Strange problem powering MiniTiouner v2.

[G8DPH]

I'm building a MinTiouner2. Got to the stage of applying power (12v current limited to 100mA). Adjusted the DC to DC module for 3.8v.
Then fitted link J2 and reapplied power. It went into current limit! I removed power and the J2 link.

Then I applied 4v to the pin of J2 marked +4v Alt. This worked fine and I could measure the correct outputs of the 3 regulators!
I fitted a new DC to DC regulator with the same effect.

Something I found strange was the adjustment range of the DC to DC converter was very limited but did cover the required 3.8v.

Have I got a duff batch of converters? Bought on eBay item number 132921707182.

Ashley G8DPH

[Nick]

Ashley,

Out of curiosity I just measured the current on my MiniTiouner and it was 220mA. Looks like it should have gone into current limit with 100mA.

You could try increasing the current limit to 300mA

Regards,

Nick - G4NKV

[G8DPH]

You test the power supplies without the tuner or USB module connected. Should take hardly any current.

[g0mjw]

I wonder if you had a higher voltage and the 5.6V zener protection diode activated. Until you fit the tuner there should be virtually no current as you would not have fitted the tuner at this point.

Mike

[G8DPH]

That's what I thought but I set the DC to DC converter to 3.8v output.

[G8DPH]

Found that the reason for the high current is that the DC to DC converter oscillates when a load is connected.
Will order another converter from a different source.

[g0mjw]

Oh dear, bad batch. Probably the capacitor isn't one, or similar. You can always use a traditional series regulator while waiting. I have a couple of spare DC-Dc converters somewhere.

Mike

[G8DPH]

4v series regulators are hard to find
Can you recommend a reliable source of the DC to DC converter?

I have a working one in front of me but it's in a working MiniTiouner V1 that I don't want to lose

[g0mjw]

Adjustable series regulators are easy to find that do 4V you can also do the diode trick on a 3,3V one. The DC-DC I bought is no longer listed - but there are many listings for identical boards. I can't recommend a reliable source as I have not bought one in 2 years, but others may be able to help.

Mike

[YL3AKC]

Sorry for offtopic, but I am using %V from USB to supply MiniTiouner. It works stable, no problems observed. You need some small (little bit ugly) mod to wire +5V from FTDI board to regulators on main board.