In article ,
Jeff Liebermann wrote:

Now working on an MFJ-259A, which looks like the usual blown diode
problem:
http://802.11junk.com/jeffl/MFJ-269-repair/

"Of course, when I got it back together (for the 2nd time), I found
the reading to be erratic and intermittent. It took a while to
discover that the owner had somehow spread the gold center contact
leafs in the type-N connector and my adapter wasn't making
contact."

My repeater cohort and I have seen quite a few N connectors which were
damaged in precisely this fashion.

One cause: some N-connector adapters floating around out there have
center pins which are either too large in diameter, improperly
tapered, or which protrude too far "forwards". I suspect that male N
connectors, if improperly installed, can have the same problem (the
pin is pushed too far into the connector).

In either case, (over)tightening such an N-male connector onto an
N-female will cause it to make excellent contact... once... as the pin
splays the female connector's contacts outwards. Subsequent
connection attempts with a properly-configured N male won't make good
contact.

In a pinch, you can try pinching the contact fingers back in, but it's
nigh-on impossible to restore them properly. Better to remove the
damaged female connector and replace it. Then, check all of your male
N connectors to make sure the center pin has the proper taper and is
in the proper position. A center pin with a rounded blunt end (rather
than a properly-tapered point) is Trouble.

This turned out to be all that was wrong with a defective TK-981 I
picked up at the De Anza ham flea market last year. Cut off the N
connector, solder-and-crimp a new one onto the pigtail, and it checks
out fine.

Dave Platt wrote:
One cause: some N-connector adapters floating around out there have
center pins which are either too large in diameter, improperly
tapered, or which protrude too far "forwards". I suspect that male N
connectors, if improperly installed, can have the same problem (the
pin is pushed too far into the connector).

With some types of cable, there is a tendency for the inner conductor
to "lengthen" relative to the outer shield when the cable is repeatedly
wound and unwound in a small radius.

This can sometimes push out the connector pin a little.

On Mon, 9 Nov 2015 11:07:16 -0800, (Dave
Platt) wrote:

In article ,
Jeff Liebermann wrote:

Now working on an MFJ-259A, which looks like the usual blown diode
problem:
http://802.11junk.com/jeffl/MFJ-269-repair/

"Of course, when I got it back together (for the 2nd time), I found
the reading to be erratic and intermittent. It took a while to
discover that the owner had somehow spread the gold center contact
leafs in the type-N connector and my adapter wasn't making
contact."

My repeater cohort and I have seen quite a few N connectors which were
damaged in precisely this fashion.

I can see that with N connectors that are assembled or crimped in
pieces, but not a 1 piece panel mount N receptacle. The PCB board
it's mounted upon would break before the connector.

One cause: some N-connector adapters floating around out there have
center pins which are either too large in diameter, improperly
tapered, or which protrude too far "forwards". I suspect that male N
connectors, if improperly installed, can have the same problem (the
pin is pushed too far into the connector).

Yep. However, I checked for that problem with some wire gauges.
Intermittent center pins, are a real problem, but not on this one.
Usually the center pin receptacle is ruined by a blob of solder on the
outside of the mating pin plug.

In either case, (over)tightening such an N-male connector onto an
N-female will cause it to make excellent contact... once... as the pin
splays the female connector's contacts outwards. Subsequent
connection attempts with a properly-configured N male won't make good
contact.

You should see the mess that problem produces when an unspecified
manufacturer of hard disk drives used power plugs that spread the
0.093 Molex connectors. Subsequent connections to "normal" size
0.093" connectors were very intermittent.

In a pinch, you can try pinching the contact fingers back in, but it's
nigh-on impossible to restore them properly. Better to remove the
damaged female connector and replace it. Then, check all of your male
N connectors to make sure the center pin has the proper taper and is
in the proper position. A center pin with a rounded blunt end (rather
than a properly-tapered point) is Trouble.

This turned out to be all that was wrong with a defective TK-981 I
picked up at the De Anza ham flea market last year. Cut off the N
connector, solder-and-crimp a new one onto the pigtail, and it checks
out fine.

Nicely done. I once saw a mobile (forgot the model) with the center
drilled out of the UHF SO-239, a pigtail inserted, and a BNC
receptacle at the end. I like it.




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Dave Platt" wrote in message
...
In article ,
Jeff Liebermann wrote:

Now working on an MFJ-259A, which looks like the usual blown diode
problem:
http://802.11junk.com/jeffl/MFJ-269-repair/

"Of course, when I got it back together (for the 2nd time), I found
the reading to be erratic and intermittent. It took a while to
discover that the owner had somehow spread the gold center contact
leafs in the type-N connector and my adapter wasn't making
contact."

My repeater cohort and I have seen quite a few N connectors which were
damaged in precisely this fashion.

The N connector is so-called because there are N different ways to assemble
it, and all of them wrong :-)