loud hum from GEORGE K Jyuoh machine

[seanp]

Thought I'd post my update on installing the volume mod. I used the Radio Shack pots mentioned earlier in the thread, and everything worked great! Buzz is gone, and I can get the volume down to a reasonable level (The first time we played the Gamera my young son nearly jumped out of his skin when a "battle" started). I was surprised that the volume knob on the pot was so sensitive - it seemed like it went from full volume to no volume in about 1/8 of a full turn. I'm sure there's a correlation between the rated pot I got (10k Audio) and the electricity rating going to the speakers... Unfortunately I don't know enough yet to understand all that. I get the basic idea of circuits, resistors, pots, etc, but don't know enough about amps / volts / etc...

-Sean

[Frank A]

The hum in the speakers on my Thunderbirds is awful. The vendor is sending me a new sound card to try and fix it. If I unplug the video screen, the hum goes away as does the video on the screen. Thus, by elimination, the hum comes from the video screen. Didn't someone say this in another thread somewhere ? Will the new sound card make it go away ? As soon as I get the new sound card, I will let everyone know. Frank A, Jackson, NJ

[cwstnsko]

Not to drag a different subject into the thread, but has anyone ever explored the possibility that some of this humming could be related to improper grounding? Most, if not all of the refurbishers cut off the ground wire that was used to ground these things in the casino. Ground loops are known to cause humming in audio installations.

[gwarzin]

The hum is indeed from the video. It is very unlikely that a new sound card will make ANY difference. AFAIK all Thunderbirds have this hum problem. I tried a lot of things with grounding, ferrite cores, etc. The only known fix is to install L-pads. Turn up the volume using the 3 position volume switch and them bring the volume back down with the L-pads. There will still be some residual hum, but, at least in my case, it brought it down to an acceptable level. If you want to find more on this topic, just search the forum for Thunderbirds.

[slotter]

Not to drag a different subject into the thread, but has anyone ever explored the possibility that some of this humming could be related to improper grounding? Most, if not all of the refurbishers cut off the ground wire that was used to ground these things in the casino. Ground loops are known to cause humming in audio installations.

Speaking of grounding the machines, you started quite a good discussion of that issue here, Chris : http://www.pachitalk.com/forums/showthread.php?t=3480

[Frank A]

Which L-pads did you specifically use on Thunderbirds ?

[gwarzin]

Which L-pads did you specifically use on Thunderbirds ?

http://www.partsexpress.com/pe/showd...number=260-248

[Frank A]

I pulled the l-pad link up and I see three lugs on the l-pad. What goes where ? I also tried to find Thunderbirds, but the new system is throwing me. All I found was the owner owned link.

[gwarzin]

There's a schematic that's printed on the side of the box that will show you how everything shoulc be connected. There's also a scanned version of that drawing on this site somewhere. Search for L-Pad or volume control and you might be able to find it.

[rbinkerd]

I know this is an old thread, but...

I have one of those Las Vegas customs built on the George K Pachislo and this thing has more than a loud hum. More like a growl. I've added a ground wire with no success. I took the sound board out (actually I think it's sound and video) and the LCD has been removed. Could this cause the growl?

Rory