B+ voltage Donkey Kong

[Robotron Jon]

How do I check the B+ and make sure that it is 108vdc on my Donkey Kong 20 EZ monitor? Every once in a while it flutters like there is either too much or too little power.

Sorry for the retread, I tried to search for the numerous threads about this but couldn't find them.

 

[ScumBum]

http://www.youtube.com/watch?v=2LqmDMEI1fI

 

[Deadly]

Black lead on ground, red on TP91

 

[Robotron Jon]

Deadly - that's the wrong lead. It's BJ.

I put it on BJ, and put the negative on the chassis.

My reading was 90 volts.

I started to turn the b+ adjustment and some white caked stuff came off it. Maybe it fell apart from age. I turned it more and more and nothing changed at some point it went to zero. Then I accidentally touched the negative and positive leads together and now the game is totally dead except for the light on the switching power supply.

Anyone have any idea why it's dead now?

Does anyone have an actual picture of the b+ adjuster on this chassis?

Fuck......


PS That video is pretty lame, you really can't see much of anything on the board when he's fooling around with it.

 

[Michael Roma]

If I recall TP and BJ 91 are the same.

Reference the below diagram (the main pwb) for where the TP/BJ and B+ locations are.

- Mike

 

[Deadly]

Telling people they're wrong and saying their attempt to help is lame and sucks isn't a real motivator for people to want to help you.

Crusty white shit off the B+ pot is old glue.
Totally dead - you probably either smoked one of the two fuses on the monitor (yes the amp depends on the chassis having power and you won't have any sound).

You never mentioned if your marquee ever worked - if it did and has no power now - then your power supply is probably toast.

 

[Dokert]

Deadly - that's the wrong lead. It's BJ.

I put it on BJ, and put the negative on the chassis.

My reading was 90 volts.

I started to turn the b+ adjustment and some white caked stuff came off it. Maybe it fell apart from age. I turned it more and more and nothing changed at some point it went to zero. Then I accidentally touched the negative and positive leads together and now the game is totally dead except for the light on the switching power supply.

Anyone have any idea why it's dead now?

Does anyone have an actual picture of the b+ adjuster on this chassis?

Fuck......


PS That video is pretty lame, you really can't see much of anything on the board when he's fooling around with it.

Brother, take a break and have a beer.

Deadly is correct TP91 and BJ are the same point.

The video isn't the best, but it was an effort to show folks what to do. Technically it is correct too.

I am a big guy, and have a hard time getting my big meats in there to adjust B+ on a Sanyo. I made a B+ wire jig, and can set B+ outside of the frame so to speak. All you need is a piece of scrap wire and a couple of red butt connectors. Slide the one end down on TP91/BJ and put your red meter lead into the other end.

You will need to check your fuses first, and hope that is all that you blew when you touched the leads together.

Also set the B+ pot to the center before starting, now that you have 0vdc.

 

[Robotron Jon]

I'll take a look. Thanks for the help and sorry for the misunderstanding. The BJ test point and TP91 are next to each other. TP 91 has a wire attached to it and the wire is so close to the board that you can't attach anything to it, at least in my situation.

I'll take a look at the fuses.

Perhaps the B+ pot needs to be replaced. Does Bob Roberts sell those?

Thanks again.

 

[Dokert]

Yes, Bob does.

Verify your fuses with a meter to get started again.

There is a cap in the B+ circuit that will cause the B+ to jump around when it is failing. Probably wouldn't hurt to do a complete cap kit also.

 

[Robotron Jon]

Thanks.

I capped this chasiss recently.

I put in a new fuse and the reading is 89v. Hmm. Turning the pot doesn't make any difference in the reading, up or down. Is this indicative of a bad pot?

Thanks again.

 

[Deadly]

Possible the pot is bad - but also possible the voltage regulator is bad on the board.

 

[Robotron Jon]

Thanks for the help.

Are there any other symptoms of a bad voltage regulator?

 

[Dokert]

I would say that the pot is suspect. The white crap that came out of the pot originally may have been part of the pot crumbling.

VR could be bad, it is possible.

 

[Robotron Jon]

I'll order the pot and see if that does the trick.

Thanks for all the assistance.

 

[Robotron Jon]

I put in a new pot and a new voltage regulator. Still getting only 89v on the test point. turning the pot in either direction has no effect at all.

Anyone else have any ideas about why the HV is low?

Hmmm...

 

[Dokert]

This one is going to be loads of fun. It would appear that touching the leads was a very bad thing.

Take a reading at the 4 amp fuse and see what you get. (AC input)

Take a reading at the little fuse and see what you get. (DC)

 

[Robotron Jon]

Thanks for the reply, I'll take a look.

This is the same problem I had before I touched the leads and blew the fuse. Turning the pot up or down makes no difference in the voltage reading. Is there a way that the pot can be bypassed in the event of the failure of something else in the chassis? I already capped it, replaced the pot, and replaced the voltage regulator.

This game also has a switching power supply. Not sure if this can cause an issue.

 

[Dokert]

The switcher has nothing to do with the monitor.

We need to identify your voltage problem and go from there.

You need 100vac coming in, and going to the little trans on the deflection board.

The DC coming off of that little trans is what I believe feeds the B+ and is adjustable.