BVM D24 Horizontal Linearity Issue, Only on High Resolutions

[wizardlarry]

I'm having a strange issue with my BVM D24 where the center of the screen is pretty badly compressed, but only on higher resolutions(480p and above). The linearity looks nearly perfect on 240p/480i.


240p. All grid squares are basically the same width



480p. Outer grid is about 30% wider than the inner grid

Anyone know what could be causing this? The fact that the linearity looks fine on 240p and only has issues on 480p and up tells me that this should be adjustable, but everything I've tried so far has done nothing. I tried changing the HLIN/HLIN bal settings in the extended menu, but they do virtually nothing. I tried playing with hphase and hcenter, but those have no affect. I'm open to removing the deflection card and changing electronic components if anyone knows what might be the culprit. Any input would be appreciated.

[fernan1234]

Is this only for the widescreen mode? How's the 4:3 picture?

[wizardlarry]

Is this only for the widescreen mode? How's the 4:3 picture?

Same effect with the center being compressed but the sides are less stretched out. Imagine the same image, just cut off on the sides.

[tongshadow]

Start by testing the capacitors on the deflection board, check for ESR and Capacitance.
The reason H-Linearity looks distorted on higher resolutions is because some part of the S-Shaping circuitry isnt working properly, since different resolutions require different capacitance values to create the correct waveform.

[wizardlarry]

Start by testing the capacitors on the deflection board, check for ESR and Capacitance.
The reason H-Linearity looks distorted on higher resolutions is because some part of the S-Shaping circuitry isnt working properly, since different resolutions require different capacitance values to create the correct waveform.

I'll do that. Could bad caps also be the reason that the HLIN settings aren't doing anything, or are there maybe some other failed components as well I should look for? Thanks for your input.

[tongshadow]

I'll do that. Could bad caps also be the reason that the HLIN settings aren't doing anything, or are there maybe some other failed components as well I should look for? Thanks for your input.

Definitely, other components can fail as well. Transistors can short/open circuit, resistors open circuit, capacitors can go out of spec or short, and capacitor fluid could corrode and damage traces on the board... here's an example:
https://youtu.be/v3CzEGq9FG4?t=320
I would first visually inspect the board before trying to diagnose further.

[wizardlarry]

I'll do that. Could bad caps also be the reason that the HLIN settings aren't doing anything, or are there maybe some other failed components as well I should look for? Thanks for your input.

Definitely, other components can fail as well. Transistors can short/open circuit, resistors open circuit, capacitors can go out of spec or short, and capacitor fluid could corrode and damage traces on the board... here's an example:
https://youtu.be/v3CzEGq9FG4?t=320
I would first visually inspect the board before trying to diagnose further.

I pulled out the E board and thankfully none of the capacitors are leaking. According to the service manual, HLIN is controlled by IC205 and IC203 on the D board (the small board connected to the E board), so I'll just remove and test each capacitor and resistor on that board and hopefully I'll find out the reason why that setting isn't working.