(Topic ID: 250796)

Harlem Globetrotters help please

By Don44

11 days ago

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  • 33 posts
  • 5 Pinsiders participating
  • Latest reply 2 days ago by frunch
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#1 11 days ago

I just picked this up and it powered on with GI working and one display. There was a blown fuse F4 on the rectifier board. I replaced it and 3 coils lock on on power up, the right sling, globe saucer and target saucer. Any help would be greatly appreciated.

#2 11 days ago

It seems all 3 coils lead to U3, a 3081 transistor array chip on the solenoid driver board (the upper right board in the backbox). Get a good look at the transistors and the U3 chip on that board.

#3 11 days ago

I took a look and there is not a transistor at Q18. Is there supposed to be one there? Could it not being there cause the coils to lock on? Any idea what transistor it is?

#4 11 days ago

Doesn't look like it's used in that game, according to the schematic. Looks the the transistors that drive the 3 coils are Q10, Q11, and Q12. I would check those 3 transistors, check U3, and check each of those coils under the playfield and make sure they're wired properly with respect to their diodes. Also check the resistance on the coils (anything generally 2ohms or less is bad).

#5 11 days ago
Quoted from Don44:

I took a look and there is not a transistor at Q18. Is there supposed to be one there? Could it not being there cause the coils to lock on? Any idea what transistor it is?

That's for an unused coil spot on your game, don't worry about that. The main driving transistors can be replaced with Tip 102's.

You should check out the predriver chip though as well. You can test things out by removing the large connectors from the board (leave the smaller ones to the right) so that you don't blow the fuse again, with either a logic probe or a volt meter - you're looking for shorts to ground on the pins that go to the game, and the 3081 chip's pins.

Head to pinwiki.com and look in the bally/stern section for information on how to do this or search for it here. Basically you're going to have shorted driver transistor, shorted pre-driver chip, or a bad decoder (unlikely).

#6 11 days ago

I will have to take a look at that pinwiki guide. I have never worked on a bally ss before so I am new to this and I am an amateur using a multimeter. I want to note that the left pop locks on as well.

#7 11 days ago

I took the driver board off and R50 appears to be burned up. I think its a resistor. I am not good at reading the schematic, can somebody tell me what resistor it is? Also, I think the 2 ca3081 chips were replaced at some point.

#8 11 days ago

R50 looks like it's part of the +5v circuit produced on that board.

Considering this is your first SS Bally, it's probably smart to read up on the pinwiki guide and familiarize yourself with some of the common problems, fixes, and upgrades. You will likely need to replace a number of connectors, for starters.

Does the mpu board have any battery corrosion? Are the boards all original or have any been replaced with aftermarket ones?

I would also recommend checking all the voltages at the rectifier board and solenoid driver board. There are test points on both boards you can hook your meter up to. It's really important to verify proper voltages before troubleshooting, bad/missing voltages can create all kinds of weird problems. If you need help setting up and using the meter, just ask! It's a *very* helpful tool, it's worth learning the basics on yours.

#9 10 days ago

There is corrosion on the mpu as well. The nicad battery was hanging on by one leg. I am going to remove that board and clean it up as best as I can. What about that R50 though? Anybody know what I need to replace that with? Also, what setting should I set the meter to to check the voltages on the solenoid driver board?

#10 10 days ago

Looks like R50 is a 2.2 ohm resistor. You can set your meter to check resistance (often an 'omega' symbol on the meter).

To check DC voltage, set your meter for DC volts--the symbol is often 2 parallel horizontal lines, one dotted and one solid. Next place the black meter lead on ground. You can tuck the lead under the ground braid in the backbox if it's easier, though you'll also see a test point for ground on the solenoid driver board as well. Either should be ok for the test, afaik.

Here's what you'll look for on the solenoid driver board:

TP1 = +4.9 to 5.2 vdc
TP2 = +190 vdc (but often turned down to 170 volts to increase score display life).
TP3 = +4.9 to 5.2 vdc
TP4 = +230 vdc
TP5 = +12 vdc to 16.5 vdc

So, black lead on ground...now with the game on, carefully touch the red probe to each of the test points on the solenoid driver board and jot down the voltages you get.

Also, you'll want to confirm proper voltages on the rectifier board. Test points and voltages are as follows:

TP1 = +5.4 vdc
TP2 = +230 vdc
TP3 = +12-14 VDC
TP4 = 5.7 to 7.3 volts AC (general illumination---don't bother checking this one for now---)
TP5 = +43 vdc (solenoid voltage)
GND = Ground

#11 10 days ago

Thanks for all of your help frunch. One question, can a 4.7k ohm resistor be substituted for the 2.2k resistor? They are both 1/4 watt

#12 10 days ago

You're welcome! Hopefully other techs will feel inclined to jump in at any point too.

Careful--that's a 2.2 ohm, not a 2.2k (2200!) ohm resistor. I would suggest only using an exact replacement.

I'd go ahead and do the voltage checks for now. Chances are you will eventually need to do at least some connector re-pinning, and I'd also recommend changing the big caps on the solenoid driver board along the way.

#13 10 days ago
Quoted from Don44:

One question, can a 4.7k ohm resistor be substituted


That 2.2 ohm resistor at R50 is there to bump the 5V power supply output from around 5.0 to 5.2 volts to improve system stability. The resistance value of that resistor is critical in determining the output voltage. Using a 4.7k (4700) ohm resistor will effectively bump that voltage output to around 12 volts which will very likely cause damage to most of the logic chips on the boards.

With the power off I suggest you disconnect the power connectors from the logic boards until you know you have a stable 5.2 volt DC supply which means unplugging the following:
J4 from the MPU board which is the board in the top left corner of the backbox
J4 from the lamp driver board which is the board in the bottom left corner of the backbox
J1 from the sound board which is the board below the solenoid driver board in the backbox
The main connector at all the displays.

Replace that R50 on the solenoid driver board with the correct value 2.2 ohm 1/4 watt resistor.
Power on and measure the voltages as per frunch's post #10.
When TP1 on the solenoid driver board measures in spec (around 5.2 volts) then plug all the other boards back in.

#14 10 days ago

These are the readings I got tp1-8.8, tp2-167, tp3-8.7, tp4-234 and tp5-12. On the rectifier board I got tp1-5.6, tp2-214 and tp3-12.5. I took off the mpu board and it was a little more burned up than I thought at j4 connector and there was some acid damage as well. I think I might go ahead and order the alltek mpu board but realize I might have other problems as well. Any indication of where my problems lie with the readings I got? A little history on the pin is that the guy said it probably has not worked in almost 20 years and been out of an arcade most of its life. Its actually in pretty good cosmetic shape.

#15 10 days ago

Definitely sounds like issues with the solenoid driver board as well. In addition to that, you're going to need to re-pin a number of connectors, including any that may have been reached by the battery leakage. Still, sounds like a good candidate for the effort! Not sure how experienced you are with board work, but you can probably get away with fixing the solenoid driver board at very least.

I'll defer to Quench at this point because he knows this stuff inside and out and we're approaching the limits of my knowledge ...but what I see so far is that your 5v on the sdb is definitely too high, possibly due to the burnt resistor? Could be more to it than just that though...

#16 10 days ago

I do have some experience repainting connectors as well as replacing parts on the driver board. I have to put a new connector on for the mpu. Any idea where I would find a 19 piece connector?

#18 10 days ago
Quoted from Don44:

These are the readings I got tp1-8.8

Oh dear, 8.8 volts on the 5.2 volt output..

You need to determine if the 5 volt regulator is still working.
Power the machine on (leaving the other boards disconnected).
Set your meter to read DC voltage.
Put the red meter lead on test point TP1 on the solenoid driver board, and black meter lead goes on the metal can part on the large transistor looking thing in the middle of the big heatsink on the solenoid driver board. Do you get 5 volts?

Your test point TP5 on the solenoid driver board is reading a little low - it should be over 14 volts. The big filter capacitor at C23 on the solenoid driver board may be suspect. Set your multi-meter to read AC voltage and measure the voltage across the two legs of that large C23 capacitor in the middle of the solenoid driver board. It should read around 0.2 volts.

Quoted from Don44:

I think I might go ahead and order the alltek mpu board

Pinsider barakandl also makes a replacement MPU board worth considering:

Post some clear high res pictures of the boards in the backbox. Let's see what you're dealing with.

#19 9 days ago

The reading I got at TP1 when touching to the piece on the heat sink is .75. Today TP5 was reading over 13 V. When I did the test on the capacitor c23 it read .2 V

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#20 9 days ago

Yikes. Just chiming in, but the MPU board has some burned components in the lower left hand corner that may be dragging the voltages down. Also, that header on the MPU needs replaced, as do the pins for the connector that goes there.

As far as the power supply board, it needs connectors replaced and the board pins replaced, too.

There’s a note on the MPU saying it does not score properly, so this board had issues before you got it.

I recommend going thru this systematically, as has been suggested previously.

Good luck - I’ve brought back boards that were in worse shape than these.

#21 9 days ago

Looks like the 12 volt and 5 volt pins on that J4 pin header at the MPU board got shorted which is what the flame damage is and also why R50 on the solenoid driver board has burnt. It looks like the 5 volt regulator might be faulty too.
I've seen this once before to a much lesser extent caused by conductive battery corrosion under the J4 pin header shorting the 5V and 12V pins.

With the logic boards still disconnected, place a jumper wire across the R50 resistor on the solenoid driver board so you short the resistor.
If you then power up, do you see 5.0 volts at TP1 on the solenoid driver board? (red meter lead at TP1, black meter lead on ground).

#22 4 days ago

I was busy the last few days but I put a jumper on r50 and I still get a reading around 9 V. I had replaced r 50 first. It’s possible I don’t have it connecting well though. I had a hard time getting the solder to stick to the board

#23 4 days ago
Quoted from Don44:

It’s possible I don’t have it connecting well though.

That's your first port of call.
If you're still getting 9 volts DC at test point TP1 on the solenoid driver board then the 5 volt regulator is faulty.

#24 3 days ago

Just to be sure, is the 5 v regulator the piece that looks like the back of a watch in the middle of the heat sink?

#25 3 days ago

Correct, just note it's the regulator on the larger heat sink on the right side of the board. I only mention this because there's another smaller heat sink for the voltage regulator for the high voltage displays on the left side. Don't want to mix those up!

#26 3 days ago

Frunch beat me to it and yes
Suitable 5 volt regulator replacements are a "LM323"


#27 2 days ago

Thanks for all the help so far but I decided there was too many problems to diagnose and that mpu was pretty roached so I wound up purchasing the mpu, solenoid driver board and power supply. I will also replace the 2 burnt or broken connectors. Anything else I should do before plugging in the new boards?

#28 2 days ago

Any plans for the old boards?

I'd recommend lots of re-pinning, but Quench should be able to steer you exactly where to focus.

#29 2 days ago
Quoted from frunch:

I'd recommend lots of re-pinning


You should get a proper crimping tool. I'll let others chime in if you haven't got one.

You'll need to replace the two wire connectors (J1 which is 8 pin and J3 which is 20 pin) at the rectifier board. These are 0.156" connectors. We recommend that you use "trifurcon" wire crimp terminals at these connectors which provide greater surface to surface contact. Look at the crimp contacts here and notice the extra fins the trifurcon crimp contacts have:
They come in two sizes for crimping different wire thicknesses. The "18-20AWG" are for the thicker wires and the "22-26AWG" are for the thinner wires.

Please don't forget to buy and install the key plugs that prevent the connectors from plugging in the wrong way or offset.
These example are for 0.156" connectors:

By the way there is a red wire missing from the middle of the J3 connector in your rectifier board picture above.

Also replace the J4 connector at the MPU board. It's a 19 pin 0.1" connector. Because of the battery corrosion on the MPU board, there's usually a good chance that corrosion has reached inside some of the other connectors on that board. Realistically you should replace the crimp terminals on those connectors (re-use the existing plastic connector housings but clean them first). The crimp terminals are cheap.

Replace the rectifier board taking special care to solder the transformer wires (about fourteen) on the rear of the board into the correct "E" positions.
Please feel free to post pictures of how/where you've soldered the wires to the rectifier board and pictures of the connectors you've redone if you want us to double/triple check wires are in the correct spots.

When you're happy, plug J2 only into the rectifier board and power up.
Verify the test point voltages as per post #10 by @frunch above.

If voltages are in spec, switch off, install the solenoid driver board. Plug in the J3 connector into the rectifier board and also the J3 connector into the solenoid driver board.
Make sure the following are disconnected:
J4 at the MPU board,
J4 at the lamp board,
All five displays,
J1 at the sound board.

Power on the game and verify the solenoid driver board test point voltages as per post #10 by @frunch above.
If the voltages all look ok / in spec then power off and plug everything else in.

#30 2 days ago
Quoted from frunch:

Any plans for the old boards?
No plans. I didn’t realize the rectifier board isn’t plug-and-play. Oh well. It looks like someone did a jumper on the back of the board and there is also two wires spliced together leading to one pin on that board So I assume one of those red wires goes to a different pin

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#31 2 days ago

I have used those trifucon connectors in the past. I need to replace the J4 connector. Is it a different size than regular connectors?

#32 2 days ago
Quoted from Don44:

there is also two wires spliced together leading to one pin on that board So I assume one of those red wires goes to a different pin

Yes, follow the harnesses to the respective connectors. the J1 connector is the playfield wiring loom. The J3 connector is the backbox wiring loom.
The red wire for the backbox goes to pin 11 of J3 (between the orange wire and the grey wire where the connector housing is burnt/broken)
These two red wires are for the general illumination circuits.

Quoted from Don44:

I need to replace the J4 connector. Is it a different size than regular connectors?

The J4 connector at the MPU board is a smaller pitch (0.1") connector compared to the connectors on the rectifier board which are 0.156" pitch. So yes they're different housings/crimp terminals/pin headers, etc but common on these old Ballys.

#33 2 days ago

Here's the kind you'll want, 0.1" pins (link is for a bag of 100):


As Quench also mentioned, you'll want to reuse some of the old housings especially if replacements aren't available. A small jeweler's screwdriver can be used to push the locking tab of the old pin so you can pull the pin out of the housing.

I'd love to take a shot at refurbishing the old boards if you're interested in getting rid of them. Maybe we could figure something out if you're interested...

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