MSF5000 problems

[motrad1]

MSF5000 int tx

anyone had any problems with digital msf5000's and the tx side of the duplexer causing the repeater to shut down ie will not key or if the unit does key up drops out immediatley

Have two units bith within in about 6 months of each other on age and both have the excat same symptoms you can bypass the pre filter on the tx where it comes out of the exciter and is filtered before it goes into the amp and couple those together and bypass that part then tie a duplexer to the other too leads of the post filter and seems to resolve issue

Motorola dosen't support it anymore says it is obsolete and replace it but you can't get the part any ideas other than outboarding a duplexer i have tried takeing the filter apart and cleaing it like /\/\ suggested

[Nand]

The MSF will shut down if it detects problems in the final PA or antenna system. It only takes a fraction a second for this to be detected. There are likely over current and temperature conditions that may cause this as well as to much reflected power because of a mismatch in the antenna system.

It actually happened to me today when I keyed a MSF. I didn’t realize that the test frequency for this station was not the frequency used for normal operation. And since it was transmitting into a multi-coupler tuned to the operating frequency, the station shut down because of a mismatch (high reflected power).

Nand.

[motrad1]

don't think it is the ant system since there spare msf5000 is working okay on the same antenna and the ant analyzer as well as watt meter show it being okay, as far as the final is is the 10 watt version and only doing about 5 watts continous duty but is inly used intermintent and has been keyed up using a duplexer like i stated above and tx fine i turned the tot off to test stability of PA and keyed it constant for 4 hours with no power drop or overheating problems

[Nand]

Bernie and likely XMO are some of the fellows here who have seen a lot of MSF failures and have solutions for them.
I just mentioned the typical causes. Others may actually have experienced exactly what you have.

Nand.

[batdude]

i had one that would do this....


and it turned out to be a flaky transmit VCO - it would for a microsecond, unlock right when the station keyed... and cause the PA to get PA KEY, but not PA FULL... zippo power out...

and the VCO lock lights on the front panel wouldn't even blink... new vco fixed the problem.



doug

[Equinox]

Are you sure you don't need to retune the TX filters? Since you're bypassing them and it's working.......

[bernie]

My two bits worth:
I think that your problem is caused by the power supply.
A bad electrolytic can allow the output voltage to dip enough for the 5 volt regulator to go out of spec.
This causes a reset and it restarts.

A battery reverting supply with out a battery can also do this, if not set to 14.5v with no battery.

I have seen the filters grow metallic whiskers.
This is usuially seen in the injection filter, but can happen anywhere.
I know of one case in Kentucky that had an ant nest in the pre-filter.

By all means completely align the station.

There are alternative tune up procedures.
I tuned one this morning.
The tracking generator on my Motorola R2600B works great for tuning the MSF filters.
Let me know if you need advice on tune up and testing.