Repair help: Wells-Gardener K7000 series

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Hi,

First of all, I'm from Denmark so please bear over with my english skills.

I got a Wells-Gardener K7000 series monitor, which I'm trying to fix. I got
a schematic of the monitor, but I can't seem to find the fault.

The problem is; when it's powered on, nothing happens on the screen. I have
measured the DC voltages, and they are all about 1/5 to small. For example,
the 12VDC is 2.8VDC, the 24VDC is 5.2VDC. If i measure directly on T1 (don't
know what the component is called in english - transformer ? ) I get 10VAC
(on the 12VDC line) and 15VAC ( on the 24VDC line) - so my DC voltages are
all messed up. The B+ is about 145VDC - according to the schematic, it
should be 123VDC - so that must be OK.

The pulses on the base of the HOT (2SD1398) are ok. On collector of the hot,
I measure 400Vpp - isn't that a bit low? When I measure the HOT aout of the
circuit, it's OK from B-E and B-C. Between C-E it's only about 51 ohms - is
that okay ? I can't finde a datasheet on the damn thing.
The flyback capacitors (C36) looks fine. It's 3 capacitors parallel with
eachother.

Any advices what to do or trye ?

Hope I have expressed myself somewhat understandable.

Best Regards Brian

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

This monitor develops many bad solder joints (especially around the
area of resistor R89).

Have you recapped this monitor?

The flyback transformer is a high failure item on this model so it
could be bad.

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Measure the DC Voltage with your meter. The black on the metal chassis
and the red on one side of the big white resistor you see mounted on
the metal part, next to the transformer. Then measure the other side.
Write them down and email me at StateStreetAmusements@hotmail.com. I
will tell you the next step in the Randy Fromm flow chart. I don't
have it in front of me at the moment.
Russ

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

The B+ regulator is shorted.....its in shutdown mode. Replace that and
you should be OK (STR30130 or STR3130 depending on chassis).

 

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Ken Layton wrote:
> This monitor develops many bad solder joints (especially around the
> area of resistor R89).

I will check that...

> Have you recapped this monitor?

Only the ones who needed - I have measured them all with an
ESR meter. C57 was BTW measures "open" - one of the legs were
disconnected from the cap itself.

> The flyback transformer is a high failure item on this model so it
> could be bad.

Hope it isn't that bad.

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

If you read 145v on *both* sides of the 25w white ceramic resistor
above the regulator ic, it's shorted. One side has the raw filtered DC
feed and the other is the regulated B+. Normal B+ for that chassis
should be around 123vDC. Very common problem for the 7000 chassis. B+
goes high, the horiz. section shuts down, thus "nothing" is happening.
Its a built in safety feature.....HV to the tube raises in tandem with
the B+ voltage. Too high a HV supply to the tube causes it to emit
x-rays.....which you don't want a dose of.

 

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

boardjunkie wrote:
> The B+ regulator is shorted.....its in shutdown mode. Replace that and
> you should be OK (STR30130 or STR3130 depending on chassis).

I will try that. I had just ruled the B+ regulator out, because I still had
a B+ around 145VDC. When I replace that, will the rest fix itself as
well - I mean, the low voltages I get from the transformer.

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

In that case......toss that chassis in your junkpile and find one that
has not had the protection circuit tampered with. Unless you know how
to calibrate it, its not worth dickin' with.....unless you like to glow
in the dark ;-)

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Before I replaced any parts in the protection circuit I'd make sure the
hold down adj pot hasn't been messed with. Its normally gooped in
varnish so it won't move....for a reason. There should never be a
reason to adjust it and WG doesn't want anyone fooling with it. If
someone has been dumb enough to disable this circuit, they may have
been dumb enough to try to break off the varnish and fool with that
pot. There is no calibration procedure detailed in the manual because
if someone tries to do it and does it wrong, everyone who plays the
game is at risk of x-radiation exposure. In other words....it's the
mfgr's ass if this circuit doesn't work.

Replace the diode with the exact part specified in the parts list of
the chassis if the shutdown adj. pot has not been tampered with.
Troubleshoot the B+ problem. If the regulator is in fact good, the B+
supply to the flyback may have opened up. When this happens, B+ will be
abnormally high due to lower than normal load...and the protect circuit
should engage. Get out yer meter and check integrity of the trace
feeding b+ to the flyback primary winding. I have seen a cracked trace
cause this on a few 7000 chassis.

I'm not intending to be a dink here, I just wouldn't like to see you or
any user of this monitor to be in danger of radiation. Its about as
good for you as eating a roll of solder.......




Brian wrote:
> boardjunkie wrote:
> > In that case......toss that chassis in your junkpile and find one that
> > has not had the protection circuit tampered with.
>
> Can't I just replace D10 ?
>
> > Unless you know how
> > to calibrate it, its not worth dickin' with.....
>
> If it ins'nt in the service manual how to calibrate it, I don't
>
> > unless you like to
> > glow in the dark ;-)
>
> I'm not using the screen myself - in this case it isn't used in a videogame,
> but in a old wheel alignment machine

 

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

boardjunkie wrote:
> In that case......toss that chassis in your junkpile and find one that
> has not had the protection circuit tampered with.

Can't I just replace D10 ?

> Unless you know how
> to calibrate it, its not worth dickin' with.....

If it ins'nt in the service manual how to calibrate it, I don't

> unless you like to
> glow in the dark ;-)

I'm not using the screen myself - in this case it isn't used in a videogame,
but in a old wheel alignment machine

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Someone messed with the hold down circuit to try to get the chasis to
operate with abnormal b+....not the best idea. You can check the horiz.
output transistor by metering from the heat sink to the tab of the
transistor. If it shows a short...replace it. Replace the jumper or
whetever goes there for the flyback feed.

Those IC regulators fail from heat or some other stress, like a shorted
horiz output. They aren't as robust as the older to-3 case regs.
Sounds like it'll live. Replace the regulator and everything else that
needs it and it should be good to go.

 

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

boardjunkie wrote:
> Someone messed with the hold down circuit to try to get the chasis to
> operate with abnormal b+....not the best idea.

All in all has the previous technician on this monitor, been somewhat lousy.

> You can check the
> horiz. output transistor by metering from the heat sink to the tab of
> the transistor. If it shows a short...replace it. Replace the jumper
> or whetever goes there for the flyback feed.

Will do - from ground to collector I got ~13Kohm

> Those IC regulators fail from heat or some other stress, like a
> shorted horiz output. They aren't as robust as the older to-3 case
> regs. Sounds like it'll live. Replace the regulator and everything
> else that needs it and it should be good to go.

Just ordered 3 new ones, I'll report back with the result.

 

[Brian]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Brian wrote:

> Just ordered 3 new ones, I'll report back with the result.

Finally got the B+ voltage regulator. Then I got another problem - smoke
from the big transformer :-(
It's shorted between pin 3 and 5/10. Where do I find a new one ?