Tempest power brick voltage - am I reading this right?

morphis72

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Tempest power brick voltage - am I reading this right?

My Tempest started acting up so I decided to check the voltages. After chasing my tail for a while and the problem getting worse the game stopped working. The +5 was reading 0.44.

I tried another known good AR II and it read the same.

So, I tried to check the power brick. I put the ground lead into pin 5 and checked the DC voltage for pins 1, 2, and 3.

I was getting about 0.88 which looks really wrong. I was expecting around 10. Here is the odd part though. While I was measuring it the voltage slowly started to rise. I watched it hit 2.2v before switching it off.

Anyone have an idea whats going on here or maybe I am reading it wrong? I am counting pin 1 as the bottom right and counting right to left. The jagged part of connector towards me.
 
Hey there

Is the meter on DC?
Sorry to ask :eek:

Stick the voltmeter on your car battery to double check the meter

Should be 10V+ on the brick on your pins above for sure
 
Definitely do a sanity check on your DMM first. Check it on a 9V battery.

Then check the brick fuses, and make sure the fuse block isn't corroded. Also look for burned wires on the slip-on connectors for the fuse block, as they can weaken and heat up.

Then check and if needed replace the bridge rectifier in the brick. (It can be tested with a DMM, as 4 diodes in a square. Google if needed.) Here's a replacement:

https://www.greatplainselectronics.com/proddetail.asp?prod=GBPC3504L


If it's not that, suspect the big blue next. Though I don't know if they fail completely like that. Usually they just develop AC ripple when they go bad.

If all of the above fails, then your transformer is suspect. Though those rarely go.
 
Definitely do a sanity check on your DMM first. Check it on a 9V battery.

Then check the brick fuses, and make sure the fuse block isn't corroded. Also look for burned wires on the slip-on connectors for the fuse block, as they can weaken and heat up.

Then check and if needed replace the bridge rectifier in the brick. (It can be tested with a DMM, as 4 diodes in a square. Google if needed.) Here's a replacement:

https://www.greatplainselectronics.com/proddetail.asp?prod=GBPC3504L


If it's not that, suspect the big blue next. Though I don't know if they fail completely like that. Usually they just develop AC ripple when they go bad.

If all of the above fails, then your transformer is suspect. Though those rarely go.

I checked it with two different DMM's as my sanity check. Didn't verify they both worked with a known DC source but they both read the same when set to 20V DC.

I pulled the brick fuses and thought that they were not as tight as normal but were making good contact.

Replaced the fuse block, tested the rectifier which came back as good. Plugged everything back in and had about 11v on pins 1-3. Plugged in my AR II and smoked it. POP! dang... checked the voltage again on pins 1-3 and it was 15v DC now. Also, two of the slip on connectors are burned as well now... The problem seems to be with the power brick still. What becomes the +5 is jumping around when measuring it at the source. 11v and then 15v. Should I suspect the transformer at this point and are there replacements? I have a big blue on order...
 
What part blew on the AR?

Were the connectors not burned before? Which connectors? If they are burned, they must be repaired/replaced, as they have high resistance, and are burning up power, which will make things unstable.

15V is a little on the high side, but not really that much, as it's usually around 13.5-14.5. But if it's really unstable, maybe it's jumping higher. I wouldn't expect the AR to blow from a 15V input alone, though.

Big blue is the only other variable left, but it sounds like the wiring issues should be remedied either way.
 
What part blew on the AR?

Were the connectors not burned before? Which connectors? If they are burned, they must be repaired/replaced, as they have high resistance, and are burning up power, which will make things unstable.

15V is a little on the high side, but not really that much, as it's usually around 13.5-14.5. But if it's really unstable, maybe it's jumping higher. I wouldn't expect the AR to blow from a 15V input alone, though.

Big blue is the only other variable left, but it sounds like the wiring issues should be remedied either way.

I gave the AR II a close inspection and it might be okay after all. The pop and flash I saw might have just been on of the fuses on the block going.

I have now replaced all of the connectors on the fuse block. The metal still looked fine on them but the plastic casing on the two fuses that were blowing was burned and brown.

I replaced Big Blue today along with the bridge rectifier and I am still popping the 4amp and 20amp fuses and that is with the 15 pin connector unhooked. I'm wondering if something is shorted together in the transformer? Location is F2 and F3 I believe. It's the two furthest back on the block.

Or maybe I put something in backwards? The positive side of big blue is hooked to the negative of the bridge rectifier and the negative side of big blue is hooked to the positive of the bridge rectifier. I'm about 95% positive that is how it was hooked up before.... I know I have big blue in and hooked to the original wires but I could have gotten the bridge rectifier backwards...
 
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I gave the AR II a close inspection and it might be okay after all. The pop and flash I saw might have just been on of the fuses on the block going.

I have now replaced all of the connectors on the fuse block. The metal still looked fine on them but the plastic casing on the two fuses that were blowing was burned and brown.

I replaced Big Blue today along with the bridge rectifier and I am still popping the 4amp and 20amp fuses and that is with the 15 pin connector unhooked. I'm wondering if something is shorted together in the transformer? Location is F2 and F3 I believe. It's the two furthest back on the block.

Or maybe I put something in backwards? The positive side of big blue is hooked to the negative of the bridge rectifier and the negative side of big blue is hooked to the positive of the bridge rectifier. I'm about 95% positive that is how it was hooked up before.... I know I have big blue in and hooked to the original wires but I could have gotten the bridge rectifier backwards...


the bridge rectifier on the power brick should be the two orange to AC on the BR and the + and - come right from the big blue positive and negative which if i recall the purple is negative and orange with a strip is positive.
 
the bridge rectifier on the power brick should be the two orange to AC on the BR and the + and - come right from the big blue positive and negative which if i recall the purple is negative and orange with a strip is positive.

Yes, I did some digging on line and it does look like I had the bridge rectifier spun 180. I flipped it around and now my fuses are no longer blowing but I am back to getting 16.5V at pins 1/2/3 on the power brick and getting about 5.25 out of the AR II. That was after having to adjust the voltage down with the pot on the AR II. I can't seem to get it to go lower than the 5.25 range. Where it was set I was getting 6 volts at the +5.
 
Yes, I did some digging on line and it does look like I had the bridge rectifier spun 180. I flipped it around and now my fuses are no longer blowing but I am back to getting 16.5V at pins 1/2/3 on the power brick and getting about 5.25 out of the AR II. That was after having to adjust the voltage down with the pot on the AR II. I can't seem to get it to go lower than the 5.25 range. Where it was set I was getting 6 volts at the +5.


The range on the AR +5 adjustment should normally vary the output from approximately 4V to 6V (give or take a few tenths), with 5V being roughly the center of the pot. That's with no load, but should be roughly the same with a load.

If that's not what's happening, you can sanity check yourself by putting another AR on the brick, and checking the range. You aren't likely to damage anything. If you find that another AR shows a normal 4-6V range, then the first thing to replace on the bad AR is the 2N3055. It's not going to hurt to replace it regardless, and it's only a few bucks.

If that still doesn't fix things, then it's likely the LM305 regulator on the AR. That's the 8-legged tin can-looking thing. They can a little tricky to find, but try ebay.

All of this said, be sure to make sure there are no other broken or burned resistors or caps on the AR, as I've seen physically damaged components cause weirdness as well.

I'd also recommend replacing the 1K pot on the AR (probably first, actually), with a sealed type 3386 1K pot, as it's not uncommon for the original ones to fail, causing range issues. Because the old ones are an open style, dirt and grime can get inside and cause issues. Also, the legs on them like to break, as they aren't that robust.

Usually when a pot failure happens though, you'll see the voltage jump suddenly as you're varying the pot, or it will get to a certain point and then not vary further, even though you are still moving the pot.
 
The range on the AR +5 adjustment should normally vary the output from approximately 4V to 6V (give or take a few tenths), with 5V being roughly the center of the pot. That's with no load, but should be roughly the same with a load.

If that's not what's happening, you can sanity check yourself by putting another AR on the brick, and checking the range. You aren't likely to damage anything. If you find that another AR shows a normal 4-6V range, then the first thing to replace on the bad AR is the 2N3055. It's not going to hurt to replace it regardless, and it's only a few bucks.

If that still doesn't fix things, then it's likely the LM305 regulator on the AR. That's the 8-legged tin can-looking thing. They can a little tricky to find, but try ebay.

All of this said, be sure to make sure there are no other broken or burned resistors or caps on the AR, as I've seen physically damaged components cause weirdness as well.

I'd also recommend replacing the 1K pot on the AR (probably first, actually), with a sealed type 3386 1K pot, as it's not uncommon for the original ones to fail, causing range issues. Because the old ones are an open style, dirt and grime can get inside and cause issues. Also, the legs on them like to break, as they aren't that robust.

Usually when a pot failure happens though, you'll see the voltage jump suddenly as you're varying the pot, or it will get to a certain point and then not vary further, even though you are still moving the pot.


BTW: i stock the LM305 and the OEM pots for the AR boards.
 
I used this video as a guide for what pins on my block should be reading.

https://www.youtube.com/watch?v=C1pVTzEF3ZA



Here is what I am getting:

Readying between:
Pins 4/5 as ground
Pins 1/2/3 = 20.5 vDC --- expected voltage should have been 10.5

Reading between:
Pins 6/7 = 54 vAC ---expected voltage should have been 36

Pins 7/8 = 9.1 vAC ---expected voltage should have been 6

Pins 10/13 = 74 vAC --- expected voltage shoudl have been 50

Pins 10/11 = 36.5 vAC --- expected voltage should have been 25

Pins 11/13 = 36.7 vAC --- expected voltaeg should have been 25
 
Just out of curiosity, there is a 9-pin connector on the top of the brick, which should be labeled J3, sort of near the middle, which has a plug that goes into it, which has looped back wires on it.

This connector is used for configuring the brick for the given supply voltage (e.g., US vs Euro, etc). Post a close up pic of what yours looks like.
 
Just out of curiosity, there is a 9-pin connector on the top of the brick, which should be labeled J3, sort of near the middle, which has a plug that goes into it, which has looped back wires on it.

This connector is used for configuring the brick for the given supply voltage (e.g., US vs Euro, etc). Post a close up pic of what yours looks like.

I am familiar with that plug and haven't touched it before now. It was putting out the correct voltages before...

Here is the photo.
 

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I have rebuilt the power brick and the AR II. I am now getting a solid 5.02V at the gameboard test point.

Sometimes the game boots now and plays fine. Other times when I boot the game I get nothing on the screen and both player start buttons are lit solid. When it does boot normally if I run it in test mode it finds nothing wrong. When it is booting with the start buttons light solid I can't get it into test mode.

Before the voltage spike the game was rock solid. Any ideas what to check next? I thought about trying to burn new game ROMs and replace them but 2716's seem a little pricey and I am feeling that's a pretty big shot in the dark.

Edit: Let the game run from about 30 min and then played a game. Everything seemed fine until in the middle of game play it rest to the start screen. So, I stated up a new game and it played fine until I started hearing a higher pitched tone intermittently.

Ran the self test again and everything looks fine.
 
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