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Author Topic: Panaxis FME 500 issue  (Read 161 times)

Offline N2NXZ

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Panaxis FME 500 issue
« on: August 08, 2018, 1618 UTC »
Going to take a shot in the dark and hope someone is familiar with the older Panaxis FME 500 exciter.
Mine was build years ago and worked perfectly.I had put it away working about 20 yrs ago and recently took it out to play around.
It powers up,but PLL does not lock.Searched around for a replacement PLL to see if that was bad,actually found one but was not easy.
Swapping that out did nothing new.
Finally went through all solder joints,swapped out the 470uf electro and both 10uf`s...a slight better improvement but still no lock.
Swapped out the 2 main RF transistors and all 3 trimmer caps and even re-wound a new coil and tap.
Although it appears to tune better and wants to lock,still drifting all over.Green LED lights on/off/on/off ...etc.
Depends how close my hand is to circuit or what I touch.
Sometimes it acts like it will lock,but never stays that way.
I just ordered new 47uh cap and all tantalum`s to see if they deteriorated over time.
After that...not sure what else to do and hope someone has an idea I am missing.
Jim

Offline Pigmeat

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Re: Panaxis FME 500 issue
« Reply #1 on: August 08, 2018, 2320 UTC »
There were enough of those things floating around in those days. I'm sure someone here will have an answer for you.

Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #2 on: August 09, 2018, 0025 UTC »
Still thinking the caps may have changed over time.
Only thing that could be different from just sitting around.
I do not think IC chips fail just sitting in a box.
Have to rebuild the common components and see how it goes.
Jim

Offline ThaDood

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Re: Panaxis FME 500 issue
« Reply #3 on: August 09, 2018, 0251 UTC »
Does yours come with the IC sockets? If so, try prying up the IC's out, then reseat them back in. That's worked on Ramsey FM-25 FM TX's as well. Also, be sure that you have very clean P.S. powering it at +12VDC. Another thing is to check the AUDIO IN. Is it for standard AF, or optioned for wide MPX audio from the FMX unit? I've seen where you have to have an RFC in series with that. Couple of things to check. Hope ya get 'er going, and I like seeing Ernie's gear still rockin' after all these years.
From DC to light, I take a huge spectrum bite!

Offline TheRelayStation

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Re: Panaxis FME 500 issue
« Reply #4 on: August 09, 2018, 1607 UTC »
something i do in cases like this is use a can of "duster" upside down as "freeze spray" and a hair dryer as heat, both applied in small areas around the PCB and the components to narrow down the area of defect.
also, using the bristles of a tooth brush to "brush" and locate a component that may have become loose and the plastic end of the tooth brush to tap around the circuits/PCB looking for cold solder joints and loose components or connections.
this type of troubleshooting is performed with the unit on while watching to see if there are any changes in operation.
depending on where it was stored, if there was high fluctuations in temperature and humidity, there will be expanding/contraction of components/solder joints as well as electrolytics that may have "dried out" and adjustments fixed with wax that may have moved out of place.
im not sure if this unit used any of the component glue to stabilize the components to the PCB but lots of older electronics were severely plagued by this yellow glue becoming conductive when it dried out and turned a dark yellow or brown color.
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Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #5 on: August 10, 2018, 1349 UTC »
Thank you all for the tips.
I had cleaned the entire PCB with alcohol and tooth brush.
Re-soldered ALL components fresh using no clean flux.
Removed all IC`s as they are all in sockets,re-seated them also thinking maybe poor connection.
Tried a replacement PLL IC.
Replaced both RF transistors,trimmer caps and some electrolytics so far.
Soon as the other new supplies arrive will replace those too.
I am not modulating it yet,just testing the unit on a 50 ohm dummy load for now
My power supply sucks and think that could be one issue.I have another PS and will try it again once the new components arrive.
I think I have a good shot to getting this working once everything is freshened up a bit.
Power supply could be the issue and was also thinking that.It is very old and probably dirty voltages.
To me,the entire system was a work of art and building it was a great challenge.
Will post new info sometime next week.
Jim

Offline Pigmeat

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Re: Panaxis FME 500 issue
« Reply #6 on: August 11, 2018, 0206 UTC »
Glad to hear the old horse still has some life left.