Checking voltage on DK power supply

Tighe

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So I am getting started diagnosing the problem with my Cabaret, and some advice would be helpful. This isn't a JAMMA power supply, and I have no manual. So if you know what pins I should be checking etc, and recommended voltages...
 
Do a search in the repair section which is where you should be anyways! Lol. Still got the baby pac waiting for you.
 
You can also measure the voltage at any of the chips on the board. The 5V and ground planes will be very obvious. Also, the "deglitching" caps at each chip will go from 5v to ground, so measuring across them will also give you 5v. You can also check at any of the ROMs, as pin 24 is 5v and pin 12 is ground.

And there's no excuse for not having the manual, Tighe. You and I both know that you've seen Google before.

-Ian
 
You can also measure the voltage at any of the chips on the board. The 5V and ground planes will be very obvious. Also, the "deglitching" caps at each chip will go from 5v to ground, so measuring across them will also give you 5v. You can also check at any of the ROMs, as pin 24 is 5v and pin 12 is ground.

And there's no excuse for not having the manual, Tighe. You and I both know that you've seen Google before.

-Ian

Thanks Ian, Very useful information! Actually I did download the manual last night. :)
 
Thanks Ian, Very useful information! Actually I did download the manual last night. :)

The wonders of the Internet! :D

I think your problem is somewhere in the clock generation circuit on the game board though - not the power supply, although you're definitely right to start by checking there. Give me a call sometime, I can help you figure it out. I actually dug up a 4 board Donkey Kong stack when I was cleaning in storage (It's amazing how much crap I have that I've forgotten about...). We should be able to narrow down what's wrong with yours by substituting boards. Granted, I don't know if mine works either, but hey, it's worth a shot.

-Ian
 
The wonders of the Internet! :D

I think your problem is somewhere in the clock generation circuit on the game board though - not the power supply, although you're definitely right to start by checking there. Give me a call sometime, I can help you figure it out. I actually dug up a 4 board Donkey Kong stack when I was cleaning in storage (It's amazing how much crap I have that I've forgotten about...). We should be able to narrow down what's wrong with yours by substituting boards. Granted, I don't know if mine works either, but hey, it's worth a shot.

-Ian

Thanks Ian! You are the best! And I will give you a call!
 
So I checked the voltage on a cap on the bottom of the stack where the clock (crystal) is. I got 4.96v. Also on that board you can see the scorch/soot marks. It is hard to describe, I will let the photo do the talking:

Here is the bottom board, not the heat marks, and at the top is where I tested the voltage:



Here is the reading:



EDIT:
You can see it looks like the marks came from the chips on the bottom with the large aluminum heat sinks. Also of to the right is the crystal.
 
Seems the voltage is low, but I don't see an adjustment knob like on all my other machines power supplies. Also what should I adjust it to? 5v? 5.25v? 5.5???
 
Thanks for the picture on how to check the voltage though. I'll be the first to admit that multi-meters confuse the hell out of me. Now I know how to do it and where I can get a good reading from the board. I never know where to put the dial on the mulitmeter. Ha! Anyway, thanks for the inadvertant help.
 
Thanks for the picture on how to check the voltage though. I'll be the first to admit that multi-meters confuse the hell out of me. Now I know how to do it and where I can get a good reading from the board. I never know where to put the dial on the mulitmeter. Ha! Anyway, thanks for the inadvertant help.

No problem! What you need to pick up is this book:

http://www.amazon.com/How-Test-Almost-Everything-Electronic/dp/0830641270/ref=pd_sim_b_6

I have had these books by Forrest M. Mims III for a long time:

Getting Started:
http://www.amazon.com/Getting-Started-Electronics-Forrest-Mims/dp/0945053282/ref=pd_sim_b_4

These are great too:
http://www.amazon.com/Electronic-Formulas-Symbols-Circuits-Forrest/dp/0945053304

http://www.amazon.com/Timer-Amp-Optoelectronic-Circuits-Projects/dp/0945053290/ref=pd_bxgy_b_img_b

http://www.amazon.com/Electronic-Ci...rs-Notebook/dp/0945053312/ref=pd_bxgy_b_img_c

Here are all his books:

http://www.amazon.com/Forrest-M.-Mims-III/e/B003UGHJVE/ref=ntt_athr_dp_pel_1
 
Just a note, there is an un-used edge on the board near the top that looks like where you would slip an Atari style edge connector on, you can measure voltages there too. I don't remember where each voltage is on it but if you walk along it with your meter it should be obvious. It's easier than measuring at chips.
 
Listen to Ian, he knows a heck lot more than I do! :D

Hehe.

I haven't read any of the books that Tighe linked, but I'm sure they will help. The manual for the multimeter will tell you how to use the multimeter itself, but it won't teach you how to apply it. Much like the manual that came with your car will teach you how to operate the car itself, but won't teach you how to drive.

The multimeter is actually very simple - while it looks intimidating with all those settings, it's very straightforward. You need to set the knob to what you are looking to measure - there are positions for AC and DC volts. On a manual ranging meter, like Tighe's, you also have to select what voltage range you're looking for. On the 20v setting, which is probably what you'll use the most, you can measure from 0 to 20v.

The meter simply displays the voltage difference between the two probes. The black probe traditionally goes to the DC ground, and the red one goes to the voltage you want to measure. But it can be used a lot of other ways too. If you want to measure the voltage drop of the harness, you'd set the knob to the 2v setting, put one probe on the power supply ground, and one probe on the ground trace on the game board, and you'll see the difference between them (it'll be small, should be less than a volt).

Measuring resistance works the same way.

ArcRevival said:
Just a note, there is an un-used edge on the board near the top that looks like where you would slip an Atari style edge connector on, you can measure voltages there too. I don't remember where each voltage is on it but if you walk along it with your meter it should be obvious. It's easier than measuring at chips.

I don't remember that being on the four board set.

While walking along an unknown connector with your meter will eventually net you a reading, remember that TTL signal levels also measure as about 5v, and unless you have the actual power rail, it won't be accurate. Also, if you hit video or something, you'll get a weird, low reading. It's better to learn to recognise the power and ground planes on the board and measure at something directly connected there. You want to *know* that you're supposed to be getting five volts at the location you're testing.

Checking pins of a chip is kind of hard - but if you remember which pins of a ROM are ground and 5v, it'll make identifying the power and ground planes a lot easier.

-Ian
 
Yeah, this is very helpful! My mulit-meter manual didn't go into any specifics about when to use certain settings and I don't even have a basic understanding of this stuff.

I just googled using a multi-meter and it says and good example of DC power is a battery, and a good examplbe of AC power is current from the wall. So, based on that, you might think you'd be measuring boards using the AC settings. I'm assuming this isn't the case though because the transformer changes the AC power from the wall to DC, and that's why Tighe is measuring DC power?

I had no clue on the sub settings, but after Ian's post that makes perfect sense. He's looking to measure 5v so he's selecting the smallest setting that covers the range he's looking for (you'd need headroom in the setting in case you're a little over.) If there was a 10v setting he'd want that but he wouldn't use a 5v setting because his reading might be 5.1v.

The other thing I could never figure out is where to take the reading off the board. I've heard of posts, caps, chips, edge connector, etc. It would seem like the cap is the easiest since there's only two places to test from, making trial and error a two step process. I guess that's just the reading on that one cap, but if you're trying to tell whether your power supply is giving off 5v instead of trying to troubleshoot the board it would seem like a cap is a good place to check.

Great post. Thanks.

Oh yeah, Ian is right on there being no edge connector on the 4-board DK set. I've got the 4 and 2 board stacks and the edge connector is only on the 2-board version.
 
Yeah, this is very helpful! My mulit-meter manual didn't go into any specifics about when to use certain settings and I don't even have a basic understanding of this stuff.
I can understand. What little I pick up had to be refreshed every few months when I get back to trying to fix something. :D
I just googled using a multi-meter and it says and good example of DC power is a battery, and a good examplbe of AC power is current from the wall. So, based on that, you might think you'd be measuring boards using the AC settings. I'm assuming this isn't the case though because the transformer changes the AC power from the wall to DC, and that's why Tighe is measuring DC power?
The AC travels to the power supply after it leaves the transformer. (And I still don't know what a transformer does, or don't remember :D). Then the DC leaves the power supply.
I had no clue on the sub settings, but after Ian's post that makes perfect sense. He's looking to measure 5v so he's selecting the smallest setting that covers the range he's looking for (you'd need headroom in the setting in case you're a little over.) If there was a 10v setting he'd want that but he wouldn't use a 5v setting because his reading might be 5.1v.
My Fluke 79III is a mystery to me also. I know what switch positions are for DC and AC, but I'm not sure about how to set the range because I have no manual for it. I didn't have trouble testing the DC voltages, but AC makes me nervous because I don't want to put the probes on the two AC leads the come from the transformer and attach to the power supply without knowing it setting a range is important. But I assume AC is ok if the Dc voltages are correct.
The other thing I could never figure out is where to take the reading off the board. I've heard of posts, caps, chips, edge connector, etc. It would seem like the cap is the easiest since there's only two places to test from, making trial and error a two step process. I guess that's just the reading on that one cap, but if you're trying to tell whether your power supply is giving off 5v instead of trying to troubleshoot the board it would seem like a cap is a good place to check.
The edge connector or pins are where I take all DC voltage readings. Just determine where the +5V, +12V, etc. are supposed to be.

Darren Harris
Staten Island, New York.
 
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