MSF-5000 900mhz TX VCO?

[Randolph A. Krenz]

I’m in the midst of trying to repair the TX VCO for a 900mhz MSF-5000.  I think the issue might be failed varactor diode(s) but not yet sure.  Assuming I can figure out what’s wrong, I’m not sure I can get the needed parts because I only have Motorola part numbers and I’m guessing they might not be available from Motorola and I couldn’t find a cross reference.  Anyone have a TX-VCO they might be willing to part with?

Randy/N3HFK

[n1...@comcast.net]

I have a few of the NJ MSF’s in my storage. They are getting dumped this summer. You are welcome to take one or more for parts before I dump them.

 

John

N1OTY

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[Roger Coulson]

John, Randy,

We think it may be the UHSO in Cumberland that has died again.  Do any of your MSF5000's have a UHSO tray with either the original oven or an aftermarket OCXO?  

We should save these.  The original UHSO can be used in an MSF and the aftermarket OCXO can be used in a 900 MHz MSF or a 900 MHz Quantar.

Roger

WA1NVC

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[Lee M. Lemoine]

definitely worth checking to make sure the VCO tray is putting out the (9.6?  14.4?  12.2?   i forget) however, there are some more clever ways around this these days... 

Mini Precision GPS Reference Clock : Leo Bodnar Electronics    this guy has a single reference output that's programmable, just set it for whatever the input is to the VCO boards; and away it goes....     there's also one with dual outputs that are programmable.

I've also got (3) chassis -- two full repeaters, and a chassis with spare PA's some power supplies, etc.    I've been wanting to toss them for several years; the floor of my shed gave in (i'm sure 1200 lbs worth of MSF's helped) however, it matters very little to me if they're heaved into the dumpster or put on the air....    

I'm sure there's other various junque I'll find out there that can go with it....    out of sight, out of mind....  lest I have to go in the back yard for something and see that eye sore LOL 

Sincerely,
Lee M. Lemoine
N3LEE - Amateur Radio
"Experience is something you don't get until just after you need it."

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[Randolph A. Krenz]

Lee,

I definitely have the 14.4mhz and the super stable 9.6V.  Uniboard operation looks OK to me.  All the right signals going to the TX VCO (power, modulation, steering voltage), but no RF out from the TX VCO.  Inside the TX VCO, I found one leg of an inductor had come unsoldered.  I fixed that but no joy.  There are a bunch of varactors and some are testing weird in-circuit.  If I test those same varactors in-circuit in the RX VCO (which is very similar design) I get the expected results.

Randy

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[Lee M. Lemoine]

certainly sounds like something went awry when the inductor came out of circuit -- I can always pull a whole new uniboard (or three) out....    and if these have the HCSO tray or at least the converters on them, I'll yank those out too.. 

I wish I could spend more time at the board level these days....   most of my day goes screwy when new IT policies start blocking multicast traffic but only in a singular direction.... LOL

--LL

Sincerely,
Lee M. Lemoine
N3LEE - Amateur Radio
"Experience is something you don't get until just after you need it."

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[Randolph A. Krenz]

Lee,

To be clear, I’m looking for a TX VCO (the spring-mounted thingy next to Uniboard).  If you have one and are coming to Nearfest, perhaps we could connect.  Otherwise, I might take John/N1OTY up on his offer.  I’d rather not take possession of an entire MSF to get one small part.  My repeater only uses the RF deck of an MSF but uses other things for power supplies, power amps, etc (e.g. eliminating all the MSF heavy stuff 😊)

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[Lee M. Lemoine]

I've got all sorts of parts here -- and much like John, I'll be junking the rest soon....    It's been 10+ years and I haven't done a damned thing with them LOL        

I'm not going to make Nearfest; it  seems to coincide with my B-day weekend every year.    Working 7 days a week as I do; it's the one weekend my wife 'makes' me take off and escape; and no.... not to more radio stuff LOL 

Sincerely,
Lee M. Lemoine
N3LEE - Amateur Radio
"Experience is something you don't get until just after you need it."

To view this discussion on the web visit https://groups.google.com/d/msgid/near-900/002101d9716a%244df9aa20%24e9ecfe60%24%40gmail.com.