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Re: My PA keeps blowing UQRSS Kit << Help >>

"G1IVG"
 

Hi Tony,

I get the problem if I run the PA at 5v (linking from the +5v to +PA connection on the kit and also if I try to run the kit from 5v by connecting to +5v and then have a separate 9v supply for the PA going to the +PA connection.

Tonight I have eliminated the GPS by completely disconnecting it and I also removed my 5v and 9v power supplies (7805 and 7809 voltage regulators and associated capacitors) by removing them from the circuit.

I've now tested the kit on it's own and supplied from an external Farnell stabilised variable PSU and get the same problem.

Therefore the problem has to be a short or one of the BS170's etc.

I'm now going to remove the two BS170's and do some more testing.

Regards
Colin
G1IVG

--- In QRPLabs@..., Tony Volpe <tony.volpe.1951@...> wrote:

Have you measured the output voltage of the 7809? The fact that the problem
doesn't happen when the higher voltage is applied to the PA suggests to me
that there may be an issue around the regulation on the PA supply.

73s

Tony G0BZB
Re: My PA keeps blowing UQRSS Kit << Help >>

"G1IVG"
 

The PA is loaded by the LPF and then I have a 50 ohm dummy load on the output.

Regards
Colin
G1IVG

--- In QRPLabs@..., Stephen Farthing <squirrox@...> wrote:

What load are you using for the PA output?

On 27 September 2012 21:48, Stephen Farthing <squirrox@...> wrote:

Tony,

Sorry to hear your bad luck.

As has already been said, if you are using BS170s as a replacement for the
2n7000 they fit the opposite way around. But I am sure you won't have made
that mistake.

Are you sure that your voltage regulators are intact and the capacitors
each side of them are ok and of the right value.? Are you sere they are
delivering the correct voltage under load?

When you unplugged the beacon did you switch the power off first? Do you
have a way of measuring the current into the beacon if so what is it?

73s Steve


On 27 September 2012 21:28, lowemmission <lowemmission@...> wrote:

**


You say you replaced both transistors in the kit; as only one is supplied
originally you have replaced them as 2N7000? or not by chance with BS170?
.Their configuration does not follow the PCB profile. lowemmission@


--- In QRPLabs@..., "G1IVG" <colinlowe_home@> wrote:

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working
fine until last night. When I unplugged the kit and plugged it back in
again after about 15 seconds I heard a pop and a burning smell and the LCD
display just had black squares across it.
On closer inspection the PA transistors had blown and either they or
the fault that caused them to blow was also dragging the power supply down
causing the display problem.

I have been running the kit for the last month from 13.8v PSU then
through a 7805 voltage regulator for the 5v supply to the kit and also the
GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage
regulator that supplies 9v to the +PA connection. This has been working
fine for a month until last night.

After it blew, I removed the two blown transistors and installed two
new ones as before. I then powered it up and noticed the transistors
heating up and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc.
but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v
going to 5v supply connection with nothing on the +PA connection the
transistors stay cold.

If I put a jumper between the 5v connection and the PA connection
therefore supping the PA with 5v the transistors heat up within a few
seconds more or less the same as when supplied with 9v. Therefore I have a
fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper
installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only
component I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
Re: My PA keeps blowing UQRSS Kit << Help >>

"G1IVG"
 

Hi Stephen,

Sorry for the delay in my reply.

I have now done some more testing and have done the following:

(1) I disconnected the GPS wiring to eliminate any problem there.

(2) I have disconnected the 5v and 9v voltage regulators and all additional capacitors to eliminate the PSU regulator I had built using a 7805 and 7809 voltage regulator.

(3) So currently I'm now supplying the kit from a Farnel stabilised variable PSU running at 5v.

If I connect 5v to the "+5v" connection on the kit and the 0v to the "GND" connection on the kit, it draws about 0.1 amperes at 5v.

Now the problem..... If I then fit the jumper between the "+5v" connection and the "+PA" connection on the kit it draws over 2 amperes at 5v and within a couple of seconds the BS170 transistors get so hot you can't touch them. The BS170's are mounted correctly at 180°compared to the original 2n7000.

I'm going to try another couple of BS170's just in case I have duff one. other than that I can't see what the problem could be.

Regards
Colin
G1IVG

--- In QRPLabs@..., Stephen Farthing <squirrox@...> wrote:

Tony,

Sorry to hear your bad luck.

As has already been said, if you are using BS170s as a replacement for the
2n7000 they fit the opposite way around. But I am sure you won't have made
that mistake.

Are you sure that your voltage regulators are intact and the capacitors
each side of them are ok and of the right value.? Are you sere they are
delivering the correct voltage under load?

When you unplugged the beacon did you switch the power off first? Do you
have a way of measuring the current into the beacon if so what is it?

73s Steve

On 27 September 2012 21:28, lowemmission <lowemmission@...> wrote:

**


You say you replaced both transistors in the kit; as only one is supplied
originally you have replaced them as 2N7000? or not by chance with BS170?
.Their configuration does not follow the PCB profile. lowemmission@


--- In QRPLabs@..., "G1IVG" <colinlowe_home@> wrote:

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working
fine until last night. When I unplugged the kit and plugged it back in
again after about 15 seconds I heard a pop and a burning smell and the LCD
display just had black squares across it.
On closer inspection the PA transistors had blown and either they or the
fault that caused them to blow was also dragging the power supply down
causing the display problem.

I have been running the kit for the last month from 13.8v PSU then
through a 7805 voltage regulator for the 5v supply to the kit and also the
GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage
regulator that supplies 9v to the +PA connection. This has been working
fine for a month until last night.

After it blew, I removed the two blown transistors and installed two new
ones as before. I then powered it up and noticed the transistors heating up
and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc.
but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v
going to 5v supply connection with nothing on the +PA connection the
transistors stay cold.

If I put a jumper between the 5v connection and the PA connection
therefore supping the PA with 5v the transistors heat up within a few
seconds more or less the same as when supplied with 9v. Therefore I have a
fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper
installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only component
I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
Re: PA voltage recommendations ?

Tony Volpe
 

I think 500mw is plenty. 200mw will be fine too. The difference is only 3db. Results will all depends on two factors: your antenna and the propagation. I will say this though, you will get FAR BETTER results with a good antenna and 200 mw than with 500 mw and a bad antenna. You can get a few spots with any bit of wire thrown out of a window, but you will get amazing results if you don't compromise on good antenna practice. I am using a full wave forty meter horizontal loop at the moment. I am very pleased with it. Its height varies between about 28 and 18 feet. It is a rectangle about twenty five feet wide over the house and longer in the other direction going down the garden. I feed it with open wire and 300 ohm ribbon and match the impedance on different bands with an atu. Works great on forty, thirty and twenty meters. I haven't really tried it above that.


Good luck with your kit when it comes. Try it at 5 volts first. You may be surprised how many spots you get. I was.
Re: PA voltage recommendations ?

"andyfoad@..."
 

Perfect, thanks Tony !

I'll stick to your advice.

500mw seems like a good power to play with.

I like the idea of having just a bit more power in order to give
a bit more advantage in discovering things like if there's another
hop in propagation becoming available, as well of course as standing
more chance of being spotted.

Did a test today on 30m using 500mw and 20ft of wire pinned to the
spare bedroom wall today to simulate what sort of results to expect
when my kit arrives.

A pretty poor antenna by most standards.

Best DX was some 6000km this morning.

Enabled me to see how within about 30 mins of sunrise the band beginning to open again and proving my propagation models.

(My main interest in having the kit).

Vy 73 de Andy G0FTD
GQRP 13690
Re: PA voltage recommendations ?

Tony Volpe
 

My recommendation if you want to operate with more power would be NOT TO USE THE 2N7000. Instead, fit two BS170 fets. They are very cheap and have a much higher dissipation.?

IMPORTANT - the arrangements of the drain, gate and source is the opposite way around to the 2N7000, so fit the transistor the OPPOSITE way to the silkscreen image. Where the curve is shown on the silkscreen, place the flat of your BS170.

I have been running a kit with two of these in now at 9.2v on the PA for weeks - 24/7. They work well and generate less heat than the 2n7000 and are less likely to go hot and blow up. At that voltage (9.2v) the pair put out 515mw at 10.140MHZ.

I have tried higher voltages and was able to get mine up to 825mw with 12.5 volts but it was counterproductive, because I got very large drift on the signal caused by heat. The PA and heatsink were very warm at that power, so I don't recommend it. 9.2 volts is absolutely fine and will get you a lot of spots if you have a decent antenna.

YOU MUST USE HEAT SINKING IF YOU USE MORE THAN ABOUT 6V. I made a very simple heat sink made from a piece of bent over aluminium. a thin strip bent over on itself can be fitted over the transistors and will stay there just by its own springiness. As fitted it was too tight to just push on, but I opened the 'U' shape with a small screwdriver and slipped it over the pair of fets.

I built two kits. On the second one, I soldered header sockets to the board that I was able to break off a strip with side cutters. This has let me fit things like PA transistors and capacitors just by plugging them into the sockets on the board, meaning I can experiment easily with parts.




Tony G0BZB
Re: UQRSS runs much too slow

Stefan Teuscher
 

Hello Steve,
hello Hans,

many thanks for the replacement of the too slow chips.
In the meantime I have got a GPS also, so there is only an antenna missing.
The new chip seems running correct.
But I had to remove capacitor C5 completely. Otherwise with "GPS on" some strange things happen when the chip can't tune to the frequency set in the parameters, but tries and tries and tries. Without C5 I can tune with C8 in test mode (GPS on) nearly exactly to 10.240.200 displayed and then the frequency locked loop (I think it is a sort of it) locks correctly.

Now I have one UQRSS running in test but only via coax cable fed directly into the receiver (Rohde+Schwarz ESV) which measures exactly 128 dB???V at 50 Ohms = 21 dBm = 126 mW (5 Volt power supply also for the PA).
I want to run it first for a while in this mode and in the meantime thinking about a suitable antenne.

Many thanks

Stefan
DL4GCS
PA voltage recommendations ?

"andyfoad@..."
 

Greetings all !

I've just placed my order for the latest Ultimate QRSS kit, mainly to
use on WSPR but I'm sure I'll play with the other modes eventually.

My plan is to use two of the 2N7000's at a higher voltage.

Is there any recommendations for this voltage ?

I've seen a few posts referring to 9v, but does anyone have any
practical experience at say 12v yet, and expected power output ?

Kind regards,

Andy G0FTD
GQRP 13690
ARRL MEMBER
Chip problems

Stephen Farthing
 

hi guys,

I have noticeded a couple of you are still having problems. I will ship replacements which i will test on my own beacon first to verify that they work when they leave me. This wont happen until after the thirteenth of october as i am away.?

Bye for now,

steve
This is getting to be spooky, someone somewhere does not want me on 160m

"woodiescbj"
 

Hi to all members, I have received the ATmega V1,6 (thanks Steve) and have inserted it the correct way round but there is nothing on the display (totally blank) when I insert the old chip the display is normal (except for the cycling of course) I just can not believe the bad luck I am having with this time.

Vy 73 Colin
WSPR beacon with the "old" QRSS kit

"Yannick"
 

Hi,

I have finished modifying my 30 meters QRSS kit into a WSPR autonomous beacon using a TI Launchpad with MSP430G2553 (4,6 USD micro-controler kit).
Here some pictures and more details (in french but you can use the provided automatic translation) :


Reports have been good with up to 6000km with the 90mW of the beacon. I will have to raise a little bit the PA supply voltage in order to get a little bit more power from the BS170.
The beacon is now running for 4 days showing no significant time drift without GPS.

I still have to do some clean up in the code but I will soon publish the code and a schematic. The Launch Pad is really cheap and the ability to reprogram it on the fly with the USB port allows you to virtually transmit any waveform. The other parts cost less than 2 USD.

73,
Yan.
Re: Ultimate QRSS: problem with set-up menu

"Paul"
 

Hi Hans,Steve,

Today the new processor arrived, I installed it and everything works well. Setting up is a breeze now.
Still don't know how the eeprom got corrupted.

Now on to the GPS module, I m going to use an old Jupiter board.

Thanks or the great service and a great kit.

73 Paul PE1OKU.

--- In QRPLabs@..., "Paul" <pe1oku@...> wrote:

Hi Hans,

Okay, I will do that, thanks for the quick response.

Paul PE1OKU
Re: My PA keeps blowing UQRSS Kit << Help >>

"lowemmission"
 

I hope you've had some success but a sideways look at this might suggest you could have replaced the first failed PAs with 2N7000 and installed them as BS170. You do say that this happens when:

If I put a jumper between the 5v connection and the PA connection therefore
supping the PA with 5v the transistors heat up within a few seconds more or less
the same as when supplied with 9v. Therefore I have a fault somewhere.


rgds lowemmission@







--- In QRPLabs@..., "G1IVG" <colinlowe_home@...> wrote:

The two BS170's are installed correctly (180 degrees compared to the original 2n7000). I have had them in the kit for over a month and it's been working more or less 24hrs a day since with no issues until I unplugged the kit and plugged it back in yesterday when they blew. They blew more or less 15 seconds after re-applying power. Then when I installed the new ones, they also heated up very quickly and I pulled the power plug out before any damage was done. I have double checked and the transistors are mounted correctly (180 degs).

It's as if there is a short, but I just can't find it which is frustrating as the kit is fairly straight forward. All components look fine and the PCB has been checked for shorts and all looks fine.

I'm wondering is IC2 74HC00 has a problem as it's really the only bit I haven't changed.

To confirm I only get the problem when either 5v or 9v is applied to the +PA connection. If I leave the +PA connection floating and just 5v connected to the 5v Supply connection the kit works fine apart from the much lower RF power output.

Regards
Colin
G1IVG



--- In QRPLabs@..., "lowemmission" <lowemmission@> wrote:

You say you replaced both transistors in the kit; as only one is supplied originally you have replaced them as 2N7000? or not by chance with BS170? .Their configuration does not follow the PCB profile. lowemmission@

--- In QRPLabs@..., "G1IVG" <colinlowe_home@> wrote:

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.

I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.

After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.

If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
Re: My PA keeps blowing UQRSS Kit << Help >>

Tony Volpe
 

Have you measured the output voltage of the 7809? The fact that the problem doesn't happen when the higher voltage is applied to the PA suggests to me that there may be an issue around the regulation on the PA supply.

73s

Tony G0BZB
Re: My PA keeps blowing UQRSS Kit << Help >>

Stephen Farthing
 

What load are you using for the PA output?


On 27 September 2012 21:48, Stephen Farthing <squirrox@...> wrote:
Tony,

Sorry to hear your bad luck.?

As has already been said, if you are using BS170s as a replacement for the 2n7000 they fit the opposite way around. But I am sure you won't have made that mistake.?

Are you sure that your voltage regulators are intact and the capacitors each side of them are ok and of the right value.? Are you sere they are delivering the correct voltage under load?

When you unplugged the beacon did you switch the power off first? Do you have a way of measuring the current into the beacon if so what is it?

73s Steve


On 27 September 2012 21:28, lowemmission <lowemmission@...> wrote:
?

You say you replaced both transistors in the kit; as only one is supplied originally you have replaced them as 2N7000? or not by chance with BS170? .Their configuration does not follow the PCB profile. lowemmission@



--- In QRPLabs@..., "G1IVG" wrote:
>
> Hi all,
>
> I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
> On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.
>
> I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.
>
> After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.
>
> I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.
>
> If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.
>
> If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.
>
> If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.
>
> Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.
>
> Looking for any ideas or other tests I could do to identify the problem.
>
> Regards
> Colin G1IVG
>
Re: My PA keeps blowing UQRSS Kit << Help >>

Stephen Farthing
 

Tony,

Sorry to hear your bad luck.?

As has already been said, if you are using BS170s as a replacement for the 2n7000 they fit the opposite way around. But I am sure you won't have made that mistake.?

Are you sure that your voltage regulators are intact and the capacitors each side of them are ok and of the right value.? Are you sere they are delivering the correct voltage under load?

When you unplugged the beacon did you switch the power off first? Do you have a way of measuring the current into the beacon if so what is it?

73s Steve

On 27 September 2012 21:28, lowemmission <lowemmission@...> wrote:
?

You say you replaced both transistors in the kit; as only one is supplied originally you have replaced them as 2N7000? or not by chance with BS170? .Their configuration does not follow the PCB profile. lowemmission@



--- In QRPLabs@..., "G1IVG" wrote:
>
> Hi all,
>
> I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
> On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.
>
> I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.
>
> After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.
>
> I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.
>
> If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.
>
> If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.
>
> If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.
>
> Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.
>
> Looking for any ideas or other tests I could do to identify the problem.
>
> Regards
> Colin G1IVG
>
Re: My PA keeps blowing UQRSS Kit << Help >>

"G1IVG"
 

The two BS170's are installed correctly (180 degrees compared to the original 2n7000). I have had them in the kit for over a month and it's been working more or less 24hrs a day since with no issues until I unplugged the kit and plugged it back in yesterday when they blew. They blew more or less 15 seconds after re-applying power. Then when I installed the new ones, they also heated up very quickly and I pulled the power plug out before any damage was done. I have double checked and the transistors are mounted correctly (180 degs).

It's as if there is a short, but I just can't find it which is frustrating as the kit is fairly straight forward. All components look fine and the PCB has been checked for shorts and all looks fine.

I'm wondering is IC2 74HC00 has a problem as it's really the only bit I haven't changed.

To confirm I only get the problem when either 5v or 9v is applied to the +PA connection. If I leave the +PA connection floating and just 5v connected to the 5v Supply connection the kit works fine apart from the much lower RF power output.

Regards
Colin
G1IVG

--- In QRPLabs@..., "lowemmission" <lowemmission@...> wrote:

You say you replaced both transistors in the kit; as only one is supplied originally you have replaced them as 2N7000? or not by chance with BS170? .Their configuration does not follow the PCB profile. lowemmission@

--- In QRPLabs@..., "G1IVG" <colinlowe_home@> wrote:

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.

I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.

After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.

If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
Re: My PA keeps blowing UQRSS Kit << Help >>

"lowemmission"
 

You say you replaced both transistors in the kit; as only one is supplied originally you have replaced them as 2N7000? or not by chance with BS170? .Their configuration does not follow the PCB profile. lowemmission@

--- In QRPLabs@..., "G1IVG" <colinlowe_home@...> wrote:

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.

I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.

After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.

If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
My PA keeps blowing UQRSS Kit << Help >>

"G1IVG"
 

Hi all,

I built my 30m Ultimate QRSS kit over a month ago and it's been working fine until last night. When I unplugged the kit and plugged it back in again after about 15 seconds I heard a pop and a burning smell and the LCD display just had black squares across it.
On closer inspection the PA transistors had blown and either they or the fault that caused them to blow was also dragging the power supply down causing the display problem.

I have been running the kit for the last month from 13.8v PSU then through a 7805 voltage regulator for the 5v supply to the kit and also the GPS, then for the PA I come from the same 13.8v supply to a 7809 voltage regulator that supplies 9v to the +PA connection. This has been working fine for a month until last night.

After it blew, I removed the two blown transistors and installed two new ones as before. I then powered it up and noticed the transistors heating up and starting to smoke !!!!! I quickly removed the power.

I have checked the PCB for shorts and all the capacitors and coils etc. but can't find any short.

If I remove the 9v supply from the +PA connection and just have the 5v going to 5v supply connection with nothing on the +PA connection the transistors stay cold.

If I put a jumper between the 5v connection and the PA connection therefore supping the PA with 5v the transistors heat up within a few seconds more or less the same as when supplied with 9v. Therefore I have a fault somewhere.

If I remove IC1 (ATmega168) from its socket and with the jumper installed as above, the transistors heat up in a few seconds.

Is it possible that I have blown IC2 74HC00 as that's the only component I have not checked.

Looking for any ideas or other tests I could do to identify the problem.

Regards
Colin G1IVG
Re: I am having trouble with the UQRSS Kit for 160m, any advice would be appreciated

"woodiescbj"
 

Will do Philip, Thanks for the idea, I will start the DVM/Circuit diagramme tests tomorrow.

73 Colin

--- In QRPLabs@..., "p19547ct" <pcteee@...> wrote:

Colin
Any chance of posting (in photo album on here) a decent quality photo
of top and bottom of your board so a few more fresh eyes can have a look for you assuming you don't spot the problem...

Philip G4JVF

--- In QRPLabs@..., "woodiescbj" <jobaco@> wrote:

Thanks for your post Steve, yes I know you are Steve I am not having a Senior Moment (I hope not or am I) ;o) I was replying to that Serling Chap Philip G4JVF, who told me he also hat problems with cycling and that it was due to short in the PA, now all I have to do is find my short, back to the old drawing board as they say, its probaly something simple but cant be seen like a bit of wire under the ATmega socket, someone up there does not want me on 160m I think, I will have a longer look at the time tonight I admit that I didn't look at it for 8 secs

Thanks Steve

Colin


--- In QRPLabs@..., Stephen Farthing <squirrox@> wrote:

Colin,

I probably did not make myself clear in the previous post.

If the seconds are going up by 1 every 8 seconds then you have a faulty
chip which I will replace FOC. You can tell this by setting the time and
observing the results. If the seconds are not going up at all it indicates
another problem.

I am shipping the chip you ordered today. It comes with the latest firmware
and without the divide by 8 problem.



And it's Steve, not Phillip ;-).

Steve



On 26 September 2012 11:15, woodiescbj <jobaco@> wrote:

**


Hi Philip and all other members,
I have not found any solder splashes or other mistakes on either side of
the PBC, this is something I will now have to check with the circuit
diagramme and multimeter (maybe a piece of wire under the ATmega ic
socket)removing the 5v to PA bridge has stopped the cycling so it is as you
said Philip PA related, I can also confirm that I also have the div by 8
bug as the seconds were not changing in the display.
73 Colin

--- In QRPLabs@..., "woodiescbj" <jobaco@> wrote:

Hi Philip, thanks for your reply you have given me an idea I have
already checked the solder side of the PBC (will check again) but I have
not checked the component side of the PBC which could also have some sort
of short.

Cheers and 73 Colin
--- In QRPLabs@..., "Philip" <pcteee@> wrote:

Ive seen this happen...(cycling)

On mine I once by mistake left a wisper of wire shorting the output of
the PA.
On switch on it would cycle between mode and welcome screen...

So Colin, double check for any shorts around the PA...

Hope you fix it..

Philip G4JVF

--- In QRPLabs@..., Stephen Farthing <squirrox@> wrote:

Hi Colin,

What you have described partly might be explained by a lack of
capacity
from your batteries to power the beacon on transmit. So there might
be
something wrong with the power supply or the PA. I have never seen
the
cycling between the welcome and transmit screens before. I suppose
this
might be explainable by the power supply lack of capacity as if the
voltage
drops below a certain level the microprocessor will shut down and if
the
voltage rises again it will switch on and display the start up
screen.

The sure fire way of checking to see if you have the "divide by 8"
problem
is to see how fast the clock runs when you set the time.

73s Steve
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