Hi everyone,

I have a Williams Bride of Pinbot with some Controlled gate issue

before i had problems with the head, but that seems to be resolved thanks to the advice here.

Problem:

The Controlled gate does not switch of. (Solenoid 4)
First i have noticed that the connector under the playfield was disconnected. (maybe by someone before me)

After connecting and starting up, i have noticed the relay switched on and stayed on, so the relay part works.

But, it does not switch of, even in solenoid test, it does not change.
So, i think it must be switched to ground at all times.

According to schematics, Q76 handles the relay.

Could there be some part failing here? could TIP36C be shorted?

I am not a electronics expert but have a base knowledge.

Thanks for the help and tips.
IMG_20240415_110030 (resized).jpg

Diode test measured something completly different on D29 compared to D30, D31, D32
The value 394 is from D29
The value 003 is from the others.
Could this diode be the culprit? it is a 1N4004. I have this part.
IMG_20240415_113309 (resized).jpg

IMG_20240415_113332 (resized).jpg

Nope, not the diode, replaced it and compared to other circuits like for Sol1 Sol2 Sol3, it measured all the same.

So, something else must ground that Sol4 relay

Test with coil test doesn't do anything, the coil stays energized (pulled) and does not release and switch within the test. So i presume, there must be something that grounds the circuit.

I have TIP36C but TIP102 is underway, i need to see if i have 2N4403.
I might replace the whole circuit for that coil.

Also, i will check if the coil pulse immediatly when powering on or not.

Thanks for the tips

Update:

When powering up, the coil immediatly activates.

I have replaced Q76 TIP36C, Q77 TIP102. I still has the same problem.
Weird thing is, when i compare with other circuits in that area, i don't seen any differences. That is with the board powered of.

I did not change Q72 for the moment, parts underway.

Could U5 cause problems? 74LS374

When J130 is pulled, it is not activated.

While i wait for the 2N4403 transistor, i am going to desolder U5 74LS374 and check it.
If that checks good, i will replace it in a socket and pull out Pin 4 or 5

If the coil is still pulled, then it must be on the transistor chain.

IMG_20240418_182944 (resized).jpg

Tested out U5, test is good.

Pulled pin5 out that connects to Q72. Coil is still activated immediatly after power on.
I.M.O. it should not be pulled in idle situation to prevent coil from burning.

I am waiting for 2N4403 transistor.
This is my final replacement, after this i won't have a clue what could be wrong.

8030.74ls374.png-550x0 (resized).png

IMG_20240419_131322 (resized).jpg

I have created the circuit into a test program to see how it should work.

The button on the left represents the inputpuls from U5.
When pulsed, the coil is triggered, when pulse is released, the coil is released.
If Q72 should have a short somehow, the coil stays triggered.

I am waiting for new 2N4403 to find out if that is the problem.

In the video, you can see normal working and what happens when Q72 is shorted.