I just finished rebuilding an Ikea Jansjö lamp into
a portable camping lantern. It's not quite Luxo, Jr. but it'll do.
The Jansjö has a very long flexible neck, and to me that's the most
essential aspect: it lets me have light on the table surface without
having anything to suspend a lantern from. All the other common camping
lanterns suck in that regard as they need to be suspended - or they
produce lots of glare and no light on the table.
The Jansjö has one 3.5W white LED and needs 4V.
I threw away the transformer and the concrete weight for the base, then glued
the base to a plastic cylinder that once held 25 dvds - that has just the
right diameter and has space for one adjustable LM2596-based step-down
converter, and one set of repurposed laptop lithium cells (four in series).
Very simple, same XT60 plugs as all my other rechargable stuff, and packs
up reasonably small.
[ published on Thu 24.07.2014 19:41
| filed in interests/tinkering
(alternate title: patience, grasshopper...)
Recently I complained about the underwhelming replacement receiver, which my readers (yes, all ten of you!) might actually remember.
The issue wasn't just that it was doing poorly in stereo mode, but
rather that it didn't drive the main/front speakers worth a damn. Next
to no sound even with the volume at 11.
Well, there's a reason for that Sony box not doing its job - and I found it
and fixed it. Poring over the service manual (yes, there is one
and I found in less than an hour) after work today
I thought Hmm, mostly digital, zero adjustments, few discrete components. As it's a deader I might as well open it up and look for obvious problems and/or gut it.
(For the youngsters out there: "service manuals" are magic tomes of
arcane knowledge, hardly heard of on this side of y2k. In the
hands of a wiza^Wstubborn old phart these can provide great
Alas, no obvious leakers of the magic smoke presented themselves. So,
after staring at the circuit schematics in the service manual a lot
more (yes, I have no life), I decided that checking the power amp
transistors and the driver IC would be Good Things To Try, given that
the manual specified test voltages for them.
This meant a total disassembly of the box as you couldn't get to any
of the test points from above. A while (and hundreds of screws) later
I had it all in pieces. The transistors proved to be ok. The driver IC
wasn't testable with everything disconnected.
A bit of online research revealed that these driver ICs (NEC
µPC2581V) do run very hot, are not unheard of dying themselves and
easily fry components in the vicinity. Sony didn't put any heatsinks
on them in this model and a number of electrolytic caps were basically
touching the IC cases - and there's your problem.
These caps weren't testable in circuit, so I started desoldering.
Three out of the four that I replaced were cooked, one still had some
marginal capacitance left.
Lots of screws later, a final function test: the thing works! Evenly firing
on all channels. Hooray for being stubborn!
(Never mind that this exercise took me a good five hours this evening, and
that in the meantime I had given up on the Sony and replaced it with a NAD
[ published on Tue 22.07.2014 23:00
| filed in brainfarts
Two weeks ago my old, well-used and -liked Yamaha CR-840 receiver lost
its magic smoke - literally: Sparks, loud popping sounds, and a fair
amount of smoke - in the room, not in the electronics
where it belongs.
Being the cheap bastard^W^Weconomical person that I am, I started
looking for a slightly more modern replacement. This may have been a
In the end I bought a Sony STR-DE695 'AV' receiver for $70. Well, the FM receiver part of it
is junk - it receives very little. With the same (admittedly lousy) roof antenna I get a quarter
of the stations. Sensitivity, zilch.
And that newfangled 5.1 stuff? I begin to think that it's just a
shorthand for "5 speakers and 1 sad sucker" . My much older Sanyo
(mid-70s, 2x2 speakers in Glooorious Stereo) sounds heaps better than
the new thing. What the Dolby PL this and DTS that and 'NEO'
whatever does to stereo inputs sounds pretty underwhelming - at least to
I'd seriously consider to disconnect my center speaker (again) and
just drive the other 2x2 speakers as two stereo pairs - if only the
Sony wasn't so totally anemic when run in stereo mode...
So, am I in danger of becoming a total loonie audiophart? At 42 I
certainly qualify for the Old Fart part, but I'm not so keen on the
Audiophool side of things. At least I'm nowhere near ordering vegan
99%-fat-free hand-spun oxygen-free enchanted platinum-plated
triple-distilled bespoke cables for digital transmission...
[ published on Mon 14.07.2014 20:35
| filed in brainfarts