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Deep equinoxe damaged [tentatively resolved]
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author Deep equinoxe damaged [tentatively resolved]
Paradigm X

I plugged in a new diy module last night which i think has some power issues. and it appears to have taken out my deep equinoxe, although all other modules appear fine thankfully. fwiw its a sympleseq, basic 8 step sequencer, but nothing was plugged into it bar the power cable.

instead of the phasing sound i get bursts of pinkish noise, with the original signal in the background. the character of the noise changes slightly when you use the switches. the lfo appears to work fine, both modulating the noise, and externally.

Do you have any suggestions other than blindly changing all the ICs? I cant think of anything else although this might be a simple starting point. I had a quick look and none appear to be obviously damaged.

Many thanks as always
Sorry to hear.
Try to change the TL072 (U2)
Maybe you find for testing the tl072 on a other module.
Paradigm X
hey thanks so much!

i reaplce the tl072 (U2) as you suggested and seems to be working fine again. many thanks Ben
Paradigm X
as an addednum; i noticed that although the bulk of the problem had gone, i still got bursts of noise at certian settings

replacing all 4 lm13700s fixed it. not sure if all had to be changed, but it fixed it back to perfect i beleive.

Paradigm X
so i seem to have an intermittent problem, or something.

had a really good play with everything last night (and forgot to record ! ) and the problem with the equinoxe came back. it was working flawlessly until then, including a few other evenings. same bursts of white noise, and only at certain settings (mainly around 2oclock-4oclock on the frequency knob, but can be anywhere far less frequently). happends on all 3 stages settings.

so i tried to record it a bit this morning and it was fine again hmmm..... very frustrating

as its intermittent, im kind of stumped, i think ill replace the lfo opamp, although that seems fine externally, and also the power caps, as this caused big issues on my cota.

but if anyone has any less guesswork inspired suggestions id be very grateful.

many thanks ben
Quite possibly the frequency pot is bad and will need replacing. I have had this before - the module mostly works then all of a sudden horrible noises and then as soon as you get it on the bench it behaves itself. So what could be happening is that the wiper of the pot loses contact randomly and rapidly changes the centre frequency of the phaser causing all sorts of horrible noises.

If you can get a scope on the wiper (middle pin of the pot) take a look at the voltage there. If it is a bad pot you'll (eventually) see the scope trace bouncing around as you rotate the control.

Paradigm X
wow thanks tony, that sounds exactly like my issue. ill try replacing the pot.

ive got a scope but not used it yet, and no psu in the 'workshop' so will probably just replace without trying to see. sounds exactly the same.

many thanks, ben
Paradigm X
well i replaced the pot, and couldnt get the noises to appear, and had about a half hour of wigglage with no reoccurence. So tentatively chalked up as resolved...

Many thanks Tony, youve probably saved me a ton of time !

we're not worthy
Paradigm X

So i had a good go on the modular last night, and it came back again! very frustrating it didnt occur til over two hours of wiggling.

flipping nora. frustrating. it worked 'perfectly', as far as i can tell, prior. Its the same periodic white noise, sounds like hihats, which fades in and out. The frequency of reoccurance is tied to the LFO. i did record a bit but need to get it off the dat.

To confirm, i have replaced the frequency pot, U2 (tl072), and all four LM13700s, and also the two main PSU caps (2.2uF). I havent changed the TL074 which im now suspecting as its tied to the reoccurance rate of the noise, or the power caps over that side of the pcb, which i guess ill try asap (its freezing in the garage!).

IS there anything else to try before giving up and sending to Tony to fix? Or things to measure? Ive got a scope but not a PSU in the 'workshop', which i really need to sort out.

Many thanks
Paradigm X wrote:
Its the same periodic white noise, sounds like hihats, which fades in and out. The frequency of reoccurance is tied to the LFO.

I don't know whether we can blame the LFO. I think the LFO is just doing its job and modulating the phaser. I'd look at Q1 and Q4. Maybe replace those. If one of those is breaking down then that could cause noise which would be modulated by the phaser core.

But the intermittency of this does point to a mechanical problem like a failing pot, joint or connector. I'd go with the transistors first and then have a look again at all the solder joints - particularly around those two transistors.

Paradigm X
Thanks again Tony. Its a really odd one, its not really intermittent, but seems to take a while to kick in.

EDIT; i agree on the LFO, it seems fine modulating other sources. Great to have a free LFO by the way!

Ill change those transistors and see how i get on.

Cheers, Ben
Paradigm X
Edit, well, typing this out and rechecking has helped, oddly. Just reread the build guide yet again and im pretty sure i was reading the deep equinoxe bit when i replaced the trannies - so i installed a bc549 in Q4, which should actually be a bc559. funny, i thought id removed a 559 but thought id imagined it after reading the BG!

ill recheck again tonight. determined to get this working.

many thanks!

well, i replaced the two transistors suggested, and now its completely dead :( well i get sporadic bursts of low frequency noise, like a hum, which fades in and out. no change at any switch settings and or pot settings.

I used BC549 instead of 550 - from what you've posted previously i guess this isnt an issue? They were previously bc549s for what its worth. they were new.

one other small factor which i dont think is relevant is that the daughter-board is connected by about 6" wires, rather than the little jumper - it was in a rack previously. as it worked previously, im guessing this isnt an issue. just thought id double check.

i also re-soldered a few possibly dodgy looking joints, but no change.


Paradigm X
well, putting in the correct part for q4 seems to have done the trick!

now back to full glory, might be my imagination, but im sure its sounding better than it has recently, a really clear phase with much more noticeable difference between the stages too.

ill have to wait and see but hopefully thats got it now.

many thanks for your help again
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