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  Adjusting Digital-Capable
and Analog-Plus
MSF5000 EEPots

By Robert W. Meister WA1MIK
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It is assumed that the reader is familiar with the various assemblies in an MSF5000 and has access to the Instruction and Service manuals for the station. Also, proper test equipment and tools will be required to perform these adjustments. There are a lot of other mechanical alignments that must be done prior to the electronic tuning described here.

Station alignment is performed by adjusting two VCOs (in all but VHF stations), three mixer injection coils, two image coils, five or six receiver front-end coils, and several potentiometers, all located on the RF tray. In addition, electronic level adjustments are manipulated by the microprocessors in the control tray via EEPots: Electrically Erasable Potentiometers. The EEPot name came from inside the marketing group of Xicor, the company that invented them (now owned by Intersil). The EEPOT appeared shortly after the same company announced the EEPROM (Electronically Erasable Programmable Read Only Memory). Despite the name, EEPOTs are not Electrically Erasable, they are electronically adjustable or controllable. Some literature refers to them as digitally adjustable, digitally controllable, or as digital potentiometers. These EEpots replaced actual screwdriver-adjustable potentiometers that were present on the various boards in the control tray on the older analog stations.

800 and 896 MHz stations also have a reference oscillator located at the bottom of the station; this also needs to be adjusted as part of the alignment process. This oscillator is located in the RF tray on VHF and UHF stations.

The following table shows all of the EEPots in an MSF5000 station. The columns are described thusly:

#EEPot Function [ see Notes ] BoardAlign. Pages
0Coded (Decrypted) RX Level SEC43
1Flutter Fighter Level SSCB39, 40, 41, 42
2Repeater Squelch Level SSCB44, 47
3Receiver Squelch Level SSCB44, 47
4Maximum Deviation Level [1] SSCB32
5Receiver (Repeater) Level SSCB38
6Coded Deviation Level [2] SEC47, 48
7Transmit Line Audio Level TTRC35, 36, 37
8Status Tone Level TTRC45
9High End Equalization Level TTRC45
ALow End Equalization Level TTRC46
bTrunking Data Deviation Level TTRC29
CLine 2 Output Level TTRC42, 46
dLine 4 Output Level TTRC43
ECoarse Line Output Level TTRC33, 35
FSam Encoder Level SAM- - -
[1]: PL/DPL deviation is not separately adjustable. It's a fixed percentage of the total deviation. When setting the Maximum Deviation Level, do it with PL/DPL activated.
[2]: The Instruction Manual incorrectly states that EEPot 6 is located on the SSCB; verification with the schematic diagram clearly shows both EEPot 0 and EEPot 6 on the Secure module (SEC).

Hints And Kinks:

The computer (RIB cable) can be connected to either the 40-pin Expansion connector on top of the SSCB, or through the 6-pin modular MIC/Control jack on the front of the SSCB. Life will be a lot easier if you plug your Diagnostic Metering Panel (DMP) into the Expansion connector and use the modular jack for programming. This way you can see the various status LEDs on the DMP, which are very important when you get around to adjusting the squelch settings.

It's much easier to adjust the EEPots with RSS, since you can increase as well as decrease any value. The front panel method lets you increase values only, but you can choose the Tens digit or the Ones digit and adjust each one independently. The same results are obtained, but it takes a bit more fiddling to get there with the front panel.

After you finish adjusting the EEPots via either method, it's a good idea to read the code plug from the station (F3, F2) and save it to disk.

Adjusting EEPots From RSS:

The EEPots can be accessed via RSS by connecting the computer to the station and reading the station's code plug (from the Main Menu, press F3, F2, F10), then entering the Service and Alignment section (from the Main Menu, press F2), then choosing Individual Station Alignments (F3). 15 of the 16 EEPots with their current values will be displayed; EEPot #E is omitted. Using the <TAB> key, step to the desired EEPot and press <ENTER>. This will bring up a slider bar that shows the current relative position (00-99) of the EEPot. Use the UP/DN arrow keys to raise or lower the current value, then press F4 to make this the current value. You can also press the PgUp/PgDn keys to raise or lower the current value in steps of 10. Always press F4 to save the value out to the station before switching to another EEPot. Press F8 to access the previous EEPot, F9 to access the next EEPot, or F10 to get back to the original list. The various active function keys are displayed on the bottom of the screen. Press F10 as many times as needed to get back to the Main Menu.

WARNING: There is a second screen page that lets you access the Forward and Reflected Power Trip Points. These are only used on stations that have an internal wattmeter connected (trunking stations). DO NOT change these or even access them on a station without an internal wattmeter connected; code plug corruption WILL result and there's no documented way to fix it. You have been warned. The best thing to do is just forget this second page even exists. Look but don't touch? Don't even look! The manual describes the proper way to set these from the front of the SSCB. That procedure is rather confusing and if you miss a step, things won't adjust or set properly.

Adjusting EEPots From The SSCB:

You can also adjust the EEPots using the front panel switches and display on the SSCB. This is accomplished somewhat differently than via RSS.

First, you must gain access to the EEPot settings by following this sequence of steps:

After a few seconds, a three-digit number will appear in the status display. The first digit is the EEPot number in hexadecimal form. Some characters will be lower case. The second and third digits are the current EEPot value in decimal form (00-99).

When dealing with the EEPots, the Select switch moves the decimal point to select the character position you wish to affect (either the EEPot number or the decimal value), and the Set switch increments the value for that character. Each character wraps around from its highest value back to zero (0).

To select the EEPot you want to adjust:

To adjust the EEPot's value, you have two decimal digits to contend with: the Tens digit and the Ones digit. Each can be incremented from 0 thru 9, then it wraps back around to 0, so if you overshoot the desired value, just keep going and stop the next time the desired value comes around. You can adjust the Tens digit and the Ones digit independently and in any order. When the Ones digit goes from 9 to 0, it increments the Tens digit automatically. It makes sense to initially set the Ones digit to 0, then move to the Tens digit and increment it until you get close to the desired value, or overshoot it. If you overshoot it, keep incrementing it until you get to the next lower value. Then select the Ones digit and bump that up to fine-tune the adjustment.

Repeat the above process as necessary for any EEPot that needs adjusting.

When you're finished, wait until the display times out (the decimal point disappears), then set the Select/Set switch to Set and verify that the display goes back to the Chan/Mode/Key display (11).

Acknowledgements and Credits:

Information came from the MSF5000 Digital Capable and Analog Plus Instruction Manual, 6881092E05.

MSF5000, DMP, RSS, and RIB are trademarks of Motorola, Inc.

EEPot is a trademark of Xicor, Inc., now Intersil.

Contact Information:

The author can be contacted at: his-callsign [ at ] comcast [ dot ] net.

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This article first posted 09-Mar-2008

This web 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.