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Hello, I’m new to the group. I got a semi-broken P800 off craigslist and have had some success fixing the thing up (fixed black key, cleaned key contacts, fixed shorted L/R outputs, reset factor patches with .wav…). There are a few more things I would like to fix and would be grateful if someone here can help. Thanks in advance. Sorry this got so long.
Questions:
1. [fluff] Anyone see this by chance? I found something cool inside my P800: https://www.reddit.com/r/synthesizers/comments/4ivht3/i_bought_a_dx7_and_a_poly800_yesterday_from/
2. Where can I buy tactile button switches? The ones soldered to KLM-597 for the menu buttons. I know you can clean them with some sort of solvent, but I would rather replace them all. I’ve had luck doing this with other synths. Before I purchased them for my other projects, I used a digital caliper to make sure the dimensions were exactly the same, but haven’t done that yet for the P800. I didn’t see any at Syntaur.com, and they usually have most everything (for $$$…).
3. The joystick on my machine doesn’t work at all (no pitch bend, no DCO/VCF modulation). I’ve done some electronic troubleshooting and am hoping someone can point me in the right direction. I have the service manual and the “joystick PCB electronics - theory of operation” from the yahoo group (thanks Gordon). If this works out, I will write up what I learned for others to use in the future. I used a multimeter to read voltages starting on KLM-599 (joystick board) going to several different ICs on KLM-596. I’ll try to keep this (kind of) brief at first. I have measurements from all pins at the ICs the joystick pots appear to be connect to. I have more photos and notes as well, if you think those will help.
3a. On KLM-599 point 8-2B reads 2V and 4V with the Bend Slider at the DOWN and UP, respectively. Appears that the Bend Slider works?
3b. On KLM-599 (with Bend Slider UP) point 1-4B reads 2V (JoyStick North), 2V (JoyStick South), 0V (JoyStick East), 4V (JoyStick West), 2V (JoyStick Center). Point 1-5B reads 0V (JSN), 4V (JSS), 2V (JSE), 2V (JSW), 2V (JSCTR). Appears the joystick changes the voltages leaving KLM-599 going to KLM-596. 1-4B is PITCH and 1-5B is DCO/VCF, this seems to agree with “joystick PCB electronics” by Gordon, right?
3c. Points 1-4B and 1-5B are connected to IC6 PIN3 and PIN5, respectively. I read the same voltages at these pins for joystick positions in Step 3b. Moving the joystick and Bend Slider, I see only one other pin with voltage changes on IC6. PIN4. At PIN4 I read 0V (JSN), 4V (JSS), 2V (JSE), 2V (JSW), 2V (JSCTR). These voltages are the same as the voltages at PIN5? PIN 5 is DCO/VCF, it looks like the PITCH BEND doesn’t change voltages out of any pin in IC6?
3d. PIN4 at IC6 goes to IC39 PIN5 and PIN7 (w/ R118, 1M in series). I measure 4V at PIN7 for all joystick positions. I measure the same voltages at PIN 5 as Step 3c. Voltage drops across R118 make sense. This is where my troubleshooting ends. I see no other voltage changes when moving the joystick coming out of IC39. It looks like PIN7 is also connected to IC38, but I see no voltage changes there either.
3e. In the Service Manual, Section 8: Check and Adjustment Procedure, Step No 2. is “D/A converter check and adjustment (KLM-596, circuit no. 12).” The step says you should get the following readings at IC10 PIN7: 2V (JSC), 4V (JSE), 0V (JSW) ∗approximately. I read 2V for all joystick positions, so something is wrong at this point. The manual also mentions IC38 here, I read no changes at with joystick movement any pin on IC38.
So that’s where I’m at. It seems likely that one of the ICs mentioned is bad (IC6, IC10, IC38, IC39), but I have no idea really. Can someone help me out with this? I would really like to bend this Poly 800!!
Thanks, Jamie