Amplifone - graphics look great but bright dot in middle. :(

jehuie

Well-known member

Donor 2011
Joined
Sep 8, 2007
Messages
10,947
Reaction score
1,672
Location
Martinez, California
Amplifone - graphics look great but bright dot in middle. :(

Ok I'm making a new thread for this just because I think the other one was getting to cluttered and confusing. This monitor on this Star Wars works good and the graphics are all there and everything but there's a constant bright dot in the middle. If I turn the brightness down enough for the dot to go away then I can't see the other graphics at all.

Here's what I've tried so far:

- Bought a whole slew of components from Bob Roberts to rebuild the deflection board and HV board
- HV is good.
- B+ is good.
- Adjusting color drives doesn't help. Brightness down and the color drives up still won't let me turn down dot enough to see graphics well.
- I don't have any spare parts to swap in. I only have 6100 vectors other than this.
- double checked continuity from focus block wiring, all connections under boots are good. Good continuity back to HV board and color drives on deflection board are good.
- Pins on neck not shorted to heater pins. (Except pin 4 which isn't used - could this be a problem?)
- W jumpers are all long gone.
- Resistors in neck board/ring are good.
- Does same thing with known working PCB set.
- Reflowed J103 and tested continuity along wires.
- Ground to neck board/ring is good.

Still not sure how to check Z signal. What components should I be looking at that are common to all 3 colors that could be causing this?

Any other idea?

Thanks everyone. I'm working on this for a friend of mine and just about at the end of my rope.
 
I am assuming your still not sure if this is a board or monitor problem?
You say you have other games with a WG 6100 ?
Why not put this game next to your 6100 game and unplug the 6100 and run the wires from the problem game to the known good 6100 and find out if it's the board or monitor. I don't have a game with a 6100 just the Amp but are they not 100% compatible? Someone here should know for sure. Once you find out where the problem lies then you can focus on fixing it.
 
I am assuming your still not sure if this is a board or monitor problem?
You say you have other games with a WG 6100 ?
Why not put this game next to your 6100 game and unplug the 6100 and run the wires from the problem game to the known good 6100 and find out if it's the board or monitor. I don't have a game with a 6100 just the Amp but are they not 100% compatible? Someone here should know for sure. Once you find out where the problem lies then you can focus on fixing it.

Do you mean the game PCB? I've swapped that out and I know it's good. Or do you mean the deflection board? I don't think it's compatible with a 6100 tube is it?
 
Do you mean the game PCB? I've swapped that out and I know it's good. Or do you mean the deflection board? I don't think it's compatible with a 6100 tube is it?
Does same thing with known working PCB set.
Guess I missed that part :eek:
Yes I was talking about the game board. I didnt know it was tested and known working . So the board set was tested in another game with another monitor with no problem. If so it must be a monitor problem.
No non of the parts of the 6100 will work in the AMP.
 
Last edited:
Ok I'm making a new thread for this just because I think the other one was getting to cluttered and confusing. This monitor on this Star Wars works good and the graphics are all there and everything but there's a constant bright dot in the middle. If I turn the brightness down enough for the dot to go away then I can't see the other graphics at all.

Here's what I've tried so far:

- Bought a whole slew of components from Bob Roberts to rebuild the deflection board and HV board
- HV is good.
- B+ is good.
- Adjusting color drives doesn't help. Brightness down and the color drives up still won't let me turn down dot enough to see graphics well.
- I don't have any spare parts to swap in. I only have 6100 vectors other than this.
- double checked continuity from focus block wiring, all connections under boots are good. Good continuity back to HV board and color drives on deflection board are good.
- Pins on neck not shorted to heater pins. (Except pin 4 which isn't used - could this be a problem?)
- W jumpers are all long gone.
- Resistors in neck board/ring are good.
- Does same thing with known working PCB set.
- Reflowed J103 and tested continuity along wires.
- Ground to neck board/ring is good.

Still not sure how to check Z signal. What components should I be looking at that are common to all 3 colors that could be causing this?

Any other idea?

Thanks everyone. I'm working on this for a friend of mine and just about at the end of my rope.

Could be the Spot Killer circuit.

Start by Checking Q26 and then work your way back to Q8, Q9, and Q10.
 
Could be the Spot Killer circuit.

Start by Checking Q26 and then work your way back to Q8, Q9, and Q10.

Thanks. I'll check that just to be sure but I'm pretty sure spot-killer is working correct for some other reasons.

Someone on vectorlist mentioned to check to be sure the Z signal is actually fluctuating and not constantly on high. I don't know how or where to measure this though. Anyone else know?
 
Could be the Spot Killer circuit.

Start by Checking Q26 and then work your way back to Q8, Q9, and Q10.

Pulled and checked each of those transistors and they test fine. Also checked CR5, CR6, CR7, CR8, CR9, CR10 and a bunch of resistors in that circuit. Nothing pops out as being troublesome. I didn't test every last component.

I do have a rejuvinator on the way so maybe it will tell me if there's a short in the tube. Any other good ideas?
 
Pulled and checked each of those transistors and they test fine. Also checked CR5, CR6, CR7, CR8, CR9, CR10 and a bunch of resistors in that circuit. Nothing pops out as being troublesome. I didn't test every last component.

I do have a rejuvinator on the way so maybe it will tell me if there's a short in the tube. Any other good ideas?

Well, I've got a similar issue with my Asteroids. I replaced the two TIS98's on it, and it fixed it for the first 5 mins the game is on, then the dot and circle appear again. I'm going to replace the Resistors in the Spot Killer section next and see if that fixes it.

While the parts may test fine outside of the monitor, they might still be bad (under load). I'll let you know how my issue works out.

According to the manual (page 8 [15 of the PDF]), when Q26 turns off, then the Z Amp is turned off. So if for some reason Q26 doesn't turn off when the beam is in the center of the screen, then I would expect you to get a dot. If that's the case, then the million dollar questions is, is why is Q26 not being turned off... Possibly an issue with CR23?
 
According to the manual (page 8 [15 of the PDF]), when Q26 turns off, then the Z Amp is turned off. So if for some reason Q26 doesn't turn off when the beam is in the center of the screen, then I would expect you to get a dot. If that's the case, then the million dollar questions is, is why is Q26 not being turned off... Possibly an issue with CR23?

Yeah, I could just buy all the parts to completely rebuild the spot killer circuit. I would do that in a second if I was sure that's where the problem is. I have a couple people telling me they are almost certain the tube is bad. But that doesn't really jive with what the seller told me when I picked up the game. Of course, sellers aren't always reliable. :)

Does the spot killer actually come on during normal game play though? I thought it only came on when there were actual problems with deflection.
 
Yeah, I could just buy all the parts to completely rebuild the spot killer circuit. I would do that in a second if I was sure that's where the problem is. I have a couple people telling me they are almost certain the tube is bad. But that doesn't really jive with what the seller told me when I picked up the game. Of course, sellers aren't always reliable. :)

Does the spot killer actually come on during normal game play though? I thought it only came on when there were actual problems with deflection.

My understanding is that the Spot Killer comes on when there is

1. No input signal (i.e. PCB is unplugged, or isn't putting out video)
2. No deflection in the X and Y (monitor problem)

Not sure how a bad tube would cause the dot in the center, but anything is possible. It won't hurt to test the tube thats for sure.

Now the problem itself might not be in the actual Spot Killer circuit, but what feeds it, which I think is the Q26.
 
Hey jehuie

Is it a 25" or a 19" tube? (IE C/pit or upright)

Have you seen my thread here
http://forums.arcade-museum.com/showthread.php?t=180892

Send me the Tube's part number and I will tell you if it's compatible

12 pin 19" and 25" TV Tubes are common

Yes, I saw that. Cool stuff. This is only a 19" monitor though. Isn't that the hard one to find a tube for? I guess it could be cool to try to cram a big 25" monitor in an upright cab and see what it looks like. :)
 
My understanding is that the Spot Killer comes on when there is

1. No input signal (i.e. PCB is unplugged, or isn't putting out video)
2. No deflection in the X and Y (monitor problem)

Not sure how a bad tube would cause the dot in the center, but anything is possible. It won't hurt to test the tube thats for sure.

Now the problem itself might not be in the actual Spot Killer circuit, but what feeds it, which I think is the Q26.

Yes, that was my thought. But I clearly have an input signal since I'm getting the other game graphics. And I'm getting deflection (same reason). So I think spot-killer is a dead end. Not smart enough to know for sure.
 
Do you have an HV probe?

Can you measure the screen voltage, focus voltage and Anode voltage?

I don't have one but I can borrow one from (FETLP) Fry's Electronics Tool Loan Program again. I've tested the voltage at the anode but not the other two places. The screen and focus are working....how would voltages being off in those two places cause this?
 
It would be good to rule it out. If one or more voltages is out of range then you could get a spot in the centre.

What is the range for focus and screen? Do I need a HV probe for those 2? Seems like it would be hard to get it down in there with the game powered on.
 
Back
Top Bottom