The Aussie Pinball Arcade
Aussie Pinball Forums => Technical Matters => Circuit Board Repair Guides => Topic started by: Sinbad79 on May 20, 2014, 11:18:33 AM
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Hi Guys
Last night picked up a Stern Galaxy - powers up, GI lights OK, just not booting.
While i havent had the time to systematically work through diagnosing the electronics, i did notice that the under playfield fuse was removed, i'm assuming becuause the driver board was locking up coils - tested it and yep, that was why.
So i removed the solenoid/driver board - which is the rev-C type and started to test the transistors - herein is my question.
The voltage readings when using a DMM with red lead to GND and black lead to TOP of Transistor are mostly around the 1.4v - the information on the net suggests that these should be around 0.6v.
Do my readings suggest that there is something else wrong on this board or do these voltages sound OK?
Additionally, Q10 on this board (as an example) was reading a lower voltage 1.05v - which is known bad because the pop bumper coil was humming (locked on - reason why under playfield fuse was removed)
Any suggestions?
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I wouldn't bother with EXACT readings as there are too many variables to stipulate a precise figure.
What you are looking for is a SHORT circuit (0 (zero) ohms) between the collector and emitter of the transistor. The transistor acts as a switch and when ON it basically shorts C to E - when OFF C to E read open circuit.
With power removed - if a transistor reads zero ohms between C and E it is stuffed and the coil will lock on as if the transistor switched it on.
That's what you need to understand and go from there.
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ok, didn't know that, thats helpful.
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Ok well according to that suggestion, all transistors are fine, which begs the question, why caused the coil to burn?
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Couldn't modify previous post, so here's another one, lol.
Tonight i spent some time on the machine to take a more systematic approach to diagnosis.
Began with testing voltages on rectifier board, both with J3 connected and not.
Results as follows:
TP. J3 off. J3 on
1 5.8vdc. 5.85vdc
2. 146vdc. 218vdc
3. 10.9vdc. 13.2vdc
4. 5.6vac 5.6vac
5. 44.3vdc. 44.0vdc
How do the above voltages compare?
TP3 which converts to the +5v regulated source seems fine, TP4 is low and outside of spec, TP2 seems low (backbox displays dont power up)
Does anyone have any direction or suggestion as to which components on the rectifier board are at fault?
What i'd really like is a components list, so i can replace everything.
Thanks
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Those voltages look fine.
A fried coil will most likely be the associated driver transistor (TIP102) on the SD board. Even though it measures correctly, it takes 2 minutes to replace it.
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Thanks Nino.
I've decided to refresh the board anyway, and upgrade the bridge rectifiers to the larger 25amp version.
I'll also replace the fuse holders, and connector pins.
There is an issue with the displays not working on the machine, so I've replaced the diodes as a precaution as well.
Here's a photo of progress.
(http://img.tapatalk.com/d/14/05/21/gazarysu.jpg)
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That looks nice - be aware that most of the PCB holes are 'plated through' so ensure you maintain the through board connection.
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Yea, will solder both sides of the board where relevant.
Factory solder on these boards is an absolute mess - tempted to completely remove silk screening and solder but wont go to that much trouble.
What rating are the fuse clips?
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do not overlook the connector pins,they DO lose their tension.
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yea ill re-pin all wires for which i change the connectors/pins.
Shame work gets in the way of having fun....
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Thought I'd docuument progress here in case anyone else does the same.
Board desoldered with solder braid and then sanded clean to expose the copper traces. I've done this to help me verify the integrity of the board and tracks.
Next step is to get the DMM onto it and check traces for good connectivity before soldering on the components.
(http://img.tapatalk.com/d/14/05/21/na7amuge.jpg)
(http://img.tapatalk.com/d/14/05/21/y5ubu4ed.jpg)
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Pins installed...
(http://img.tapatalk.com/d/14/05/21/ezaryru7.jpg)
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Next.... Fuse clips.
Make sure they are soldered in the correct way!
(http://img.tapatalk.com/d/14/05/21/ebu5yzej.jpg)
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Ran out of fuse clips last night so parked the rebuild of the rectifier board for the night and moved onto the M-200 MPU
Board powered up in the Machine gave a solid LED light, so i've pulled it out and powered it up on the bench with a modified PC-PSU to run some diagnostics.
Preliminary tests on the CPU pinouts suggest the VMA voltage is too high and is an issue.
CPU
Pin40: Rest - 5.28V
Pin03: Clock - 2.52V
Pin36: Clock - 2.60v
Pin37: Clock - 2.60v
Pin05: VMA - 3.68v ..... should be 2.8v
I dont have a logic probe so am limited to what i can test - so any advice or pointers would be helpful
Thanks all !
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Does anyone know where i can source a new U9 CPU Chip for the M-200?
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if you need them in a hurry,i have all the parts for theese boards here.or i buy them from gpe greaplainselectronics
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Thanks Studley I'll call you later today for a chat.
Meanwhile, last night's effort was to replace all the components in the reset section of the board. Didnt think that was the issue initially but thought it couldn't hurt.....turns out it wasn't the issue and there is something else going on.
I think next step is to start swapping out IC's
(http://img.tapatalk.com/d/14/05/23/rajusy7e.jpg)
(http://img.tapatalk.com/d/14/05/23/eraqynuh.jpg)
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what is that ram daughterboard contraption?
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No fkn idea
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i am guessing it is doing the work of the old 2x5101 ram chips
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yea likely.
Probably an attempted fix by previous owner/operator who likely didnt have any 5105's laying around.
5105 below it is still there.
I guess what i need some of these chips to be swapped out to see if that helps - if i made the drive up to your place this weened, do you think we could get it running?
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definitly mate remember i also have a galaxy
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Lifesaver!
I'll buzz you later on tonight - hopefully you're coherent and not drunk ^^^
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i probally will be drunk but coherent,trying to cut down to zero AGAIN.lol
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theres no fun in that mate!
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Does anyone know where i can source a new U9 CPU Chip for the M-200?
Don't worry about that just yet, you stil have the old sh&*t sockets on the board, first port of call is to replace them.
That add on board is to run a 6116 instead of a 5101
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yes criss i also suspected that as he still has the 4 eproms installed
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Does anyone know where i can source a new U9 CPU Chip for the M-200?
Don't worry about that just yet, you stil have the old sh&*t sockets on the board, first port of call is to replace them.
That add on board is to run a 6116 instead of a 5101
I'm powering up the board on the bench with a modified PC PSU, so connectors aren't the issue just yet, however that said, it's on my list of things to change.
(http://img.tapatalk.com/d/14/05/23/y3une4uq.jpg)
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criss is talking about the ic sockets
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yes criss i also suspected that as he still has the 4 eproms installed
interesting, should i be trying something different with these proms?
I have an Eprom burner so can try a few things tonight before i head up tomorrow - any pointers?
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the eprom x 4,mpu,pia x2,ram,rom will probally all need to be replaced with new machined pin sockets.
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not yet even.but you can bring it with you and teach me how to use mine nfi
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OK i'll do that tonight in prep for tomorrow's visit
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do you have an antistatic wrist strap?
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nope!
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without using one you run the risk of destroying chips on removal and re-install.especially the ram as it is a cmos device.
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would you prefer to do it, im just thinking of your time is all.
I use an IC removal tool to remove the chips, and try not to touch the legs.
In all honesty, the IC sockets seem OK, they've all tested fine for continuity with a DMM and so have the chips when installed in them.
I would say that some of the IC's are bad anyway - previous owner has probably had these in and out a hundred times before anyway - probably why it doesnt boot.
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the sockets loose there tension on the legs and become unreliable,remember they are 35 yrs old
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I'll grab an earth strap tonight and do the work so we can focus on diagnosis tomorrow
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Pinrepair Guide:
No Flashes: the LED is Permanently On.
If you turn your Bally game on, and the LED stays on continually, this is one of the hardest problem to fix on these boards. A stuck on LED can be caused by any (or all!) of the following:
* The reset circuit is damaged (after all, it's in the battery corrosion area!) This includes transistors Q1 and Q2 (both 2N3904), Q5 (2N4403), and diodes CR5 (1N4148 or 1N914) and VR1 (1N959B or 1N4738A).
* The program ROM (read only memory) at U6 is bad.
* The ROM jumpers are incorrectly set for the U6/U2 ROMs installed.
* The U9 CPU microprocessor is bad.
* The U11 PIA (peripheral interface adapter) is bad.
* ANY of the sockets for chips U6, U9, U11 are bad.
* The ground trace to U11, U6 or U9 are bad. U11 is especially important to check the ground trace, as it's right in the corrosion zone. And corrosion just loves to travel up the ground traces. Use a DMM set to continuity to check ground at U11 pin 1 (and U11 pin 20 for +5). Also check U6 pin 12 for ground (and U6 pin 24 for +5). U9 pin 1,21 (gnd) is less of a problem as it's well outside the corrosion area.
The first and last two points are probably the most common problems.
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Thanks Boots
i've checked most those, even rebuilt the reset section of the board - tested the boot voltage on U9 and it seems to be fine. I dont think its a reset relate issue.
Is there any way to verify the program rom? ie can i read-out the chip contents and verify against an online bin file somewhere?
I have noticed that the VMA voltage on U9 is too high, so if i was a betting man i'd suggest the issue lies therein...
Check U9 Pin 5. This is the VMA line. It is a pulsing signal and reads about 2.8v with a DMM. If incorrect first try a new U9. Next check U14D, U15C, U19B. U15 is the most likely IC to have failed.
A legible M200 Schematic would be of help- those available on the net are very poor quality
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if you know how to use your eprom reader/writer ? then you should be able to check the checksum against a known goodone.or just re-program
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by just changing all the sockets should fix your prob.if you dont introduce further damage.lol
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I highly doubt thats the issue - but hope it is
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I highly doubt thats the issue - but hope it is
Regardless of what the issue is, the sockets should be replaced, as Studley says they are 35 years old (and not that good quality to start with).
You could go around in circles checking roms and whatever and all along it was the sockets that should've been replaced before even starting anyway.
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thanks criss for re-afirming this crucial point.it i is a must do
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We will do it all tomorrow.
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So rectifier board now complete. Started pinning the wires into the plugs and realised that the J1 connector has two identical red wires and two identical yellow.
Does anyone have a pinout from the Molex square plug, back to the board J1 connector?
(http://img.tapatalk.com/d/14/05/23/uvu8e8az.jpg)
(http://img.tapatalk.com/d/14/05/23/yhuza6es.jpg)
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Here's a better picture of what I mean...
(http://img.tapatalk.com/d/14/05/23/uhuqered.jpg)
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Spent the day up with Studley working on the MPU board.
We tested systematically, fixing problems we came across as we went but to no avail. Just couldnt get the board working, so after a day of trying, i decided to grab one of his spare Alltek MPU Boards.
I can't thank this guy enough for his afforts & troubles, a very friendly and helpful guy who wants to impart his knowledge to others - he even fed me lunch!
Thanks Damien!
Next - onto the solenoid board driver - some wierd AV voltages so will be replacing the large capacitors and any known bad transistors and working from there. This project has been a very good learning curve!