So further to my experimenting with Plutos, I have been looking at the one (rev C/D ) I have that has a low output. It is around 25dB low. I have used a cheap Chinese amp to raise the output and drive a 437MHz linear. This made the system a lot more stable than just a Pluto with high output and no Chinese amp. Infact I now use a good Pluto at reduced output and the Chinese amp to drive the linear.
Back to the low output.
When I tried this Pluto against a full power Pluto on the bench next to a receiver they both gave a similar power reading. This was using just the aerials supplied with the Pluto. This gave a clue to the possible fault. Could there be a short circuit near the SMA socket and the pickup from both Plutos was from the internal circuits of it? Looking at the circuit diagram there is a protection diode near the SMA. Could this be shorted?
Investigation continues....
Martin G8LCE
Low output power from a Pluto
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Re: Low output power from a Pluto
So I tried fault finding.
This showed that it was probably was not a shorted diode but the results were not good either. The output from this point was lower and when I put the circuit back with a link, the output was even lower!
However the test with the Pluto near the receiver on the desk showed a signal again when the transformer ( T5 ) was touched and 'rocked'. That will be the next investigation....
Martin G8LCE
- 20230519_162510.jpg (1.9 MiB) Viewed 6566 times
This showed that it was probably was not a shorted diode but the results were not good either. The output from this point was lower and when I put the circuit back with a link, the output was even lower!
However the test with the Pluto near the receiver on the desk showed a signal again when the transformer ( T5 ) was touched and 'rocked'. That will be the next investigation....
Martin G8LCE
Re: Low output power from a Pluto
T1 and T5 are very fragile and easily damaged. I know from experience. I suspect the ferrite core has been broken. Last time I looked they were available from several sources. Tricky, but not impossible, to replace.
Colin G4EML.
Colin G4EML.
Re: Low output power from a Pluto
Further investigation (by cutting the track between the output socket and D9) showed that D9 was short circuit! So I have wired between T5 and the output socket directly with a piece of wire by-passing D9. The output is still low but usable with the cheap Chinese amplifier.
To others with low output. It is very difficult to fault find as the transformer T5 is a DC short to earth. Cutting the track as I did and measuring across the output socket might show if the diode is blown.
T5 may still be a problem but I don't want to push my luck soldering a new one in.
When it becomes possible to select the other output then that should be at full power - I hope!.
Martin G8LCE
To others with low output. It is very difficult to fault find as the transformer T5 is a DC short to earth. Cutting the track as I did and measuring across the output socket might show if the diode is blown.
T5 may still be a problem but I don't want to push my luck soldering a new one in.
When it becomes possible to select the other output then that should be at full power - I hope!.
Martin G8LCE
Re: Low output power from a Pluto
Thanks Martin and Colin, good and useful info.
Re: Low output power from a Pluto
Got a surprise today! After leaving the setup on for several days with just the linear power off, I tried a transmission and got maximum output power!! Turned it all down until a sensible output and it appears the 'fault' has self healed! That does not help the fault finding and now I don't want to disturb it....
Any ideas why this should happen?
Martin G8LCE
Any ideas why this should happen?
Martin G8LCE
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radiogareth
- Posts: 1236
- Joined: Wed Jan 06, 2016 9:46 am
Re: Low output power from a Pluto
Vary strange. No suggestions why though....I traced my own 'low output' problem to the simple fact that when I refitted my (bare) Pluto PCB back into my Portsdown, I put it in upside down.......memory not what it was it seems....
Gareth
Gareth
Re: Low output power from a Pluto
Just to dot the i's the powered on Pluto is on a network connection so only it is powered. The transmission is done using streaming from vMix over the gigabit network.
I think that anyone that has a low output Pluto should first try transmitting with it near a receiver. It was this that gave a clue to the fact the Pluto still had life in it. The signal still came from the Pluto but did not come out the SMA connection. I did this at 437MHz and a piece of wire in the receiver and was able to compare with a working Pluto. The results were similar.
The other thing I found from all this was the ease it is to put the extra connections into a rev C/D Pluto for the 2nd TX and RX and external clock.
I can see why Gareth had the problem as the RX and TX would be reversed on the labels!
Why the power has returned is a mystery but the other thing I found was that by putting the cheap Chinese amplifier between the Pluto and linear amplifier, the Pluto does not get disturbed by the possible earth currents that caused lockups. The Pluto would lockup and need to be powered off and on without the little amplifier quite often. Now it never needs this.
My next investigation is a Pluto that has lost its USB connection! It DFU's but the computers do not see it........... (or get my Cariboulite working for DATV ? )
Martin G8LCE
I think that anyone that has a low output Pluto should first try transmitting with it near a receiver. It was this that gave a clue to the fact the Pluto still had life in it. The signal still came from the Pluto but did not come out the SMA connection. I did this at 437MHz and a piece of wire in the receiver and was able to compare with a working Pluto. The results were similar.
The other thing I found from all this was the ease it is to put the extra connections into a rev C/D Pluto for the 2nd TX and RX and external clock.
I can see why Gareth had the problem as the RX and TX would be reversed on the labels!
Why the power has returned is a mystery but the other thing I found was that by putting the cheap Chinese amplifier between the Pluto and linear amplifier, the Pluto does not get disturbed by the possible earth currents that caused lockups. The Pluto would lockup and need to be powered off and on without the little amplifier quite often. Now it never needs this.
My next investigation is a Pluto that has lost its USB connection! It DFU's but the computers do not see it........... (or get my Cariboulite working for DATV ? )
Martin G8LCE