Anyone know how to adjust Midway power?

smello

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Here's the manual for the Space Zap.
http://arcarc.xmission.com/PDF_Arca...Zap_Parts_and_Operating_Manual_(Oct_1980).pdf

I tried putting a new bulb in the marquee, and didn't light up. I tested the socket and was getting like .5v.

I tested the 5v power, and it does seem to be really low, not even a full volt. I put the multimeter on Pin 19 which should be +5v and on pin 14 which should be the ground.

I see 3 pots on the board, but not sure which adjusts what. Here are some pics of the Power supply board itself.

normal_CIMG1390.JPG

normal_CIMG1381.JPG
 
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The manual says:

Voltage Control Pots
Located on Power Supply Board and are preset at the factory. These pots should not be tampered with unless the distributor service department is contacted.
 
Guess no one knows...

I seem to have figured out 2 of the pots the 12v and the 5v and labled them on the image... Not sure what the other one does.

The silver caps I outlined are blown. The pot next to them was pretty much cranked all the way up.

I Must not be getting power to the audio board because when I measure pin 1, I get no voltage. I am assuming that is the cause.

Wonder if Mr. Roberts has these caps?
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The third pot is for the -5VDC adjustment.

Also, if you've got less than one volt on the 5VDC rail....something's bad. An out-of-adjustment pot will never change the voltage that much. I'd start checking the regulators/transistors in the 5VDC line.

Edward
 
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So you have low power to the marquee (you looked for AC right?) and low power coming out of the power supply. What power is coming out of your isolation transformer? Page 34 of the wiring schematic displays the expected power output. If the iso is not delivering correct power to the power supply then it can't convert it correctly.

Why do you assume the caps are blown? I have seen many more problems with the voltage regulators than the caps when working with these old power supplies. If you are going to order parts I suggest getting the caps, voltage regulators, and possibly new adjustment pots as well.

Also, this is a linear power supply. It needs to "see" a power return from the board (the sense lines). If it doesn't see power supplied to the board it will shut down.
 
the 4700uf at 35vdc can be found at many places including radioshack but there a bit pricy, about 5-6$ for that cap. uum the 4700uf 25vdc i have found from a really nice guy who works at debco electronics for 1.25 a piece. he also has the 4700uf 35vdc cap for the same price. he is on ebay too so check there by searching for debco elecronics ebay. hey where did you get the 10000uf and 20000uf replacements at? (gold looking ones)
 
. hey where did you get the 10000uf and 20000uf replacements at? (gold looking ones)

Someone must have already repaired mine at one point...
My picture is the top ones, the second post with a picture is a reference picture I found on the web... Not mine. I just highlighted the silver ones that are blown on my board.
 
The third pot is for the -5VDC adjustment.

Also, if you've got less than one volt on the 5VDC rail....something's bad. An out-of-adjustment pot will never change the voltage that much. I'd start checking the regulators/transistors in the 5VDC line.

Edward

Thanks for the help..
I must have been measuring it wrong... Don't know where I got that from.
But yes, there is now a proper 5v coming out of the board. It was at like 4.75 or something.
 
So you have low power to the marquee (you looked for AC right?) and low power coming out of the power supply. What power is coming out of your isolation transformer? Page 34 of the wiring schematic displays the expected power output. If the iso is not delivering correct power to the power supply then it can't convert it correctly.


Why do you assume the caps are blown? I have seen many more problems with the voltage regulators than the caps when working with these old power supplies. If you are going to order parts I suggest getting the caps, voltage regulators, and possibly new adjustment pots as well.

Also, this is a linear power supply. It needs to "see" a power return from the board (the sense lines). If it doesn't see power supplied to the board it will shut down.

I assumed the caps were blown because there are two holes in them, and swilly residue all over them. Must have vented.

The funny thing is, When I was testing everything, I had the harness to the PCB unplugged at it was still providing power from the pins when I took the multimeter to it.
 
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