Film-Tech Forum ARCHIVE: RCA Dual Amplifier MI 9263

This is topic RCA Dual Amplifier MI 9263 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=011483

Posted by Charles Murphy (Member # 6443) on 04-05-2013, 03:06 PM:

I recently dug up an old RCA amplifier in our theatre. The tag reads MI-9263 200 wat Dual Amplifier. I opened it up and all of the tubes are inside, I have no way of testing them at this time. Can anyone tell me anything about this equipment?

Posted by Louis Bornwasser (Member # 3063) on 04-05-2013, 03:36 PM:

Ah, yes! MONO sound. See if tubes include 2-6L6, 5U4, 2-6J7, maybe 6SN7. I can't remember all the MI-numbers. If I am right, there are serious collectors for that amp. Louis

Posted by Donald Brown (Member # 5427) on 04-05-2013, 04:03 PM:

On RCA parts, the number is preceded by the prefix MI. Does any one know what the MI signifies?
Thanks,
Don Brown

Posted by Charles Murphy (Member # 6443) on 04-05-2013, 06:27 PM:

1-6SN7-ST, 2-RCA 1622, 2-RCA1620.

Posted by Richard Fowler (Member # 893) on 04-05-2013, 07:56 PM:

Master Index......generally used on systems or assemblies versus a part.

Posted by Louis Bornwasser (Member # 3063) on 04-06-2013, 07:55 AM:

I believe that all MI-s were made in Camden NJ on the same assembly line. Identical build-quality on cinema, P.A., and broadcast equipment; probably same people. I have been working on MI equipment since I was 12, now 64. Louis

Posted by Rick Raskin (Member # 1561) on 04-06-2013, 08:41 AM:

There are common subs for those tubes. Ask Mr. Google.

Posted by Robert Koch (Member # 3728) on 04-06-2013, 02:46 PM:

MI in RCA parlance says Master Item.The amplifier in question is an MI9257 with a power output of 15 watts used as a amplifier in RCA PG 220 systems and as monitor/emergency amplifier in larger systems PG 240 and PG 242. PG stands for Photophone Group. The tube compliment for the MI 9257 was 5U4G rectifier,2 1622[6L6] power output;2 1620[6J7] voltage amplifiers; 1 6SN7 phase inverter.They also stuck a couple of 991 neons as voltage regulators for the 868 gas photocells. These,charitably said, did`nt do the job. Any further requests for information in the "dark ages" I will try to answer.

Posted by Louis Bornwasser (Member # 3063) on 04-06-2013, 03:55 PM:

I've probably got the manuals for those. Before Dolby they were common in small town indoor theatres and as preamps in drive ins. Louis