Vastelec V-FM02 stopped working...

[IdunBenhad]

Hi:
Looks like Santas elves have been busy. Glad it's working now. I wouldn't even breath on it! Could there possibly be a temperature problem? When you get a chance, you might try a can of freeze spray and see if you can get it to fail with cold.

I started my FM02 this morning and ran it all day playing music through it from Windows Media Player.

The transistors and other components show very little heat. The inductor may have a small heat rise, but it is very little. Almost non-detectable. (couldn't spell imperceptible.) There was no hum and had a good 1/4 mile range. Could hear it out to 1/2 mile, but noisy.

However, I found another problem, which I had last year. The second harmonic of my frequency , 101.7 Mhz is getting into my HDTV on channel 11 here in Yuma. I am going to order a low pass filter and put on it, as I don't have time to build one. The operating frequency of channel !! is ~200 Mhz. I may have to move my frequency and get away from that harmonic.


The symptom in the TV was breaking up of the audio and pixelization of the video.

Send those elves over this way, please.

Edit: 1737 MST: Moved the frequency to 99.7 and the TV channel 11 interference stopped. This means I will have to have a new sign made! Maybe I'll just have a small sign to cover the present 101.7.

2nd Edit: 1815: Still experiencing interference: moved to 98.7 and I think it has cleared up. This transmitter output must be really dirty. Additional note: did not see interference with carrier only. When I applied the audio, the interference started.

[Ekuth]

I was having intermittant problems with mine:

Pocket radio would pick up signal but car radio would not.
After unplugging everything, and letting it rest a few, it would work properly; 1/2 mile range nice and clear. And then it would not go more than a few feet..

WTH? :confused:

After reading the suggestions here, I went over both boards: cold solder joints. Redid all those myself, and checked the ribbon cable connections.

Not as tight as I'd like, so I added a dot of hot glue to make sure they stayed put.

Tonight?

Flawless. No problems, great range, crystal clear. :D:D:D

So, from my experience anyway, it looks like the main troubles with this lot of boards are the cold solder joints and wiggly ribbon cable connections.

[rogue9607]

Yeah, I'm not touching it until the new one gets here. If temperature is an issue, it's certainly not on the cold side (I'm in central Florida). I haven't noticed any issues with the frequency I'm using yet, though I haven't made up a sign yet. I plan on doing that tomorrow, so I'm sure any issues wouldn't come up until Sunday.

[IdunBenhad]

Hi:
Well, it happened! My FM02 quit transmitting at full power yesterday afternoon. It had been on almost continuously since Sunday after Thanksgiving. This unit was almost a year old, so it was not one of those from the recent group buy.

There is still some power out, but it is very little. I have not had a chance to check it out, so I replaced it the Belkin type transmitter I used last year. This thing provides plenty of range. I connected it to a converted PC supply using the 3.3 vdc output. No hum and it sounds good.

I had been very happy with the FM02 until it fouled up. I'm thinking the output transistor is gone.

As no one seems to have a schematic on this radio, it is very hard to work on.

If there is a schematic available, please let me know where and how I can obtain it.

[david_1]

no schematic ;-(...
how about someone talking some hi res photos may be a part schematic could be made ??
would need both sides of the pcb's :-)

David

[RFBurns]

Causes for finals to go in these are static buildup on the antenna and being fed right into the transmitter through the coax. The best fix for this is to place an inductor across the RF output and ground. The inductor will shunt any spikes or static buildup to ground but allow the RF signal to pass through as the inductor isolates the RF AC signal from ground, but provides that direct DC path to ground for static charges.

Chances are..this is what is happening to everyone encountering range issues after awhile. It is also possible that the antenna is not quite tuned correctly and there is high VSWR causing the finals to over work and thus..over heat and finally...POOF!

Happy Holidays!

RFB

[Jrd]

no schematic ;-(...
how about someone talking some hi res photos may be a part schematic could be made ??
would need both sides of the pcb's :-)

David

There is actually a schematic posted in the Wiki now directly from Vast here.

[david_1]

thanks i had noticed i have been looking at it..
i was interested in the output stages :-)
this site is cool its hard to justify building anything when they produce so much for so little.

unless anyone really has the rds pic code to encode a signal ?