Help with Hantrex Polo 25 monitor

[shilmover]

Hi all,

I am new to this forum and have not been able to find an answer to my problem.  Here it is:

I have a Neo-Geo system that is being coverted to Mame.  I have an ArcadeVGA video card and a J-PAC board.  All was working great!  I was doing some work on the system last night and had both an external monitor and the Hantrex connected (with the Hantrex being the primary, external monitor the secondary).  I left the system for a bit and power saver mode kicked in.  Moving the mouse brought the external display back, but no the Hantrex.  Now it will not work. 

Here is what happens:
- When I power everything on, I can hear the Monitor start to warm up.
- Sometimes, I can start to see video come up (tried both with Mame and Neo-Geo with the same results).
- I then here a click (like a relay kicking in) and the display disappears to a bright dot in the middle of the screen and then goes black.
- Checked ground from the metal frame holding the Monitor PCB on to the power supply ground and its good.

While new to arcades and monitors, i have fairly a strong electrical background and I am very good at taking things apart, putting them back together, soldering, etc.  and I am willing to get dirty.   

Any idea what might cause this?  From reading the posts on the site, it does not appear to be due to the Caps (although I will probably do that too assuming I get my monitor back).

Thanks in Advance...

B

[grantspain]

its probably one of the electrolitic capacitors  in the power supply circuit of the monitor,it is worth changing all the electrolitics on the chassis as polo were very prone to cap problems
also you should check for bad solder joints giving special attention to the flyback transformer and the adjustment remote connector
worst case scenario is the horizontal deflection transistor or/and the flyback transformer

[shilmover]

Thanks.

I will try to find out where to get the Cap kit and do that.

I will let the Forum know how it goes.

[Ken Layton]

Hantarex monitors are well known for lots of bad capacitors. If your monitor has NOT had a capkit installed then do that first by all means.

Capkits are available from either Bob Roberts or Zanen Electronics or a dozen other commercial coin-op parts distributors (like Happ Controls or Amusements Plus).

[shilmover]

I don't believe it has.

One question.  I will go through the process of discharging the monitor, but I have heard that most "modern" monitors discharge automatically...  Is this one of those?

[grantspain]

all the polo's i have worked on do not keep any sizable charge,you may get a very small spark but nothing serious

[shilmover]

Thanks.  I will keep you posted.

[shilmover]

Okay...

I replaced all the Capacitors and the Flyback.

When I power the monitor back up, i get a quick flash of white at the edges, then nothing...  It makes the sound as if it is starting up and then quits...  Once I had a completely white picture for a little bit, but it went black again...

If I listen at the back of the monitor, i can hear a light click every second followed by a very faint hum, then click (hum), click (hum)... etc.

Ideas? 

Worse case, is there anyone in the Seattle area that can fix this?

[grantspain]

probably the horizontal deflection transistor shorted

[shilmover]

Okay. 

Remember, I am a real noob when it comes to monitors...   

Where is it?  How to I replace it? 

Any assistance would be greatly appreciated.

[grantspain]

did you replace the caps and the flyback yourself?if so you should be quite capable of change a transistor

[shilmover]

   I did replace them myself...

I guess what I should have asked is...  Where is it?  The board diagram in the manual I found online did not match the board I have...

[grantspain]

the transistor is at position t114 (its a bu508a)  ,the transistor may or may not have an insulation strip between it and the metal frame and depending on what transistor you get you may need some heat conductive silicon grease
normally a transistor with a part metal body will need an insulation strip whereas a plastic body transistor will need heat conductive grease
this transistor is held in place by a clip
there are one or two other things that cause your problem but this is the most common

[shilmover]

Thank you kindly...

I will check it out and replace it... 

Will update the site with how it goes.

[shilmover]

Got the replacement.  it has a metal back...  when I went to get an insulation strip, I was told that the metal has to contact the heatsink...  I am assuming that the person there is mistaken?  I did notice that there are 2 other transistors on the heatsink and only 1 is connected directly... 

Just wondering... what would happen if no insulation was used?  (just for my own info).

the transistor is at position t114 (its a bu508a)  ,the transistor may or may not have an insulation strip between it and the metal frame and depending on what transistor you get you may need some heat conductive silicon grease
normally a transistor with a part metal body will need an insulation strip whereas a plastic body transistor will need heat conductive grease
this transistor is held in place by a clip
there are one or two other things that cause your problem but this is the most common

[grantspain]

most polo1 chassis i work on have BU508AF transistors as opposed to BU508A,the AF type is a full plastic package and as so there is no need for the insulation heat strip and only heat conductive silicon grease is required.
Whilst checking some older polo chassis today i came across one that had a BU508A transistor and it did indeed have the insulation strip.
I am pretty sure without that strip your chassis will go in to shutdown as there will be a short between ground and the collector of the transistor.
If your transistor is the same then you should have that insulation strip on the metal fixing plate still.

[shilmover]

Thanks...

The original one was plastic, the new on is metal...  i will get an insulating strip.

Need to get a new clip too... the original just snapped when I took it off.

[grantspain]

the insulation sheet is heat conductive,you would be better off getting a BU508AF plastic package transistor-i am not sure where you could get a clip apart from an old chassis.
are you in the states or europe?

[shilmover]

I am in the States... 

One more quick question... when I connect the clip from the flyback, how far in does it need to go?

[grantspain]

I am in the States... 

One more quick question... when I connect the clip from the flyback, how far in does it need to go?

do you mean the transistor retaining clip?

[shilmover]

no, the clip with the suction cup that attaches to the tube

[grantspain]

ohhh the anode cap,basically if you look you will see that the clip  bends out on each side-you need to pull back the rubber cap so you expose the clip(only just so you can see the clip) then push one side of the clip in to the hole of the tube then you just push the other side of the clip in-using left to right pressure(not too much)
if you pull on the anode lead it should then stay in place,after that point you can let the rubber anode cap back into position

[shilmover]

Ok.

I have swapped the capacitors, the flyback and the Horizontal Transistor.  Same problem.  I have even tried a couple of different transistors (just to make sure) and put the original flyback back in.

Nothing.  Nada...

Powers on... flash of white along the edges, makes the sound of starting up, then nothing...

Just checked the voltage going to the monitor...  there is about 125V going into the cabinet and about 137V going from the Powersupply to the Monitor board.

Ideas?  Getting dis-illusioned...   

[grantspain]

do you have a orange glow from the neck of the tube?
does the monitor make a ticking/chirping noise?
if you turn up the screen volts do you get a white screen?

[shilmover]

do you have a orange glow from the neck of the tube?

No

does the monitor make a ticking/chirping noise?

Yes, at the start, then quiets down

if you turn up the screen volts do you get a white screen?

No

[grantspain]

check d117,d115 check 145v at tp6

[shilmover]

check d117,d115 check 145v at tp6

Sorry for the noob question...

How do I check d117,d115 (been a while since high school electronics)   

[cw]

with a multimeter


http://img.epinions.com/images/opti/f9/2e/hmgd-Shop_Tools-All-Fluke_112_Digital_Mulitmeter_112-resized200.jpg
 


wow what a link

[grantspain]

be careful these are lethal voltages in this circuit,don't attempt unless confidant

[shilmover]

I am confident in doing it, but which lead should i check across?

B

[cw]

ground to chassis

[shilmover]

Thanks...

I am out of town for next week, but will try next weekend...  Will keep everyone informed.

[shilmover]

Okay..

I ended up getting another board for this monitor (complete).  When I plug it in, i get a "chirp" every second or so...

I did notice that this board had a flyback replaced and one of the contacts seems to have lifted.  Also, on the neck board, the wire going from the flyback to the white connector seems to be soldered then glued on (on mine, there is a plastic cover protecting it).

Ideas?

[grantspain]

thats the monitor supply circuit in trip,normally caused by bad transistor at T114 or bad solder joints.
not getting much luck are you

[shilmover]

thats the monitor supply circuit in trip,normally caused by bad transistor at T114 or bad solder joints.
not getting much luck are you

Nope

But learning lots   

[grantspain]

the new monitor was seen working?

[shilmover]

the new monitor was seen working?

I bought it (BTW, it was just the control boards, not the tube) as unknown state.  However, after seeing the mods done to the board, I think I was had.

BTW, I am assuming from your name that you are from Spain?  where?

[grantspain]

i am near malaga

[shilmover]

I'm going to be in Barcelona in November...  only 1000KM...   

[grantspain]

barcelona is one hell of a great city,i hope you have a great time
back to your polo problem,i suggest you reinstall the original monitor and then let me know if you have a glow from the neck