Parts Puzzle - Resistors, poly caps, POTs

johnvv

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Repairing the motor board on a Midway Wild Kingdom EM shooter and am having trouble identifying replacement parts. Probably an easy task for most, but hard for me... The board is circa 1971.

The only known documentation for the game is the schematic. From that, I have the value of some the parts. Attached is a picture of the board with either part value (from the schematic) or part # (from the actual part). It has taken me a bit to get this far and am hoping the gurus here can help me get to the home stretch so I can get modern replacement parts ordered.

Questions:

1. There are 5 x 3 leg "22K Trim POTS' on the board. No other specs known. Any suggestions on replacements? This the part that is in greatest need of replacement as they barely move anymore and are control the targets.

2. In the top center, you'll see a 4.7K ohm resistor, per the schematic. The color bands are (left to right) yellow, silver, red, green, brown. I'm guessing this is really a four band resistor and the brown is 'extra' as it makes no sense. Suggestions on what type of resistor and associated values to replace with?

3. Middle of the pic, 2 x .022uF +/-10% @ 250V polyester cap (thick red on top, orange, yellow, red). Leads are 10mm apart. Any suggestions for a modern, in stock, replacement?

4. Lower middle of the pic, 2 x .1uF +/-10% @ 250V polyester cap (thick brown on top, black, yellow, white, red). Leads are 10mm apart. Any suggestions for a modern, in stock, replacement?

5. For the resistors, what composition of resistor should I replace with: carbon comp., carbon film., ceramic comp., etc.?

The parts in question appear to be original parts based on their solder points, but you never know. I'm most confident the POTs are original. Other parts on the board have been replaced over the years (e.g. parts on left side are mostly replacements while parts on right side appear mostly original).

Thanks in advance for any suggestions and help.
 

Attachments

  • WK Motor Board Parts v2.jpg
    WK Motor Board Parts v2.jpg
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1. How much power is heading to these trimpots? Voltage, amps? This'll help folks source a replacement for you. There's a couple of trimmers I've found that'll probably work, but it depends on how much power's being pulled through there. Also need to know if they are single or multi-turn. Also, 22k's are really hard to find! 25k's may be your only replacement option now.

2. This one is weird. The pic looks like Grey Green Red Silver Yellow.. Which isn't standard. If you treat it like a 4-band, it comes out to 8.5k 10%. Yellow Violet Red Gold is the standard 4-band 4.7k 5% coloring. No idea here. If the spec calls for 4.7k, I'd throw a modern 4.7k in there and hope for the best. You could also measure that one and see what comes up.

3. You can replace these with modern Ceramic caps.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=445-2614-ND
Move quick on that, because once they run out, it'll go non-stocking.

4. More ceramics.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=490-4816-ND
Big leads on these, too. Should help with the huge 10mm lead spacing.

5. Metal Film.

Hope I could help.
 
I would stick with polyester caps there, not ceramics. Polyester/polypropylene caps are easy to get and common.

If the schematic calls it a 4.7k, then replace it with the same. What does it measure, and why do you need to replace it?

The trimpots should probably be replaced with 25k's if 22k pots aren't available. Small trimpots like this are common, those look like 1/4w units or so.


Why do you think you need to replace all those parts though? Aside from the trimpots, the other components (resistors and poly caps) very rarely fail. And resistors are quick and easy to check with the meter.

-Ian
 
1. How much power is heading to these trimpots? Voltage, amps? This'll help folks source a replacement for you. There's a couple of trimmers I've found that'll probably work, but it depends on how much power's being pulled through there. Also need to know if they are single or multi-turn. Also, 22k's are really hard to find! 25k's may be your only replacement option now.

My poor schematic reading skills come into play here... The only power I see coming to/from the board is 15VAC and 60VAC. The 15VAC looks connected the right side of the board and 4 of the trimpots (4 targets, makes sense). The 60VAC is tied to the single trimpot in the middle (the game opponent). All the trimpots are the same in the schematic and on the board (I can see 22K on each one)

2. This one is weird. The pic looks like Grey Green Red Silver Yellow.. Which isn't standard. If you treat it like a 4-band, it comes out to 8.5k 10%. Yellow Violet Red Gold is the standard 4-band 4.7k 5% coloring. No idea here. If the spec calls for 4.7k, I'd throw a modern 4.7k in there and hope for the best. You could also measure that one and see what comes up.

Per the suggestions here, I did check the resistor values on the board (d'oh!):

-The top center one tests at 1.5K, so it is the wrong part.
-The lower left that should be 15K tests at 4.8k.
-The lime green one in the lower middle left that should be 47 ohm tests at 30 ohm.

That for the suggestions on the replacement parts. For the resistors (e.g the 4.7K one) that I don't have other values for, any suggestions on what tolerances I should use on the replacement?

Oh, I was considering at least ordering replacement parts for everything on the board so I would have full spares going forward. It looks the like the sun is setting on some of these parts, so I figured I'd protect myself going forward. Not real expensive parts to begin with.
 
I would stick with polyester caps there, not ceramics. Polyester/polypropylene caps are easy to get and common.

If the schematic calls it a 4.7k, then replace it with the same. What does it measure, and why do you need to replace it?

The trimpots should probably be replaced with 25k's if 22k pots aren't available. Small trimpots like this are common, those look like 1/4w units or so.


Why do you think you need to replace all those parts though? Aside from the trimpots, the other components (resistors and poly caps) very rarely fail. And resistors are quick and easy to check with the meter.

-Ian

I'm going to ditto Ian. I didn't realize there's AC floating around that board, so yeah, poly caps it is.

Here's the 0.22uF Cap, in polyester film.

http://www.mouser.com/ProductDetail...GAEpiMZZMvOcEq4GH1AAsCHDlOl%2bACvzxmH7chcWFg=

And 0.1uF.

http://www.mouser.com/ProductDetail...=sGAEpiMZZMvOcEq4GH1AAsZnxcGorqHeV9lvwDIYATE=

Best I can find for your pots are..

25k, Vertical Standing: http://www.mouser.com/ProductDetail...=sGAEpiMZZMsEGgLEzQVydmFA56OEN7E8ydaxCLkT7kg=

25k, Horizontal: http://www.mouser.com/ProductDetail...=sGAEpiMZZMsEGgLEzQVydmFA56OEN7E8zVLyaIb52WE=

Note those are 1/2 Watt models. The 1/4's looked really dinky.

For your resistors, 5% is cheap and common for metal film. I'd just use that unless you've got an area that specifically calls for 1% or 2%.
 
I'm going to ditto Ian. I didn't realize there's AC floating around that board, so yeah, poly caps it is.

Here's the 0.22uF Cap, in polyester film.

http://www.mouser.com/ProductDetail...GAEpiMZZMvOcEq4GH1AAsCHDlOl%2bACvzxmH7chcWFg=

According the schematic these should be 0.022uF poly cap and not 0.22uF. Would the following work?

http://www.mouser.com/ProductDetail...=sGAEpiMZZMvOcEq4GH1AAnpR/KEGjjBf71/lHVZsHrE=

or these Panasonic brand:

http://www.mouser.com/ProductDetail...GAEpiMZZMvOcEq4GH1AAsCHDlOl%2bACvTNUQGcVAUkA=
 
It looks the like the sun is setting on some of these parts, so I figured I'd protect myself going forward.

I don't really see anything on that PCB that I'd be worried about having trouble replacing any time soon.
 
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