Oklahoma City, OK
Quoted from german-pinball:Means, when you press first button, motor turn CW and if you press the other button motor turns CCW, correct??
Yes
(Topic ID: 182422)
Linked Games
Twilight Zone
Bally, 1993
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And you also tested the voltages on the homepin board at the TPs for +5V and +12V? Are these voltages present and OK, if yes, we will do another test ....
OK, we next ground the 2 inputs separately.
Therefore you should build a short "testcable" (eg. a wire with an alligator clip or so to clip it to a good ground point), one side connected to GROUND (somewhere) and with the other end of the testcable you do the following:
1.
connect to Input DIR1 (you can e.g. put the wire to banded side of Diode D2) - Motor should turn CW
2.
connect to Input DIR2 (you can e.g. put the wire to banded side of Diode D3) - Motor should turn CWW
Do NOT do this test, while the clock test menu is running. And be careful, not to cause a short.
Post the results, what happens,
1.
when you ground DIR1
2.
when you ground DIR2
Quoted from german-pinball:OK, we next ground the 2 inputs separately.
Therefore you should build a short "testcable" (eg. a wire with an alligator clip or so to clip it to a good ground point), one side connected to GROUND (somewhere) and with the other end of the testcable you do the following:
1.
connect to Input DIR1 (you can e.g. put the wire to banded side of Diode D2) - Motor should turn CW
2.
connect to Input DIR2 (you can e.g. put the wire to banded side of Diode D3) - Motor should turn CWW
Do NOT do this test, while the clock test menu is running. And be careful, not to cause a short.
Post the results, what happens,
1.
when you ground DIR1
2.
when you ground DIR2
I think you may have it backwards. If I ground DIR2 I get clockwise movement. If I ground DIR1, I get nothing.
Such a simple test. Embarrassing that this wasn't the first thing that I tried. 
Though it does make one wonder what is the purpose of the test buttons.
This thread is a great example to people how not to troubleshoot.
The purpose of the test buttons is the same. But as I do not have the schematics of the homepin-board and I do ot know, how he wired his test buttons, we do it this way. If homepins testbuttons ground behind the optocouplers, we cannot test, if the optocouplers are OK.
Using my way and motor turns cw and ccw, the homepin board is OK, if not, we can identify, if one of the optocouplers on the board is bad.
Quoted from german-pinball:The purpose of the test buttons is the same. But as I do not have the schematics of the homepin-board and I do ot know, how he wired his test buttons, we do it this way. If homepins testbuttons ground behind the optocouplers, we cannot test, if the optocouplers are OK.
Using my way and motor turns cw and ccw, the homepin board is OK, if not, we can identify, if one of the optocouplers on the board is bad.
So then, U1 is bad?
Quoted from zaza:If you make a short between pin 4 and 5 on IC1 (or IC2) then you skip the opto-isolator and drive U4 directly.
Better unplug the aux.8-drv in the backbox.
It looks from pictures that the Homepin bi-dir motordrive ver1.4 (also) grounds pin 5 of the opto-isolator.
I'm not sure I fully understand. Do you think U1 is bad?
Quoted from zaza:If 'grounding' J1-2 (violet dot) doesn't make the clock motor spin but 'grounding U1-5 (green dot) does,
you can say that U1 or R2 or D2 is the problem.
Got it! Thanks!
It seems (to my uneducated brain) that there should be a simpler way to design this function without a failure-prone optocoupler in the circuit.
The two test switches are connected to the output side of the optocouplers. Their function is to make it easier to operate the mechanism and adjust and repair it. Not for testing the board so much.
The purpose of the optocouplers is to isolate the motor driver circuitry from the circuits and preventing a major issue. Optocouplers are usually very reliable from my experience. Homepin does not normally change the original circuitry, we make numerous changes for improvement but keep the original design where possible. On this board we simply added the two test switches, everything else is as the original.
You can easily work out which components might be faulty by looking at the part diagram of the board below.
If SW1 (DIR1) is NOT working, suspect one of the following - U1, D2, R2.
If SW2 (DIR2) is the one not working suspect one of these - U2, D3, R6.
All of these parts are exactly the same as they are on the original board.
The color code indicates indeed a 10 Ω resistor (same as R5) . That will take out the ir-LED inside U1 in a very short time.
Replacement of both components is needed.
Quoted from zaza:The color code indicates indeed a 10 Ω resistor (same as R5) . That will take out the ir-LED inside U1 in a very short time.
Replacement of both components is needed.
You eagle-eye 
Indeed, both resistors have the wrong value.
Replacement of both resistors and at least U1 optocoupler is needed. It seems, that U2 is still alive.
By the way: R3, R7 + R8 are silkscreened 2K7, but installed are 2K6, but this should not matter in this application.
Quoted from german-pinball:both resistors have the wrong value.
I think -but not sure- that the other resistor (R6) is correct.
Made it slightly lighter and then 3rd color looks brown.
Quoted from zaza:I think -but not sure- that the other resistor (R6) is correct.
Made it slightly lighter and then 3rd color looks brown.
R6 is indeed correct. Band 3 is brown and it measures 680 with a meter.
Mike has graciously agreed to send out a new board. If he does not want the old one back, I will probably try to fix it at some point.
While I have the experts here: Can a 4N35 be substituted in for the 4N25 opto coupler?
Quoted from alveolus:Can a 4N35 be substituted in for the 4N25 opto coupler?
Yes, but it needs another current limiter resistor for the input LED. Something about 1200-1500 ohm if I calculate correct.
Quoted from zaza:I think -but not sure- that the other resistor (R6) is correct.
Made it slightly lighter and then 3rd color looks brown.
Indeed the upper resistor value is incorrect and very likely has taken out the optocoupler.
The bottom resistor looks correct.
Please feel free to replace the resistor and the optocoupler but I would advise using a 4N25 or 4N28.
I will still get another board sent out but s I am currently traveling I haven't had the opportunity to do that yet, sorry about that.
1 week later
Quoted from alveolus:I received my parts from GPE, installed the correct resistor and replaced U1. The clock now works correctly!
Thanks to all who helped.
homepin , no need to send out the replacement. All is well.
Great news! The replacement board was sent about a week ago so you will have a spare when it arrives.
2 years later
Ottawa, ON
9 months later
And just to bump this...
I turned on my TZ a couple days ago and the clock went wild immediately. It did turn off during testing through. Only went backwards (at both speeds). Did some digging, looked at the manual's schematics, and suspected it might be U1 on the A-16120 Motor Control board. Also tested the inputs to the motor board were operating correctly.
I decided to search and see what was out there on the topic and found this! It was great to see some data confirming the likely cause (or maybe a common cause?).
Got a new 4n25, replaced it, working perfectly.
Thanks for this info.
... Altan
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