Pico Tuner - LNB Voltage? (RESOLVED)

[g0mjw]

I suppose with all other possibilities eliminated what remains must be true. Duff chip. Removing it may be difficult. If you unsolder the pins on top and it comes off, the ground wasn't connected. Otherwise, unless you have a hot air SMD station, you are going to need to cut the pins I expect to remove it. You might be able to lift them with de-soldering braid.

Mike

[g0mjw]

If you got the original from Digikey, they should replace it FOC. Where did you get it?

Mike

I got the whole lot from DigiKey, I will drop them an email but I suspect they will suggest I have damaged it. Just how I could partially damage it is a good argument I suppose as its clearly switching power just not enough of it.

It would do exactly this if the ground were not connected, but you have tested for that.

[g4eml]

Are you sure the ground connection is good? It would take quite a bit of heat and agitation to ensure a good connection and there is a chance the via could fill with solder and still not make contact with the chip. I would make sure the soldering iron tip goes all the way through the hole until you can feel it scratching on the chip.

Colin G4EML

[G1INU]

Are you sure the ground connection is good? It would take quite a bit of heat and agitation to ensure a good connection and there is a chance the via could fill with solder and still not make contact with the chip. I would make sure the soldering iron tip goes all the way through the hole until you can feel it scratching on the chip.

Colin G4EML

Hi Colin,
Well if it's not got a good ground I don't know what more I could have done. When I revisited all the solder joints I reheated the pad with a soldering gun as it is too big an area for a small tipped soldering iron, and whilst it was heated with the soldering gun I used my VERY fine point soldering iron down in through the hole in the centre.

[F5LCT]

Bonjour ,
i was have the same voltage on pin 1 3.5 when i have selected 18 v and 0.6 when i was selected 12v ,
the probleme it was a bad ground after doing a nice ground i got 18v for 18 v and 13 for selected 12. on
the builder document they say :
The LNB supply chip, if used, is the most challenging as it is an SMD device and has a pad on the base that needs to be soldered to the ground plane on the back side of the PCB for heat dissipation. So, start with this chip. First solder the chip pins to the PCB, taking care to get it in the correct place and flat against the board. When happy, turn over the board and with a large soldering iron, heat the pad and poke some solder through the small slot intended for this purpose. Do not use too much solder. It's not hard if you take care, but you need a large iron to give a decent thermal mass due to the copper ground plane. Use the correct tools, don't be tempted to try a small 25w iron that will take a long time slowly getting the joint up to solder melting point, as that will damage the chip.
they say use a large iron don't use a small 25w me i have use a large 60w
73

[G1INU]

Bonjour ,
i was have the same voltage on pin 1 3.5 when i have selected 18 v and 0.6 when i was selected 12v ,
the probleme it was a bad ground after doing a nice ground i got 18v for 18 v and 13 for selected 12. on
the builder document they say :
The LNB supply chip, if used, is the most challenging as it is an SMD device and has a pad on the base that needs to be soldered to the ground plane on the back side of the PCB for heat dissipation. So, start with this chip. First solder the chip pins to the PCB, taking care to get it in the correct place and flat against the board. When happy, turn over the board and with a large soldering iron, heat the pad and poke some solder through the small slot intended for this purpose. Do not use too much solder. It's not hard if you take care, but you need a large iron to give a decent thermal mass due to the copper ground plane. Use the correct tools, don't be tempted to try a small 25w iron that will take a long time slowly getting the joint up to solder melting point, as that will damage the chip.
they say use a large iron don't use a small 25w me i have use a large 60w
73

Hi Hubert,
Thank for the reply but as I said to Colin, if it's not got a good ground I don't know what more I could have done. When I revisited all the solder joints I reheated the pad with a soldering gun as it is too big an area for a small tipped soldering iron, and whilst it was heated with the soldering gun I used my VERY fine point soldering iron down in through the hole in the centre.
I am just going down the workshop to desolder the whole chip and if it comes off in one piece I will test it off the board with wires to the opins and back. If not I will have to source another chip, depends if DigiKey decide to send a replacement when they open again on Monday.

[radiogareth]

Following this thread made me test my 2nd unit - as I use them mostly for terrestrial (and having long since burned out the NIM inductors in my first unit I built an external LNB power unit) I was a bit puzzled that I wasn't seeing the expected voltages. So I hooked it up to my Portsdown-4 and then went to the config menu (Rx-Config-LNB Volts). Cycling through the three options did not produce any output UNTIL I actually selected Receive and it started scanning for a signal. Then it came alive (0,12 or 18 as selected), and off again when stopping Rx.
Just in case (like me) you assumed the voltage should be present 'when selected' rather than actually when TRYING to receive.

Good luck....

Gareth

[G1INU]

Following this thread made me test my 2nd unit - as I use them mostly for terrestrial (and having long since burned out the NIM inductors in my first unit I built an external LNB power unit) I was a bit puzzled that I wasn't seeing the expected voltages. So I hooked it up to my Portsdown-4 and then went to the config menu (Rx-Config-LNB Volts). Cycling through the three options did not produce any output UNTIL I actually selected Receive and it started scanning for a signal. Then it came alive (0,12 or 18 as selected), and off again when stopping Rx.
Just in case (like me) you assumed the voltage should be present 'when selected' rather than actually when TRYING to receive.

Good luck....

Gareth

Hi Gareth,
Thank's for the heads up. I had spotted that during the testing process but it may well help anyone further down the line who comes across this thread, which is about to get a final update from me.

[G1INU]

Firstly, a HUGH thank you to everyone who got involved in helping me resolve this issue. I have learned a lot about the Portsdown 4 software and the Pico Tuner in the process.

So the low voltage from the U1 (RT5047) chip was as many suggested due to the grounding or lack thereof of this chip.

This was not for want of reading the instruction in the wiki, the forum or the data sheet and it was not due to using the wrong tools. The chip was soldered in place with all 8 pins showing a nice clean soldered joint under very high magnification. The board was flipped over and using the good old Weller soldering gun, flux and lead free solder I created a pool on the pad and whilst the pool was still liquid I pushed solder into the hole using a 400 degree fine tipped soldering iron.

On no less than three subsequent occasions I revisited and re-melted the ground pad solder and got no change to the now much documented issue.

Resigned to the belief that I had a faulty chip and nothing would be lost if I destroyed it whilst removing it, I desoldered it and it came away in one piece as soon as the pins were desoldered. A clear indication that despite 4 attempts it had still not soldered the rear of the chip to the grounding pad

On closer inspection I could see the rear of the chip had flux residue on it and there was solder filling the now exposed hole on the grounding pad. However the chip was still not soldered to the pad.

After cleaning up the pad with solder wick and alcohol, I tinned the rear of the chip by soldering directly onto it and wicking off the excess with braided copper solder wick.

I refitted the chip, soldering the pins one by one rather than relying on flux to do them all together and I desoldered the grounding pad as before.

Subsequent testing showed the full voltages expected were present at TP1 and on the output to the LNB.

My tip which may already be common practice to those in the know is to tin the rear of the U1 (RT5047) before installing it.

[Basil]

What I do, rightly or wrongly, with chips with a soldered ground plane / heatsink pad, is to tin the ground plane pad on the chip, and its mating surface on the PCB. I try to line it all up perfectly, initially ignoring actually soldering the legs, and firstly solder the ground plane to the PCB and establish it's now very securely adhering to the PCB.

I then solder the legs, pushing each down onto its pad if the chip ends up sat a tad high. People are probably cringing, but checking the ground plane is properly secured is easy with no legs soldered, far far less so once the legs are done...

I am very pleased that you have finally sorted the issue Mark