CED VideoDisc and Player Discussion

scupbucket · Joined: 07 Oct 2015 Posts: 10

Hey gang! I received a new to me sgt100w. It's in really nice shape but I'm stumped with a playback problem. I can't tell if it's mechanical or electrical though. The stylus tested ok with another unit btw. If I load a disc and switch to "play", there's no playback, the display reads "- -", and the servo motor just keeps running, continuously pushing the tonearm backwards. If I switch the unit off and back to play again the motor doesn't run at all. If I switch to "load" and back to "play", the motor keeps on churning in reverse. Its a head scratcher. Would love a little help on this one if possible. Very Happy

lynx · Joined: 30 Jun 2018 Posts: 100

scupbucket · Joined: 07 Oct 2015 Posts: 10

Thanks for the reply, lynx. The servo belt is in very good shape and I disassembled the reduction gear assembly and lubed it up. Ran a bunch of voltage tests and adjusted cams, sensor drum adjust etc. according to the service manual. I also disassembled the turntable and lubed that guy up. I checked all switches and all test functional and are properly adjusted.

Aside from the servo motor constantly running, I also noticed that the stylus is not dropping when the disc is loaded. The "- -" on the display is waiting for a signal. But I'm guessing there isn't the possibility of getting a signal in the first place as the issue of the servo motor running isn't allowing the stylus to drop? I haven't tested the Q16 and Q17 transistors yet for the stylus lifter. I researched the troubleshooting topics in the manual. Unfortunately I don't have a scope to complete some of the more involved tests as I'm starting to think this might be a microcomputer issue?

I was also toying with the possibility of swapping in a new servo arm to see what happens but I don't want to invest in a parts machine just yet. I've done a lot of pinball machine board work so I could try swapping a new IC in but I'm trying to eliminate the easy stuff before I start shotgun replacing parts. I think this unit was barely used and stored well as it's in very nice condition! I'd hate to scrap this one.

scupbucket · Joined: 07 Oct 2015 Posts: 10

Made a bit more progress on this. I gave in and bought a parts player. I swapped the arm assembly, nada. But swapping the pw500 board made a huge improvement. The servo motor no longer runs non-stop and I can confirm the stylus drops down onto the disc.

Unfortunately I still have playback problems. The stylus is getting no signal from the disc therefore the servo isnt advancing. The forward and reverse scan and search buttons don't work but pause does. Here's the weird part, and I've only seen it mentioned on the forum a few times. Going back to play after pause results in only one dash... "-" instead of *--*. Very weird and I don't see anywhere in the manual about a single dash problem. I'm thinking I bought a parts player with another bunk board?