WG 7501 - Change 25k to 27k

SiLeNtNiNjA1

Active member
Joined
Mar 13, 2010
Messages
1,071
Reaction score
7
Location
Farmington Hills, Michigan
I know that there is a different flyback between the 25k and 27k versions of this chassis. Is there anything else I would need to change to make a 25in chassis work with a 27in tube? Is this even possible?

Thanks!
 
I thought I read the other day that it was the exact same chassis except the 27" has a pincushion board. I could be wrong though.
 
May very well be, im not sure. I was poking around on google and found an old post where someone mentioned it had a diff flyback, if I can find it again, ill link it here.
 
Besides a bigger tube, degaussing coil, and dag wire - the only thing you need to change on the chassis to change a 25" K7500 to a 27" K7500 is that R620 needs to be changed to a 220-ohm 2-watt +/-5% resistor, and the pincushion board needs to be added. Yoke, neckboard, and remote board are the same.

Here is the K7500 service manual, with the 27" parts difference at the end:

http://www.wellsgardner.com/pdf/Service/K7500.pdf
 
Resistor is easy enough to swap. I have the tube w/ the degausing coil, yoke, ect still attached - just no chassis came with the cab. Any chance someone has either a spare pincushion board or a diagram of the pincushion board? I looked over the rest of the manuals on the WG site, and didnt see much beyond the parts list. Somehow I doubt there are a ton of these without affixed chassis's floating around, so worst case i guess ill try to make my own.


Basically, Ive been offered a 25in chassis to try and get the 27in monitor going.
 
I realize this is an ancient thread, but I wanted to add info to this. The P777 pincusion daughtercard schematics here are correct for a 27k7501. There are a few small component value differences on this little pcb for the 7502.

I figured I would add to the archive here by posting the schematic for the P777 for the 27k7502 model.

P77 on a 27k7502:
20230424_180434.jpg

Maybe this can help someone. Also, i would like to point out that my P777(this schematic was inside the game) does not have C771 populated and R774 actually has a 22uf 25v cap across it with the negative side connecting to VR771 on the pcb (schematic for some reason says UR703). Here is a pic of mine 20230424_183730.jpg
 
Last edited:
I wonder if this is the one that matches the APAR kit. I capped a few 27" monitors last year and none of them matched what the APAR kit called for. there was a swap between 100 uf and 10 uf or something to that effect. let me look at the pincushion board I have in my case and see if it's a P777.
 
Back
Top Bottom