SCC-8 PCB

[paradisecs]

So on removal of the PCB from my SCC-8 I found this:


Is this salvageable at all or do I need to track down a replacement? I'm thinking not. As you can see from the backside, it's cracked all the way to the F3101 socket.  It looks like someone attempted to jumper/patch it before.





Stephen

Attachments:

[robnyc]

That is caused by heat. Chances are any other boards will be the same. Since the edge connector and supports are Ok, I'd just repair and jumper.

I would replace the simple solder jump at just below R3106 with an actual wire across the board. That kind of jump is not reliable in an area where the board can flex and heat up.

The bigger potential problem (as I see it) is the forming of carbon across the phenolic. That has long been a problem in older boards dealing with high voltages. Given the high impedance in that area, it is possible the readout source could be drained by board leakage. If the voltages check out go ahead and use it.

RobNYC

[paradisecs]

Thanks. What is the phenolic? I've only seen that term in relation to asbestos in plastic.

Selections on this unit are flaky. When I got a bunch of phonographs last year this is the first one I gave away before I knew anything. I did nothing to the machine in any way, but it worked. Shortly after getting it to my friends house it would only make selections randomly, maybe once out of every 40.

I pulled the controller last week and brought it home to discover this and all I could think was "crap, now what do I do."

Stephen

[Ron Rich]

Hi Stephen,
That's the material that PCB is made from-- Most likely the SCC is not the source of your problem. You need to read the trouble shooting guide for that model--oh, sh-t, they failed to publish one for it--- so read the last good one published--one for the SS-160. There will be a few little differences including the speed change differences, but other then the way the WI was accomplished, all systems are the same. Ron Rich

[robnyc]

Mar 3, 2019 17:56:49 GMT paradisecs said:

Thanks. What is the phenolic? I've only seen that term in relation to asbestos in plastic.

Selections on this unit are flaky. When I got a bunch of phonographs last year this is the first one I gave away before I knew anything. I did nothing to the machine in any way, but it worked. Shortly after getting it to my friends house it would only make selections randomly, maybe once out of every 40.

I pulled the controller last week and brought it home to discover this and all I could think was "crap, now what do I do."

Stephen

Ron answered the phenolic question and I agree that your random trip problem is not likely due to a control unit problem.

Removing-reinstalling the control unit may improve the plug connections, but if you still get random selections, start the machine scanning with the service sw --make sure you put it back to "operate" once scan begins. Does the mech ever trip now with no selections made? If so, slightly tighten the shell of the RCA plug from the tormat. I also add a short lead from that shell to a screw on the surface of the control unit chassis.

Separate the tormat and keyboard plugs (BTW: is there a stepper in there?) use a good contact cleaner on both male and female sides, replug and test. Clean the Write-n contacts in the credit unit.

All of that assumes the source voltages in the control unit are normal.

Have you checked the tiny wires and plungers on the readout block under the tormat?  IIRC by the LS2 Seeburg eliminated the ground plungers i the center of the block, but make sure the remaining plungers are connected and have slight overtravel (approx 1/8 in).

Has that machine been properly oiled?

RobNYC

[paradisecs]

An update. The board may not have been the only problem but I have fixed what I can on it. There were several traces that didn't give me any continuity that are now fixed.  





I also found this:  I see these as C3111 & C3112 which the schematics and parts list show and .01 MFD 500V.  Whats there say .1 200V on them.  Those need to be changed back to the correct value, right?


Stephen

[Ron Rich]

Stephen,
Those were changed at the factory--the update for them is .1/200. Later (DCC types) were changed again to .22/200. Ron Rich

[paradisecs]

Thanks Ron. I'll note that on my schematics. Are there updated ones? I'm using the ones from the LS-2 supplement.

Stephen

[Ron Rich]

Hi Stephen,
Perhaps--one of the later 100 select models used a similar SCC (9)-- I would need to look at that schematic. That's really of no consequence, as it was changed to further reduce the audio "Pop" thru the speakers, when one of the scan control coils was energized. Ron Rich

[paradisecs]

What should the voltage be at TB3101-1 (high voltage) when testing on the bench? I'm getting around 205V but I thought it should be 150V. I've tested the components in the circuit according to the schematics and I don't see anything noticeably out of specs.

Stephen

[Ron Rich]

Stephen,
It's not regulated--see the schematic--200 should be just fine.
Ron Rich

[paradisecs]

Thanks Ron. I've looked at my copies of the schematic and I don't see the voltage listed. It has the other ports but not that one. Or if it's there my glasses aren't strong enough to see it. I'll make a note on there for next time.

Stephen

[Ron Rich]

Stephen,
What's it say at the "test point" ?? "Hi" don't stand for "Hello" !! LOL Ron Rich

[paradisecs]

I'm a computer tech by nature with some CNC controller repairs under my belt. I rarely working with anything over 12V. When I start seeing voltages higher than the wall outlet I start to question my sanity.

Stephen

[Ron Rich]

Stephen,
OK-- I guess that's why I have no "sanity" left !!
Ron Rich