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  Technical Information on Test Equipment from Helper Instruments
Compiled by Mike Morris WA6ILQ
Maintained by Robert Meister WA1MIK

Helper Instruments, of Indian Harbor Beach FL, went out of business around 1999 and the remains were acquired by Zetron. Zetron elected to continue some of the Helper line of audio test equipment, but not the RF testers, such as the SM-512, SM520 and SM-1000 Service Monitors. Zetron, in turn, was acquired by JVC / Kenwood.

Sinad Alignment For Optimum Performance   354 kB PDF
This is the writeup that got Helper started - it's a quite readable explanation of the the theory behind SINAD measurement.
Helper Instruments Catalog   1.43 MB PDF
I believe that this PDF is of the last catalog that Helper released.
Helper Instruments Desktop Reference   439 kB PDF file   Donated by John K3KR
A collection of charts, tone lists, SINAD test procedures, "and an occasional discrete mention of the time saving, money making test instruments by Helper Instrument Company."
Sinadder model S-101   508 kB PDF file     Photo 1   Photo 2
This is the manual for the original small sloping-front "Sinadder" unit from the late 1970s, complete with parts layouts and schematics. After they came out with the Sinadder II this became known as the "Sinadder I". Despite the age, it's still a very useful test bench instrument.
Sinadder model S-101   305 kB PDF file
This is another manual for the original small sloping-front "Sinadder" unit, with a 1992 schematic revision and a 1999 parts list.
Sinadder 3   Front Photo 1   Front Photo 2   457 kB PDF file Donated by Eric Lemmon WB6FLY   This is the manual for the later flat-front Sinadder model 3.
Sinadder model SL-105 with optional CML-1 addendum   3.4 MB PDF
The SL-105 was available both with and without the CML-1 option (used in cellular applications). There were later units that had a different front panel (see this photo).
This is the manual for the "Sinadder Linear 5" with the descriptive addendum page for the CML-1 option. It is complete with parts layouts and schematics for the plain unit. This PDF file does not have the schematic for CML option.
Here's a photo of the front of a CML-1 Sinadder provided by Gary KJ4RED.
Here's a photo of the rear of a CML-1 Sinadder provided by Gary KJ4RED.
Note that SL-105s were initially built in the SL-101 case, and mid-production switched to the case shown.
Lineman model LM-106   416 kB PDF file   This unit is used to test the AC and DC characteristics of the leased phone lines used to control remotely located base stations. It is also a very useful bench test instrument.
Modulation Monitor model MM901   476 kB PDF file   Donated by John K3KR
This unit works with an FM receiver. It gets its input signal from the 400, 450, or 455 kHz IF circuit. ICs: U1 = MC3357P; U2, U3, U7, and U8 = LM348N; U4 and U5 = CA3130E; U6 = LM741CN. Service Note: "If readings appear low, check and replace C24 and C25."
Audio Frequency Counter model Toner-II   769 kB PDF file   Donated by John K3KR
This unit displays frequencies from 50 Hz to 9,999 Hz. ICs: U1 = LM348N; U2, U3 = CA3130E; U4 = MC14046B; U5 = CD4518BE; U6 = SCL4077A/BE; U7 = ICM7207AIPD; U8 = ICM7224IPL; LCD CISPLAY = PURDY/AND # FE0202-C. Service Note: "If the unit has difficulty locking onto CTCSS tones (but higher tones are OK), check and replace C1."
Millivoltmeter model RF-801   506 kB PDF   Both this file and the one below donated by Mike Felack WA3WOM
Photos: Front panel       Rear panel
Helper Instruments RF-801 Millivoltmeter hi-res Schematic   196 kB PDF   This is the component layout and schematic only.
Test probes for this unit are rare - if anyoene has documentation on a probe, or has fabricated a homebrew probe please consider writing an article for this page.
Matchbox model MB-500   990 kB PDF   Both this file and the inside photo below were donated by Don Mosher WB5BRY
Photos: Inside       Front panel       Rear panel

Additional photos:

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This page initially created 22-November-2012 by splitting all of the Helper equipment from the Test Equipment page.

This web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.