Wells D9400 woes..

Dr. Willy

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Received need for speed with this monitor in it. Upon power up the monitor had a very very faint chirp to it (so faint you could not hear it unless you head was in the cabinet right next to the chassis. Pulled the chassis found R288 burned right off the board. Recapped chassis and replaced r288. Chassis had same faint chirping issue. Repulled chassis and started looking around, q207 measures short on both sides. Replaced q207. Reinstalled chassis and now upon power up it has a very audible hard click about every 3 secs.

I can't seem to find to much info as far as repair logs on these chassis. Any opinions on where to start?
 
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I apologize I should have said. I got a pair of these cabinets and 2nd monitor works fine. used the 2nd chassis to identify the burnt resistor. I thought the yoke might be bad measured both with my meter and both ohm the same. Just to rule it out farther when I tested this chassis I put it on the known working tube. R288 and q207 both connect directly to t205 so my next test is to test that transformer.
 
The D9400's are almost as good as the D9200's when
it comes to cascade/domino failures. Basically - there's
seldom just one bad part. It's usually a string of bad parts.

Also with D9400's - you need to pull the yoke off the tube.
Many of the tubes were made in Mexico where they used a
nasty insulation coating between the yoke and the glass. The
coating destroys the yoke wires and shorts them out.

JD
 
After more component testing tonight found q206 to be shorted/open. Replaced it and now the chassis it trying to boot up but doesn't seem like it can quite full power up. The clicking is completely gone. I do have neck glow now but no HV still. Calling it a night and will keep at it tomorrow. Any suggestions are always welcome.
 
You should search previous post

but when replacing Q206 you need q205 and d208 at same time.

and check or replace r260 and c908

Q207 is the horizontal scan output transistor for deflection only.


Q901 is the HV output transistor for the flyback only pulse.

Need to know if you have no shorts around the horiz- scan transformer t203


The yoke you

need to ring it out as well with a ringer, or inspect it for damage to the windings.

you don't need the yoke for High voltage you would just have a vertical line up the center

if not working.


This chassis you need to confirm good connections to the parts on the heatsink

and no broken legs on parts.

next you have no hv you need to check voltage and if open or increased

in ohms on R901 a .33 1 watt resistor and no shorts on q901 and q903

and all the scan mosfets on the heatsinks q216-219 any of those can damage r288

if shorted using a ohm meter. just looking for a obvious short to the drain and ground.

heres the manual

http://www.wellsgardner.com/wp-content/uploads/2016/08/D9400.pdf

Your call on which circuit to fix first but I would get the high voltage up first.

whats the status of r901?
 
R901 meassure .4 ohm on my meter which isn't as sensitive as others. It measures the same on the 2nd working d9400 I have.

Q901 & q903 measures fine, no shorts.

Can't find any shorts around t203

Q216-219 also measure fine.

Any other places to check?
 
R901 meassure .4 ohm on my meter which isn't as sensitive as others. It measures the same on the 2nd working d9400 I have.

Q901 & q903 measures fine, no shorts.

Can't find any shorts around t203

Q216-219 also measure fine.

Any other places to check?

Of course you can check your yoke by subbing in the working chassis.

Need to check for missing voltages..

You need to remove or replace the vertical ic

it could be causing shutdown and no high voltage.

need to know the dc on ic201 pin 26? for horizontal drive?

What are the posted voltages measured on the electrolytic in the power supply

like c532,c534,c535.c536,c538,c537?
 
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The D9400's are almost as good as the D9200's when
it comes to cascade/domino failures. Basically - there's
seldom just one bad part. It's usually a string of bad parts.

Also with D9400's - you need to pull the yoke off the tube.
Many of the tubes were made in Mexico where they used a
nasty insulation coating between the yoke and the glass. The
coating destroys the yoke wires and shorts them out.

JD
What can be done to avoid this? Once the yoke is removed, what can be used to clean and replace the isolation coating?
 
@Hackcell @Ohmerone here's the photos of the one I've fully pulled for reference. Note the yoke on this one seems ok-ish with some small pits (most of the black stuff I was able to remove) but I don't think it's toasted. would love to know if we can scrape the coating and it'll work ok, recoat with something else, or just assume the tube is done. IMG_3162.jpegIMG_3159.jpeg
 
I'm kind of in the same boat. As my first cabinet purchase mine came with a D9400 chassis that can't be repaired. I've already purchased a D9800 chassis not knowing if it was compatible or not with my existing tube.
 
I'm kind of in the same boat. As my first cabinet purchase mine came with a D9400 chassis that can't be repaired. I've already purchased a D9800 chassis not knowing if it was compatible or not with my existing tube.
whats the symptom?
Why is the D9400 not repairable?
 
Here's a couple of pics to explain what I mean. I picked up the 9800 chassis thinking that it would be compatible with my tube. I still haven't gotten yet. Just trying to get answers before it gets here and I damage it also.
 

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Thats not the same as a open yoke.
That I haven't seen open yet,,
Just board problem's.
Looks like more that any normal failure
If you don't want to try, don't send it in they may not fix it either
I would try after i cleaned of the PCB with circuit cleaner, but
that may be a screw fell in the chassis, Or a bad connection around the HV caps
when it was working, Maybe.
Anyway Need to get a D9400 used chassis
and check it. Before switching to a unknown chassis
In my Opinion.
 
Thats not the same as a open yoke.
That I haven't seen open yet,,
Just board problem's.
Looks like more that any normal failure
If you don't want to try, don't send it in they may not fix it either
I would try after i cleaned of the PCB with circuit cleaner, but
that may be a screw fell in the chassis, Or a bad connection around the HV caps
when it was working, Maybe.
Anyway Need to get a D9400 used chassis
and check it. Before switching to a unknown chassis
In my Opinion.
That's the problem I'm having. Can't find a new or used d9400. Was only able to source a NOS 9800 chassis. My main question is is it compatible with my tube? I appreciate your help brother.
 
That's the problem I'm having. Can't find a new or used d9400. Was only able to source a NOS 9800 chassis. My main question is is it compatible with my tube? I appreciate your help brother.
Ask Chad via e-mail ONLY @arcadecup
with photos of new number and Chassis in mind
and yoke number on the yoke you going to use.
with the D9800 chassis, and if compatible
And if he has a D9400 chassis?
Check it out.
 
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