pentranic series chassis dark/dim *fixed* (mostly)

[lilshawn]

I have a pentranic 1432 series chassis on a 34" tube that is dark/dim running in CGA mode.  I tried to crank up the flyback screen control, and recieved no increase in brightness, only washing it out in white. tested the tube and the gun emittance is still good, great in fact.

The b+ while running averages 102v (low 97v high 104v) at D501 cathode. the "Manual" says it should be 126.6v. I also checked the voltage at D404 (just before it hits the flyback) it reads 124v (should be 162v) seems awful low.

I tried to adjust the B+ up to see if the voltage would come up, but after i started turning it up , I noticed no change in the voltage so I left it. For fear something in the circuit is loading it down, that it be best to find the fault first.

anyone have any ideas?

EDIT:

I displayed a static black/white cross hatch image for convergence size adjust checking. the voltage is 99v steady. if i turn up the b+ i can get it as high as 107 before the chassis goes into power supply shutdown. something is amiss.

2ND EDIT:

today I stared at the schematic for an hour and a half until I fell asleep, I noticed that it took some time (about 3 seconds) for the B+ to come up to voltage. hmmm...a voice told me to check the b+ filter cap. When I awoke, I replaced c315 (220uf 250volt... had a 400v on hand) my voltage is back up again. booted up right off the bat at 112 volts. (I turned the B+ back down again before starting up just in case it worked)

3RD EDIT:

I turned up the voltage to 122... something i was comfortable with... since the manual I have for it is full of conflicting info/wrong/errors not to mention the undocumented changes/tweaks/fixes. The picture is great now. I also had an issue with the top folding over. replaced C398, C393 and c326 for good measure.  foldover gone.

grant: I checked the cap you mentioned too as well.... all the high voltage stuff is mounted on the main board. I found a few 10uf 250volt caps with the ESR is a little low, but I replaced them anyways.

[lilshawn]

 

[grantspain]

any caps on the g2 circuit at the neck card?
something like a 10uf 250v