Hi Dave

My QS1R “bit the dust” after many years a year ago. W3LPL bought it and fixed it. I bought a Red Pitaya SDR that runs 24x7 for RBN spotting

Jim K7EG

From: Skimmertalk <skimmertalk-bounces+57jndenneny=comcast.net@contesting.com> On Behalf Of Dave
Sent: Friday, July 17, 2020 7:14 AM
To: Alexander Ranaldi <alexranaldi@gmail.com>; skimmertalk@contesting.com
Subject: Re: [Skimmertalk] QS1R (Rev C) over heating?

Thanks for the feedback Alex

I’m glad it’s not just mine! My second option is either a switching regulator based on an LM2596, or a big heatsink on the LM317, with a large hole in the case and a cooling fan. I prefer the switching regulator option, subject to it not generating QRM.

73 Dave, G4AON

On Fri, 17 Jul 2020 at 13:22, Alexander Ranaldi <alexranaldi@gmail.com> wrote:

I placed some enormous copper heatsinks on my regulators and put the QS1R board itself in a new enclosure with a built-in linear power supply and two 80mm fans running at ~2k RPM. Seems pretty stable in that configuration. I haven't checked the heatsink temperatures though.
Alex w2axr

On Fri, Jul 17, 2020 at 7:49 AM Dave <dave.g4aon@gmail.com> wrote:
My QS1R failed recently. The fault was the 1.2V supply, which is fed from an L1117 1.2 regulator.

Running the 1.2V rail from an external supply showed a current draw around 300mA when listening to a broadcast station with SDRMAX V software, but around double that current when running 7 slices with CW Skimmer.

The original regulator, which uses the PCB as a heatsink, seems inadequate for the current needed by the Cyclone III FPGA. I tried an LM317 (TO220) regulator with a small heatsink, however the heatsink reaches over 90C running 7 x slices with Skimmer.

Before I bolt the regulator to the case, has anyone checked their QS1R for boiling hot regulators, modified theirs, or has mine an overheating fault? By the way, Skimmer works with multiple slices, as does the QS1R when used to listen “single channel” as in broadcast station listening.

Thanks
Dave G4AON
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