DK Sanyo 20EZ Low B+ Voltage

[rye]

Hi everyone. I have a Donkey Kong cabinet I am restoring and am having some difficulty with the monitor.

I have been able to adjust it so the video is fairly reasonable, but notice the B+ voltage is quite low ~88V. There is the typical bit of a wave across the screen and also the screen kind of shakes with varying amounts - almost like it is slowly breathing

The problem is adjusting B+ via VR601 does not change the B+ voltage much (maybe only +- 1V).

Does anyone have any advice what I might be wrong or advice what I might start to look at in order to get the B+ up to the required 108V?

Thanks,
Ryan

 

[Dokert]

Test the B+ pot through it's range with no power applied, your B+ pot may be bad.

If you have a wave across the screen, your filter cap C606 is bad and needs to be replaced.

Next in line is IC601 the voltage regulator, followed by the current limiting transistor.

 

[rye]

Dokert - thanks for the quick reply.

I've checked the B+ pot as you've suggested and it does go through the 5k range as expected. I will seek out a source for the regulator and replace as you've suggested. The monitor was re-capped but none-the-less I will also replace C606 while I am at it as the wave is incredibly annoying.

Thanks for the help - will post the results once the parts arrive.

 

[Dokert]

Bob Roberts has the filter cap, regulator IC and current limiting transistor.

Cap kits do NOT normally include the filter cap.

Also while you are waiting for the filter cap to come in, verify that the caps were installed correctly as far as polarity goes. Look for broken and or cracked traces in the 600 section of the chassis. Don't be afraid to meter out the traces from point to point in the 600 section, as rough handling during a cap kit install can lead to broken traces and or cracked solder joints.

 

[Michael Roma]

Dokert,

Where is the current limiting resistor on the chassis?

- Mike

 

[Dokert]

Dokert,

Where is the current limiting resistor on the chassis?

- Mike

Q901 on the silver heat sink, left side of the chassis. (Opposite side from the fly)

 

[rye]

Hi Dokert. I was able to replace the regulator IC, the current limiting transistor as well as the filter cap with parts from Bob Roberts.

Good news - After adjustments, I now have full B+ with an AMAZINGly nice bright picture. It looks great!

I still do have the wave however....

Can you think of anything else causing the wave?

Thanks for all your help,
Ryan

 

[Deadly]

Ensure you have a ground pin on the AC cord.
Run a seperate ground wire from the monitor chassis to the ISO
If plugged into a power splitter - eliminate it
Try running electrical cord to a different power outlet (different circuit)
If possible swap power supplies.

If all items fail wait for Dokert

 

[rye]

Ensure you have a ground pin on the AC cord.
Run a seperate ground wire from the monitor chassis to the ISO
If plugged into a power splitter - eliminate it
Try running electrical cord to a different power outlet (different circuit)
If possible swap power supplies.

If all items fail wait for Dokert

Hi Deadly. Thanks for the suggestions.

The monitor actually didn't have a separate ground cable, so I added one. Unfortunately, neither this, nor a newer power supply I swapped in, nor another power circuit made any difference.

Ryan

 

[rye]

Update: I have seen a few other posts as well describing the same wave as I am getting. In addition to trying each of those suggestions I have also swapped out my DK board for a DK Jr. board to see if the game PCB was the culprit.

No such luck. The wave is identical on both game PCB's. The monitor appears to be the problem.

Does anyone have any other suggestions? I am a little lost to what to try next... Short of buying a new monitor that is.

Everyone's help is much appreciated.

Thanks,
Ryan

 

[Dokert]

Set your meter for 200vdc and take the readings for IC601 on pins 1 thru 9. Post readings. Also take a voltage reading on the collector of Q901. (Center pin is the collector) http://www.datasheetcatalog.org/datasheet/toshiba/3233.pdf

 

[rye]

Dokert, I have the following readings:

IC601
Pin Voltage
1 122.0
2 118.8
3 108.0
4 116.0
5 115.3
6 123.6
7 106.9
8 124.6
9 123.5

Q901 Collector
132.4 V

Thanks,
Ryan

 

[Dokert]

Dokert, I have the following readings:

IC601
Pin Voltage
1 122.0
2 118.8
3 108.0
4 116.0
5 115.3
6 123.6
7 106.9
8 124.6
9 123.5

Q901 Collector
132.4 V

Thanks,
Ryan

Test resistance with power off on the following:
R605
R606
R607
R608
R610
R614
R615

 

[rye]

Test resistance with power off on the following:
R605
R606
R607
R608
R610
R614
R615

R605 39k3
R606 9k93
R607 9k99
R608 3k89
R610 99k9
R614 Jumper - Has spot for, and is labelled as R614, but factory jumper is installed
R615 Not found on PCB... (Or on schematic I have been using)

Thanks,
Ryan

 

[Robotron Jon]

Well, if you have given up on doing it yourself, you could send it to P&L Monitor Repair in Baldwin Park, Ca. I had them fix a few of these monitors and had no problems afterwards.

I think it's $44 flat rate for repairing that chassis.

There is a 30 day warranty.

 

[Dokert]

R605 39k3
R606 9k93
R607 9k99
R608 3k89
R610 99k9
R614 Jumper - Has spot for, and is labelled as R614, but factory jumper is installed
R615 Not found on PCB... (Or on schematic I have been using)

Thanks,
Ryan

Pull R605 & R608 and measure them out of the circuit. R615 should be the big ass white one that connects to BJ/TP91 IIRC.

I have seen some of P&L's work and I can not in good faith endorse them for monitor chassis repairs.

 

[rye]

Pull R605 & R608 and measure them out of the circuit. R615 should be the big ass white one that connects to BJ/TP91 IIRC.

Hi Dokert. The big white one connecting BJ / TP91 is R609. It's in-circuit resistance measurement is 180 - Bang on.

R605 and R608 out-of-circuit measurements 39k0 and 3k80 respectively. All the resistors I measured were to specification. The schematic I have been using, which seems to match my PCB is: http://www.jrok.com/schem/20ez.pdf

Thanks,
Ryan

 

[Dokert]

This is really weird, 6 out of 9 voltages measured on IC601 are out of tolerance. It looks like everything feeding IC601 is good. Makes me wonder if you got ahold of a bad IC601?

Check IC601 for solder bridges/splash, and take a really close look at the traces going to and from IC601.

 

[Dokert]

Dumbass question of the day... Did you remember to hook up the ground wire when you put the monitor back into the cab?

 

[rye]

Not a dumb question at all. Yes, all the grounds are connected...