Coming from an age of mainframe computers, I have got the
habit of reading manuals and following them word by word. I found the
instructions good to follow, in general. However, being academic, I get trapped
in minute details at times. For the experienced customers what I will point out
might be obvious. However, being a novice in QRPLabs products, I have to admit
I got confused from time time, although not very often. So, to help other
novice builders from repeating the mistakes I have been through, I will suggest
some updates for QMX+ Assembly Instruction Manual.
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I presume a great part of the instruction manual was written
when 0.60 mm wire was used. It is clear that now 0.33mm wire is the standard.
but I had the impression certain instructions still relate to 0.60 mm wire.
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Firstly, in the section about L502 (p.28), there was no
mention of any length of wire to use. So, I had to make a guess and used (if I
remember correctly) 15cm. I presume 20cm would be more than enough. (At this
point, I have to say the lengths suggested for other toroids were a lot more
than enough. I had to throw away lengths varying between 7 and 10 cm.s.) When I
wound 10 turns, I realized the bottom of the toroid showed 9. So, I had to
count the windings in the assembled picture of the product on p. 1. I suggest
to move the expression "Remember: each time the wire passes through the
center of the toroid counts as ONE turn" on p. 29, to p. 28.
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Again, towards the end of p.28, the manual says "DO NOT
tin the wires before inserting into the holes: the holes are not large enough
to accommadate tinned wires." Similarly on p.3 of the instruction manual
for the transformer, the same warning under item no.5 is repeated. (However,
contrary to this warning, the photo on p. 10 show them very THICKLY tinned.)
The instructions for the transformer are definitely for 0,60mm. In contrast,
the instructions for band pass filter toroids suggest tinning the wires (p.30).
I have got a feeling, if I had read this before installing the transformer, I
may not have experienced the soldering problem I had.
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Another confusion I had was in winding the band pass filter
toroids. When I start counting the windings at 0, there is an additional
winding that go through the center. So, when winding L403, I had to count the
windings in the assembled picture on p.1 again. Thankfully on p.31 the manual
states number of turns as 0-33-44, 0-19-30, 0-21-31. So, I was sure I was on
the correct track. However, some other novice may try to follow the
instructions for L401, 403 and 404 when winding L405 and start counting at 0
again.This will cause him/her to wind 26+1 and 29+1 respectively. I suggest to
clarify the difference in counting these windings.
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Again, as a result of what I call a "professional
deformation" :) I tend to correct typos. There is only one that I have
encountered so far: On p. 29, towards the end of the second paragraph, the
manual says "vertially" instead of "vertically."
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Also, the instructions warn against using pins to clean out
a hole. It might be best to move this warning right to the beginning, before
soldering anything. Perhaps, if needed, one may add that people can cut the
legs of a component and solder the new one onto legs of the wrongly soldered
one, as suggested in the mailing list. An alternative is to solder from the top
of the PCB.
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On p.28 the manual instructs to apply the soldering iron for
at least 10 seconds. That is when I figured out what is meant by "plenty
of heat, time and solder". I cooked my board applying 450 degrees C for 25
seconds several times. (I normally use 300 degrees but I use 325 on QMX+
because I remember someone mentioned (I think on the mailing list) that the
ground on the board requires a little more heat to solder. May I suggest to
define the heat level and time duration at the beginning of p.27.
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In winding trifiliar toroid T401, I followed the steps in
the associated manual. However, 20 cm was not enough, although I tried to keep
the parts on the screwdriver at minimum. Using 25 cm wire did the trick. .
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The manual suggests cutting the extra pieces of component
legs and wires to a length of 2mm before soldering. However, I find it easier
to keep them at full length, bend them at the back to keep the component or the
toroid in place, solder them, and then cut the excess.
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BTW, I am sure I had soldered it properly but I my
continuity checks on T401 fail except for the B connection. I suspect my DVM is
the culprit because its probes are a little thick. So, future builders may
prefer to use DVMs with sharp pointed probes.
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Anyway, in the section on transformer T507 the manual,
again, suggest not tinning the wires. However, in this case I doubt if it
relates to 0,60mm wire because the holes were quite small, although just enough
to accommodate tinned wires.
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To ease aligning the right angle male pins (p39) taping them
was suggested in the mailing list (would it create an ESD problem?). I wanted
to postpone this stage until after installing the females and using them as a
guide for correct alignment, but at this point in time I am not sure about this
since I could not do it properly: I had soldered the right angle male pins
wrong way around. So, I suggest adding a warning to install the bent part into
the main board, and the straight part into the silkscreen.
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Similarly, I suggest moving the instructions on installing
and soldering the 16 pin header strip to stage 1 and 2 of the front panel and
LCD assembly.
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A note about this stage: Installing and soldering the 16 pin
header strip onto the LCD may make it difficult to fit its pins to the front
panel at a later stage. To overcome this problem, keep the plastic spacers and
nuts loose, fit the 16 pin header to the front panel and tighten the spacers
and nuts using a screw driver and needle nose pliers.
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On another note, on the last page, the manual refers people
to the QMX+ web page for updates and tips but the link itself takes people to
QDX page.
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73!
de Bekir TA2RX
NF6P - Dave
Dj Merrill