USM-223 Multimeter

Background
Description
Photos
Manuals
Patents
Related
References
Links

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Background

Description

Fuse

After installing some batteries, there was no response to any switch position.  The fuse was blown.
1-1/4" (32mm) long x 1/4" (6.3mm) dia (3AG);   5 Amp @ 250 Volts on the blown fuse.
The manual says 2.5 Amp Fuse.
27 Oct 2017 - Installing the new fuse did NOT fix the problem.

Batteries

There are three batteries:

BT-1

This is a common "C" battery.

BT-2 & BT-3

This is a stack of three each BA-1312 batteries.
I ordered LR50 cells as replacements for the BA-1312 mercury battery(Wiki) .
The LR50 is the correct size and a stack of three of them fit correctly.  Note that the LR50 batteries on eBay don't have brand names.
My web page for the TS-183 Battery Test set lists the BA-1312 as follows:

Battery Type No.	Jack No.	Minimum Permissible Voltage	Load Resistance Ohms	Used On	Replacement
BA-1312/U 6135-00-269-5843	4	1.00	19.7	PAS-5, SU-43/PAS-6 IR viewer, PDR-10, PQS-1(XN-1), USM-223, VRC-53, VRC-64, KS-19B, GRC-9 Bias Battery	Duracell: PX1, RM1N, RM1R, EverReady: 1, 1A, EVG PC1A, Gold Peak: PC1A, I.E.C. LR50, Mallory MR50, Military BA1312/U, NEDA 1100M,  1109M,  1110MP, Panasonic MR50, Radio Shack:23-9011 Rayovac RPX1,  T1N, UCAR EPX1, Varta V1PX,  VPX1 BT-70265, E1N

Photos

Fig 1	Fig 2	Fig 3
Fig 4	Fig 5	Fig 6 Inside

Manuals

TM 11-6625-654-14

Operator's, Organizationalo, Direct Support, and General Support Maintenance
Repair Parts and Special Tools List (Including Depot Maintenance Repair Parts and Spedial Tools List) for
Multimeter AN/USM-223
13 September 1974

TM 11-6625-654-24P

Organizational, Direct Support, and General Support Maintenance Repair Parts and Special Tools List for
Multimeter AN/USM-223
NSN 6625-00-999-7465

Patents

Related

References

Links

PRC68, Alphanumeric Index of Web pages, Contact, Products for Sale
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