I'm back at my Toshiba CX1467 after a long hiatus. While initially working on it, it experienced vertical collapse and I had to basically recap the whole Vert sections and replace the V output IC. Fun.
So, I pretty much got it back to working good again (Vert is back!), minus a few caps that I'm waiting on, and I'm going to get into the mod pretty soon.
The mux chip is called a AN5352N. Here are the conditions as I have been able to determine:
1) There are 2 sets of RGB inputs on the chip. One is for the TV signal, the other is for the OSD text. (TV and Tx)
My main concern is which one makes more sense to use.2) Tx has a 3x gain for Contrast, which adjusts in conjunction with the display contrast.
I'm not sure what to make of that. Perhaps it's designed to always be visible, even if the screen brightness is turned down? Perhaps I simply need to feed it a lower input signal because that's what it expects from the character generation chip?
This is the spec for the voltage amplification of the OSD input signal from the datasheet:
Here's the part of the AV chip's output that has the tie-in for the contrast (pin 8 output) and the brightness control (pin 15).
3) Tx has a brightness control input that isn't used on my set. (it's just tied to ground)
Would I need this is if I used Tx?I was thinking I could maybe hack it in if I had to.
The unused pin is PIN 9, you can see it in the schematic below on the right side:
4) TV input on this chip seems to bypass both the contrast and brightness circuit on the main AV chip.
I'm unsure if I will get contrast and brightness if I used them.However, looking at the schematic, it seems like the contrast and brightness controls are also hardwired to the screen control. Can anyone give me confirmation that I'll still have those controls?
Here's that signal path:
5) The Green Tx input on my chip isn't populated, it's just out to a capacitor to ground. That confuses me. I suppose maybe that it giving it "all green" somehow, but I can wrap my head around why that would be so. I suppose it has something to do with the clamp inputs. Not sure.
6) The RGB Tx inputs are referred to as clamp, and there is a single "pedestal clamp" at pin 6 that goes to Rtx,Btx, and Gtx. I'm assuming that defines the on screen position of the OSD, but I don't understand how that factors into the HV sync, which I assume it replaces in some way. Perhaps the clamp can just be luma?
Here are some additional schematic bits:
The AN5352 input schmatic:
Here is the schematic from the datasheet:
This is the character gen chip if that makes any difference. You can see the signals which end up at the mux chip:
Here where the signal comes out of the character generator for the on screen menu.

This is the Character Gen pin output, showing the RGB outs on pins 12, 13, 14:

Here is the pinout descriptions of the char gen chip:

Much obliged if someone could help me sort it out.
Thanks,