GBH
Member
On my MZI-45, the upper controls would sometimes get in a mode like this-
Input---Result
Down---Down
Up------Down
Out-----Out
In-------Out
Left-----Left
Right----Left
It would return to normal sometimes for hours. If I turned it off and back on again, sometimes it would work properly, sometimes not. On occasion, tap or wiggle the board and make it work correctly. I suspected a cold solder joint, bad trace or cracked board.
If you have seen the control board, it is covered on both sides with a very thick silicone conformal coating. (I don't have a pic) I removed the coating on the solder side with a heat gun and allot of patience. It came off by heating it then gently pulling it up, watching that it did not tear at the traces. in my case, it came off easily, sometime in small pieces. Pic 1 shows the board stripped of the conformal coating.
I re-soldered every component pin and edge connector pin on the board. In pic 2 you can see a diode which was not securely soldered to the trace. It was just touching the trace but not soldered in. the diode next to it is still covered in Coating. It was secure and there was no need to try and pry the coating off. I caution people on the removal of the coating. This is a 27 year old circuit board. If considering doing this, you need to be comfortable doing this kind of work. It is easy to short pins together with solder if not paying attention. I always inspect a board for a long time with a magnifier and use a toothbrush to remove any solder splash. Then I inspect it again. It may be worth taking your board to an electronics shop and have them do it, if they are willing.
Pic 3 shows the new conformal coating I sprayed to protect the board after the re-solder.
I have used the lift a number of times since doing this repair and it has worked flawlessly. I'll update this post if it goes back to intermittently working.
Input---Result
Down---Down
Up------Down
Out-----Out
In-------Out
Left-----Left
Right----Left
It would return to normal sometimes for hours. If I turned it off and back on again, sometimes it would work properly, sometimes not. On occasion, tap or wiggle the board and make it work correctly. I suspected a cold solder joint, bad trace or cracked board.
If you have seen the control board, it is covered on both sides with a very thick silicone conformal coating. (I don't have a pic) I removed the coating on the solder side with a heat gun and allot of patience. It came off by heating it then gently pulling it up, watching that it did not tear at the traces. in my case, it came off easily, sometime in small pieces. Pic 1 shows the board stripped of the conformal coating.
I re-soldered every component pin and edge connector pin on the board. In pic 2 you can see a diode which was not securely soldered to the trace. It was just touching the trace but not soldered in. the diode next to it is still covered in Coating. It was secure and there was no need to try and pry the coating off. I caution people on the removal of the coating. This is a 27 year old circuit board. If considering doing this, you need to be comfortable doing this kind of work. It is easy to short pins together with solder if not paying attention. I always inspect a board for a long time with a magnifier and use a toothbrush to remove any solder splash. Then I inspect it again. It may be worth taking your board to an electronics shop and have them do it, if they are willing.
Pic 3 shows the new conformal coating I sprayed to protect the board after the re-solder.
I have used the lift a number of times since doing this repair and it has worked flawlessly. I'll update this post if it goes back to intermittently working.