Hantarex 900/E display problems

[SJP0tato]

Hello all,

I'm having some trouble with my Hantarex 900/E, in a Gauntlet 2 cabinet.  Initially the display worked (albeit somewhat dim) for a few weeks, after which it finally gave up and no display was rendered.

I recently removed the chassis, replaced all the capacitors with a kit, removed and tested the HOT and voltage regulator transistors (They showed the proper directionality using a multimeter at least). 

Now when powered on there is a display, but it comes up as a green square, similar to what the display would look like with the horizontal/vertical frequency set incorrectly (like a scrambled/wavy set of lines).  I think it's better than previous where I'd get no display at all, but I've tried adjusting every one of the tuning mechanisms for output, and none seem to make much difference to clarify the output.

I've seen Ken Layton's guide (Thank you for that btw), and tested R56 just in case (it tested out within spec).  Does anyone have any other areas to check?

Thanks for any help/suggestions!

[grantspain]

post a photo of a screen shot

[SJP0tato]

Here's a few screenshots, thanks again for any suggestions:

[grantspain]

looks like green drive transistor is full on,desolder one end of r146 on the neck card and then report the result

you either have a shorted drive transistor or bad track/solder joint on the green or the green gun in the crt is shorted

[SJP0tato]

grantspain, you are awesome!

I de-soldered R146 (well, the leg broke during the de-solder process, but no biggie), and the following is the result after much adjustment:

I'm guessing this means one of the transistors on the neck board is bad?  I'm looking at the schematic, but having a tough time figuring out which one would be the culprit. 

[grantspain]

yeah do a job lot so change the following
r146 3k3 0.5w
tr31 bf871
tr30 bf871
tr29 bc237
d11 1n4148
d31 1n4148

check with meter r137 and r134

use solder braid(wick) on these components as the tracks will be delicate

[SJP0tato]

I finally got around to getting the new parts in.  I replaced all 3 transistors, both diodes, and tested r146 (it was within spec).  I also tested the potentiometers for the green gun, and they seem to fall within spec for their range, but still get the following:

[grantspain]

if that is a bright white screen then its possible the 200v is missing,not sure why though as all you had previously was a fault on the green drive circuit

[SJP0tato]

if that is a bright white screen then its possible the 200v is missing,not sure why though as all you had previously was a fault on the green drive circuit

Sorry, I should have clarified:  It's blindingly green now/still.  I wonder if there's something not on the neckboard but on the main board that controls the brightness also that might be defective?

[grantspain]

you can prove that by desoldering the green at sp206,there is a circuit on the main chassis for each colour
you have tried the gain and cut off pots on the neck i imagine?

there is also a 3 way contrast pot,they can get dirty and cause colours to go high

[SJP0tato]

you can prove that by desoldering the green at sp206,there is a circuit on the main chassis for each colour
you have tried the gain and cut off pots on the neck i imagine?

there is also a 3 way contrast pot,they can get dirty and cause colours to go high

If I fully adjust the gain + cutoff pots, it dims some, but it's only a change from blinding down to completely washed out in green.

I'll try de-soldering the sp206 and see what happens.  What should I expect if it's good/bad after de-soldering?
I'll see if I can ifnd that 3-way POT and clean it up too. 

Thanks again

[grantspain]

if you remove sp206 and the green issue changes/goes then the problem is in the green colour circuit on the main board,if it remains the same then the problem is on the neck card-you could swap the blue and green wires to see if the problem shifts
that pot will just need turning a few times

[SJP0tato]

if you remove sp206 and the green issue changes/goes then the problem is in the green colour circuit on the main board,if it remains the same then the problem is on the neck card-you could swap the blue and green wires to see if the problem shifts
that pot will just need turning a few times

I swapped the output from the blue gun over to the green, and it appears to work properly (Only Red and Green appear on the display, and the image looks okay/playable).  I guess that only tells that the tube itself is okay.  I'll get to removing sp206 & see what happens next.

[grantspain]

i reckon there is a broken track on the neck card