Alarm Clock 7 Segment LED display

Question

I recently got an alarm clock from goodwill and took it apart and am probably going to use the display for some tests. Here is a picture of the front of the display:

1. The text on the left is YC-60525S 3
2. The text on the right is 94HB
3. On the back is WS6055 L S and 0306

Here is the display schematic I made as a PDF.

You will notice that pins 23-29 were never connected to the clock's other PCB; although pins 22 and 23 are soldered together. Also worth noting is that pins 7 and 8 are never used. And lastly a, d, e, f, and g do not currently function in any sense on digit 1 (hence '1' is the only digit it can make).

My problem is that I was messing around with the unused pins on the right of the board and managed to do a couple different things.

1. I duplicated the controls Pin 1 had as ground to Pin 29 (Red/Purple in the PDF).
2. I moved the majority of controls Pin 2 had as ground to Pin 25, leaving only control of the 1st digit to Pin 2 (Blue/Black in the PDF).

I am unsure what did to cause the board to change its configuration. I was trying to be pretty thorough labeling the pins, and at one point I brought in a second voltage line. I would like to know why/how this occurred, but also how I can then manipulate the boards settings to my liking.

Answer 1

It's years later but I found the OP useful so here's some more info, on a similar module also salvaged from a clock. It's a common-cathode display which was driven by a Sanyo Semiconductor LM8560 - datasheet still widely available.

Label on the front is WK6052 (c.f. 'YC-60525S 3' for OP). On the back, 'TB 0.6" 12H 01 06' where 0.6" corresponds to the digit height and perhaps '01 06' to a manufacturing date. 12H matches the fact the clock offered a PM LED and 12-hour display - no 24-hour display option - and accordingly the display itself (like the OP's) had connections for digit 1 to segments b and c only.

Like the OP's, common-cathodes pin 1 is shared with pin 29. Common-cathodes pin 2 is shared with pin 26 (c.f. 25 on OP's - 25 on mine is n.c.). Also like the OP's, pins 7 and 8 were shorted off-board but unconnected to anything else; I don't measure any on-board connections to them either but presumably there's something.

Referring to the OP's diagram above: L1 was used as the PM LED; L2 as the "alarm set" LED (lit when the clock's On-Off-Auto switch was set to Auto); L3 and L4 are the colon LEDs (connected in parallel on-board, so they can't be driven independently); L5 is available on the display but was unconnected (n.c.) in the clock.

Using shorthand 'nx' (e.g. 2d) for the anode of Digit n Segment x, the pinout is:

Pin(s)    Purpose

1, 29     Common cathodes for: L1; L3 and L4 (colon); 2d - 2g; 3a - 3c; 4d - 4g
2, 26     Common cathodes for: 1b, 1c; 2a - 2c; 3d - 3g; 4a - 4c
3         L2 cathode
4         L2 anode
5         L1 anode
6         1b
7, 8      ?? Shorted off-board
9         1c, 2e  (N.B. One common LM8560 datasheet incorrectly has 1c, 2c
          in its Pin Assignment diagram but shows correct pinouts in its
          recommended schematics.)
10        2b, 2g
11        n.c.
12        2c, 2d
13        2a, 2f
14        n.c.
15        3a, 3f
16        3b, 3g
17        3c, 3d
18        3e, 4e
19        4b, 4g
20        4c, 4d
21        4a, 4f
22        n.c.
23        n.c.
24        n.c.
25        n.c.
26, 2     (See 2 above)
27        L5 anode
28        L5 cathode
29, 1     (See 1 above)
30        L3 and L4 (colon) anodes