thought I'd got something weird, but read on it gets worse.

I've a confession to make, picked up my multimeter tonight and reales I'd taken a AC reading when I thought I had 5v at output not this shit again oops

Anyway...

Tested MTA on LED as you suggested & found I had no continuity on 0v on MTA , got the MTA tool out again and did it much harder, still no continuity, made another lead and connector then YEY!! LED lit up!!

But it never turns off in loop mode, it remains solid regardless of attack or decay setting. Back to component checking again, but maybe not tonight
Guinness ftw! needs my attention smile.

Thanks again for your patience Tony.
Scorchi
OK all resistors correct, and all capacitors correct (checked twice)

Just had a thought though, having cooked a BC549 in one of my TM3030 builds, I assume the BC550 & 560 are as sensitive to heat. Just wondering if I've fried one again (got plenty spare).

UPDATE: All replaced not the case in this instance.

Phil
Synthbuilder
Scorchi wrote:
But it never turns off in loop mode, it remains solid regardless of attack or decay setting.


What is the DC voltage at the output when in loop mode? Does it change with sustain value?

What is the output voltage in normal mode with no trigger, ie. LED off?

Tony
Scorchi
Hi Tony

Apologies, work and other stuff gone into overdrive this week so building will be on hold for 1 or 2 weeks.

Will let you know next time I get a chance to power up.

Regards & thanks
Phil
Scorchi
Ah, now where were we......

Output Voltages Loop Mode

7.44v With no input
0.27v with input

Sustain pot has no effect on either.

Output voltage normal mode no trigger

Zero Volts.

I've run a test this eve in normal mode.

Attack = works as expected
Decay = Has no audible effect
Sustain = Has no audible effect
Release = works as expected

Mode switch = works as expected
Speed switch = works as expected
Synthbuilder
Sounds like the Sustain pot could be busted or at least the sustain pot isn't having any effect because of another fault. Measure the voltage on the wiper (the middle pin) of the pot with respect to ground. Make sure it moves from 0V to 8V or so when you turn it up. This should happen irrespective of whether the EG is triggered or not.

If it does then check that very same voltage is to be found at the removable jumper that connects pins 1 and 2 on the S-R header. If it does you may want to swap out the 4052 with a fresh one.

Tony
Scorchi
OK the sustain pot is working fine, 0 - 8.4v on pot and S-R Header. I swapped out the 4052 (Twice I have 3) and no change.

Would it be worth changing Q1 also?

Phil
Synthbuilder
Scorchi wrote:
Would it be worth changing Q1 also?

It could be Q1. It's certainly worth a try. A failure in Q1 would indeed cause the attack mode not to end.

What's the voltage on pin 7 of U4 in norm mode and with the gate enabled?

Tony
Scorchi
UREKA!!!!!!

Q1 Faulty, dont know if I killed it but missed it when swapping out other BCs.

Many thanks for your help on this Tony & thebot, you'll be glad / relieved to hear that all the other modules I ordered from you are now all built tested & calibrated.

Very happy bunny here. Time to make some noise!

Phil
thebot
It's peanut butter jelly time! Glad you got it sorted!
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Page 1 of 1
Powered by phpBB © phpBB Group