Yes Garey:
Any of the rigs with lots of connectors, card edges, and switch wafers
are an issue.
I never had done any cleaning on these switches at all since they looked
brand new. Even now, not a hint of the normal dark color on the
switches. But I could see the shiny rub mark on them so just a small
speck of Deoxit did the trick.
Thanks for the help tho. This is a great resource.
Garey Barrell wrote:
Curt -
OK. Yes, that would indicate incorrect offset information from the
Digital control board to the Translator board. I guess I didn't
understand that your '12 MHz' was a 'locked' 12 MHz, rather than a
'wandering' VCO.
Cool! As we say, and as the 'Welcome' message now says, "90% of Drake
R-7/TR-7 'failures' are the result of corrosion on switches, card edge
or cable connectors."
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Curt Nixon wrote:
Welll...no it was not unlocked. I know what that looks like. and it
was /is 33MHz and 17MHz when fixed Rx is depressed.
This was stable, normally operating in all other senses but wrong
frequency.
It must have been getting bad selection information out of the band
select switch because once I applied a small amount of deosit to the
bandswitch, it is now fine.
Curt
KU8L
Garey Barrell wrote:
Curt -
This just means that the 'low band' VCO is unlocked. The 'low band'
VCO covers 14 MHz and down. You should read about 17 MHz rather
than 12, which is probably why it's losing lock. If you switch to
any of the 'high' bands (21 and up) and depress the FIXED - RCV
button you should see ~32 MHz, and any of the 'low' bands (14 and
down) should be ~17 MHz. Of course both are 'wandering' frequencies
as this is the VCO's running 'unlocked'.
One common problem that can cause this is a loose or missing core
top half on the DC-DC converter transformer on the power supply
board just behind the GAIN and DELAY adjustments. The transformer
core consists of two halves, each 'E' shaped, super-glued together,
'facing' each other. If the top half becomes loose or even falls
off, the +25V supply drops considerably. So if you look at the
transformer on the board, you should see a solid bar across the
top. If you see three square legs sticking up, check the bottom
cover for the transformer core top! If you see the 'bar', make sure
it's tight to the other half. You may touch it and have it fall
off. A few drops of super glue will fix it.
If this is NOT the problem, check the +25 VDC bus. If it's good,
then something has changed the VCO 'unlocked' frequency and you'll
need the service manual information to find out if it's an
adjustment problem, or some other failure.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Curt Nixon wrote:
GM All:
Hope you all are keeping warm. 10F here and all antennas iced up.
Have a problem that just started over the weekend with the TR7 here.
All works fine except when I try to select 14MHz. the display goes
to 12xxxx MHz.
If I start at 21 and step down with the 500K dwn button, it goes to
14500 and then the next step goes to 12000 stepping back up 14
comes back on.
I havent checked yet to see if it is actually running on 14 but
displaying 12 but it is stable there...not flickering or anything.
Common problem?
Boards have not been re-seated in a while but rig has not been stored.
Use this rig nearly every day. and it has been running great.
Curt
KU8L
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