LM13-need help-tube filament trouble
 

My faithful LM13, been working for years, suddenly stopped.

Found green oil inside case, oil leaking out the case at front, and no
HV at plates and filaments not lighting were the first problems.
Found 2 bad oil filled bathtub caps, one leaked oil, and fixed both
which restored plate HV to the 67 plate. HV at 77 and 6A7 is unknown now.

A serious problem is filaments of 6A7 and 77 tubes will not turn on
unless I do strange things to position those tubes in sockets and then
carefully tighten their chassis clamps. HAve to jam styrafoam between
6A7 and metal frame to make filaments light no matter how I tighten tube
base clamps.

I see that all 3 tubes pins are barely touching the socket contacts
during insertion. Do not know why pins do not push deeply into socket
contacts.

Since LM13 worked for years, apparently this shallow barely touching pin
to socket WAS OK originally and STILL must be ok and normal. Nothing
has changed about this tube set. The filaments all measure 5 ohms.
Possibly there is corrosion on the socket contact where tube pin
touches. CAIG contact cleaner DEOXIT does not help corrosion.

Using two screwdriver blades to supplement the filament pin to socket
contact connections, I can make the filaments of both 6A7 and 77 light
up. Their filaments are in series.

Really need help, suggestions, hints with this filamanr problem.
The problem is NOT INTERMITTENT...rock solid.

Thanks, 73, W6MIK, Dave

LM13-need help-tube filament trouble
 

Hi,

Just a wild thought, the oil in a capacitor *is* a dilectric, and
if the socket/s are contaminated with it it might prevent contact
if the fit was the least bit loose. Sounda bizarre but try
cleaning the sockets with solvent and a pipe cleaner. Might just
work! I would use Toluene.

Bill
N4ZZO

LM13-need help-tube filament trouble
 

Bill Kehm wrote:
Hi,

Just a wild thought, the oil in a capacitor *is* a dilectric, and if the
socket/s are contaminated with it it might prevent contact if the fit
was the least bit loose. Sounda bizarre but try cleaning the sockets
with solvent and a pipe cleaner. Might just work! I would use Toluene.

Bill
N4ZZO

Thanks Bill, I will try the solvent idea.

I can use ANY ideas from any LM series owner whose LM uses type 76,
77, and 6A7 tubes. I am baffled why the tube pins insert so little into
the socket contacts. Have the socket contacts lost their spring action?
Can I GENTLY readjust my socket contacts?
Do type 76,77, and 6A7 tubes in LM series units really insert pins so
there is only a slight KISS contact at the pin's tip, no real deeper
insertion with good wiping?

Thanks for any suggestions, hints, etc to improve contact between tube
pins and tube sockets. Contacting me by direct email is sure OK. 73,
Thanks, W6MIK, Dave