voltages at Asteroids fuseblock?

mc300baud

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i have an Asteroids with a terrible hum and i think it may be a bad transformer.

when testing AC voltages across the fuseblock, what should i be seeing for F2-F6? (F1 reads fine at 120v.)

and where do i connect the negative lead on my meter to get an accurate reading?
 
Could be but do some searching here first - several fixed for Asteroids hum issues. Many are relating to the ARII board, some are the main board, etc.
 
i already did that and have done most of the standard stuff (rebuilt AR, cap kit for PCB, new big blue, etc.) and so far nothing has helped.

i suspect the transformer as it hums pretty loudly on its own which i don't recall either of my other two Asteroids doing (one cabaret, one AD cocktail, now both sold.) and the monitor has a nice, really high-speed flicker that seems to go with the hum. i want to at least make sure the transformer is outputting proper voltages. it may even if it is the source, but at least if i know it's not working right i can get a replacement that is.
 
I saw that flicker on Mundoman's Asteroids when I fixed the board for him, but never really investigated it past that...it worked fine otherwise and had a nice picture. In regards to the hum mine would hum pretty bad then go away. Moving around the wire harness seemed to fix it...wondering if its the +5v on the edge connector being dirty/burnt. I haven't looked at it that close to see if it needs attention.

Here's the power supply/wiring diagram for Asteroids, the brick wiring is in the upper left corner. Just pop off the large 15 pin plug and you can test it right there.

Use the ground pins on the plug for grounds, not sure if the metal casing of the power brick doubles as DC ground or not.

http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Asteroids/Asteroids_DP-143-7th-01A.pdf
 
Last but not least - just curious, what monitor is it? 801 or 802? (801 has the board in the middle with the huge honkin caps).

Just wondering if the monitor/flicker is related to the hum. Try unplugging the monitor and see if that makes a difference?
 
i did unplug the monitor and the hum was still there. unplugged the marquee light and the speaker each and it made no difference (well, of course there was no hum through the speaker when it was unplugged but the screen flicker and transformer hum was still present.)

the monitor is a WG 19V2000 and is super clean with almost no burn. the previous owner did a cap kit but did not replace the transistors which i may end up doing just as a matter of course.

Here's the power supply/wiring diagram for Asteroids, the brick wiring is in the upper left corner. Just pop off the large 15 pin plug and you can test it right there.

cool. i missed that drawing package; i have the regular one but it either doesn't show the voltages or isn't as clear or i'm just really retarded and couldn't read it right. that one makes it nice and obvious. instead of going to be like i should be i think i'll go test the voltages right now.
 
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ok, here's what i get when tested with J5 unplugged (which of course means no load) and negative lead at GND at pins 4 or 5, correct voltages listed in ():

1: 13.96vdc (10.3)
2: 13.97vdc (10.3)
3: 13.97vdc (10.3)

6: 18.57vac (36 hi)
7: 2.4vac (36 lo)
8: .45vac (6.3 hi)
9: 4.84vac (6.3 lo)

11: 30.69vac (65 hi)

13: 25.56vac (65 lo)

i'm assuming since pins 6 and 11 are close to halves i probably don't have my negative lead on the right ground point to see the full AC value and they're correct. so what explains the really low reading on 8 and relatively high reading on 9 unless the two are reversed on my cab or the drawing is wrong? bad transformer?
 
ok, here's what i get when tested with J5 unplugged (which of course means no load) and negative lead at GND at pins 4 or 5, correct voltages listed in ():

1: 13.96vdc (10.3)
2: 13.97vdc (10.3)
3: 13.97vdc (10.3)

6: 18.57vac (36 hi)
7: 2.4vac (36 lo)
8: .45vac (6.3 hi)
9: 4.84vac (6.3 lo)

11: 30.69vac (65 hi)

13: 25.56vac (65 lo)

i'm assuming since pins 6 and 11 are close to halves i probably don't have my negative lead on the right ground point to see the full AC value and they're correct. so what explains the really low reading on 8 and relatively high reading on 9 unless the two are reversed on my cab or the drawing is wrong? bad transformer?

I have posted on this many times, and a simple search would show you where and what to test.

First 3 voltages are correct as it is unregulated.

You are incorrectly reading the other voltages, and that is why your numbers are skewed.

Feel free to borrow an Atari Test Aid from one of your local SMAC/KLOV brothers. It will make testing your voltages a lot easier.

Now I must go and listen to some Garth Brooks. :rolleyes:
 
i did try to search for it but there were so many Asteroids threads that i couldn't find the exact directions.

now that i know i have to search for "Dokert" as well i have had better luck. http://forums.arcade-museum.com/showthread.php?t=57258#Post815738 gave me the info i needed.

and yeah, after i went to bed late last night i thought "huh, i wonder if "hi" means positive and "lo" means neutral?" which it seems it does.

i'll have to wait until i get back from work tonight to do another test.

oh, and the DC readings on the AR are just fine.
 
ok, here's the corrected readings:

pins 6 to 7 (36vac): jumping all over between 15 and 18v

pins 8 to 9 (6.3vac): 6.98v

pins 11 to 13 (65vac): 61.8v

removing the coin door lights made no difference. hum was present with just the PS powered and AR & PCB disconnected. hum was increased significantly through the speakers when the AR was connected with no PCB connected.
 
ok, here's the corrected readings:

pins 6 to 7 (36vac): jumping all over between 15 and 18v

pins 8 to 9 (6.3vac): 6.98v

pins 11 to 13 (65vac): 61.8v

removing the coin door lights made no difference. hum was present with just the PS powered and AR & PCB disconnected. hum was increased significantly through the speakers when the AR was connected with no PCB connected.

It would appear that you may have a transformer problem. I think I have an Asteroids power brick, will have to take a look.
 
that's what i was thinking. i tested the AR-I-03 that was in here when i got it in an AD and there was no screen flicker (though there was some hum with the AD PCB) and the PCB in the same machine with a different AR-I-03 (no hum and no screen flicker.) i have since picked up a couple of used AR-I-01's and i'll be putting cap kits in 'em soon.

the line filter is putting out a solid 120vac so i doubt it's that and the Big Blue is brand new and the fuse block is one of the nicest originals i've seen on an Atari. other than the transformer the diodes are the only other suspects i can think of and i don't know if they'd be causing the low and fluxuating voltages.
 
The 36vac comes directly from the transformer, so if it is askew then the transformer is most likely bad.

I have a complete power brick or two for Asteroids.
 
sweet! someday i will not be working and will have time to drive all the way up there to pick it up. i suppose i can bring this one as a partial exchange (and heck, we can retest it up there with your nifty gadget thing.)
 
Based on your original readings...I'd re-check fuse F5. Pin 7 to ground should be 18v just like pin 6. That would also explain the flaky readings your getting across pins 6-7. If the fuse is good (Check with meter, out of the fuse holder)...check the wire going from the transformer to the fuse where it clips to the fuse holder. Those quick disconnects they use to connect to the fuse holder get brittle with age and I've seen them fall apart.

You can also take a reading across the transformer side of the fuses f4 and f5- should be 36vac total, or 18vac from each of f4 and f5 to ground.

The reason I say to remove the fuse out of the fuse holder is something I came across once...fuse was good...looked good, and for all intents and purposes nothing wrong with it, but just wasn't getting the right voltage. Went to remove the fuse and both ends popped off the glass instantly with no effort. New fuse fixed it.
 
Based on your original readings...I'd re-check fuse F5. Pin 7 to ground should be 18v just like pin 6. That would also explain the flaky readings your getting across pins 6-7. If the fuse is good (Check with meter, out of the fuse holder)...check the wire going from the transformer to the fuse where it clips to the fuse holder. Those quick disconnects they use to connect to the fuse holder get brittle with age and I've seen them fall apart.

You can also take a reading across the transformer side of the fuses f4 and f5- should be 36vac total, or 18vac from each of f4 and f5 to ground.

The reason I say to remove the fuse out of the fuse holder is something I came across once...fuse was good...looked good, and for all intents and purposes nothing wrong with it, but just wasn't getting the right voltage. Went to remove the fuse and both ends popped off the glass instantly with no effort. New fuse fixed it.

Just experienced that with my newly acquired Dig Dug. Good fuse tested with my meter, bad fuse holder and quick disconnect.
 
well, good news and bad news.

the fuse tested good. i reseated the QD's on the fuse block again making sure to check them over for corrosion or cracking (some have been replaced, others are original.) then i checked the wiring from the fuse to the J5 female end on the power brick and forced the pins to move around in the connector, making sure the wires were still connected. retesting of the voltages at J5 now shows 36vac across 6 and 7, and retesting at F4 and F5 show 36vac across those and 18vac each to ground. so now the voltages look pretty decent.

but no change in the hum, unfortunately.

i'll take this offline with Dokert for now and post later if we find anything that fixes this.
 
dont loose windings cause hum?

i take it you mean you are getting a hum from the actualy transformer block and not the actual speakers?

i got a mc cocktail and it BUZZ'S real bad but,i was told that it was probably loose windings in the transformer winded power block.i had trouble with my asteroids and an annoying buzz from the speakers and i changed the edge connector after checking round and it went away.

have you replaced the big blue?
:)
 
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