(Topic ID: 190266)

SS Newbie - please help before I have a breakdown!


By 4Max

2 years ago



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  • 20 posts
  • 5 Pinsiders participating
  • Latest reply 2 years ago by 4Max
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IMG_4569 (resized).JPG

#1 2 years ago

I'm new to SS, only Em's to date, so please be gentle!

Looking at a World Cup Soccer for a friend. First thing I noticed is the ball lock release coil was not working - the metal rod was stuck inside as the tube had shrunk through no doubt over heating (wrapper was toast). So I have ordered a new coil, but I have read I should test the transistor that drives it; Q76.

I found these testing instructions from Clay, and all voltages read ok except the last one that reads 0.077. I just wanted to check that does indeed mean I have to replace the transistor?

TIP36c: Put the red lead of the DMM on the metal tab of the transistor. Put the black lead of the DMM on each of the two outside legs of the transistor one at a time. A reading of .4 to .6 volts should be seen. CORRECT

Put the black lead on the center transistor leg (collector) and the red lead on the metal tab, and a zero reading should be seen. CORRECT

Put the black lead of the DMM on the left/top (base) leg of the transistor. The red lead on the center transistor leg should
show .4 to .6 volts. CORRECT

The red lead on the right/bottom leg should be .2 volts. NO, READS 0.077

Any other value, and the transistor is bad and will need to be replaced. (I know Clay spells it out, but thought I would check as I dont really want to replace the transistor!)

thanks

#2 2 years ago

Regardless of any transistor testing - think about WHY the coil fried??

Yes, it was locked on by a shorted transistor more likely than not.

Replace the transistor when you fit the new coil AND make sure you have the diode mounted on the coil the correct way around or you will be replacing the transistor again.

Also make sure you have ordered a new sleeve for the coil as well. Some come with a new sleeve, some don't.

#3 2 years ago

When a coil gets toasted it stresses the driver transistor. If it isn't bad already it might go bad soon and take out the new coil.

#4 2 years ago
Quoted from Homepin:

diode mounted on the coil

I believe that none of the coils on this machine have a diode actually on them, as the diodes are on the board in the back box next to the relevant transistor.

However the new coil arrived today, with a diode!
IMG_4569 (resized).JPG
I assume I should simply remove this diode?

#5 2 years ago
Quoted from 4Max:

I believe that none of the coils on this machine have a diode actually on them, as the diodes are on the board in the back box next to the relevant transistor.
However the new coil arrived today, with a diode!

I assume I should simply remove this diode?

yes, cut it off

#6 2 years ago

Ok, thanks - in fact can I use that to replace the one on the board below the transistor? (Although I'm not sure how to test that yet )

1 week later
#7 2 years ago

Ok, I need help. I am being driven nuts with this.

Steps:

1. Replaced coil and TIP36c - result: solenoid not working. Took closer look at circuit board and one of the paths had burnt. So,

2. soldered a jumper across the burnt path - result: solenoid works! Play a few games, solenoid locks on. Powered off straight away.

3. Rechecked every component in that circuit according to Clay's tests. All test ok, except I notice that the diode (IN4004) tests 0.5 one way, and 1.2 the other - just like all the other in4004s on the board. But when I leave the test leads on for a few seconds, the 1.2v drops to 0. So:

4. I replace the diode - result: solenoid works again. BUT play a few games and it locks on again!!

5. Retest all components in circuit, and all good except the diode is doing the drop from 1.2 to 0 thing again. I could replace it, but I assume something it causing to fail

Any ideas?

Or do I have to replace all the TIP36, TIP102, 2N5401 and the IN4004 all in one go to be sure (even though they all test OK in situ according to Clay's tests (see below). I also tested the TTL involved, and that also tested ok (0.4-0.6v on every leg tested against ground)

Quote
Testing Transistors INSTALLED in the WPC driver board.
TIP36c: Put the red lead of the DMM on the metal tab of the transistor. Put
the black lead of the DMM on each of the two outside legs of the transistor
one at a time. A reading of .4 to .6 volts should be seen. Put the black lead
on the center transistor leg (collector) and the red lead on the metal tab, and
a zero reading should be seen. Put the black lead of the DMM on the left/top
(base) leg of the transistor. The red lead on the center transistor leg should
show .4 to .6 volts. The red lead on the right/bottom leg should be .2 volts.
Any other value, and the transistor is bad and will need to be replaced.

TIP102: Put the black lead of the DMM on the metal tab of the transistor.
Put the red lead of the DMM on each of the two outside legs of the transistor
one at a time. A reading of .4 to .6 volts should be seen. Put the red lead on
the center transistor leg (collector), and a zero reading should be seen. Any
other value, and the transistor is bad and will need to be replaced.

2N5401, MPSD52, 2N4403 (predrivers):
Put the black lead of the DMM on
the center leg of the transistor (note this transistor doesn't have a metal
tab). Put the red lead of the DMM on each of the two outside legs of the
transistor one at a time. A reading of .4 to .6 volts should be seen. Any other
value, and the transistor is bad and will need to be replaced.
ENDQUOTE

#8 2 years ago

You should never replace one transistor in a string. The new one will possibly short straight away because of others in the string potentially being faulty.

It is good practice to replace ALL transistors in a DC connected string at the same time BEFORE applying power.

I wouldn't get too hung up on measuring them, meters all give different readings and transistors can often test OK but fault under load or when stressed.

All of these parts are dirt cheap - I just replace them all when in doubt. Sure, use your meter to quickly find a shorted transistor, that's easy - then replace all in that string and you will fix 90% of your issues.

The same as diodes across coils and switches, they are $0.01 each - I don't even bother getting the meter out - just replace them if in doubt.

#9 2 years ago

Thanks, Homepin.

So I should replace the TIP36, TIP102 and 2N5401 transistors, plus the IN4004 diode all in one go.

There are 5 resistors "involved" that tested ok in situ - do you think these are ok to leave in?

Similarly the 74LS374 TTL chip tested ok in situ (and all other solenoids are ok) - ok to leave this?

thanks in advance!

#10 2 years ago
Quoted from 4Max:

Thanks, Homepin.
So I should replace the TIP36, TIP102 and 2N5401 transistors, plus the IN4004 diode all in one go.
There are 5 resistors "involved" that tested ok in situ - do you think these are ok to leave in?
Similarly the 74LS374 TTL chip tested ok in situ (and all other solenoids are ok) - ok to leave this?
thanks in advance!

I would certainly replace all three transistors and the diode at the same time. I wouldn't be too concerned about the resistors but, when the transistors are out, it's pretty easy to run the meter over them just to confirm they read close to the original values.

The 74XXX chip usually fares OK so I wouldn't replace it for a start. In any case, if the 74XXX chip is faulty it might cause the coil to either lock on OR not work at all BUT it is unlikely to take out the transistor string.

#11 2 years ago
Quoted from 4Max:

I also tested the TTL involved, and that also tested ok (0.4-0.6v on every leg tested against ground)

To rule out an error with the 74LS374 chip you can measure pin 16 on it. It should be high when the solenoid is off and low when it's on.

#12 2 years ago
Quoted from RonaldRayGun:

To rule out an error with the 74LS374 chip you can measure pin 16 on it. It should be high when the solenoid is off and low when it's on.

Sorry, not sure how to measure high and low plus the solenoid locks on as soon as I power on the machine.

Is there any harm in leaving the TTL chip alone, replacing all the transistors, checking, and if still locks on, then replace TTL - or could that damage the transistors again?

#13 2 years ago
Quoted from 4Max:

Sorry, not sure how to measure high and low plus the solenoid locks on as soon as I power on the machine.
Is there any harm in leaving the TTL chip alone, replacing all the transistors, checking, and if still locks on, then replace TTL - or could that damage the transistors again?

You can measure high/low with a DMM. High is 2-5VDC and low is 0-0.8VDC.

Yes, you can change the transistors but if the problem is with the TTL (or the signal coming from the CPU) then you will have the same problem again.

You can disconnect J130 from the driver board so that the coil won't lock on. Then turn on the machine and measure the output from the TTL. If it's high then you know the problem is in the transistors and you can just replace all of them and the diode. If it's low then the solenoid is just doing what it's supposed to and the problem is with the TTL (or the signal from the CPU).

#14 2 years ago

Thanks, Ronald. So I'm starting to understand. Chip goes low to activate solenoid (via transistors). Kind of opposite to what this EM guy would have guessed!

When you say measure with a DMM do you mean in volts mode or diode mode? And that's red to ground and black to pin 16?

Sorry for the basic questions!!

Thanks again.

#15 2 years ago
Quoted from 4Max:

Thanks, Ronald. So I'm starting to understand. Chip goes low to activate solenoid (via transistors). Kind of opposite to what this EM guy would have guessed!
When you say measure with a DMM do you mean in volts mode or diode mode?
Thanks again.

Volts DC - with the meter set to the 20V DC scale (if it has different scales).

#16 2 years ago

Oh. Thanks guys. Just edited my post with another basic question. Is it red DMM lead on ground pin of chip and black lead on pin 16?

#17 2 years ago
Quoted from 4Max:

Oh. Thanks guys. Just edited my post with another basic question. Is it red DMM lead on ground pin of chip and black lead on pin 16?

Red lead on pin 16 and black on ground on chip or just put it under the ground braid below the boards. Reversing black and red will just give you a negative voltage reading.

#18 2 years ago

Thank you so much HP & RRG - I'll try that this weekend when I'm back home and report back.

#19 2 years ago

Was the wiring continuity already tested?
Was the game validated not to have ground shorts?
Were high power voltages confirmed within proper specifications?
Were predriver and diode components tested first prior to the transistor?

As was already stated, ask yourself the question, "What are all the reasons this coil COULD have shorted?"
The question is not, "Why it *might* have shorted?" as this is guessing.
There are missing diagnoses of troubleshooting fundamentals in these sets of advice above.

Testing electronic components first especially ICs without checking the above is chasing a circle.
We are not even at the point of testing the 74LS374 chip.
Don't be an amateur, learn the right way.
Stop trying to learn 201 tasks, before the 101 training ends.
There is jumping around here with no logical progression.
This information I am asking is important, because repairing electronics without validation leads to repeated damage and more work.

Start simple, understand fundamentals, be methodical, work forward.
Don't immediately jump to PCBs, but do test coil diodes properly by clipping a lead.
If everything above is validated, and the transistor does test bad, replacement of the diode on the coil is recommended.
Game logic integrated circuit testing is LAST, and should be performed before powering up the game with new components.

There are reasons there are advantages to learning how to repair EM pinball machines first.
It like learning to drive a car with a standard transmission, before driving an automatic.

1 week later
#20 2 years ago

Thanks Homepin took your advice and replaced all three transistors and the diode. Left the chip alone.

Played around 20 games to date, coil working correctly!

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