- 20180129_133506.jpg (543.64 KiB) Viewed 2410 times
Found the balun but not able to resolder it so have ordered two more......
Martin G8LCE
Filter board no output T1 problem..
Filter board no output T1 problem..
Just incase someone has the same problem I have just found out why my Portsdown stopped working.
T1 has dropped off!!
Found the balun but not able to resolder it so have ordered two more......
Martin G8LCE
T1 has dropped off!!
Found the balun but not able to resolder it so have ordered two more......
Martin G8LCE
Re: Filter board no output T1 problem..
Once I replaced the T1 I still had no output. Using the 71Mhz output from the Portsdown I was able to trace the signal with my 100Mhz scope (Tektronix 2245 off Ebay) and found the new T1 worked but the output amp U51 had input but no output. I probably blew it while fault finding!! Luckily I ordered some spare ones with the T1. The new T1 seems to be better fixed to its base than the one that fell off. Replacing U51 when I get a little more time......
Re: Filter board no output T1 problem..
So for those of you following this thread....
After years since being in the electronics fault finding feild as a job I forgot one of the first principles. Check the volts!. The output IC U51 was changed as there was signal in but no signal out. Still no output!!! Look at the circuit and the volts are fed to it via L50. Check it with a meter with the power off and it is open circuit. Check it with the volts on and no volts on U51!!!. Change it for another choke (the only one I had was rather big but still a choke) and the output returns. BUT the signal is not looking good.
This does not lock any RX as you might expect so back to fault finding....
Martin G8LCE
After years since being in the electronics fault finding feild as a job I forgot one of the first principles. Check the volts!. The output IC U51 was changed as there was signal in but no signal out. Still no output!!! Look at the circuit and the volts are fed to it via L50. Check it with a meter with the power off and it is open circuit. Check it with the volts on and no volts on U51!!!. Change it for another choke (the only one I had was rather big but still a choke) and the output returns. BUT the signal is not looking good.
- Output with fault 01.JPG (86.39 KiB) Viewed 2302 times
Martin G8LCE
Re: Filter board no output T1 problem..
So who spotted the problem?
One of the data wires had broken in all this fault finding (D2) and therefore the receivers would not lock.
So to sum up:
It all started with T1 falling off. This may have been either a faulty balum - not being stuck down to its base - OR I may have knocked it off. The new one looked more robust.
I used a 100Mhz oscilloscope and the Portsdown set to 71Mhz to trace the signal.
Once the T1 was replaced the signal got as far as U51 input but no output. Was U51 broken? I don't know becuase I assumed it was and had a spare and replaced it.
Still no output! Then I did what I should have done before and checked the volts. I found L50 was open circuit. It could have been this causing the problem with U51 or I broke L50 replacing U51, I will never know!
During all this one of the data wires broke so the output was not what was needed to lock a receiver. Using a SDR to check the output showed the narrow bandwidth so indicated the area of the fault.
Back to working Portsdown now.
Hope this may be of use to someone. Still don't know why the output failed while doing all this.
Martin G8LCE
One of the data wires had broken in all this fault finding (D2) and therefore the receivers would not lock.
So to sum up:
It all started with T1 falling off. This may have been either a faulty balum - not being stuck down to its base - OR I may have knocked it off. The new one looked more robust.
I used a 100Mhz oscilloscope and the Portsdown set to 71Mhz to trace the signal.
Once the T1 was replaced the signal got as far as U51 input but no output. Was U51 broken? I don't know becuase I assumed it was and had a spare and replaced it.
Still no output! Then I did what I should have done before and checked the volts. I found L50 was open circuit. It could have been this causing the problem with U51 or I broke L50 replacing U51, I will never know!
During all this one of the data wires broke so the output was not what was needed to lock a receiver. Using a SDR to check the output showed the narrow bandwidth so indicated the area of the fault.
Back to working Portsdown now.
Hope this may be of use to someone. Still don't know why the output failed while doing all this.
Martin G8LCE