VCO Alignment Troubles

[Tim Cailloux]

Hello all (again).  I'm attempting to align the VCO and am having
trouble making it lock on all bands or get to the right voltage range.
 I've verified all components on the board and touched up the solder
on the pertinent components and relays (and verified all
paths/continuity), but nothing changed.  Here are the voltage values I
get when attempting to set L30:

     Low     High
80M  1.937V  6.000V
40M  8.000V  8.000V
30M  0.597V  0.710V
20M  0.589V  1.148V
17M  3.054V  3.250V
15M  1.962V  2.944V
12M  1.131V  1.251V
10M  2.336V  4.060V

No setting of L30 will cause 40M to lock.  I also hooked up the
frequency counter to TP3 per a suggestion previously on the list and
it measured 8.something MHz on 40 (which doesn't seem to be right.  I
adjusted the spacing on the turns of T5, either pushing them apart or
moving them closer.  I was able to bring the lower 20M voltage up to
1.5V, but then the VFO wouldn't lock on 80.

Thanks in advance for any help you can provide.  (And thanks to Don
for correctly surmising that my previous problem was due to a
thermistor board issue.)

tim
--
Tim Cailloux
W4EGT
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[Don Wilhelm-3]

Tim,

Check and re-check the capacitor values.  From the bands that seem to me to
have strange voltage readings, C73 (should be 47pf) and C74 (should be 20
pf) are the most likely culprits.
Other things to check: be certain the menu parameter for D19 is OFF - check
the relays K13, K14 and K15, set the K2 for the band to be checked and
compare the set/reset condition of each relay by checking continuity from
pin to pin.  The chart on the manual page just before the schematics shows
which relays are set for each band and the schematic shows all relays in the
reset position.  The relay pin numbering is similar to that of an IC - you
can locate pin 1 by finding the round solder pad on the board.

73,
Don W3FPR

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of Tim Cailloux
> Sent: Saturday, February 26, 2005 11:20 AM
> To: Elecraft E-mail List
> Subject: [Elecraft] VCO Alignment Troubles
>
>
> Hello all (again).  I'm attempting to align the VCO and am having
> trouble making it lock on all bands or get to the right voltage range.
>  I've verified all components on the board and touched up the solder
> on the pertinent components and relays (and verified all
> paths/continuity), but nothing changed.  Here are the voltage values I
> get when attempting to set L30:
>
>      Low     High
> 80M  1.937V  6.000V
> 40M  8.000V  8.000V
> 30M  0.597V  0.710V
> 20M  0.589V  1.148V
> 17M  3.054V  3.250V
> 15M  1.962V  2.944V
> 12M  1.131V  1.251V
> 10M  2.336V  4.060V
>
> No setting of L30 will cause 40M to lock.  I also hooked up the
> frequency counter to TP3 per a suggestion previously on the list and
> it measured 8.something MHz on 40 (which doesn't seem to be right.  I
> adjusted the spacing on the turns of T5, either pushing them apart or
> moving them closer.  I was able to bring the lower 20M voltage up to
> 1.5V, but then the VFO wouldn't lock on 80.
>
> Thanks in advance for any help you can provide.  (And thanks to Don
> for correctly surmising that my previous problem was due to a
> thermistor board issue.)
>
> tim
> --
> Tim Cailloux
> W4EGT
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
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> Elecraft web page: http://www.elecraft.com
>

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[Tim Cailloux]

> Check and re-check the capacitor values.  From the bands that seem to me to
> have strange voltage readings, C73 (should be 47pf) and C74 (should be 20
> pf) are the most likely culprits.

Not the caps (after a quick trip to Radio Shack to pick up a new 20pf and 47pf).

> Other things to check: be certain the menu parameter for D19 is OFF - check
> the relays K13, K14 and K15, set the K2 for the band to be checked and
> compare the set/reset condition of each relay by checking continuity from
> pin to pin.

Would the voltages I got make sense if I had a K14 that wasn't
latching?  I checked it out and it appears to be staying in the reset
position.  It seems that the bands I'm having voltage issues on are
all connected through K14 (40, 30, 20, 12) .  (The first time I
checked the relays, I did the check when 80M was the last band I used.
 This time I checked with 40 being the band.)  D19 was off.  I didn't
even know about the second menu until I had to look up to verify the
setting!

I really hope it isn't K14.  I'm not looking forward to having to
replace a relay.

tim
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