Author Topic: Missing resistors  (Read 231 times)

soop

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Missing resistors
« on: June 11, 2011, 03:12:14 AM »
I just picked up a PC Engine which has been moded to output RF PAL.  It's a horrible hacky mess inside, but I can totally reverse (read RGB) it.  The only thing that I need that's missing is two resistors, R137 and R138.

They're 3 band resistors, and I can see from another PCE that they are "green red red" and "red green green".  Using this:
http://www.hobby-hour.com/electronics/resistorcalculator.php That's:
red red green 2.2MΩ 20%
green red red 5.2kΩ 20%
But if this has anything to do with it, that may not be the case:
http://wiki.pcengine.info/pmwiki.php?n=Hardware.HuC6260

Does anyone know what value each one should be?  I don't even know which way you read the bands.

soop

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Re: Missing resistors
« Reply #1 on: June 12, 2011, 10:15:49 PM »
I forgot I had a multimeter.  Just as well I remembered, the values are rather different.

Measuring on another PCE, I get 6,100 for R137 and 8,260 ohms for R138.  With 3 band resistors they have a tolerance of 20% apparantly, so that means I can use a 6.2k and an 8.2k in there.

Not sure about the wattage.

Charlie

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Re: Missing resistors
« Reply #2 on: June 13, 2011, 12:34:42 PM »
On the DUO, the part numbers are different.  But the IC pins are obviously the same.  Here's what I have:

Pin 40, 4700 (4.7k)
Pin 33, 6200 (6.2k)
Pin 26, 8200 (8.2k)
All three of these resistors connect to a 1000 (1k) that connects to a transistor.
There is a 27000 (27k) on pin 20 that also connects to the same point on the transistor.

These values seem close to what you found.

Charlie