CurtPalme.com Home Theater Forum

[bomrat]

i am looking at the lvps mod and i have a couple questions...

install the 20 ohm pot at r223 (bare location) right.

remove the filament voltage connector (where is this)

and check the heater voltage, where to test and what voltage.

thanks

[bomrat]

please help guys.

[JustGreg]

Hi

You don't want to solder in the 20ohm pot at R223. Nothing goes "in" that spot, although you'll be cutting a trace and installing a SMT 425 ohm 1/8 watt 805 size resistor off one leg of that location.

The pot you need to replace is on the very edge of the PS board and was designed to be adjustment accessible through a hole in the LVPS metal housing. Once replaced with a good quality 20-ish turn 20 ohm one and adjusted you won't need to ever touch it again. I believe the originial pots came in two flavors, a grey one or a blue one.

The voltage measurement you need to take is at P14, at the large connector located at the rear of the blue tube on the motherboard. You'll see the P14 connector immediately as it's the only one with printing on it at the large connector. Do your tests with it connected and don't yank it off with the pj powered on or plugged in. With the pj off but plugged in you'll see the heater filaments lit in each tube and get around 3.85v at P14. With the pj on you want to be as close to 6.35 as possible after the mod.

It's easy to be tempted to just adjust the 20 ohm pot if the reading is off but the whole idea behind the mod is to prevent drifting of the filament voltage which can turn a working tube into a conversation piece and cost you a couple hundred (used) to replace.

Here's the link to show some pics of the SMT part of the mod. I don't have time to look for the entire thread that also shows the 20 ohm pot part of the procedure. Search for member Sly (pix and procedure are his) over at the A site and then root around a little more for his post specifically concerning the mod. It has more info and pics.

http://www.avsforum.com/avs-vb/showthread.php?p=3283239#post3283239

Have fun!

Greg

EDIT:The entire procedure may also be here in the Mike Parker Marquee Maint thread although I wasn't able to find it. I'm juggling this and work so I apologize for not being more complete. EDIT:Although this is waaaay more fun!