Atari power brick problems

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I bought a Centipede that worked except the monitor wouldn't sync. Took care of that and tore it apart for a resto. I replaced the big blue and fuse holder and rebuilt the AR as part of the resto. Worked fine for awhile and the sound started cutting off then died. I checked the voltages and the 12v was only reading 2. I tried another rebuilt AR and the same. When I took the voltages from the brick my 80 and 65 were both running at 1/2 of what they should be. Everything else was within 1v.

I tried 2 different BRs just for the hell of it. So what would cause this and am I right in thinking that it would have something to do with the 12v which is what the sound runs on?

Thanks,
Rob
 
I bought a Centipede that worked except the monitor wouldn't sync. Took care of that and tore it apart for a resto. I replaced the big blue and fuse holder and rebuilt the AR as part of the resto. Worked fine for awhile and the sound started cutting off then died. I checked the voltages and the 12v was only reading 2. I tried another rebuilt AR and the same. When I took the voltages from the brick my 80 and 65 were both running at 1/2 of what they should be. Everything else was within 1v.

I tried 2 different BRs just for the hell of it. So what would cause this and am I right in thinking that it would have something to do with the 12v which is what the sound runs on?

Thanks,
Rob

Hi Rob,

Not sure what you are referring to when you say "80 and 65".

In any case, power for the audio amps is the "10.3VDC" line (or 10.6VDC, depending of where you look in the schematics). It typically measures 11-12. This voltage is created by the BR in the block and "big blue." It comes off the brick on J5, pins 1 2 & 3 carry the voltage (relative to GND on pins 4 & 5). Check this, with the AR disconnected.

If this were only 2V, you woudn't get the 5VDC either and the PCB wouldn't boot... so I'm a little confused if the audio is the only problem.
 
Hi Darren,

I was using Dokert's instructions for testing, http://forums.arcade-museum.com/showpost.php?p=1073965&postcount=5 this is where I got the 80 and 65 from. Like I said both of those on my brick are measuring half what they should be and not sure what they do.

So if the 12 comes from the 10.3 I guess it would have to be in the ARs I have or wiring as my 10.3 is perfect coming from the brick. At the AR and on the PCB I am only reading about 2v but my 5 is perfect so the game plays great.

Hope to see you at Gamewarp. :)
 
I bought a Centipede that worked except the monitor wouldn't sync. Took care of that and tore it apart for a resto. I replaced the big blue and fuse holder and rebuilt the AR as part of the resto. Worked fine for awhile and the sound started cutting off then died. I checked the voltages and the 12v was only reading 2. I tried another rebuilt AR and the same. When I took the voltages from the brick my 80 and 65 were both running at 1/2 of what they should be. Everything else was within 1v.

I tried 2 different BRs just for the hell of it. So what would cause this and am I right in thinking that it would have something to do with the 12v which is what the sound runs on?

Thanks,
Rob

Looking at the Centipede drawings you should have the following:


pin1 10.6 vdc (usually higher by a few volts)
pin2 10.6 vdc
pin3 10.6 vdc
pin4 ground
pin5 ground


pin6 36vac(CT)
pin7 36vac(CT)


pin8 6.1 vac
pin9 6.1 vac


pin 10 60vac (CT)
pin11 0v(centre of pins 10 and 12 windings) 30 volts ac between pins 11 and 10 or pins 10 and 11.
pin12 60vac(CT) 60 volts across pin 12 and 10


Pin13 60vac (CT)
Pin14 0v(Centre of pins 13 and 15 windings) 30vac between pins 14 and 13 or pins 14 and 15.
Pin15 60 vac (CT) 60 volts across Pin13 and pin15



The +12 and -5v that are used in the final audio stage of the board come from the 36AC that supplies the power board which is converted to the various DC supplies.


The manual has a detailed description. http://www.mikesarcade.com/arcade/manuals.html
 
The 12VDC circuit is a pretty small circuit......diodes CR5/CR6/CR7/CR8....capacitor C18.....resistor R25.....and the regulator Q8 are the likeliest suspects. Also, 12VDC only feeds one chip (LM324 at J10)on the motherboard......and NOTHING else. This op-amp could be shorted and sucking the voltage down.

Regarding the transformer assembly voltages reading half.......these are AC voltage. I bet you're reading them in reference to ground. This means you're only reading half the wave.....thus, half the voltage.

Edward
 
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this is where I got the 80 and 65 from. Like I said both of those on my brick are measuring half what they should be and not sure what they do.

Were you reading across the pins, or each pin to ground? The latter will give you half the AC voltage.
 
I was taking the voltages as listed:

Red lead to pin 10
Black lead to Pin 14
Reading should be 80vac


Red lead to pin 11
Black lead to pin 13
Reading should be 65vac

Unless that is somehow wrong? I'll pull it out tomorrow and recheck everything, thanks for all the help so far. I'm now in the middle of re-arranging games to fit another one in so hopefully tomorrow I'll get back to it.
 
I was taking the voltages as listed:

Red lead to pin 10
Black lead to Pin 14
Reading should be 80vac


Red lead to pin 11
Black lead to pin 13
Reading should be 65vac

Unless that is somehow wrong? I'll pull it out tomorrow and recheck everything, thanks for all the help so far. I'm now in the middle of re-arranging games to fit another one in so hopefully tomorrow I'll get back to it.

For now, forget about those voltages......The audio/regulator board (should) have two separate test lugs, both labeled 36 volts. Set your meter to AC volts and measure across these two lugs. It doesn't matter which lead you use (red or black) on which lug....just stick red lead on one...and black lead on the other. Report back with the reading.

Edward
 
Hi Darren,

I was using Dokert's instructions for testing, http://forums.arcade-museum.com/showpost.php?p=1073965&postcount=5 this is where I got the 80 and 65 from. Like I said both of those on my brick are measuring half what they should be and not sure what they do.

So if the 12 comes from the 10.3 I guess it would have to be in the ARs I have or wiring as my 10.3 is perfect coming from the brick. At the AR and on the PCB I am only reading about 2v but my 5 is perfect so the game plays great.

Hope to see you at Gamewarp. :)

The linked post is part of a discussion about an Asteroids Deluxe power brick, and AFAIK is only true for early Asteroids power bricks (early rev drawings show the 80VAC taps, later ones have it blacked out). In any case, it's not (all) relavent to your Centipede power brick. And beside all of that, there's no real reason to check your 60VAC taps if your monitor is working--all they do is serve as an isolation xformer for monitor power, so if the monitor is working fine, don't sweat them.

Getting back to your original issue. I looked at the Centipede schems, and I now see that I contributed to some confusion about "12V". The confusion arises because the "10.3V" (aka 10.6V) line normally reads closer to 11.5V... which is nearly 12V. However, I forgot that there is an actual 12VDC line on -02 ARIIs. It is totally seperate from the 10.3V line which comes from the power brick already rectified and filtered. Instead, it is derived from 36VAC on the ARII board (as Edward was pointing out).

SO... the you should have 36VAC on pins 6 & 7 of P5 (just as Dokert's post, and Ed, suggest). There should also be test points on the ARII board for 36VAC, check it there as well. If you don't have 36VAC, check your fuses (F4 & F5). If you do have 36VAC, then your ARII is the problem; either the regulator (7812, Q8), or the filter caps (C23, C22, C18).

This regulated 12VDC is not used ON the ARII board for audio amplification (it uses the unregulated 10.3VDC instead), BUT it IS sent to the game PCB where it powers an LM324 op-amp which pre-amplifies the audio.

Yup, I'll be at Gamewarp, Sat. & early Sun. Good to hear you'll be there as well... at least there'll be one person I know :)
 
Finally got back to this and the 36 is good on the AR so it looks like it is time to get to work on the AR. Thank you everyone.
 
I haven't ruled out the LM324 yet since it could drop the power down but would a bad pokey cause a power drain?
 
If you only get 2V on the 12V line with the PCB disconnected, of course the LM324 isn't pulling it down.
 
With the PCB disconnected I get 8.40v so it seems the AR is to blame. Now since with it connected it drops all the way to 2v could the LM be bad too and maybe hurt the AR somehow?
 
Sounds like a bad A/R II. Check the 4 diodes on the right side of the A/R II and the 7812 regulator on the heatsink.

The power brick for Centipede does not have 60VAC & 85VAC, that was either an Asteroids or Asteroids Deluxe. Atari power bricks are different between raster games and vector games for monitor power. Pretty much the rest of the power brick is the same.
Dok
 
I have a related question for an Atari power supply that is reading zero voltage across pins 8 + 9 (which should be ~6.1 vAC). Does this point to the rectifier or something else? All other voltages read fine.
 
I have a related question for an Atari power supply that is reading zero voltage across pins 8 + 9 (which should be ~6.1 vAC). Does this point to the rectifier or something else? All other voltages read fine.

There is no rectifier on this AC output.
Some causes would be -

1. fuse open (4A)
2. wire open
3. connection at fuse block is poor
4. bad wiring inside transformer

Meter must be AC mode; not DC mode when testing. (DC will be zero VDC)
 
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