[R-390] 390a audio

[Roy Morgan]

At 10:54 PM 6/22/2004 -0500, Don Reaves W5OR wrote:
>  ... a multi-channel 600 ohm mixer, rack mounted in a 2U box.  Marked Audio
>Mixer - Amplifier Assy Eight Channel Model No. MAA-8/600 made by G.R.M 
>Corp ...
>Each channel has way too many input/output pins (24) to casually reverse
>engineer.

Well,

It would be a simple matter of a few minutes with a voltmeter to find the 
output pins among those 24. Put a signal into the thing with a pot half way 
up. Then start with pin1 and measure to each of the other twenty three 
pins.  Then mesure from pin 2 to pin three through 24, then pin three to 
pin  4 through 24. Soon you will fiind at least two pins that have 
output.  If you find two pairs (likely with a common pin) the common one 
will be the center tap, and may or may not be grounded.

Good luck.  I recently bought an uncompleted mixer with a pot and switch 
for each of four channels and a master, octal tube sockets, and little 
else. I plan to build a mixer for receivers with it. I'll feed a 1950's 
home brewed Williamson amplifier with triode connected 807's and a period 
"hi-fi" speaker.  That plus a modest patch panel and I'll have a very 
flexible system for sound.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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