Re: {Collins} Centron 811A

I have sat silent on the topic but I have had and have several Cetron 811A
NIB where slight handling has led to the plate cap coming off.  It is not
just re-binding to glass that is the problem but more importantly the
re-soldering of the plate pin to the cap that I have found problematic.  The
caps appear to be filled not with solder but with some kind of material that
has crumbled with age.  I have looked for new plate caps for this size tube
with no success... lots available for smaller ones like 6146 but those never
come apart.

73 Jerry

-----Original Message-----
From: Collins [] On
Behalf Of Joe
Sent: Friday, May 29, 2015 7:13 AM
To: 'john nelson'; collins@xxxxxxxxxxxxx
Subject: Re: {Collins} Centron 811A

John -- I'll take you up on that for all three. However, will you agree to
letting the group know how it works out and if you were successful or not
with your process? Please note that some of tubes are also loose on the
base. Joe kv4pn

-----Original Message-----
From: Collins [] On
Behalf Of john nelson
Sent: Friday, May 29, 2015 5:38 AM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} Centron 811A

I have 3 sets of 811A from NB but never had an issue like some have. I have
fixed a few rare tubes in the past that had plate caps that came loose.
Talking with a friend that was a chemist he said that the silicon based
adhesive used in old tubes needed to be heated to set the adhesive and in
cases of some they just were not cured long enough and over decades the
adhesive just broke down. Now as many of you know when restoring old radio
equipment sometimes we have to reinvent past engineering and do it our
self's. Their is a company called Flexbar that makes several products that
bond glass and metal from -350 to 2200 deg F it is about $30.00 also there
is a half dozen venders on fleabag that sell similar products. I have never
had an issue after rebounding old plate caps back on. So let me know if you
have (NEW) old Centron 811A's that have loose caps and I will give you five
bucks apiece for them and even pay the shipping.

John W0XAZ
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