Yes that sounds right. One thing: I don't think that crash and ride share their accent in the Nava. That is the case in the original 909 but not here.
You can verify this by checking for continuity on the accent inputs between crash and ride. There should not be continuity.
How did you check the 2SA798? When one of mine was broken I still saw waveforms that seemed plausible on my scope on its legs, when triggering the cymbal. Only when carefully reading the schematics did I realize it was the wrong waveform. The transistor might have had short in my case.
Either way, chasing those envelopes down from the EG resistor array as your other source suggested should help you pinpoint the problem.
Cymbal decays
Thanks for the reply jvq. I will check the accent circuit and confirm (just about to take it apart shortly).
For the 2SA798, I simply checked with a DMM using the diode measurement and measured the usual voltage and no shorts between any pins. Maybe not the best check. I've not yet tried checking for waveforms.
Here's a video of whats happening exactly:
https://www.youtube.com/watch?v=P7DU3sZ__b8
Will start tracing again shortly, hopefully I can pinpoint the issue!
For the 2SA798, I simply checked with a DMM using the diode measurement and measured the usual voltage and no shorts between any pins. Maybe not the best check. I've not yet tried checking for waveforms.
Here's a video of whats happening exactly:
https://www.youtube.com/watch?v=P7DU3sZ__b8
Will start tracing again shortly, hopefully I can pinpoint the issue!
Diode check sounds good. One of my mistakes at the time was that I only measured in-circuit. I put the 2SA798's in sockets when I replaced them.
I now have a Peak transistor checker but that's overkill for diagnosing if a transistor is fried.
The EG circuit is not that big so you should be able to find the problem with a scope by chasing.
I now have a Peak transistor checker but that's overkill for diagnosing if a transistor is fried.
The EG circuit is not that big so you should be able to find the problem with a scope by chasing.
Ok, I tried swapping out the 2SA798 with 2x 2N3906s (matched) but same issue, so I swapped it back.
I found that if I short the pins of R437, I was getting the decay back. R437 goes between pin 3 of the 4011 and the 2SA798. Shorting it gets the decay back but then I get a repeating signal even with the machine stopped.
I feel like I'm getting closer but also so far..
I found that if I short the pins of R437, I was getting the decay back. R437 goes between pin 3 of the 4011 and the 2SA798. Shorting it gets the decay back but then I get a repeating signal even with the machine stopped.
I feel like I'm getting closer but also so far..
So with a lot of guidance from a very helpful 909 tech from another forum, we managed to pinpoint the issue to be from IC111, or in the case of v1.02, one of the MUX boards. I swapped them and managed to get my ride back and didn’t notice any loss in any other instrument but decided to reflow the suspect MUX board anyway and things are now as they should be.
Hopefully this helps anyone else!
Hopefully this helps anyone else!
Similar issues here. Little to no HH decay, can barely hear OH. Ride and Cymbal are fine, however cymbal envlope is triggered by OH... What...? I'm guessing it's probably the MUX board, but I have no idea where to look and the PCBs are seemingly so fragile I'm afraid of screwing them up more.
Swapped out the MUX boards to see if it would fix it. Well I can hear the HH and OH perfectly, and all the levels are great. Still strange issue regarding cymbal and ride being trigger by the OH but I'd guess that's probably due to the MUX board that isn't working properly....?