Synth-DIY Yahoo! Groups Archives

Issue with patch Led's and Bank Led's after replacing buttons

2015-01-16 by yanbu@comcast.net

Hello, I just soldered on new buttons for patch select buttons 2 and 4, and the 'Poly' button since they were not responding on my Polysix. This was an easy enough task, once I placed the board back and re-attached it to the faceplate / front panel using the screws, there is a weird issue with the LED's. After turning it on it defaults to bank A and patch 1, however if I press the button for Bank D, both the Bank A and Bank D LED's stay lit. The same goes with the patch select buttons 1-8.

What's weird is that when the entire board assembly with the metal cage that holds the individual PCB's together is not screwed to the faceplate / front panel, it works normally. But as soon as I touch the metal of the supports that hold the PCB's together to the metal of the front panel, the issue occurs.

What on earth could this be? I checked my work and the solder joints are clean, nothing shorting out that I can see. The wires look fine as well. Has anyone run in to this before? Any tips on what to check for this kind of behavior? Really hoping to get some ideas, any help is appreciated.

Re: [PolySix] Issue with patch Led's and Bank Led's after replacing buttons

2015-01-16 by Bob Grieb

A short to +5V on D0 would cause Bank A LED to be turned on

whenever IC2 on KLM371 is written to. It would also cause Program

1 LED to be turned on whenever IC4 is written. If you have a scope,

I would suggest looking at that data bus bit right at pin 2 of each of those

two chips, with the board in place. If not, check resistance from that pin

to gnd, and also to the KLM-367 signal that drives it, with the board in

place. Compare the resistance measurements from that signal to another

data bus pin. D2, for instance. Also, if D0 at those two chips is not

connected to the KLM367 driver, it is the same as if it's high (+5V).

That seems the most likely to me.

Bob

From: "yanbu@comcast.net [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Friday, January 16, 2015 4:05 PM
Subject: [PolySix] Issue with patch Led's and Bank Led's after replacing buttons

Hello, I just soldered on new buttons for patch select buttons 2 and 4, and the 'Poly' button since they were not responding on my Polysix. This was an easy enough task, once I placed the board back and re-attached it to the faceplate / front panel using the screws, there is a weird issue with the LED's. After turning it on it defaults to bank A and patch 1, however if I press the button for Bank D, both the Bank A and Bank D LED's stay lit. The same goes with the patch select buttons 1-8.

What's weird is that when the entire board assembly with the metal cage that holds the individual PCB's together is not screwed to the faceplate / front panel, it works normally. But as soon as I touch the metal of the supports that hold the PCB's together to the metal of the front panel, the issue occurs.

What on earth could this be? I checked my work and the solder joints are clean, nothing shorting out that I can see. The wires look fine as well. Has anyone run in to this before? Any tips on what to check for this kind of behavior? Really hoping to get some ideas, any help is appreciated.

Re: Issue with patch Led's and Bank Led's after replacing buttons

2015-01-20 by yanbu@comcast.net

Thanks for that info Bob - I do not have an oscilloscope, not sure I know anyone out here that could check that. When you say to check the resistance from pin 2 on IC2 on KLM371 to ground, and then compare the resistance measurement from that signal to another data bus pin, what would I do if these are not identical? I think I see the steps that you recommended for me to test, but I am not sure if I understand what it is that I should do if the measurements are different.

I'll try to look at those tonight, plus the D0 for those two chips. I'll study the schematic some beforehand to see if I can pinpoint these, this isn't something I have a lot of familiarity with but I will do my best since I really want to get rolling with playing my polysix again. Thanks.

Re: [PolySix] Re: Issue with patch Led's and Bank Led's after replacing buttons

2015-01-20 by Bob Grieb

Hi,

Easiest is to simply make the measurements and post the results to

this group. We can sort it out. Resistance measurements are not expected

to be identical. We are looking for big differences between similar circuits,

not small variations.

Of course you must make any resistance measurements with the power

turned off.

Bob

From: "yanbu@comcast.net [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Tuesday, January 20, 2015 11:03 AM
Subject: [PolySix] Re: Issue with patch Led's and Bank Led's after replacing buttons

Thanks for that info Bob - I do not have an oscilloscope, not sure I know anyone out here that could check that. When you say to check the resistance from pin 2 on IC2 on KLM371 to ground, and then compare the resistance measurement from that signal to another data bus pin, what would I do if these are not identical? I think I see the steps that you recommended for me to test, but I am not sure if I understand what it is that I should do if the measurements are different.

I'll try to look at those tonight, plus the D0 for those two chips. I'll study the schematic some beforehand to see if I can pinpoint these, this isn't something I have a lot of familiarity with but I will do my best since I really want to get rolling with playing my polysix again. Thanks.