Emu XL-7 & MP-7 User's Group

Someone mentioned this problem awhile back.  I didn't have any 
problems with this until I added a rom chip.  Then I noticed a low 
but noticable hum.  Since I do most of my work with monitors it was 
no big deal and I just chalked it up to more xl-7 weirdness and 
forgot about it.

Then I added a second rom chip.  When I tested it with phones before 
screwing it completely back together the hum was very bad at that 
point.  I thought maybe there was some kind of current draw problem 
with the chips so I removed both of the roms I had added and listened 
again and it was still very bad.  It sounded 60 hz and only happened 
when the panel button leds were on or flashing.  The lcd display and 
backlight didn't seem to have any effect.

I'm not an electronics engineer but years of tinkering with audio 
equipment has taught me that 60 hz noise of that kind is usually 
caused by some component not being grounded correctly.  Either 
something is fried or there's a bad connection somewhere.  The only 
connection between the panel, where the phone jack and leds are, and 
the main chassis are a few ribbon cables.  So I juggled and reseated 
all of the connectors and powered it up again.  Sure enough that 
fixed it!  No more hum.

So it would appear that the design of some grounding connection 
between the panel and the chassis is defective.  Like maybe a ribbon 
cable wire is not totally adequate for the load the leds are 
drawing.  Or maybe they're just el-cheapo cables.  Whatever it is if 
it happens to you try pulling the panel off and reseating all of the 
ribbon cable connectors one at a time.  It probably wouldn't hurt to 
clean the pins with electro-wash or something like that either.

cheers,


qwanta