(Topic ID: 255383)

Weak insert lights (Bally 1978)


By nibre

8 months ago



Topic Stats

  • 25 posts
  • 10 Pinsiders participating
  • Latest reply 8 months ago by Quench
  • Topic is favorited by 2 Pinsiders

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#1 8 months ago

The insert lights (and the center bumper light) are weak on my Strikes and Spares. I measured the voltage to 1.8V. The test points TP1 and TP3 on the lamp driver board is 5V. The GI lights are ok.

Any advice?

#2 8 months ago

Take your meter,follow the 5V along until it drops. Then fix the bad connection, solder joint, light bulb socket.

LTG : )

#3 8 months ago

Sorry, but I have trouble understanding where to measure along the way...

#4 8 months ago
Quoted from nibre:

Sorry, but I have trouble understanding where to measure along the way...

Follow the wiring from where you get 5V, and every connector, solder joint, light bulb socket, you see. See if you still have 5V there. You have 5V on one end and 1.8V on the other end. Try and find where it drops.

LTG : )

#5 8 months ago

Bad SCRs can test ok with a meter, but fail by not turning on all the way...which makes the bulbs look dim when they are on.

I'm assuming your sockets and header pins are ok?

#6 8 months ago

May be weak rectifier on power supply along with burnt plugs on power supply as well.

#7 8 months ago

Since there is one wire for each controlled insert lamp and they are all weak, my assumption is that the problem is central.

I measured the test points on the rectifier board and all except one showed the correct voltage. The one that didn't is TP1 (feature lamps). The meter showed 2.6V DC (should be 5.4V). So, is it likely that BR1 is broken? Can I measure it while it is on the board or do I have to desolder it? Could it be something else?

#8 8 months ago
Quoted from nibre:

The meter showed 2.6V DC (should be 5.4V). So, is it likely that BR1 is broken?

Maybe. I'd grab a meter and check continuity across the board and through the board, see if weak traces or connections are causing this.

LTG : )

#9 8 months ago

A quick although sometimes temp fix is to reflow the pins on the bridge. I had a meteor that had zero controlled lamps. Reflowed the bridge and they’ve been working solid for 2.5 years. I’ve always meant to rebuild the bridge board but because it keeps working I keep finding more important fixes to do on other machines. Still working fine 2.5 years later though.

#10 8 months ago

The incoming voltage to BR1 is 7.7V AC so I find it very likely that BR1 is broken. I didn't think of the possibility of reflowing the BR1 pins. I will try that first, before ordering a new rectifier.

#11 8 months ago
Quoted from nibre:

The incoming voltage to BR1 is 7.7V AC so I find it very likely that BR1 is broken.

Half voltage out of the bridge rectifier indicates one of the internal diodes in the bridge is open circuit. You are on the right track.

#12 8 months ago

Yup I agree. I usually rebuild every one of those power supplies before I even plug them in. Once done right, they will last forever.

#13 8 months ago

I guess BR1 has given up because it has become too warm. Maybe the thermal paste has dried up or something. I will clean all three rectifiers (after replacing one) and put on new thermal paste.

#14 8 months ago
Quoted from nibre:

I guess BR1 has given up because it has become too warm. Maybe the thermal paste has dried up or something. I will clean all three rectifiers (after replacing one) and put on new thermal paste.

I'd replace all three if going to the trouble or replace the board with a Weebly kit. New fuse holders and connections and stouter bridges.

https://nvram.weebly.com/new-pcbs.html

$35 shipped for the kit is little money for a nice upgrade.

#15 8 months ago
Quoted from nibre:

I guess BR1 has given up because it has become too warm. Maybe the thermal paste has dried up or something. I will clean all three rectifiers (after replacing one) and put on new thermal paste.

The feature lamp bridge is the one that typically dies because it's running at maximum current capacity. Always mount and screw the bridge in first with new thermal paste, and then solder the bridge last so there is no mechanical stress on the solder joints.

#16 8 months ago

I looked into My Eight Ball and found an interesting solution: wires to a stronger rectifier. Maybe I should try that instead. I have already ordered the correct rectifier but they aren't that expensive. I have a KBPC3510W and a CBR35-020W in store. Will one of those make a longer lasting solution? Moving BR1 will also take some heat away from the cooling plate where BR2 and BR3 are located.

IMG_20191114_134640 (resized).jpgIMG_20191114_134723 (resized).jpg
#17 8 months ago

Your rectifier board looks in reasonably good condition for its age. It ran for many years with the original bridge.

If you're running/planning to change to LEDs then you reduce the current draw through the bridge.

A KBPC3510W will still run HOT, it's a matter of how much thermal mass you give it to dissipate the heat. Use heavy gauge wire if you're going this route.

Quoted from nibre:

I have already ordered the correct rectifier

Where did you order from?

#18 8 months ago

Id put 3 br3506's in there with heat sinks on all. Do the jumper mods along with all headers to make it more reliable and reduce stress on connectors.
Then its bullit proof.

1 week later
#19 8 months ago

I decided to follow the cheap path this time: I just replaced BR1 and put new thermal paste (11 W/mK!) on all three rectifiers. Now it works! If this won't last I will try another solution. Thanks for all the advice!

IMG_20191120_185921 (resized).jpg
#20 8 months ago

Glad its working again - interested to see how long this holds up -

#21 8 months ago

I will let you know when/if it fails again!

#22 8 months ago
Quoted from nibre:

I just replaced BR1

I can't tell from the picture but the replacement looks larger. Are all three bridges flush against the aluminum spacer when you screwed the board back onto the metal assembly? Do you remember the part number of the new bridge?

Quoted from nibre:

new thermal paste (11 W/mK!)

Nice!

1 week later
#23 8 months ago

I used the following one:
https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=00602-0003

It´s the same thickness, so all three bridges are pressed against the aluminum by the screwes. The image gives a false impression.

#24 8 months ago
Quoted from nibre:

I looked into My Eight Ball and found an interesting solution: wires to a stronger rectifier. Maybe I should try that instead. I have already ordered the correct rectifier but they aren't that expensive. I have a KBPC3510W and a CBR35-020W in store. Will one of those make a longer lasting solution? Moving BR1 will also take some heat away from the cooling plate where BR2 and BR3 are located.

This "works" but is a hack - it's really just matching what WMS did on their similar era games. You can mount that size of bridge directly on the rectifier board (and add a heat sink). Obviously it's mounted on top instead of underneath, but that's no big deal. That would be my preference, but the way your 8 ball is if I weren't removing the rectifier board for other work I'd probably leave it.

#25 8 months ago

That's really an 8 amp part, not 10 amps. The '8' in the KBPC802 part number specifies 8 amps max. You'll notice it doesn't have the metal face like the original bridges.
But anyway since you have it thermally well connected to the aluminum/metal plate it should be ok. Using LEDs can reduce the current draw if you're worried.
I'll have to find me some of that 11 W/mK thermal paste you used! A far cry from the old white silicon compound junk used in years gone.

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