Flash Pinball Troubleshooting second thread

dieseldogpi

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Starting a new thread becaus ethe last one got kind of long. Just got my Logic probe today, but before I was able to use it, I was checking for the voltage at the reset pin (IC1, Pin 40) and it was only at 3.75 volts. Pinrepair says if the voltage isn't at least 4 volts, to check transistors Q1-4, Q6, and diodes D17, D18 and ZR1. How do I test the transistors?
 
going to try and help here. Others might want to chime in. From a thread I started

to test the transistors you check with a DMM on the C and G legs. Test others around the ones you think might be bad to compare.

How I tested the SCRs
On my DMM I used ohms setting and connected the C and G. Then I switched to the diode setting and got better results testing C and G again. Set to diode most SCRs would show .66X and on the one I replaced it was .006 That is what I based my checking on. All others were at .66X so I figured they were good.

This pic shows a 2N5060 circled in purple.

4852902641_d0c034aaf4_o.jpg


here is a schematic of them

4852809005_c3677bc1d2_o.gif
 
do I need to remove them from teh board to test?

Nope. Test them right on the board. You might get some funky readings off a bit because they are connected to other stuff, but should be in range. You will be able to tell when one is bad because it will be way off.

Diodes are in that same category. I would swap probes and compare to others as well to get a good reading.

Someone else needs to chime in here. I am still a newb and others will have beter info, but this is how I roll and it has worked decent for me.

Good luck.
 
I know that Clay talks about a 4v minimum a lot, but in all honesty I've got 4 working boardsets right now that all have voltages in the 3.8v-3.9v range. Newer stuff is more voltage sensitive, but I just haven't found the System3-7 boards to have much issue there. That old 70's era circuitry has some pretty high power usage and voltage drops compared to newer stuff..... but at the same time it also doesn't seem to care as much about out of spec voltages.

If you're testing the reset circuit, I find it easier just to jumper a known good 5v source to pin 40 and see what happens. If that wakes it all up, the reset circuit is dead. If nothing happens, move on to the clock circuit. If you were seeing 2v or less, I'd say dig deeper into the reset circuit, but if you're seeing just shy of 4v..... I'd move on. Usually that circuit is either alive or dead, with no in-between.

-Hans
 
Oh OK. The clock circuit had the same 3.75 volts, so I'm guessing that should be good enough. I also tried jumping it by putting good 5 volt supply to pin 40, and the board locked up. With a logic probe the reset circuit was doing what it should.
I did go on to check IC1 and IC17 on the appropriate pins with the logic probe but I didn't take note of the exactly what happened. Most of the pins that are supposed to pulse did not. And pin 33 on IC1 had a very irregular high pulse, it was very very fast and did not keep a steady rhythm. When I get home today, I will retest the exact ones and post the results. Thanks guys.
 
OK, so I sat down to jot down some notes on whats going on. With the logic probe, I checked for the clocking signal on IC1, pins 3,36,27 and IC5 7,13,15, all seems to be well, had the pulsing signal. Also the reset signal at pin 40 did what it should.
I then moved on to IC17. Following the pin repair guide, I checked IC17 and had pulsing signals everywhere I shoudl except for pins 1-4. According to the guide, i should check the continuity to check for broken traces. So IC 17 Pins 1-4 correspond to IC1 pins 16-12 respectively. Now here my inexperience is really going to show, my DMM doesn't not have the continuity I am used to (one that beeps when there is continuity), this one doesn't beep, it shows a value, when the two leads touch, the value goes from 1 down to zero. I'm sure this is all old news to everyone. Now for when I'm checking the pins. When I check from IC17 pin 1 to IC1 pin 16, I get a value of 1.340. the same goes for all the IC17 to IC1 pins. If I touch IC17 pin 1 to IC17 pin 2, I get a value of around 1.5. Then I tried IC17 pin 1 to IC1 pins 16-12, all read the same value of 1.340. I think i'm confused. Does this sound crazy?

Oh and the blanking signal at interconnector pin 37 did not start low then go high. It starts low, blips high for a milli-second, then stays low.
 
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OK, so I sat down to jot down some notes on whats going on. With the logic probe, I checked for the clocking signal on IC1, pins 3,36,27 and IC5 7,13,15, all seems to be well, had the pulsing signal. Also the reset signal at pin 40 did what it should.
I then moved on to IC17. Following the pin repair guide, I checked IC17 and had pulsing signals everywhere I shoudl except for pins 1-4. According to the guide, i should check the continuity to check for broken traces. So IC 17 Pins 1-4 correspond to IC1 pins 16-12 respectively. Now here my inexperience is really going to show, my DMM doesn't not have the continuity I am used to (one that beeps when there is continuity), this one doesn't beep, it shows a value, when the two leads touch, the value goes from 1 down to zero. I'm sure this is all old news to everyone. Now for when I'm checking the pins. When I check from IC17 pin 1 to IC1 pin 16, I get a value of 1.340. the same goes for all the IC17 to IC1 pins. If I touch IC17 pin 1 to IC17 pin 2, I get a value of around 1.5. Then I tried IC17 pin 1 to IC1 pins 16-12, all read the same value of 1.340. I think i'm confused. Does this sound crazy?

Oh and the blanking signal at interconnector pin 37 did not start low then go high. It starts low, blips high for a milli-second, then stays low.

Blanking signal problems are usually just another symptom of a non-booting issue. If the CPU program isn't running, the blanking signal disappears in order to (theoretically) shut down all the solenoids and keep them from frying. Given the other symptoms I'm seeing, the blanking circuit should also be ok.

Just a bit confused on that continuity check. Is the 0v or the 1.5v for good continuity?

-Hans
 
Yes, 0 is zero ohms which is continuity. Any other number than 1 or 0 would be a resistance measurement. Touching the probes together may not give 0 depending on your meter's range setting. If I put my meter on the most sensitive range, I'll get a reading of about 0.60 ohms between the probes. I have to remember to subtract this from any small readings I am taking. Usually this isn't an issue as I'm not typically measuring resistance in the 1 ohm or less range although it is sometimes necessary on crossovers for speaker building projects.
 
the blanking signal at interconnector pin 37 did not start low then go high. It starts low, blips high for a milli-second, then stays low

ya, the tough part is KNOWING what state it should be
its easy to measure what it is

hard to teach experience. given up a few times but then i got a chance to buy a second working machine i was having trouble with and then figured out what a working one was doing and can then compare outputs etc which helped a lot. kind of expensive way to troubleshoot but eventually sold them both so it worked out in the long run. problem was having the space...

try this site, kind of useful and beerorkid has it good too
http://www.pinballnews.com/learn/seminar.html

i got tired of having to look up at my logic probe so many times that i bought one that beeps now which speeds up things
 
As far as knowing what to look for, I've been going along with the pinrepair.com guide, so really if it isn't in there, I'm clueless. I think I need to get a DMM with a continuity buzzer feature just to clear up MY confusion. My very cheesey DMM doesn't have this. I'm going to try to grab one today to double check the board traces. Just as a check though, the way I was reading the scehmatics was correct right? IC17 pin 1 is A&, which on IC1, A7 is pin 16? Thanks.
 
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