WG4901 odyssey

saltbreez

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Hey all [Ken, Dave aka Dokert]

My 4901 odyssey continues. To date I have replaced the fly, and hot. I'm using Fromm's flowchart and have hit a dead end.

Pull out your flow chart and follow me if you will:

Start here: Blank screen -> yes
Blow Fuse F501 -> yes -> replace HOT Q352 -> retest

Start here: Blank screen -> yes
Blow Fuse F501 -> no
Check the regulated power supply at resistor R503 ( that's the 150 ohm, 15 watt ceramic resistor) The terminal closest to the fuse should be measure +130VDC -> low
Check the voltage at the other end of R503. It should be around +145 VDC -> 0 VDC
R601 may be open ... R601??? Where the @#!% is R601???


Hey thanks guys...

Saltbreez
 
Hey all [Ken, Dave aka Dokert]

My 4901 odyssey continues. To date I have replaced the fly, and hot. I'm using Fromm's flowchart and have hit a dead end.

Pull out your flow chart and follow me if you will:

Start here: Blank screen -> yes
Blow Fuse F501 -> yes -> replace HOT Q352 -> retest

Start here: Blank screen -> yes
Blow Fuse F501 -> no
Check the regulated power supply at resistor R503 ( that's the 150 ohm, 15 watt ceramic resistor) The terminal closest to the fuse should be measure +130VDC -> low
Check the voltage at the other end of R503. It should be around +145 VDC -> 0 VDC
R601 may be open ... R601??? Where the @#!% is R601???


Hey thanks guys...

Saltbreez

Did you visually check the fuse or test it with a DMM?

EDIT: The second time, of course. After you replaced it.

Then again... on my flow chart for the 4900's, I'm showing different numbers (steps... sorry, the word is steps... I count everything in my head so I let that spill out when I typed).

Sorry in advance for the bit picture below...




4900FlowChart.jpg
 
Last edited:
Wow... that was big... but atleast you can see R601 in the upper left of the picture, just to the right of C505 (big ass cap) in the other picture I decided to not post. ... it's big also
 
R601 is mounted on the chassis black frame IIRC. White WW 5W, don't recall the value.


OK Dave,

replaced R601, Now I have neck glow...

Looks like I'm down to a horizontal deflection failure. Replaced Q351. Before I go any further, I might just drive this unit down there and have you take a look...


Saltbreez
 
You don't offen see horizontal deflection failure. Usually if you have a problem with the horizontal deflection, you don't see anything.

not to say that it can't happen....
 
Brightness all the way up.
Black level all the way down.
Focus maxed out.

Picture comes up, but is still out of focus and colors are kind of washed out.

Swapped out the tube with another known good tube, and no picture no matter what.

Bad Fly?
 
if it looks like horizontal failure , look at the width coil too , I had a GO7 width coil break right off on me once and it looked like deflection failure when the pic came on. not sure if the 4900 reacts the same. I just replaced the coil and viola , crisp freshly capped picture goodness
 
if it looks like horizontal failure , look at the width coil too , I had a GO7 width coil break right off on me once and it looked like deflection failure when the pic came on. not sure if the 4900 reacts the same. I just replaced the coil and viola , crisp freshly capped picture goodness

The picture was the right dimensions, just really faded and unable to focus.
 
On the neckboard....

Well, I am not really certain how to go about checking for connectivity here. I am assuming that the focus wire is the tan wire coming off of the fly back and that it lead to the shielded pin and socket on the neckboard. This odes not leave a lot of options for testing connectivity...

The stargate screen comes up with the settings Dave [dokert] describes, it is WAY out of focus and convergence is out by 2 cm.
 
Well, I am not really certain how to go about checking for connectivity here. I am assuming that the focus wire is the tan wire coming off of the fly back and that it lead to the shielded pin and socket on the neckboard. This odes not leave a lot of options for testing connectivity...

The stargate screen comes up with the settings Dave [dokert] describes, it is WAY out of focus and convergence is out by 2 cm.

Replace the wire that has the wire nut on it, that is the focus wire. It is just soldered on both ends. If you don't know how to get the socket connector open, just bring it back down and I will do it.
 
Replace the wire that has the wire nut on it, that is the focus wire. It is just soldered on both ends. If you don't know how to get the socket connector open, just bring it back down and I will do it.

When I popped the cap off of the neck board socket, the area around the focus connection was burned black. I swapped the entire neck board from a donor chassis...

The picture in now at about 95%, mostly crisp and clear with the exception of the top of the screen. I cannot seem to find the vertical position adjustment, when I adjust the Williams scratch pad flicker line [that appears at the top of any Williams screen] off of the screen using the Vertical size adjustment, the top of the screen gets broken up into horizontal lines and a screen fold appears to be happening...

Any suggestions for these symptoms?
 
Since you don't have the vertical raster pot, you could try shifting the vertical postion jumper. You could also try tweaking the vertical hold just a hair.
 
Since you don't have the vertical raster pot, you could try shifting the vertical postion jumper. You could also try tweaking the vertical hold just a hair.


OK that helps, I'm gonna say this screen is at 96% now. I still cannot adjust the screen to full height with out it fragmenting, and the scratch line is very much visible in any clean screen.
 
Check the number screened on the back of the chassis, Does it end in -023? if so, that's why....
 
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