Batboard

I have a working UHF MSF5000 CLB repeater and wish to install and use a known working CXB (digital) control tray (SSCB & TTRC). The CXB tray is set up for the same UHF range 2 repeater configuration. Question is will it work as a straight swap or is there more involved?

Any help greatly appreciated.....

Bryon K0BSJ

There is more involved.

Actually, it's not terribly complicated. The CLB Station Control Module supplies 5V through the radio interface connector J801 on pin 9. The station interconnect board uses this to source 5V to the Rx synthesizer and power control circuits on the Uniboard.

The CXB stations use J801 pin 9 as RX2 Strobe. Hence if you put the CXB control tray on a CLB RF tray, you will have a non functional station.

Motorola did sell a conversion kit to update the CLB to CXB. It included a new interconnect board.

Your options are:

1. Find a CXB interconnect board to swap out the one on the CLB RF tray.

2. Put your own 5V regulator circuit on the existing interconnect board.

3. Modify the CXB control tray to replace RX2 Strobe on pin 9 with 5V.

Your best bet is to have the service manuals for both the CLB and CXB.

My two bits worth:
At one time the factory's position was buy a new station, it can't be easilly done.
After some research I came to the exact conclusion as xmo.
I have had success with option 3. Only one jumper on the bottom of the board. (Jump around the R 2 strobe driver)

Replace the Electrolytic on the interconnect board. This is a very high failure item, as is the same part on the analog control board.

Thanks for the insight. I looked through the manuals last night and didn't see that. Too many hours in front of the station I guess. I will just put a 5 volt regulator on the interconnect board. I wonder if 5 volts @ 1 amp would be enough?


Bryon K0BSJ

My two bits worth:
I suppose you like to build things, I am lazy.
The VCO draws very little current.
Be sure to by pass the 3 terminal regulator input and output with .1uf caps as close to the body of the regulator as practical.
The reason is some regulators like to oscillate at a meg or so, and causes all sorts of problems, as well as problems caused to the regulator by stray RF.
Have FUN.

Well Bernie I did it your way. Not because I was lazy but I couldn't find a 5 volt regulator in the stash. I ran 5 volts over to pin 9 on the SSCB after cutting the RX 2 strobe trace. All is well and it is making RF.

Thanks guys for the help!

Bryon K0BSJ

I'm playing around with a MSF5000 also and may swap out the SSCB.

What's the trick to physically removing it? It looks like it's snapped very tightly into the plastic tray and barely moves. I don't want to destroy the tray to get it out.

Am I missing something?

Thanks,
Ken

My two bits worth:
Be careful, the plastic WILL break if you force anything.
Be very careful that the RF drawer is fully extended before you open the tray.
To remove the entire top cover with control board:
Un plug all external cables, Wire line, control, power.
dis engage support arm from tray. Do not remove the metal plug from the tray, the arm can be dis-engaged by the "eye hole"
The tray may then be dis engaged from the casting.

To remove boards:
It is not necessary to remove the entire assembly.
Note that the front panel of the board to be removed is held in by small fingers. Note that there are fingers that engage the front of the board.
Gently work the front panel off, then the board can be moved forward
and dis engaged from the fingers that secure it in the housing.
It is not necessary to force anything.

Installation:
If this is a new factory spare board, especially the TTRC it may be necesssary to trim the edges of the board. (Soda cracker construction)

The board has to be wiggled into place. Beware the mick jack, it can get bent up, which will prevent the front panel from seating.
Engage the front panel fingers on the board, continue pressing into place until it is seated.

Caution!! Never power up the station with the ribbon cable dis connected, or the 9.6V regulator disconnected.

If you do you may have to replace the switch transistor. This is because the 5V regulator uses the 9.6 as a reference. 9.6 originates on the IPA module.
I hope this answers your question.

Thanks Bernie,

That's a big help.

Ken

My two bits worth:
Since we are discussing MSF disassembly, and assembly there is another thing that needs to be mentioned:

When working on the RF casting, be VERY careful about the pins on the feed thru caps that connect the UNI board, inerconnect, and Mixer board .
These pins are long and thin and are easilly bent.
It is possible for a pin to miss the connector entirely, or be forced into an adjacent female pin.
This can result in many hours of trouble shooting some very wierd symptoms.
This will never happen if the station is left alone. This is a technician problem.

When removing the front end casting, or interconnect board always remove the feed thru caps, install the module, then carefully install the caps. Be very careful about installing the UNI board.

this can save you much grief.

Bumping for I got my hands dirty with the same project, and here's what I found out:

The CXB station interconnect board doesn't just pass 5V, it contains the actual 5V regulator. Since I like to keep things factory, I went ahead and yanked the interconnect from my donor drawer (using an 800 CXB drawer to uplift a UHF CLB station) and did a side-by-side:



Imagine my surprise when I saw that the power and PA control connections on the CLB interconnect weren't socketed. After comparing with my other factory CXB station, here are the connections for power and PA control, since they're not included in the digital-capable/analog plus instruction or user manuals:

Main Power (Top to bottom):
1 - Red
2 - White
3 - Brown
4 - Black
5 - Blue
6 - Orange
7 - Green (blank pin, not connected)
8 - NC
9 - NC

PA Control (Top to bottom)
1 - Red
2 - White
3 - Brown
4 - Green
5 - Black
6 - Orange