Hi,
Normally I would agree with you that not having good voltages at R152 would indicate the 4051
would be bad, but if the gate LED's are not shutting off, but only turning on, that indicates a digital
problem around the key assigner and gate latch area. Sounds like you may still have a problem
in that part of the circuit, which could interfere with the key assigner selecting the 4051 properly.
You can check the digital control inputs to the 4051 and see if they look OK. Actually, I uploaded
some waveforms a while back to the files area that show some of these signals.
If you can set it up, trigger your scope on the latch enable signal to the gate latch chip, pin 9 of IC5.
With the other probe, look at the data input to the latch for gate 0. If you don't have a storage
scope you may need to press the key a bunch of times to see what's happening. Actually, using
the arpeggiator might allow you to write to that latch at a faster rate and see the signal
better. Anyway, you want to see what voltage level is on the data input when the latch enable
signal is high. A good high level should be about 4V or so, and a low level should be maybe 0.5V or less.
Did you check the power supply inputs to the KLM-366 board?
I would scope all of the key assigner MCU signals on the top side of the chip in the schematic,
and see if you have good logic levels on all of them. Something strange is happening here.
Bob
From: "mpe1969@tpg.com.au [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Friday, May 1, 2015 8:37 AM
Subject: Re: [PolySix] Re: Key assign mode issue
Thanks Bob. I had a look tonight. All I get on that pin is a noise looking wave. I was reading some earlier messages on this forum last night and thought I would probe r152. (Vco input) all I get on that resistor is a saw tooth wave shape about -8 dc. But what is weird is that when then oscilloscope probe is touching that resistor I get sound out the headphones for that oscillator. I can change the wave shape of that wave and alter it with the filter. Still just the same tone (key) though. This seems to be pointing to a faulty 14051?
Also when I put the hold button on and push sound keys (1 after the other) all the oscillator diode lights turn on) I would have expected the previous one to turn off when the next one turns on...
Not sure what to make of this as yet.
Thanks again.