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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Sandman on February 02, 2013, 11:52:55 PM

Title: Could someone please look @ their CD32 pcb for me... need a toasted resistor value
Post by: Sandman on February 02, 2013, 11:52:55 PM
Hi All,

Just picked up a nice non-working CD32 and I traced the problem to a open surface mount resistor, R801, located between the power connector and on-off switch.

Problem is that I can't read the value as the print is worn/burnt off.  

Thanks!
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: Jeff on February 03, 2013, 01:30:44 AM
I replaced those years ago on several machines. As I recall they are (ZERO) ohm smt available from Digi-Key or someone like them.
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: Sandman on February 03, 2013, 04:45:28 AM
Thanks Jeff!

I guess I just didn't look close enough at the schematic.... still learning.

I just used a piece of 30g a. kynar wire to make a jumper.... seems to be working fine.

Thanks again!
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: A6000 on February 03, 2013, 08:43:29 AM
Why did they fit a zero ohm resister?
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: r.cade on February 03, 2013, 03:15:27 PM
0 ohm resistor = fuse.  You should replace it with another.
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: mechy on February 03, 2013, 04:05:21 PM
Quote from: r.cade;725151
0 ohm resistor = fuse.  You should replace it with another.

zero ohm resistors is not a fuse, it is simply a jumper with negligible resistance. It was mainly to make it easy for pick and place machines to jumper 2 pads since they cannot work with wire for jumpers. Its also easier/cheaper than jumper pins and a jumper block where the design doesn't need to be switched/changed.
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: r.cade on February 03, 2013, 05:04:12 PM
Quote from: mechy;725157
zero ohm resistors is not a fuse, it is simply a jumper with negligible resistance. It was mainly to make it easy for pick and place machines to jumper 2 pads since they cannot work with wire for jumpers. Its also easier/cheaper than jumper pins and a jumper block where the design doesn't need to be switched/changed.

Well, if that is the case, then you have to think about "why did his fry/blow in this circuit"?

If not a fuse, then he will have another problem soon, eh?
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: Sandman on February 03, 2013, 05:47:50 PM
Thanks everyone for the help and and the great replies.  

My guess is that since the original power supply was missing, somewhere along the way someone might have try to plug in some other type if improper power supply and that was what fried that zero ohm resistor.  I made sure that the ATX PC adapter I made was right and checked and re- checked with my meter so I hope that I am safe using the jumper.

I love the feeling that I was able to save it from the scrap bin....to me it feels better to have fixed something nostalgic than to buy it new. :). Amiga mid-life crisis, hahaha.
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: mongo on February 03, 2013, 06:16:02 PM
Quote from: mechy;725157
zero ohm resistors is not a fuse, it is simply a jumper with negligible resistance. It was mainly to make it easy for pick and place machines to jumper 2 pads since they cannot work with wire for jumpers. Its also easier/cheaper than jumper pins and a jumper block where the design doesn't need to be switched/changed.


Zero ohm resistors are often used as fuses, as they were in this case.
Title: Re: Could someone please look @ their CD32 pcb for me... need a toasted resistor valu
Post by: Sandman on February 04, 2013, 08:26:19 PM
I went to both Digikey and Mouser and located the 0 Ohm surface-mount resistors but I am assuming that I would need to know the power rating for the replacment.

Any idea what that would be?  1/8w to much or sufficient?

This is getting way beyond my pay grade. :)