[R-390] Strange 5R4

[Steve Hobensack]

Miles,
 
Apply a megger across the filament pins. If it is open, try sparking a T model Ford coil across the pins. Sometimes you might get lucky
and burn in a poor connection. I have had success with rare old tubes doing this, but since 5R4s are still cheap and plentiful, It probably 
isn't worth messing with. There could cause some grief in the future.
 
Steve N8YE
 

> Message: 2
> Date: Thu, 01 Dec 2011 09:03:22 -0500
> From: k2cby <k2cby at optonline.net>
> Subject: [R-390] OT Strange 5R4
> To: R-390 Mailman <R-390 at Mailman.qth.net>
> Message-ID: <17F73F245D2F41DBB754141229EB8A61 at milesdesk>
> Content-Type: text/plain; charset=us-ascii
> 
> I recently acquired a Viking 1-1/2 transmitter (that's a Viking I with the
> TVI suppression and audio mods from the Viking II).
> 
> 
> 
> Before I fired it up - and before I re-fastened the umpteen 6-32 screws that
> hold the top shield in place - I thought I ought to check the tubes on my
> trusty TV-7.
> 
> 
> 
> The power supply uses two 5R4 rectifiers.
> 
> The first one I popped in tested fine.
> 
> The second one didn't move the needle at all - not a flicker.
> 
> I said to myself "Well, that's obvious: open filament."
> As I reached over to pluck the tube out of the TV-7 and throw it in the
> trash I got a surprise - it was hot and glowing.
> I then figured maybe there was a solder fault in one of the base pins, so I
> sweated all of them and applied additional solder - no cure.
> 
> 
> 
> I never heard of a rectifier with a good filament that wouldn't conduct at
> all.
> 
> 
> 
> Did 5R4s have an internal fuse?
> 
> 
> 
> Any other ideas?
> 
> 
> 
> 
> 
> 
> 
> Miles B. Anderson, K2CBY
> 16 Round Pond Lane
> Sag Harbor, NY 11963
> Tel.: (631) 725-4400
> 
> Fax.: (631) 725-2223
> e-mail: k2cby at optonline.net 
> 
> 
> 
> 
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> End of R-390 Digest, Vol 92, Issue 1
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