TECH: TIP107 testing at 0.606V

[Guest]

Archived from groups: rec.games.pinball (More info?)

I'm trying to track down a problem with my Road Show. I'm looking at
the TIP107s on the dual power driver board. Two of the four are
reading above 0.6V. Specifically, they are reading 0.604V and 0.606V
(using the marvin3m fix guide method).

Is 0.4 to 0.6 is just a rule of thumb? Or, is it fair to assume these
TIP107s must be replaced because of these readings?

(I would just replace them, but I don't have any right now...)

Thanks

.... Altan
www.aaarpinball.com

 

[martin]

Archived from groups: rec.games.pinball (More info?)

Rule of thumb. Different manufacturers, different lots. The big
giveaway is a dead short across two of the pins.

What' s the problem?

 

[pt]

Archived from groups: rec.games.pinball (More info?)

( I just posted a reply, but I guess it got lost in the bit bucket)
When testing silicon different meters can give different readings.
Also, different manufacturers or batches can vary slightly as Martin
pointed out. The important thing is how do those two TIP107's compare
to known good TIP107's on the same board? Test them all and compare.

John

 

[pt]

Archived from groups: rec.games.pinball (More info?)

Different meters can give different readings when testing silicon, so
yes it is a rule of thumb (IMO). The important thing is how do the
readings compare to known good transistors of the same type on the same
board? Test all of the TIP107's. If those two are different than the
rest then they are probably bad.

John

 

[martin]

Archived from groups: rec.games.pinball (More info?)

Also, check to see if they have been replaced before - that could give
you different readings but the transistors could still be good.

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Martin, John, Thanks.

There are only 4 TIP107s. Here are the readings

Q9 0.606V 0.490V
Q7 0.600V 0.489V
Q4 0.606V 0.491V (the 0.606V read as 0.604V earlier)
Q2 0.591V 0.490V

They don't seem out of wack with themselves... what do you think?

I'm digging into an issue where Ted's mouth opens and closes faster
than Red's. I've shown it's not the motor. Also, if I swap the wires
driving the motors, then Red's mouth is slower than Ted's.

.... Altan
www.aaarpinball.com

 

[martin]

Archived from groups: rec.games.pinball (More info?)

err... so changing the wires made no difference in speed? Not sure you
meant to say that. Please confirm what you meant:

then Red's mouth is slower than Ted's.

then Ted's mouth is slower than Red's.

Which one is correct?

 

[martin]

Archived from groups: rec.games.pinball (More info?)

and those voltages look fine.

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Sorry. I should proof read better.

The problem is that Ted's mouth opens and closes SLOWER than Reds.
After swapping the wires that drive Red and Ted, I found Red is slower
than Ted (or, put another way, Ted is faster).

.... Altan
www.aaarpinball.com

 

[martin]

Archived from groups: rec.games.pinball (More info?)

Can you measure the voltage across the motor drive pins when the mouth
is moving for each head? The best way to do this is with alligator clip
leads.

This will tell us what the drive voltage is.

The symptoms sound like a driver problem. We are going to have to walk
back through the chain.

A couple of things:

1) Are JP1 and JP2 either both installed, or both not installed? That
could cause the problem right there.

2) measure the voltage to ground (example, the braid) and the banded
ends of D5; D6; D8;D9; D13;D14; D16; D17

These are pairs, each pair should show similar voltages.

If they do, then measure D6; D9; D14; D17 with the jaw working. This
will tell us a lot about the circuit's operations. Sounds like there
might be a signal problem back up the line.

Also check the banded end of D10 and D18 whne the jaw is running. These
aree controlled from another board and could also slow the jaw. You are
looking for a low voltage when the jaw is running.

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Martin, thanks. I did some more digging tonight and can answer some of
your questions.

Neither Jp1 nor jp2 is installed. There are 5.6Ohm resistors
installed.

I looked at the diodes. D5, D6, D8, D13, D16, and D17 read about
13.6V. D9 and D14 read 0V (well, 183mv). After looking at the
schematic, I believe this to be correct. I read these values while the
motor was set to keep running in the "close mouth" direction.

The readings for D10 and D18 were only slightly more interesting.
While I've forgotten if D10 or D18 goes with Red or Ted, I can say the
Ted diode bounced between 10.5V and 11.2V while the Red diode mostly
stayed around 11.2V. I'm not sure if this is significant.

I'll keep digging.

Just a side note. It's interesting that voltge to a motor that is not
enabled (not running) is around 13V. The motor that is running is
-13V...

.... Altan
www.aaarpinball.com

 

[martin]

Archived from groups: rec.games.pinball (More info?)

Those voltages all sound correct. Both motors have 13.6V across their
circuit when running. Puts us between the diodes and the motor. Next
step, read the voltage across the 5.6 ohm resistor while the jaw is
running. That voltage will directly reflect the current through the
motor, which in turn relates to the force applied to the jaw.

The D10 and D18 readings appear consistent. You can test the motor by
grounding the banded end of D10 without damage, that will cause the
motor to run.

I have to think about that -13V - that should not be possible.

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Martin,

Thanks again! It looks like we may be getting somewhere.

I measured the voltage across the resistor by placing the DMM
connectors on each pin from the resistor. Reading the voltage across
Red's resistor, I get a swing from

-1.7V to 2.0V (the motor is changing direction during the test).

However, when reading Ted's resistor (the slower guy), I get

-0.7 to 1.0V.

Using V=IR (I=V/R), can we state the current going through the resistor
ranges from

-0.125 to 0.18A for Ted and

-0.3 to 0.36A for Red?

Does this at least explain why Ted is slower?

.... Altan
www.aaarpinball.com


martin wrote:
> Those voltages all sound correct. Both motors have 13.6V across their
> circuit when running. Puts us between the diodes and the motor. Next
> step, read the voltage across the 5.6 ohm resistor while the jaw is
> running. That voltage will directly reflect the current through the
> motor, which in turn relates to the force applied to the jaw.
>
> The D10 and D18 readings appear consistent. You can test the motor by
> grounding the banded end of D10 without damage, that will cause the
> motor to run.
>
> I have to think about that -13V - that should not be possible.

 

[martin]

Archived from groups: rec.games.pinball (More info?)

Sure does! 2x the current means 2x the torque.

Next step, test the bridge voltages. Let's get:


Black lead on the banded end of D9, red lead on the banded end of D6
" D17 "
D14

The earlier diode readings all looked good, so there's a measure of
re-checking here. These really ought to be different!

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Yeah! I believe it's fixed. Although transistor Q6 tested fine using
the diode test, the voltage across it (collector to emitter) looked
funny. I replaced it with a new TIP102 and Ted appears to be working
great!

I left my notes at work, so I cannot state the before and after
voltages, but to my eye Ted is working great!

Martin, as I wrote you privately, thank you for your assistance.

.... Altan
www.aaarpinball.com