MSF 5000 Limited has a problem...beeps twice...No TX

[radioservice]

Hello,

I have an MSF 5000 Limited VHF base C63RLB7106B that has no TX operation. I have no schematics and the digital display keeps reading "11". When I try a local handset in the front panel it just beeps twice and continues to beep twice every 10 secs until I cycle power.

Any tips or ideas?

Bill

[kcbooboo]

Two beeps are a "PA Failure". Since you aren't getting any TX output signal, something is obviously wrong, either the IPA or PA itself. Also, if the output power is turned up too far, the station might briefly key up (for a few milliseconds) then come up with a PA Fail alarm.

Check the RF connections. Check the RF output of the RF tray; it should be a few watts. The IPA on the RF tray is capable of 9 watts or so, and if it's that high, it'll overdrive the PA and cause the fault. Also make sure the antenna relay is working. Check the 6-pin cable going to the PA.

Any RED LEDs on the control tray would usually indicate a problem. You should have all the GREEN and AMBER LEDs on when transmitting.

The "11" on the display just indicates the station is on channel 1, mode 1. That's normal. It might change to three decimal points after several minutes, if you're running new-enough firmware.

When you first apply power, watch the display for any error codes. There's a definite power-up sequence: SSCB version, TTRC version, secure board version if present, then you would get the "11" display. The error codes consist of a letter (possibly lower-case) and two hex digits.

Once the station keys up successfully, the error beeps will stop, but you're stuck with them once they begin until you clear up the problem. Setting the output power too high is one sure way to get that alarm, so crank the pot fully CCW, put a wattmeter and dummy load in the output line, and continue from there. The station is rated for about 75 watts but you should be able to get more unless something is wrong.

Bob M.

[George]

You have, what could be, power amp problems.

Is everything connected inside? Do you have power to the power amp? You should see about seven watts from the exciter output going into the prefilter.

I forget how to do it, but you can put the station in test mode and make some basic checks. I think it's hold down the transmit and push reset at the same time or something like that. Then you can push the transmit switch and it will override the alarm condition.

You could also rock the power control back and forth a bit to make sure you are not on a dead spot in the pot. I have had that happen before.

You really need the RSS to see if there is something goofy programmed in it. Severe mislignment can cause this condition also.

George

[kcbooboo]

Also, the VHF power supplies put out 14V and 28V to the PA, but the RF tray utilizes just 14V. Check for failure on the 28V supply.

There's no pre-filter. The IPA output on the RF tray goes right into the PA.

There is a peripheral box on the PA output that has a T/R relay and possibly a filter.

I wish I had a VHF station here to play with! I've only worked with UHF stations.

Bob M.

[George]

Oh, silly me...that's what I get for not reading closely enough.

You are correct, there is no prefilter. I have UHF on the brain because I have to deliver four UHF MSF stations for my latest amateur project.

George

[Dan562]

The MSF5000 VHF IPA fed directly into a RF Wattmeter / 50 Ohm load should provide between 12 & 15 Watts output. There isn't any form of Power Control while testing the IPA by itself. The RF Power Control detection voltage is developed in the High Power RF Amplifier and looped back to the Station Control Board through the multi-conductor cable.

If I were to make an educated guess what might be wrong with your station, I would open the plastic tray where the Station Control Board is located, looking on the far left hand side for a Burnt Regulator, Filter Capacitor and Blown Fuse. These were notorious components that always failed when they were sent into /\/\'s Infrastructures Depot for repair.

[kcbooboo]

I would expect if those parts on the SSCB were cooked or burned out, then the station wouldn't do nearly as much as it is right now.

I probably was thinking that the IPA would put out about 3 watts when connected to the power amp and running normally. I don't know what it would do if the power amp had problems. Hopefully it won't go to full output and burn something out.

People actually sent modules back for repair? I didn't know that MSF5000s ever broke! I guess I lead a sheltered life.

Bob M.

[Dan562]

Like I mentioned, if you were to disconnect the IPA from the RF Power Amplifier, connect the coax to a Bird 43 RF Wattmeter and 50 Ohm Dummy load, the IPA will put out 12 to 15 Watts without Power Control. I know you can try this on your UHF station too Bob. Your correct with the 3 Watt RF Drive to the RF Power Amplifier. There's a possibility that the IPA might be bad or the RF Power is set a bit too high.

I don't know if the /\/\ / CTDI Infrastructure's Depot still maintains Flat Rates on the MSF5000 Station modules but first radioservice must determine what is at fault.

[FMROB]

Hold the phone,,,,,

I don't know if the VHF is the same as the UHF, BUT if it is,

there is on the RF tray front panel a TX power adjust POT, which is a s h i t component, and over time gets very dirty and will short.


Take the appropriate tuning tool and some contact cleaner, spray and operate back and forth. Wait till it dries and turn it back to a low to medium setting, about 6 o'clock position and see if it works.

We have noted on numerous units the very problem you describe. If it is shorted or set to high this condition will occur.

The other guys are correctet though, ipa or pa problems if that doesn't fix it. It frustrated the hell out of us until we found that a $3.00 part was causing all the problems.

- Rob

[Equinox]

I have a unit with a similar problem. This has been a unit that would not work, I would go out and do the old power off/on reset, and it would be okay for a month, 2 months, etc. This time it is down for good. I have tweaked the settings, put a wattmeter on the IPA directly into a dummy load, etc, and even with the PA unconnected I still get the two beeps, lights flash on for a second, then no TX most of the time. Sometimes the station will stay keyed if I turn the Power adjustment pot all the way down before I key, and when it does I measure about 6 watts out of the IPA. But when I turn it up even a little it shuts off. And when I try it again, it may or may not come up. My problem is I'm about to be out of town for 2 weeks and I need an answer quick, so I called the depot. No flat rate now, it's all T&M. $275.00 per hour plus parts. Any ideas before I take this drastic measure?

[radioservice]

I finally got into my MSF and tracked down a defective can relay in the antenna relay assembly mounted on the back of the cabinet. If I unhooked the PA from the relay assembly and fed it directly into a metered dummy load, I got LOTS of power out and no beeps.

I'm not sure our problems are identical but you might gain from my brief experience.

Problem has been finding the motorola part...got any extra 80D83134D01 relays just layin' around?

Bill

[kcbooboo]

radioservice:

I'd try to fix the relay first. If the coil isn't open, it's just mechanical contacts. I have never seen a VHF station up close, but I suspect the peripheral box assembly is able to be taken apart. Maybe you'll find something simple inside has gone wrong, like a trace burned out, or a connection unsoldered itself due to excess heat.

If the relay coil is open or the contacts are beyond repair, you could obtain an external coaxial relay with female N or UHF connectors, make some jumper cables, and install the relay outside the box - somehow. New ones of good quality can be bought from Henry Radio through Radio Dan, for under $100.

There are some parameters in the programming software that delay the PA output while the relay switches. The times are fairly short, around 40 mSec. You should verify that they're set to their default values or longer, especially if you find the relay contacts badly pitted or arced. This could be because the PA is generating RF before the relay has switched.

Equinox:

6w out of the IPA is way too high at minimum power. It should go down to almost nothing, certainly below 1w. 6W is probably overdriving the PA, which is creating way too much output power, hence the SSCB is shutting it down. If you disconnect anything that reduces or eliminates the PA output power, you'll get the two beeps when you key it up.

You didn't say if it was VHF or UHF, base or repeater. If it's a base station, there will be an antenna relay between the PA output and the junction panel on the right side of the station. You can bypass that, or hook your dummy load and wattmeter to the output of the PA. Make sure you set the output power properly; it's derated for repeater stations (i.e. a 110w PA should be set for 55w out of a duplexer). I have seen plenty of stations cranked way up past their rated output; this is just asking for trouble.

Bob M.

[Equinox]

Sorry. It is a UHF repeater.

[kcbooboo]

Connect the output cable from the PA directly to a known good wattmeter and dummy load, and key the station up. Make sure it's not putting out more than the true rated power; a C74 is good for 110 watts; a C64 is good for 75. See if it holds that power level. Disable the power control circuit from the front panel if the station won't stay keyed long enough, or set the power adjustment fully CCW and ramp it up. I've seen my 110w repeater put out just over 100 watts after the duplexer; that's almost 200 watts out of the PA. These things have power to spare, but don't abuse them.

There's always the possibility that the circulator has been fried due to a bad or missing load on the PA. They're rather small and can only deal with perhaps 15-20 watts of reflected power coming back into them; they have a built-in ceramic dummy load and the entire assembly is pretty small.

If the station has the Motorola internal filter/duplexer, tuning is critical. If there's too much loss in the pre-filter, the IPA will put out more power than it should to get the proper power out of the PA. Try bypassing that with an N-female barrel connector. You should only need 3-4 watts of drive to get the rated output power. Check this with a thru-line wattmeter as well.

Then it's back to more basic troubleshooting, unfortunately.

Bob M.

[George]

The antenna relays I have seen on these stations are the little glass reed relay types that get the contacts burned off them. Once they are dead, they are dead. However, you could try using a relay from an 800 MHz X or X9000 and modifying the leads to the application.

Desperate times require desperate measures.

George

[kcbooboo]

I've only seen a UHF base station, and that relay is large, mechanical and has accessible contacts. However, since the station takes great pains to switch the relay when no RF is present, it should last quite along time.

Of course, a repeater would have no need for an antenna relay.

Bob M.

[radioservice]

Problem has been finding the motorola part...got any extra 80D83134D01 relays just layin' around?

[kcbooboo]

Sorry, none just sitting around in my back pocket looking for a better place to live.

Didn't Micor mobiles use these? Even Micor base stations did. Maybe not the same part number, but the same function. Smaller in a mobile radio too. Japanese radios like Kenwood, Icom, and Yaesu, use PC-board mounted relays, nothing special, as long as it can handle the voltage and current through the contacts.

Bob M.