Pico Tuner - LNB Voltage? (RESOLVED)

[G1INU]

Hi Michael,

I don't know enough about the support components and circuit so it's probably not relevant, but the schematic lists U1 as an RT5047A and that is the data sheet on the link you posted above Michael. However the component listed in the BOM and supplied is an RT5047BF. Probably not relevant to the issue I am having but I noticed it when I started looking around to order another Single Output LNB Supply and Control Voltage Regulator chip as that's the only thing I think might be the issue?

[g0mjw]

I can't see anything wrong. Are you sure all the chip pins are properly soldered? Especially the one on the back.

Mike

[g0mjw]

Hi Michael,

I don't know enough about the support components and circuit so it's probably not relevant, but the schematic lists U1 as an RT5047A and that is the data sheet on the link you posted above Michael. However the component listed in the BOM and supplied is an RT5047BF. Probably not relevant to the issue I am having but I noticed it when I started looking around to order another Single Output LNB Supply and Control Voltage Regulator chip as that's the only thing I think might be the issue?

No, I don't think that matters. I used the one in the BOM and mine works. Assuming it is actually switched on/off by the software, which seems to be the case from the voltages, all I can think of is a short or open circuit somewhere. Again, are you sure the pad underneath is connected?

[G1INU]

No, I don't think that matters. I used the one in the BOM and mine works. Assuming it is actually switched on/off by the software, which seems to be the case from the voltages, all I can think of is a short or open circuit somewhere. Again, are you sure the pad underneath is connected?

No, I just thought it was worth a mention. I was as certain as I could be about the solder through but I have revisited it with the soldering iron today and made sure. No change in voltages though.

Am I correct in thinking in basic terms the LNB supply circuit operates as follows;

1 : LNB - 0v until LNB Output is enabled via EN from GPIO6. Once enabled it is at 13v or 18v depending upon SEL controlled by GPIO9.
2 : BOOST (I read but don't quite follow but appears irrelevant to my issue)
3 : LX (I read but don't quite follow but appears irrelevant to my issue)
4 : VIN - A constant voltage = to whatever voltage is fed to J1.
5 : EN As per (1) above
6 : SEL As per (1) above
7 : Will take LED to ground (ON) when a fault state exists within U1.
8 : Receives a 22kHz tone from pin 40 of U3 and routes it to the LNB via pin 1.

[Basil]

Can we assume you are doing these voltage tests *without* the LNB co-ax connected to the Minitiouner?

In one of the photos it shows the device with all cables including the one to the LNB connected... In which case might it not be a cable / connector or even LNB problem?

Just putting thoughts to print. I am not sure how the chip would react to an excessive load on its output.

Presumably it has some sort of internal protection?

[G1INU]

Can we assume you are doing these voltage tests *without* the LNB co-ax connected to the Minitiouner?

In one of the photos it shows the device with all cables including the one to the LNB connected... In which case might it not be a cable / connector or even LNB problem?

Just putting thoughts to print. I am not sure how the chip would react to an excessive load on its output.

Presumably it has some sort of internal protection?

Hi, Yes I have done the tests both with and without the coax and land attached and the results remain constant. The input's from the Portsdaown4 via the pico and tested at both the GPIO pins and the U1 pins are all switching as they should dependent upon the LNB volt setting in PD4. The only issue is that instead of the U1 chip putting out 0v/13v/18v it is putting out either 0v, 0.6v or 3.28v. I have been round all the components in the LNB supply circuit with the soldering iron and checked at huge magnification for shorts but there is nothing.

It is clearly a faulty RT5047.

Of course to order one from DigiKey or Mouser is going to take a week and cost half the total I paid for the whole parts kit due to postage

[g0mjw]

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

Mike

[G1INU]

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.

[g0mjw]

Can you check the diodes and inductor? It could also be one of those that has failed. Also make sure neither of the LNB supply jumpers is fitted so we can rule out a short in the NIM. The schematic is here:

Screenshot 2024-06-22 082132.png (46.46 KiB) Viewed 3394 times

You should be able to test them in-situ.

Mike

[G1INU]

Hi Mike,

No it’s none of the components in the LNB supply outside of U1. All tested (several times ) and the voltages were measured with the NIM both in circuit and isolated.