FIXED!!!!!!!!!!!!!!: WG 19K4901: Blue Color Missing - Thanks Guys!

[WhereEaglesDare]

I have a StarGate Cabinet that was converted to Rough Ranger.
The gameplay has a bad yellow tint.



It is a WG 19k4901



Here it is with Red Down and Green Up



Here it is with Green Down and Red Up

When I adjust the blue nothing happens so there is no reason to post that picture.



Here it is tuned as well as I can get it.



GamePlay



This is how it should look.

I checked the cabling and I reseated the neckboard...  any ideas?  any help?

[WhereEaglesDare]

Found that one of the transistors had a lot of flux built up on it so I reflowed all the transistors and cleaned them up some.


Q401
B  9.73    Typically should be 9.7
E  8.97    Typically should be 9.3
C  64.7    Typically should be 139

Q402
B  9.77    Typically should be 9.7
E  9.00    Typically should be 9.3
C  79.7    Typically should be 139

Q403
B  10.4    Typically should be 9.7
E  10.2    Typically should be 9.3
C  135.9  Typically should be 139

As you can see both Q401 and Q402 are reading low on the Collectors when both the Base and Emitter voltages should be within tolerance.

Ironically the Q403 is the only one with a Collector in tolerance and that is the blue out.

What do you think is the culprit?

[lilshawn]

well... switching the blue transistor with the red one will provide you with a few answers.

if the red no longer works, it's the transistor.
if the blue still doesn't work, it's something else... maybe r415? or r407 / r408 maybe even VR405 could be bad... quick and dirty check is to set it to about the same value as the red or green one and compare the reading.

[shagster]

If you wanted to be sure its not the Q403,you could remove it and do a diode test with your dmm.You prob dont need this,but it helped me http://www.elexp.com/t_test.htm Scroll down the page to transistors

[WhereEaglesDare]

Okay I think my measurements are off, I was looking at the schematic and it looks like the dials are on the emitter of the transistors and controller the collector's voltage.  I'm going to get new readings, I think they all may be in tolerance.

[Kevin Mullins]

Also check the header pins where the video cable plugs into the main chassis for cracked solder joints as well.

I don't know how many times I've seen missing colors simply because there was no input for that color because of a bad solder joint.

You could also swap the red and blue, or green and blue video input wires to verify if it is a chassis or game pcb issue.
If you apply the red (or green) signal to the blue input and get blue on screen, then it is a game pcb or cabling issue.

Has the tube itself been tested with another chassis or crt tester/rejuvinator ?

[WhereEaglesDare]

Has the tube itself been tested with another chassis or crt tester/rejuvinator ?

no, i dont have a way to test it, it wasnt working when I got it.

 but great idea swapping inputs, put red on the blue and checking the input pins.

Lets see what happens...

[WhereEaglesDare]

Okay I tested the blue line in the JAMMA Harness and it is good.

I OHMed out the input pin to the first contact on the chassis which is to R232, so it is going from the JAMMA Board to R232 on the chassis, so I know that is good.

I swapped red and blue and I still couldn't get any blue, but I was able to get the Red and Green Signals.  If I pull the red splice open I get only green and no blue.

I went back and retested the transistors on the neck board and found that they are indeed within tolerance, when the gain is turned down.

It is safe to say that the problem is inside the monitor somewhere...  unfortunately...

Back to the drawing board...

[lilshawn]

your blue gun might be toast...

you can check by taking the red/green signal coming out of the transistors and injecting it to the blue... if you get blue, you missed something in the blue circuit...if still no blue, bad gun.

just lift out the front side of R415 right before it goes to the gun and the front side of r413 solder a wire to the free end of the 413 resistor and into the blue hole left from r415 this will bypass everything blue... since red/green is working if you can't drive the blue gun and get ANY blue using the red/green circuit, the gun is done... you will need to consider having the gun cleaned/rejuvenated.... but most possibly a tube swap.

[WhereEaglesDare]

A guy on the KLOV forums AND LILSHAWN HERE suggested swapping Q401 and Q403 to see if blue will come up and if the red goes away and the damnest thing happened...



HAHAHAHAHA  

Now I just need to order some replacement transistors (I'll go ahead and replace all three) and I should be in business!

Will follow up after I get the neckboard repaired, I'm also planning on ordering a cap kit.

Thanks guys for all your help.  We'll see if this will fix it.

BTW its a NPN Transistor 2SC2068 or 2SC1514
PN: 200x3206-800

and Mouser doesn't have either PN or Description on their site so its now time to decode this!

Any help?

[smalltownguy]

Yeah, that 'guy' was me

Glad to see you're tracking this one down.

If you need assistance in crossing xsistor parts, use Digi-Key's 'chat' service. If you can get hooked up with a tech, they'll get your answer in a jiffy. I LOVE their chat service for that.

[newmanfamilyvlogs]

Is it just me or does it seem like blue goes out the most commonly? This makes at least the third mo.igor I can think of recently with missing blue due to bad transistors, my own included.

[WhereEaglesDare]

Yeah, that 'guy' was me

Glad to see you're tracking this one down.

If you need assistance in crossing xsistor parts, use Digi-Key's 'chat' service. If you can get hooked up with a tech, they'll get your answer in a jiffy. I LOVE their chat service for that.

Talked to Digi-Key

Here is the datasheet for the 2SC1514
http://www.datasheetcatalog.org/datasheets2/44/44397_1.pdf

They said that don't carry it, but according to them this may be the closest that they carry.
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000930.pdf

I see some discrepancies between the two.  Could you take a look and see what you think?

[MKFan4Life]

Is it just me or does it seem like blue goes out the most commonly? This makes at least the third mo.igor I can think of recently with missing blue due to bad transistors, my own included.

Yeah, I was another guy with a bad transistor causing missing blue output recently on a WG-K7400.  Replaced all 3 and everything has been great for a while now.  Before that, my K7197 had poor blue and it was an almost dead blue gun in the tube.  Rejuvenation didn't help it though it improved red and green emissions making the problem MORE noticeable, lol!  Blue... dang you!!!

[shagster]

These guys do them and they ship worldwide http://www.littlediode.com/components/2SC1514_Transistor.html?gclid=CMf4zafA1KYCFQJO4QodagKVHw

[Ken Layton]

MCM Electronics has it:

http://www.mcmelectronics.com/product/2SC2068

[WhereEaglesDare]

 

2SC2068 - Neckboard Amplifying Transistors - $.60 http://www.mcmelectronics.com/product/2SC2068

I'm going to buy a handful so if anyone else needs some in the future contact me if you can't find any.

[shagster]

Good spot ken
Huge price difference,as usual we get fleeced for anything like that over here

[Ken Layton]

Anytime you need any kind of 2SAxxxx, 2SBxxxx, 2SCxxxx, or 2SDxxxx series transistors, check with MCM Electronics. They stock a lot of semiconductors for television/monitor/amplifier applications. They also have the "STR" and "STK" series of regulators and the "LAxxxx" series of vertical output IC's.

[WhereEaglesDare]

Capped the chassis and replaced all 3 transistors on the NeckBoard.





Thanks again guys!  Look great!

[smalltownguy]

Very nice! Always nice to see one more saved from the scrap heap.

[MKFan4Life]

Glad you got her working again.