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Hi Everyone,

I'm new to electronics and this forum, but I've already learned a lot just reading - thanx!

I've put together an AWM 633 Tx circuit and I'm getting nothing at the RF out.

I've got a solid 3.28v going in and there is definitely connectivity between the power in and the chip, and there is also definitely connectivity between the centre of the SMA connector and the chip with no shorts (at least I can't find any and I've tested it to death!)

Also when its powered, nothing is even getting slightly warm which can't be good!

As I said I'm new to this so I'm sure it'll be something dumb, so please take a look and tell me what an idiot I'm being!!

Thanks for any comments......

AIRW%20TX1.jpg

AIRW%20TX2.jpg

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Sounds odd. With power and gnd connected, the module should get warm after a few minutes of operation. So I suspect that one of these signals is not electrically connected to the module. When making your measurements, are you simply probing the header posts you installed, or are you probing the actual PCB trace on the module where it really matters?

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Sounds odd. With power and gnd connected, the module should get warm after a few minutes of operation. So I suspect that one of these signals is not electrically connected to the module. When making your measurements, are you simply probing the header posts you installed, or are you probing the actual PCB trace on the module where it really matters?

Hi Mr. RC-Cam,

Thanks for the comment - the chip is mounted at the top of the posts and there is room to get in underneath with a probe. I'm testing between -ve and the copper rectangles on the bottom of the chip which correspond to the half circle connections, and I'm getting voltage at that point. (had fun trying to take this picture - why do they make these things so hard to attach to anyway?)

Are there any other tests I can do?

What sort of reading should I be able to detect at the aerial with a volt meter (I'm getting nothing at all so far)?

Thanks for your help!

AIRW%20TX4.jpg

Edited by Xelax

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Are there any other tests I can do?

Hold one meter lead on the tin metal case of the RF module. Place the other meter probe on pin 9. Do you read 3.3V? If you do, then I am out of ideas.

What sort of reading should I be able to detect at the aerial with a volt meter (I'm getting nothing at all so far)?

You can't use a voltmeter to troubleshoot the RF port. It is not advisable to connect DMM's to RF ports.

By the way, what battery voltage are you using? The reason I ask is because your Vreg is not heatsinked and will easily go into thermal shutdown if it gets too hot. It may be running cool right now, but once you get the module working the Vreg's temperature will change dramatically.

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How do you know there's no RF out? What are you measuring it with? It could be your receiver (if you're using it to detect signal) could be bad.

If all you have is a DMM then put a small signal diode (either polarity, + or -) on the DMM probe and use that to get an indication of RF until you can buy an RF Probe that'll work at 2.5 gc.

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Hold one meter lead on the tin metal case of the RF module. Place the other meter probe on pin 9. Do you read 3.3V? If you do, then I am out of ideas.

Thanks for the input!

I've got nothing at pin9, but I've checked and re-checked that its connected to the chip (and all the other pins too!)

As for voltage, I'm running it from a 12v wall power supply - if I can get it to work, I guess I'll have to rethink the layout with a heatsink!

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How do you know there's no RF out? What are you measuring it with? It could be your receiver (if you're using it to detect signal) could be bad.

If all you have is a DMM then put a small signal diode (either polarity, + or -) on the DMM probe and use that to get an indication of RF until you can buy an RF Probe that'll work at 2.5 gc.

I had no idea how to test for rf output - thanks!

Tried it and still nothing I'm afraid - still no temp either so I guess there are still problems.....

I may be able to borrow an oscope tomorrow - what would I look for?

Thanks for the help!

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If you are getting nothing at pin 9 then there may be something wrong with the module. Do you have another module to test with?

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If you are getting nothing at pin 9 then there may be something wrong with the module. Do you have another module to test with?

Thanks and no I don't have another - looks like I'll be ordering one tomorrow!

I've no idea why it may be damaged - this is its first installation, it hasn't been sent any excessive voltages etc, its taken some heat during soldering but that can't be avoided.....

Any ideas or advice on keeping these things alive much appreciated !! Any really obvious do's and don'ts ? Being new to this, I need all the info I can get - I can't afford to keep breaking them......

Thanks again for all the help!!

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I've got nothing at Pin-9

Ah-ha! Now we are getting somewhere.

Pin-9 is internally connected to the 3.3V input (Pin-15). If Pin-9 is 0V then you are missing Gnd or 3.3V power to the module. You need to revisit those other pins. I suspect that you will find that one of them is not connected.

If the Airwave module is actually getting power it will run warm/hot after a few minutes of use. It will also draw about 500mA of current. Use this information to help your troubleshooting.

Don't use the wallwart for power (most are not good V+ sources for this application). Grab a suitable battery such as a 2-cell LiPO or five cell NiCD.

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Ah-ha! Now we are getting somewhere.

Pin-9 is internally connected to the 3.3V input (Pin-15). If Pin-9 is 0V then you are missing Gnd or 3.3V power to the module. You need to revisit those other pins. I suspect that you will find that one of them is not connected.

If the Airwave module is actually getting power it will run warm/hot after a few minutes of use. It will also draw about 500mA of current. Use this information to help your troubleshooting.

Don't use the wallwart for power (most are not good V+ sources for this application). Grab a suitable battery such as a 2-cell LiPO or five cell NiCD.

Took the module and header posts off the board and checked all connections and they're all OK - replaced it and still nothing.

Guess that means the module has had it.........?

Are these really that easy to damage? Any extra precautions I can take next time?

Thanks again for all the help!!

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Are these really that easy to damage?

I have privately helped several folks get various Airwave RF modules to work. Not that it applies here, but in every case they had a wiring/assembly issue. I don't recall any that were destroyed by the misdeeds, which frankly is a miracle; Electronic components are very unforgiving and are easily damaged.

For that reason it is best to consider this a problem that is caused by your board assembly. If there is any chance of this then the next module will be in the same predicament. So, don't replace it until you are 110% certain that your installation is correct.

But at this point I'm reluctant to say your module is dead. It seems odd to me that you cannot measure continuity between Pin-9 (By-pass) and Pin-15 (3.3V)? These are internally connected together in the module. They should be a dead short when measured by the ohmmeter. For that reason, any voltage that is on the 3.3V input should appear on Pin-9.

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Maybe the trace going to Pin 15 has been damaged when soldering the pins to it. Those traces easily break if you apply a bit of force on the connections, and it's usually rare to be able to see it with bare eyes.

What I'd do is try to connect the +3.3V to pin 9 instead if Mr.RC-Cam says they're internally connected.

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For that reason it is best to consider this a problem that is caused by your board assembly. If there is any chance of this then the next module will be in the same predicament. So, don't replace it until you are 110% certain that your installation is correct.

I think you're probably right - my new chip arrived this morning and I'm going to start again with the board assembly - I've got to include things like heatsink and I'm sure I can get a more efficient and smaller layout. This time I will take extra care over it and make certain of eveything step by step!

A question, is my choice of components OK? I notice people talking about tantalum caps and things, am I OK with elctrolytics?

Also, connecting the commons either side of the rf out to the sma was really hard, is there a trick or good technique to this?

Thanks for your help and advice - without you guys I'd be nowhere right now!

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Maybe the trace going to Pin 15 has been damaged when soldering the pins to it. Those traces easily break if you apply a bit of force on the connections, and it's usually rare to be able to see it with bare eyes.

What I'd do is try to connect the +3.3V to pin 9 instead if Mr.RC-Cam says they're internally connected.

Quite possible I've damaged it, the chips been in and out a couple of times. Before I start my new board, I'll try direct connect of 3.3v to pin 9 - fingers crossed!

Can anyone tell me why the modules are made with these connections (they're so awkward) - are they designed for a specific installation method and if so, what is it?

Thanks again - will let you know how I get on!

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Quite possible I've damaged it, the chips been in and out a couple of times.

There's a chance the internal connection has been damaged by an assembly error. If it was me, I would double check to see that the Bypass pin (pin-9) is not shorted to ground by the wiring. Then I would jumper it to 3.3V. Then check to see if the module is drawing the recommended current. If all goes well, this may salvage it.

Before I start my new board, I'll try direct connect of 3.3v to pin 9 - fingers crossed!

I don't advise you do that to a perfectly good module. Just install it as directed by the data sheet.

Can anyone tell me why the modules are made with these connections (they're so awkward) - are they designed for a specific installation method and if so, what is it?

It's intended for surface mount installations. There are SMD pads on the bottom. They allow for easy machine installation on a PCB. Plus, the module runs hot, and the intimate SMD connections provides ideal thermal conduction (heatsinking) to the ground plane of a properly designed PCB to help mitigate the heat issue.

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Just to let you know.....

Joined across to the bypass pin and finally got some temperature in the module but no picture. Then decided to build a new board with new module, which tested up fine straight away, but still no picture.

Tested over my Rx board and finally found a dodgy earth and I'm away!!!

Absolutely perfect, clean A1 video !! (am not using sound at this time) - am going to rebuild the damaged Tx module circuit now I know the Rx is fine to see if the 3.3v to bypass pin is a valid fix - will let you know>>>>

Can't thank you all enough - would never have got there without your help!!

BRILLIANT!

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OK - thought I had this sussed.........!

My setup worked yesterday and today I rebuilt it to a more compact layout and guess what - it doesn't work yet all the reading seem OK.

I've rebuilt it twice now and gone over and over it but still no pic.....

Here's what I'm reading:

V In : 4.99V

Bypass: 3.61V

Ch Select pins: 1.1V

Audio Outs: 2.45V (nothing connected - not even the caps)

Video Out: 3.52V (nothing connected - 470uf 35v in place)

2.45V (TV connected)

1.63V (Tx on & TV Connected)

Do any of these reading mean anything to anyone, they look OK to me, although the Video output seems a bit high...

Would really appreciate the help!

Edited by Xelax

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The AWM633 is a 3.3V device. It looks like your voltage is higher, which is probably a bad thing.

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The AWM633 is a 3.3V device. It looks like your voltage is higher, which is probably a bad thing.

REALLY SORRY Mr RC Cam!

Forgot to mention, this is my AWM 634 Rx I'm talking about (I can be very dumb at times!)- as far as I know the Tx is now working!

I should also mention that when the Rx was briefly working and connected to the AV input on the TV I got snow (until the Tx was turned on), but now when its connected I just get the blank black AV stanby screen, yet as I say there is voltage at the video out.....

Any thoughts?

Edited by Xelax

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If you know anyone that has electronics experience, then ask them to check over your work. Often these problems are related to the wiring and fresh eyes will find it.

The AWM634's pins are soldered in place. Too much heat during PC board soldering can reflow the connection at the module and cause problems with the factory's connection. So, keep that in mind as you work on it.

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AWM634RX measurements

V In Pin 13 = 4.99V: GOOD

Bypass Pin 12 = 3.61V: GOOD

Ch Select pins 18-20 = 1.1V: Can't comment, mine are driven from a microcontroller.

Audio Outs pins 9-10 = 2.45V (nothing connected - not even the caps): SEEMS OK

Video Out pin 8 = 3.52V (nothing connected - 470uf 35v in place): Mine is about 3V.

2.45V (TV connected): Mine remains at about 3V.

1.63V (Tx on & TV Connected): Mine remains at about 3V.

The video out voltages are probably not valid comparisons. They are an AC signal with a DC offset, so the voltage your meter reads might not be the same as what I see. Your observation that your monitor no longer shows snow suggest the Rx is goofed up. But, there is no way to know at this point if the Tx is the also bad.

Are you sure both the Tx and Rx are set to the same RF channel? If the DIP switch wiring is wrong then setting the freq channel would be hit and miss.

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AWM634RX measurements

V In Pin 13 = 4.99V: GOOD

Bypass Pin 12 = 3.61V: GOOD

Ch Select pins 18-20 = 1.1V: Can't comment, mine are driven from a microcontroller.

Audio Outs pins 9-10 = 2.45V (nothing connected - not even the caps): SEEMS OK

Video Out pin 8 = 3.52V (nothing connected - 470uf 35v in place): Mine is about 3V.

2.45V (TV connected): Mine remains at about 3V.

1.63V (Tx on & TV Connected): Mine remains at about 3V.

The video out voltages are probably not valid comparisons. They are an AC signal with a DC offset, so the voltage your meter reads might not be the same as what I see. Your observation that your monitor no longer shows snow suggest the Rx is goofed up. But, there is no way to know at this point if the Tx is the also bad.

Are you sure both the Tx and Rx are set to the same RF channel? If the DIP switch wiring is wrong then setting the freq channel would be hit and miss.

BRILLIANT thank you - exactly what I needed to know!

Back to testing.........

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AWM634RX measurements

V In Pin 13 = 4.99V: GOOD

Bypass Pin 12 = 3.61V: GOOD

Ch Select pins 18-20 = 1.1V: Can't comment, mine are driven from a microcontroller.

Audio Outs pins 9-10 = 2.45V (nothing connected - not even the caps): SEEMS OK

Video Out pin 8 = 3.52V (nothing connected - 470uf 35v in place): Mine is about 3V.

2.45V (TV connected): Mine remains at about 3V.

1.63V (Tx on & TV Connected): Mine remains at about 3V.

The video out voltages are probably not valid comparisons. They are an AC signal with a DC offset, so the voltage your meter reads might not be the same as what I see. Your observation that your monitor no longer shows snow suggest the Rx is goofed up. But, there is no way to know at this point if the Tx is the also bad.

Are you sure both the Tx and Rx are set to the same RF channel? If the DIP switch wiring is wrong then setting the freq channel would be hit and miss.

Hi Mr RC Cam,

Just to let you know my system now works!!

The problem was (unsurprisingly) my lack of knowlege of electronics. I had fitted a 470 uf cap to the video output and this was preventing it working. as soon as I removed it, it worked fine. The caps are on the circuit diagram though, so I assume I'm not understanding something here. Is this a different type of cap that needs to be used? If so, how can you tell as the icon used is the same as other caps?

Confusing, but you live and learn!

Thanks for all the help!

Edited by Xelax

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Glad to hear you are working. The 470uF cap is needed and is customary in the video path, so you should add it back into the circuit. Your cap may have been installed backwards or was defective. Or, maybe it was 470pF rather than 470uF.

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