Hello Bob,
I do appreciate your input. Thank you.
I sorta had my head up a 'dark place'. I think I had originally stated
it was 15/17. Something in the back of my mind had told me that they
used the same low pass filter, but it is indeed 12/15 that do NOT share
the same filter. Based upon that bad memory, and having heard that the
relays can be an issue, I bought a few relays.
With relays in hand, I just replaced the two relays on 15m. Then, out of
the circuit, I checked them and they were both fine. It was only on the
15 m section that I did check all the components. And, I did find the
inductors that you mentioned, which were fine. I did check the
resistors, caps and inductors feeding each relay set. With the
connectors supplying the DC to/from the board (#'s 8 and 14) I applied
my own DC from a bench supply and could easily hear each pair of relays,
on all filters, switching in/out. I had previously confirmed that I did
have voltage at conn #14, on the appropriate pins, when each band was
selected. This is the connector and cable ass'y that comes from the
front end board. So, have voltage and relays are switching. Used a head
mounted jewelers loupe to check out the traces and the solder joints for
issues.
This, of course, doesn't reveal why 12 m isn't working either, but first
things first. Not going to worry about 12m, when I can't get 15m
working either.
I did as you suggested and looked around the front end board. After
disconnecting all the RF and control cables, the diodes looked fine, as
least the same. About 800~ ohm forward and inf reverse. Checked anode
to anode to see that the two inductors feeding the diodes were not open,
the bypass caps weren't shorted and the 100 ohm R was fine. I did not
check any of the discreet filter components, as I left the board in the
chassis and could not access the solder pads.
Of course, if/when I figure this out, it will all make sense, as it
always does. I'm a retired R&D machinist, so this is not in my DNA, but
like doctors, my first rule is 'to do no harm' and, so far, I have not
made things worse.
73 de Steve, NR4M
On 4/29/2018 11:12 PM, Bob McGraw K4TAX wrote:
The best thing is to pull the Low Pass Filter board and check all of
the relays. This can be done with the relays on the board. The coils
are wired parallel. Typical resistance for the pair of good relay
coils as I recall will be about 450 ohms, if a relay coil is open then
you'll see about 900 ohms. The relay pairs for the 10/12M band and
the 17/15M band will measure a bit higher as there are inductors in
series with the coils.
The 10M and 12M bands are handled by K2 and K3 where as the 15M and
17M band is handled by K4 and K5. Also check the inductors which are
in series with the relay coils. Those are L12, L13, L14 & L15 I
have found instances where one or more may open.
Your description of no output on 12M controlled by K2 & k3 and 15M
controlled by K4 & k5 indicates both filters sections are not
switching correctly. I doubt than any of the specific filter
inductors or capacitors have failed. Relays are prone to have open
coils.
As to no receive, this is more likely on the Front End Band Pass
Filter board. There are 2 diodes per filter sections. You can check
them on the board with a normal diode test using an ohm meter.
Replace any which are suspect.
73
Bob, K4TAX
On 4/29/2018 8:40 PM, Steve Bookout wrote:
Hello all,
Several days ago, I reported my Omni 6+ had no power or receive on 12
meters and 15 meters. From what I remembered and what I saw here, I
thought it would be in the output filters. I bought and received
some replacement relays and installed them. When I checked the ones
I removed, they were fine. Put it back together and fired it up,
with the same results.
Tore into it again. Made sure I had 12 volts on the connector
terminal when the switch was on 15 meters. I applied my external 12
volts to the dc input connector (#14?) and relays would click just
fine. Inspected the 15 meter trace under a magnifier and checked
the 100 ohm R's on one end of the 12 volt buss and the inductors on
the other end. In the selected filter, all L and C components looked
to have nice shiny and clean solder joints. I removed all caps
specific to the 15 meter filter and checked them. I removed
everything but the inductors specific to 15 meters
My actual power is about 1 watt out, not totally zero.
What else might cause this issue? I'm confident I've done all I can
on the LP filter board. Or, does someone have a suggestion?
73 de Steve, NR4M
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