Re: QDX Deaf with high current. #qdx

Mike Easterbrook

I think the 100ma RX current value was from early QDX history and with the various upgrades most recent builds have been averaging out in the 140-150 ma range. I believe there was a note to this effect but can't locate it right now - away from home with poor search facilities (v.poor internet connection but great scenery - in Langkawi).
73 Mike 9M2LXM

On Mon, 1 Aug 2022, 22:24 Alan G4ZFQ, <alan4alan@...> wrote:
On 01/08/2022 12:42, Dave, M0OOR wrote:
> I did do the sweeps with a dummy load on all bands and the USB graphs
> look fine albeit that the LSB graphs don't look as low as possibly they
> should do, so maybe the unwanted sideband rejection isn't what it should
> be? (I don't know what affects this).


This test shows if T2 is wound and installed correctly.
How much down is LSB? If it is around possibly 50dBthen the secondaries
must be wound and connected correctly. Fundamentally there is no
adjustment. Seems to me if the secondaries are correct then the primary
must be.

Again, if you get good RF sweeps it shows L12 and the capacitors are

> The 5v regulator gets hot enough that you can't keep your finger on it,
> but I can't work out what is causing it, IC3 and IC4 get slightly warm
> and I'm worried that one of these may be faulty.

My QDX uses about 140mA RX when I feed it 7.5 volts. Others have said
150mA, I wonder how Hans got 100mA?

But I have just checked mine, the regulators run warm out of the case.
I cannot see how L12 or T2 could cause these to run as hot as you say.
It does seem something that requires investigating. Apart from measuring
the 5 and 3.3 volts outputs I'm not sure how best to check. The normal
procedure is to lift the relevant pin of an IC and note the difference
in current.
Make absolutely sure there is no solder splash or wire shorting something.

If IC3, 4 are at a similar temperature they are either both faulty or
like many ICs just at normal working temperature.

73 Alan G4ZFQ

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