Siel DK600 issue..this is a WEEIIRRD one...
2014-12-25 by sounddoctorin@...
I have this thing sold. It worked swell but as has been the custom for I don't know how long..when I get it tested one final time it doesn't work. Sounded like all the knobs were all the way up. Dac?
Sure enough they were but it's not the DAC. In fact the 'x' inputs (common lines on all of the 4051 analog switch chips) show the 'vwr' signal just fine. You can move knobs and see them moving the voltage at their particular window in the cycle of refresh signals.
Hmm. ok so I find the source of that problem as nothing is getting to the sample and hold cells. They're just sitting there at 5V on all of them. I did notice that the CV and velocity S+H's..curiously... were showing a BLIP as the particular channel number would be triggered that you are monitoring. The signal would dive but then go right back up very quickly.
Hmm. Well IC 13, the flip flop that latches the data which represents the inhibit states for the 6 4051's... is outputting 2 perfect square waves with a 40% duty cycle or whatever. Just what you'd expect and that's why the front panel knobs are all reading fine.
However all FOUR of the other inhibit lines are showing a double pulse spiking down to 2V or something. I have a slow scope on it at the moment but whatever the case it's not turning the chips on long enough to do anything IF at all... and then when the square wave should be returning to it's 5V state there are two more little spikes down. So anyway that's why it's not working. I tried swapping IC13 of course but to no avail. IC3? Why would the bus tranceiver just decide to stop working on those 4 ? OH and something else to sweeten the deal! I tapped on it initially and got the thing to work perfectly for a brief 10 or 20 seconds. lol. So I was thinking 'just a bad solder joint cropped up somewhere'. Well.what solder issue could potentially cause *this*?? Certainly one of the strange issues of all time. Merry Christmas. lol
Sure enough they were but it's not the DAC. In fact the 'x' inputs (common lines on all of the 4051 analog switch chips) show the 'vwr' signal just fine. You can move knobs and see them moving the voltage at their particular window in the cycle of refresh signals.
Hmm. ok so I find the source of that problem as nothing is getting to the sample and hold cells. They're just sitting there at 5V on all of them. I did notice that the CV and velocity S+H's..curiously... were showing a BLIP as the particular channel number would be triggered that you are monitoring. The signal would dive but then go right back up very quickly.
Hmm. Well IC 13, the flip flop that latches the data which represents the inhibit states for the 6 4051's... is outputting 2 perfect square waves with a 40% duty cycle or whatever. Just what you'd expect and that's why the front panel knobs are all reading fine.
However all FOUR of the other inhibit lines are showing a double pulse spiking down to 2V or something. I have a slow scope on it at the moment but whatever the case it's not turning the chips on long enough to do anything IF at all... and then when the square wave should be returning to it's 5V state there are two more little spikes down. So anyway that's why it's not working. I tried swapping IC13 of course but to no avail. IC3? Why would the bus tranceiver just decide to stop working on those 4 ? OH and something else to sweeten the deal! I tapped on it initially and got the thing to work perfectly for a brief 10 or 20 seconds. lol. So I was thinking 'just a bad solder joint cropped up somewhere'. Well.what solder issue could potentially cause *this*?? Certainly one of the strange issues of all time. Merry Christmas. lol