- Joined
- Sep 2, 2012
- Posts
- 348
I may have "fixed" this issue.
I had pretty much given up on this one and bought a 14M2U off eBay as a replacement. That one turned out to be junk. I opened it up and found the 14M2U has the same power supply (G board) as the 20M2U. I swapped the power board into my 20M2U and still had the waving issue, but at least this eliminated the power board as the source. I started looking into the IC's as James had suggested. The 2 PVM models share nearly all the same IC's on the main board.
I found IC507 (uPC1377C - SYNCHRONIZATION SIGNAL PROCESSOR) looking through the service manual and thought it might be a possible source. I desoldered IC507 from both boards, installed sockets, and swapped chips. I managed to rip 2 traces running under the chip since it is in a really tight spot and spent quite a bit of time figuring out where they went to install jumpers. I fired up the PVM and had a stable picture, left it on for an hour and still no waving. I did lose all my settings for some reason.
Now here's the strange part, when I power it up I get the same waving immediately for about 30 seconds then it stabilizes and runs perfectly fine. This didn't happen the first couple times I power it up after swapping chips. The service manual states that when this chip is replaced you should check b+ maximum and confirm hold down circuit so it is possible that adjustments are needed (section 4), but I can't make any sense of it.
I'm going to say this one is fixed for now.
I had pretty much given up on this one and bought a 14M2U off eBay as a replacement. That one turned out to be junk. I opened it up and found the 14M2U has the same power supply (G board) as the 20M2U. I swapped the power board into my 20M2U and still had the waving issue, but at least this eliminated the power board as the source. I started looking into the IC's as James had suggested. The 2 PVM models share nearly all the same IC's on the main board.
I found IC507 (uPC1377C - SYNCHRONIZATION SIGNAL PROCESSOR) looking through the service manual and thought it might be a possible source. I desoldered IC507 from both boards, installed sockets, and swapped chips. I managed to rip 2 traces running under the chip since it is in a really tight spot and spent quite a bit of time figuring out where they went to install jumpers. I fired up the PVM and had a stable picture, left it on for an hour and still no waving. I did lose all my settings for some reason.
Now here's the strange part, when I power it up I get the same waving immediately for about 30 seconds then it stabilizes and runs perfectly fine. This didn't happen the first couple times I power it up after swapping chips. The service manual states that when this chip is replaced you should check b+ maximum and confirm hold down circuit so it is possible that adjustments are needed (section 4), but I can't make any sense of it.
I'm going to say this one is fixed for now.