This is a recording from the HC out: http://yocto-e04b97363876c567e1fb.s3-eu ... -noise.mp3
There is a continuous noise, like radio static. The clap itself sounds fine (I think).
I just finished my build today. Anybody got a clue what might be going wrong here? No weird noises on the other outputs (except Master, but I presume that is just the noise from the hand clap again).
[RESOLVED] Various handclap / maracas issues
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Last edited by jvq on Oct 11th, '16, 17:51, edited 4 times in total.
The static noise stays the same even if I turn the volume of the hand clap to zero!!
Interesting: this blog post about an (original) TR 808 repair describes what might be the same problem.
https://obsoletetechnology.wordpress.co ... 08-repair/
Anybody know a good way to test the BA6110?
https://obsoletetechnology.wordpress.co ... 08-repair/
Not quite the same because my handclap does not sound faint (it sounds fine I think) but I do have the noise. They fix it for them by replacing the BA662 (with a BA6110, ha).... handclap sound, from which one could only hear a faint ‘reverb’ tail as well as some continuous noise on the output.
Anybody know a good way to test the BA6110?
Fixed it! I had a long look at the solder side of the handclap section and touched up some solder joints that looked a little 'thin'. Noise went away.
I am not quite done because now the maracas (the alternate instrument of the handclap) are silent. I will have to come back to that another day.
I am not quite done because now the maracas (the alternate instrument of the handclap) are silent. I will have to come back to that another day.
Cheered to soon, removed '[RESOLVED]'. Now alternating between two states:
- static noise, handclap and maracas both working
- no noise, maracas not working
- static noise, handclap and maracas both working
- no noise, maracas not working
When the maracas are working:
- 5-10V at R337 with drops when notes are triggered
- ripples of -1/+1V at R338 when notes are triggered
When the maracas stop working the ripples at R338 are gone.
- 5-10V at R337 with drops when notes are triggered
- ripples of -1/+1V at R338 when notes are triggered
When the maracas stop working the ripples at R338 are gone.
I am having a harder time chasing the static noise through the circuit because it is not rhythmical.
What I understand about the circuit so far: the maracas seem to be a minor part of the handclap circuit (built around Q65, Q66, Q67, Q68). The only thing the HC/MA switch does is direct trigger pulses to HC or MA. So even when the switch is set to HC, the MA circuit is wired up to the output.
Both the HC and MA use white noise from the noise generator. I wonder if white noise is leaking to the outputs. It does not sound like the high-pass filtered noise the maracas use. So either the noise is leaking 'before' the HPF in the maracas (Q68) or it might be the band-passed noise of the handclap. I cannot quite tell if the noise I am hearing has been through the band pass filter.
If Q65 occasionally craps out that might explain why the maracas stop sounding. I can see their envelopes run on the scope (at R337) but if the VCA is stuck at 'zero' no sound will be generated.
When tracing around the noise with the scope I also seemed to hone into Q70, the VCA for the handclap reverb tail. But it does not sound like the reverb tail is not there.
One thing I should mention again is that these faults come and go over time. For the past few days it was mostly quiet (with no maracas). Tonight I tried to touch up some more solder joints and now the noise is back in full force. But the maracas work.
Another thing: when I turn down the channel volume (VR17) the noise keeps sounding. When I plug a jack into the HC/MA output the noise disappears from the main mix. This has to mean something about where the noise comes from but I just don't see it (yet).
What I understand about the circuit so far: the maracas seem to be a minor part of the handclap circuit (built around Q65, Q66, Q67, Q68). The only thing the HC/MA switch does is direct trigger pulses to HC or MA. So even when the switch is set to HC, the MA circuit is wired up to the output.
Both the HC and MA use white noise from the noise generator. I wonder if white noise is leaking to the outputs. It does not sound like the high-pass filtered noise the maracas use. So either the noise is leaking 'before' the HPF in the maracas (Q68) or it might be the band-passed noise of the handclap. I cannot quite tell if the noise I am hearing has been through the band pass filter.
If Q65 occasionally craps out that might explain why the maracas stop sounding. I can see their envelopes run on the scope (at R337) but if the VCA is stuck at 'zero' no sound will be generated.
When tracing around the noise with the scope I also seemed to hone into Q70, the VCA for the handclap reverb tail. But it does not sound like the reverb tail is not there.
One thing I should mention again is that these faults come and go over time. For the past few days it was mostly quiet (with no maracas). Tonight I tried to touch up some more solder joints and now the noise is back in full force. But the maracas work.
Another thing: when I turn down the channel volume (VR17) the noise keeps sounding. When I plug a jack into the HC/MA output the noise disappears from the main mix. This has to mean something about where the noise comes from but I just don't see it (yet).
I am making slow progress on this by reading the circuit diagrams and reflowing solder joints. I think that for whatever reason I made lot of bad solder joints in the handclap.
I am now down to sometimes having bursts of noise after switching from maracas to handclap but this goes away. That means the maracas and handclap are usable now as long as I let the machine warm up. I hope to find the last bad solder joints and fix this eventually.
I am now down to sometimes having bursts of noise after switching from maracas to handclap but this goes away. That means the maracas and handclap are usable now as long as I let the machine warm up. I hope to find the last bad solder joints and fix this eventually.
Changed the topic title because I am talking about different noise now compared to the top post. Here is a sample. http://yocto-e04b97363876c567e1fb.s3.am ... 160926.mp3
The maracas behave well but the handclap gets weak phantom triggers (at times where I did not sequence them) and sometimes fires continuously. I am thinking this is an envelope / VCA problem.
The maracas behave well but the handclap gets weak phantom triggers (at times where I did not sequence them) and sometimes fires continuously. I am thinking this is an envelope / VCA problem.
A week and a half ago I went in again and reheated all solder joints in the handclap that I had not already reheated so far. Since then I have had no issues anymore! I think I will mark this issue as resolved.
It seems the root cause was a number of bad solder joints. This is not surprising because the Yocto was my first big soldering project. Looking at the handclap section and the sections that came before and after it I can clearly see I was doing something different in my soldering that weekend (I don't remember what I was thinking). Whatever I did must have been leading to a lot of bad joints.
Luckily my soldering got better after that (although I also had to fix soldering mistakes on the sequencer LEDs, sequencer switch resistors, and Grayhill selector resistors).
In case it helps anyone else, my 'reheating technique' means: I reheat the soldering joint until the solder becomes liquid and the solder can flow into the hole a little better. If the joint looks a little 'flat' I add some more solder.
It seems the root cause was a number of bad solder joints. This is not surprising because the Yocto was my first big soldering project. Looking at the handclap section and the sections that came before and after it I can clearly see I was doing something different in my soldering that weekend (I don't remember what I was thinking). Whatever I did must have been leading to a lot of bad joints.
Luckily my soldering got better after that (although I also had to fix soldering mistakes on the sequencer LEDs, sequencer switch resistors, and Grayhill selector resistors).In case it helps anyone else, my 'reheating technique' means: I reheat the soldering joint until the solder becomes liquid and the solder can flow into the hole a little better. If the joint looks a little 'flat' I add some more solder.