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DIY Mutant Bassdrum died - fine last night, any ideas?
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Author DIY Mutant Bassdrum died - fine last night, any ideas?
wonkychris
I posted this ten days ago in the Hexinverter subforum but not getting any response over there, so thought I could try here...


I built a Mutant Bassdrum a couple of weeks ago, but this morning when I hit go on the patch that I had up last night, no Kick drum

If I cycle the power the ENV LED flashes. The distortion section works fine.

I can't see any burnt components and it was sounding mighty like beating heart of pissed off bear last night!

A bit of background on the build as it may be relevant...

I got the whole thing finished but made a booboo plugging up the first time. I had run out of sockets on a uZeus supply, so add a new flying busboard cable, but in my hurry plugged it in upside down!

When I first plugged in the Mutant Bassdrum all the LED's lit and some magic smoke appeared. Disaster! It was only plugged for a couple of seconds and amazingly when I re-plugged correctly and adjusted knobs to get a sound, it worked.

Something that may have been a result of this damage is that if I had the tone, decay and BD lvl controls all the way up there was a very harsh "crack" sound, which wasnt a distorted normal signal as such, but a different 'bad' sound.


Any ideas where I might start?

(oh one other thing is if I accidentally plug a trigger into the clean output, the ENV light flashes with the gate and there is some output from the distorted out, but just a pulse, no decaying sound)

(on a positive note I finished the Mutant HiHat last night and that zings along happily making crunchalicious ghetto housey beats sneak would be proud of, switches make it really playable)


Here are the results of some further testing/work

I spent a while going through the module yesterday.

1. I tested all the didoes, resistors and capacitors. They seem to be resisting and capacitating happily (?). One diode gave a slightly odd reading so i took it out, it was tested in circuit, replaced it with a fresh one.
2. I swapped all the IC's out one by one and it made no difference. (didnt have enough spare IC's to do a complete swap.
3. I tinned the header pins to make a tighter contact. No change
4. I re-blobbed every solder joint in case of dry joints. No change although I seemed to have knackered the purple LED's in the distortion section doing this. I replaced them and the distortion section came back.
5. I prodded bits of the circuit with jack carrying a trigger signal. If prodded the 2nd pin down on the left header if you're looking at the PCB with jacks and pots from the front(see pic below), the bassdrum triggers, all the controls work and the level seems about right. ALso the decay trimmer works correctly.
6. It was late so I went to bed.



I'm not too hot at reading traces on PCB's so don't really know what point 5 is telling me. Is the socket knackered? Which component could be out? I guess I dodged part of the circuit but am not sure which bit

spotta
Mine did the same, worked, then suddenly didn't, and if I remember correctly there was a third person who also had a similar problem. I'll need to have a search, I haven't been around here as much recently as real life's gone a bit crazy recently...
wonkychris
I'm all ears!

I'll have a poke about as well if there are others...
Don T
At a quick glance, I'd check C7 again.
wonkychris
Don T wrote:
At a quick glance, I'd check C7 again.


Ah. I'll check. I think I see why you suggested that but confusingly those pcbs mount back to back, so the left header on the left pcb mates with the right header on the right pcb.
Don T
wonkychris wrote:
Don T wrote:
At a quick glance, I'd check C7 again.


Ah. I'll check. I think I see why you suggested that but confusingly those pcbs mount back to back, so the left header on the left pcb mates with the right header on the right pcb.


Oh, well, nevermind then grin
Jack Gull
A bit hard to tell without the schematic..

Anyway, probably the trace for that pin is on the other side of both the pcbs as i can't see it anywhere.

Going by memory, but the mutant bassdrum is based on the 808. The 808 bassdrum is created with a twin-t filter which step responce is a damped oscillation.... or, in other words, you send the trigger and you get an oscillation that gets attenuated.

From what you've said both the trigger and the envelope work. So my guess is that there is no oscillation happening. (Not that i'm surprised by that, i've always had lots of headaches with twin t filters) As i said, without the schematic it's a bit hard to tell but i think that the culprit lies in the Q2 Area.. or wherever you have 2 adjacent capacitors with the same value. I'd try to substitute the transistor there
wonkychris
Hi Jack,

Thanks for the reply and insight. I also got a reply back from Hex last night who was thinking a dead transistor was likely, so I shall start with Q2 and work from there.

Fingers crossed. thumbs up
tweakfilter
any luck wonkychris?
i was very satisfied with my hex buildings, hihats work fine and today the bass simple died. it has been in my rack since 3 weeks with no problems and now woah
tweakfilter
very frustrating very frustrating
problem solved nanners it was a jack socket not corrrectly grounded; i used thonkiconn jack from thonk.co.uk) and its ground leg is to wide for pcb hole, so i needed extra diy to manage it. Everything works now!!
wonkychris
Hi Tweakfilter

real life bloody reared its head so Ive been away from this.

I tried the Q2 swap mentioned above, no joy...

I will have a check around all the jacks and grounds as your problem sounds very similar to mine...

I miss its stompy goodness!
bleedmachine
I ended up getting mine working - im 98% i had blown one of the op amps on the front panel board. I also resoldered the headers on both sides but they seemed to be okay - i just did this as a precaution. it should be pointed out that the chips appeared to be fine at first glance - voltages seemed fine etc. but once a signal was put in via the trigger nothing changed... purely speculative (and therefore potentially completely incorrect) but i suspect that by applying the signal directly to the headers you bypass that op-amp (and associated components).
AndrewHP
Did you ever manage to sort this out? I have exactly the same problem with the same symptoms!

I built mine and it was working fine last night when I tested it - every feature seemed to be working well - now it responds in exactly the same way you described.

It's quite frustrating - It even fires out a good kick on power up but then goes quiet. I continuity tested both headers when plugged together and they responded fine.

I know the sound is in there somewhere!
strewya
wonkychris

I hope you managed to fix it?

I want to build this module but struggling to find right components. Would you mind sharing BOM?

Many thanks
Thomedwards
I built mine last night, and no joy. Both LEDs flash on power up, and the distortion works. But, when sending a trigger, there is nothing--no LED flash or anything. I'm pretty disappointed about this. I was looking forward to having a nice kick...

This thread is a little old, but I'm wondering if anyone can steer me a bit in the right direction. I do a lot of DIY, but I am not very well versed in troubleshooting beyond checking solder joints. Basically, if it works great. If not, OH NO!!!!
flts
1) Do you have the default accent jumper set to either of the positions? As the manual says, the module won't really work if there is none.

2) Have you tried if adjusting the pots make a difference? Try turning the tone to maximum, BD lvl up, and adjusting decay and pitch. I was a bit disappointed that I'd messed up something with my build quite a while ago, until I realized that the LED really follows the BD envelope, and if the BD is filtered out or attenuated enough with the knobs, it won't really sound at all and hence no LED action either.

3) Is something (in particular, the electrolytic caps) in the lower PCB of the PCB touching contacts on the upper PCB? A friend of mine had an issue with either BD or HH where it wasn't working properly / at all, and it turned out to be an issue with the caps touching the upper PCB and shorting something.
neonjung
wonkychris

Hey man, I just built the MBD and I'm having the exact same symptoms that you first described; dist circuit works, bd does not, LED's flash with power cycles. Hmmm. Did you get to the bottom of this? I feel very confident that I've put this board together correctly so it's pretty frustrating, but then when I saw this thread I thought maybe it's not my error and instead is perhaps a common, easily fixable problem?
flts
Did you check my suggestions in the last post? I'm not sure if they'd work or not, but I personally fell for (2) for a minute and my friend did (1) and wondered why the BD didn't work...
neonjung
flts wrote:
Did you check my suggestions in the last post? I'm not sure if they'd work or not, but I personally fell for (2) for a minute and my friend did (1) and wondered why the BD didn't work...


I did, yes. All those things are fine. Well, tt least I have a distortion unit with cv input atm confused

Do you have any links to guides about troubleshooting circuits by any chance?
neonjung
Thomedwards wrote:
I built mine last night, and no joy. Both LEDs flash on power up, and the distortion works. But, when sending a trigger, there is nothing--no LED flash or anything. I'm pretty disappointed about this. I was looking forward to having a nice kick...

This thread is a little old, but I'm wondering if anyone can steer me a bit in the right direction. I do a lot of DIY, but I am not very well versed in troubleshooting beyond checking solder joints. Basically, if it works great. If not, OH NO!!!!


Hi, did you manage to fix the problem in the end? I'm experiencing the same problem as you. Dist circuit works fine but nothing from the actual bd section. I know all my components are placed correctly, so I'm not too sure what to do next. From studying the basics of circuit troubleshooting, I think I need to test various points of the circuit for shorts, but I'm not sure how to go about doing that. Stacy from Hex sent me the schematics for the module, just need to learn how to make use of it.
Thomedwards
I haven't had any time to follow up on this problem. In fact, I hopped on here with the intention of checking this thread since I've got a break to try to fix this. I'll post back any success or findings when I'm done. I hope I don't get distracted, though. I've got a few other projects gathering dust, too
neonjung
Thomedwards wrote:
I haven't had any time to follow up on this problem. In fact, I hopped on here with the intention of checking this thread since I've got a break to try to fix this. I'll post back any success or findings when I'm done. I hope I don't get distracted, though. I've got a few other projects gathering dust, too


I actually got mine working. I'd made an error and placed a transistor where an IC voltage regulator should have been. They look the same as transistors confused

Now my pitch is off though. The lowest is too high. Gonna double check all resistor values tonight.

Let us know if you fix yours!
Thomedwards
Well this is strange. I just plugged it in and it worked. And I did absolutely nothing to it. I wish I could give some tips on how to fix this but I have none other than to plug it in again.

Maybe I should plug Cascade back in and see if I have similar luck...

EDIT: I just saw you got yours right. I guess the Mutant stars are in line. Good deal!
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