Looks like my measurements weren’t that off. I had some problems with a few 
pots, as they were corroded and the resistive traces were broken. I measured 
them from one end to the gap and the other way round, added it up and here’s 
what I got:

 

VR401   74k

VR501   10k?

VR502   4k7

VR402   200k

VR404   0k6

VR403   10k?

VR503   3k3

 

Sure it helps a lot, thanks again. The PCB is mostly populated now, I’m only 
missing a few parts I didn’t order for some reason and the biggest ones like 
the flyback transformer and heatsinks. I’ve been cleaning them today using a 
dremel with a wire wheel attached. To this very moment I’m removing those small 
wires from my beard J I will definitely create a blog soon and describe the 
whole process.

 

Cheers.

 

From: nathanael.hasbro...@gmail.com [mailto:nathanael.hasbro...@gmail.com] On 
Behalf Of theonetruestick...@gmail.com
Sent: Monday, February 19, 2018 5:16 PM
To: vintage-macs@googlegroups.com
Subject: Re: Macintosh 12" RGB Display M1296G owners please help

 

The markings weren't obvious to me either - not enough numbers for the normal 
designations! Based on measurements it looks like the numbers are a two-digit 
code, so the 53s are 5K (5+000), 25 is 200K, etc. Letter designations are 
probably log/lin taper, though 'z' is not common - not sure about that one. 
Maybe they are alternate codings or a custom taper?

They all are somewhere in the middle of their ranges on my monitor, so it's 
likely a close value will work if the exact isn't available. You can't quite 
see from the traces, but the four I was able to test in-circuit are wired as a 
rheostat (wiper shorted to one leg of the pot).

Photos uploaded, and measured values as follows:

H-CENT  VR503  2.5K out-of-circuit

V-CENT  VR403  9.3K out-of-circuit

V-HEIGHT  VR404  500-ohm out-of-circuit

V-LIN   VR402   174K in-circuit

H-HOLD  VR502  5K in-circuit

H-PHASE  VR501    4.6K in-circuit

V-HOLD  VR401  90K in-circuit (probably 100K)

Hope that helps!

 

 

On Thu, Feb 15, 2018 at 12:20 AM, zgbapl <z...@o2.pl> wrote:

Hi there, just wanted to say, that I'm still working on the PCB and making some 
progress, but unfortunately I can't spend as much time on it as I'd like to. I 
hope that I got all the resistors right, I'm just not sure about those pots on 
the edge of the board, they were totally corroded and their markings don't tell 
me much. If your monitor is still open, maybe you could get more info on them? 
Cheers


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