Another of my "antique" SP-352 clocks

[N9KTW]

Well I found another clock to work on, using SP352 displays........ It is marked DIGITAL CONCEPTS CORP, EC102 electronic calendar clock.

It uses 3 SP352's for a 6 digit display. A MOSTEK 5017BA chip to run things.

The display doesnt light up, at all. In attempting to check voltages, I cannot find any above about 125 (this seems VERY low for the panaplex displays) I have been told that this is similar to a HEATHKIT GC1092d.

Anyone got any ideas, maybe a schematic for this guy?????

T I A

de Howard, N9KTW

[J Forbes]

did you see this?

http://www.decadecounter.com/vta/pdf/gc1092d_schematic.pdf

[N9KTW]

Yes, thank you I have seen it.  I am currently trying to make a schematic of the power supply that is on the clock that I have. I have no voltages higher than about 125 ish in the clock.  The 15Volt for the chip is derived from a zener  on a 55 Volt line.  Also Heath uses NPN transistors , and my unit is using PNP's.  I am going to look and see if I have any other panaplex  clock diagrams .......

Howard

[Dekatron42]

There is one MK5017 clock that uses PNP transistors in the book I scanned which you can download from here: https://groups.google.com/g/neonixie-l/c/Ov-mzZ_pDig/m/G95NMJPKBQAJ it doesn't seem to use SP352s but at least a Panaplex display.

/Martin

[martin martin]

Hi have the same 6 digit Heathkit.  I do have the complete schematic if you need it.  My issue (not solved yet) is the power transformer runs too hot to touch. All my voltages are good and the clock still keeps time - I built it back in '77

[gregebert]

Have you checked/replaced the electrolytic caps ? I've had one fail as a short-circuit; coincidentally, that was in a Heathkit but it was a scope calibrator.

[N9KTW]

Here is the latest:

1 Swapped out the caps on the power supply board, and noted voltages (they dont seem right for an SP-352, IIRC it needs at least 170V)

2 Drew a power supply schematic (which I have attached)

At this point does anyone know will the SP-352's even fire at 135 Volts? If so, Maybe I have a bad 5017 chip......

Any ideas?????

Howard

[Dekatron42]

The Panaplex display most probably sees the whole voltage span 56V + 137V = 193V, the circuit is just built this way to provide lower voltage to the MK5017 and as bias voltages for the transistors driving the display. Have a look in the book I mentioned above, if you haven't done so already, on page 74 you can see a transformerless design but with similar voltages and design for the MK5017.

/Martin