PVM-8041Q, losing chroma signal on composite and svideo

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shikikanzero
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Joined: Sat Jan 02, 2021 9:33 am

PVM-8041Q, losing chroma signal on composite and svideo

Post by shikikanzero »

So I have a PVM-8041Q I'm working on for someone, RGB/component inputs work fine, but I'm losing the chroma signal on the composite and S-Video inputs. I've already tried doing some solder reflowing to no avail. Anyone know of any common known issues or what circuit lines to check? I got the service manual but it doesn't have any line to line or board diagrams. Do these share the same boards as a 8045Q? Thanks for any help!
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buttersoft
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Re: PVM-8041Q, losing chroma signal on composite and svideo

Post by buttersoft »

shikikanzero wrote:So I have a PVM-8041Q I'm working on for someone, RGB/component inputs work fine, but I'm losing the chroma signal on the composite and S-Video inputs. I've already tried doing some solder reflowing to no avail. Anyone know of any common known issues or what circuit lines to check? I got the service manual but it doesn't have any line to line or board diagrams. Do these share the same boards as a 8045Q? Thanks for any help!
The 8041/8044 were superseded by the 8042/8045 as the pairs of low TVL / high TVL 8" models. So the 8044 would be closer, in theory. These are also going to be very, very similar to the PAL variants - same model numbers but starting with 9 instead of 8. So the schematics for a 9041QM might be closest.

Excellent pedantry, zero help. Me in a nutshell.
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NewSchoolBoxer
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Re: PVM-8041Q, losing chroma signal on composite and svideo

Post by NewSchoolBoxer »

Sorry if you already have good circuit knowledge. I would turn the knob on a basic multimeter to the diode setting, which is a continuity check. It beeps if a small amount of voltage can flow between the two points. So if you get to a part of the trace where there is no beep between points A and B, something is wrong in between.

Famous issue to blame in a CRT is a bad capacitor but if you don't see any sign of wear and tear or fluid leakage, you probably need an expensive ESR meter to check them. Is probably overkill but if you're working on PVMs, is a device you'd want.
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