Ls1 Spectra with a UDPU6 a SCC-8 and a TSA-9 scan twice.

[ss]

Hi there in the mighty US!

I have the common problem scan twice no selction, done the battery test and it works, and now I wonder if it always should be around 395V on the Write-in test point (with everything disconnect from the SCC) since I have 0V with the price unint disconnected and around 36V with it connected, on the Write-out post I have 350V in rest position 200V in forward scan and 160V back scan and on hi Volt post I have 208V and last 27V at 27V post. I have also discovered that if I disconnect and reconnect the Tormat phono contact on the SCC under scanning it picks a record. I have no stepper and no auto speed unit, only the pass by plug. Whould be very happy if someone have any solution on this.

Many thanks from Stefan in Sweden and sorry for my bad English.

[Ron Rich]

Hi Stefan,
If the battery test results in the picking of record slots, this proves the Read-Out/Sense/Detent is functioning OK. The SCC-8 and -9' used a different WI circuit. Often times the 150 volt ZD, along with the choke next to it and a resistor failed. I suspect the reason was that the UDPU stayed in the subtract credit mode for too long (?)-- I just change the bad component(s), and away they went--You should also check the WI insulator, in the UDPU--It MUST be clean, and free of oil ! Clean, the timing relay contacts too -- if you do not know how that should be done, look above in our FAQ's section. Ron Rich

[robnyc]

If you don't already have these diagrams, here are basci functionals of the Write-in and Read-out for that era:

www.flickr.com/photos/90641375@N06/23972257317/

www.flickr.com/photos/90641375@N06/38837646091/

www.flickr.com/photos/90641375@N06/38837641961/ -SCC8 schematic.

RobNYC0

[ss]

Thanks Rob!

So if I understand the schematic for the SCC8 right there would not be 395V on the Write-in test point all the time with all plugs disconnected like the SCC7 and erlier since the Write-in voltage coming from the Write-out point to the write-in switch in the UDPU and then to the write-in circut in the SCC8 board?

Stefan.

[robnyc]

Stefan, there should be full source voltage at pin 5 of J3104 with or without a UDP plugged in.

Looking at the diagram there should be no voltage present at pin 6 of the UDP plug (J3104) except for the instant where the W-I contacts are closed. That voltage gets clamped at 150v by the zener.

One simple test here is to remove all power, then connect one lead from your ohmmeter function to pin 12 of J3104 and the other to the chassis. Then go down the buttons on the keyboard pressing A1, B2 C3 etc. Each time press both letter and number at the same time and read the ohms reading on your meter. You should see approx. 190 ohms with each combination and open with no buttons pressed.

This will test the continuity of the keyboard circuit.

Have you tried the battery test? Remember that on these solid state phonos, battery positive goes to chassis and negative to the tormat RCA tip. This is critical in determining where to look for this problem.

Rob

[ss]

Yes I Have full voltage at pin 5 plugged and unplugged and the battery test works, will try to clean the W-I insulator/contacts and the timing relay and probably change the 150V zener (which seems to be the error in most cases) like Ron whrite. Thanks for the tip on the keyboard test I will do that to, only wonder if the J3104 shall be connected or not.

Thanks Stefan

[Ron Rich]

Stefan,
If the zener is bad, the choke next to it is too, and usually a resistor close by---Ron Rich

[ss]

Ok Ron I suppose that is the R3109 27ohm and the L3101 130uH in the SCC8 diagram you mean?

Thanks Stefan.

[robnyc]

Apr 2, 2018 18:54:11 GMT ss said:

Yes I Have full voltage at pin 5 plugged and unplugged and the battery test works, will try to clean the W-I insulator/contacts and the timing relay and probably change the 150V zener (which seems to be the error in most cases) like Ron whrite. Thanks for the tip on the keyboard test I will do that to, only wonder if the J3104 shall be connected or not.

Thanks Stefan

Yes, all plugs should be in place. You are going to test from the W-I source at TB3101 through the keyboard to chassis ground.

RobNYC

[Ron Rich]

Stefan,
The 130 choke for sure--and I have seen several of the resistors in that area "change value"-- Ron Rich

[robnyc]

Stefan, if you test the chokes you should find around 4.8 ohms for the 130mH and 4 ohms for the 100mH.

RobNYC

[ss]

Long time no see, some update, both choke where cut a lot of resistors where out of range at the board and I changed the zener diod to so now it´s working only some small adjustments left so all the numbers and letters on the display is the same as the record playing  .
Many thanks to Ron and Rob for helping me out with this.