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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Phonic on January 14, 2006, 06:21:26 PM

Title: Burnt resistor on A1200 motherboard - Help!
Post by: Phonic on January 14, 2006, 06:21:26 PM

I'm not sure if this is critical or not but I'll post it anyhow...

E232R to the left of the IDE port on my A1200 2B board has burned a slight hole in the substrate of the board, the resistor (4R7) has removed itself through heat.
Before I replace it does anybody know what this resistor does? My best guess is that it's something related to the RF modulator however I really want to be sure.
If it doesn't affect anything else I'll remove the RF modulator from the board.

Thanks all.

Here's a picture:
130K Pic. (http://members.cox.net/cascade/4r7.JPG)

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: Doobrey on January 14, 2006, 07:11:04 PM

Looks like it's limiting the current that powers the modulator (the schematics I've got here are unreadable on the pin names!), so removing it and the modulator shouldn't affect anything else.If you're not planning on replacing it  just cut the 3 long pins connecting it to the motherboard instead of removing the whole thing.

I'd be more worried about why it burnt out, maybe C239 has gone bad and created a short to ground (there's another unlabelled cap between gnd and E232R to check too), or the modulator is fscked.

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: Phonic on January 14, 2006, 07:31:06 PM

I'm guessing the modulator is duff, when I tried it back home in England I couldn't tune it in at all which would explain the resistor failure - whoever owned it before me had taken a screwdriver (Hammerdrill) to the trim pot for some reason.

I think I'll remove the modulator, I can't use it over here (USA) and it'll give me a little more space for my IDE cable project :)

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: Boot_WB on January 14, 2006, 07:40:15 PM

Didn`t buy it fom Dommmaster did you? :-D

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: Doobrey on January 14, 2006, 07:46:10 PM

Quote

Phonic wrote:
 whoever owned it before me had taken a screwdriver (Hammerdrill) to the trim pot for some reason.

 :-o  :-o  :-o
Reminds me of something I read about a tech support guy removing DIP switches with a cold chisel to stop employees from fiddling about with them !
(And then having to phone the manufacturer cos it didn't work anymore..
 :roll: )

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: adolescent on January 14, 2006, 08:04:59 PM

You can remove the RF modulator without any problems.  I did this on my 1200 to put the VGA connector from my internal SD/FF in it's place.

Title: Re: Burnt resistor on A1200 motherboard - Help!
Post by: Phonic on January 14, 2006, 08:12:38 PM

VGA port, that's a great idea and it'd fit perfectly.
Now all I need is an internal scandoubler.
And an accelerator, more RAM, 3.1 ROMS, OS3.9........

I ought to hawk some of this PC hardware I don't really need anymore.