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sgt250 nothing out of rca jacks

 
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jsdspif



Joined: 16 Jan 2016
Posts: 101

PostPosted: Fri Aug 11, 2017 7:31 am    Post subject: sgt250 nothing out of rca jacks Reply with quote

I thought I saw a topic about this a while back. I have audio and video out of the coax but not out of the rca jacks. I then swap the stereo boards between a working player with working rca jacks and the problem follows the stereo board (so the player that did have no a/v/ out of the rca jacks now has it and the player that did have it now no longer does) so I'm sure it's a problem on the stereo board. I've done voltage comparisons of the 6 ic's on the boards and they all match pretty close except for U4401. On the working player there are a few "legs" of the chip that match the schematic and are about .5 volts lower than the non working player. Such as one leg on working is 1 volt and on non working it's 1.5, there is actually 4 legs of that one that follow that scenario, working player legs are about a volt and non working is 1.5. That's the audio portion. The video portion looks to pretty much go from the input of video to the stereo board(which I knjow I get video at that point) and then just goes to a few components to the rca jack. There is one transistor there and it has voltages matching the schematic and working board.
I'm thinking of just sending it to cedatum , he told me they have a test fixture for the boards and I'm kind of stumped. I thought maybe for some reason the jacks were faulty but they test out good.
as I said I thought there was a topic a while back that discussed the output at the coax but no a/v from the rca jacks??
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jsdspif



Joined: 16 Jan 2016
Posts: 101

PostPosted: Sun Aug 13, 2017 12:58 am    Post subject: Reply with quote

quick semi-update on this. For some reason, as I was waking up this morning, a thought was in my head, maybe the small tv I use for my ced testing purposes needs a video input to allow the audio input to work. So I connected the tv's video and audio inputs to the working players audio video rca outputs and everything worked as it should. I then unplugged the video input and the audio stopped. So my little "testing" tv needs a video input to have audio output (that's just about "clear as mud"). I'm guessing now my player I thought had no video or audio output, probably does have audio output but not video. I have the stereo board removed from the player at this time so I can't re-test at the moment.
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jsdspif



Joined: 16 Jan 2016
Posts: 101

PostPosted: Mon Aug 14, 2017 8:59 am    Post subject: Reply with quote

the solder points where the positive terminal of the rca jacks connect to the board are cracked. I noticed messing with the cable at the rca jack/plug I could get the video to flicker. I needed pretty strong magnification to see the break in the solder. One of the audio jacks is also looking as though it will break soon. I'm going to re-solder all of them. I checked the pins that all the jumper plugs (?) plug onto and they all look ok. They don't get the abuse that the rca jacks get. I did run into another problem. I put a new turntable belt on (from cedatum) and the turntable will only spin about 440 rpm and that throws the color off. I then put the old belt back on and it spins at 450 rpm and operates properly. I've done the swap on this player 3 or 4 times going from new belt back to old belt and same thing every time. At least after I re-solder the rca jacks I think my video will be restored and I shouldn't encounter audio problems related to the rca jacks for quite some time.
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cbertra2



Joined: 29 Dec 2004
Posts: 169

PostPosted: Mon Aug 14, 2017 9:17 am    Post subject: Reply with quote

It's probably not the belt but the motor is getting weak and can not take the extra tension from the new belt.
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Daxi Don



Joined: 24 Dec 2006
Posts: 64
Location: Indiana

PostPosted: Wed Aug 16, 2017 12:18 pm    Post subject: F/G player turntable belts. Reply with quote

I agree with cbertra2, a new unstretched belt requires good torque to move it. Try the following on the turntable motor. Oil the motor shafts top and bottom with fine oil - sewing machine oil is a fine grade. Also add oil to the top and bottom reservoirs on the motor body.
Note: remember that CED turntable rotation uses a '2 speed system'.
1/ The turntable motor and belt spin the turntable to approximately 450 RPM. 2/ The rotation has then to be synchronized to the 60Hz power line frequency. This is done by two magnetic poles of the motor plate which drive a 16 pole magnetic ring inside the turntable pulley flange. A stable picture with color is only obtained when the turntable is at 450 RPM and synchronized. There is a screw on the motor plate ' Speed adjustment ' that can be adjusted if turntable sync is intermittent. Using a CED strobe disc aids this adjustment.
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