Hantarex MTC900e - white screen

[CathalDublin]

I’ve a hantarex MTC900e
It’s the European model that takes 128v and 220v for the degaus.
I acquired this a long time ago but hadn’t got a stepdown isolation transformer to test it.
Finally came across an isolation/stepdown the other day and plugged it in and nothing, finding some posts from grantspain I found he’d mentioned the most common issue with these chassis is corroded coil/TR20 which indeed it was corroded and broken, I repaired this and the monitor now comes on but all I’m getting is a white screen, if I plug in a game the picture does kinda roll, see video with game running. I’ve re-capped the neck board and adjusted the screen pot which just makes the black area brighter/darker. The resistor on the left hand side does get very hot.
I have only the 128v connected, I haven’t got the 220v connected but I believe this is only for degaus.
Any ideas

[grantspain]

next test voltages, 200v video b+ and 12v and -5
refer to the schematic for test points

[CathalDublin]

My b+(Sp4)is reading about 180ish v, my 12v(SP8)is 10v and my -5v(sp7)seems to be reading +5v, is that possible?
I’m measuring these from the neck board

[grantspain]

if someone has replaced the 7905 at ic1 with a +5 reg then yes
the +12 is a bit low, you can read again at ic4

[CathalDublin]

I may have read it wrong, doesn’t look like anyone’s every worked on this before, I’ll re-check them tonight at ic4
Thanks

[grantspain]

ic4 is the +12 reg

[CathalDublin]

OK I re checked my voltages from the main board, see video, maybe I’m doing something really stupid but I’m getting 19.2 on the 12v and 13.9 on the -5v
Measuring from here



See video


Measuring the input on IC1(7905) reads 0 and the output reads 13.9/14

[grantspain]

i read at the neck card with chassis fully connected and running

[CathalDublin]

19.3 and 14 from the neck card with a game running
Can see interference on screen with game running, no colour, everything’s white

[grantspain]

what is the chassis b+ reading, use one of the centre 2 pins of the deflection coil connector and frame as ground- should be around 126v

[CathalDublin]

It’s 217.

Edit: actually I should be testing DC? I’ve my meter set to AC.
So that’s 138v b+
12v is bang on 12v
And I’ll need to retest my -5 tomorrow 🤦🏻‍♂️

[grantspain]

yes dc volts
set your b+ to 126vdc by adjusting RV12

test the video b+ at SP4 neck card- should be around 190-200vdc
test the -5 at SP7 neck card

[CathalDublin]

I’ve my b+ Dialled in at 126v now, and at SP4 it’s about 215v
My 12v is stable at 12v
But my -5v is reading 7.5v

[grantspain]

check the following
c25, c83, c36- replace in any case
all diodes around that area
ic1 7905  -5v regulator

the input to ic1 should be 12v