Tektronix 2213 CRT Modification

[Steve]

I have a great Tek 2213 that was purchased form a TV station. The
scope is in great condition, but CRT is very dim. IIRC, I've read
that these scopes had a slightly high filament voltage resulting in
short CRT life, and there was a mod that Tek did to fix this problem
by removing a few turns on the XFMR. Is this right? I also remember
someone saying that there was a marking on the back of the scope or
the xfmr if they had been modified. Well, I found a replacement CRT
with plenty of life left in it, but I don't want it to fail
prematurely again. Is this a user modification, or is it pretty
lenghty? Any info on this subject appreciated.

Thanks,
Steve

 

[Jim Yanik]

I have a great Tek 2213 that was purchased form a TV station. The
scope is in great condition, but CRT is very dim. IIRC, I've read
that these scopes had a slightly high filament voltage resulting in
short CRT life, and there was a mod that Tek did to fix this problem
by removing a few turns on the XFMR. Is this right?

Yes;a half-turn was removed from the T940 inverter xfmr's HV filament
winding,the brown wire at the top of the bobbin.

You have to re-adjust the CRT grid bias after the mod is done.

I also remember
someone saying that there was a marking on the back of the scope or
the xfmr if they had been modified. Well, I found a replacement CRT
with plenty of life left in it, but I don't want it to fail
prematurely again. Is this a user modification, or is it pretty
lenghty? Any info on this subject appreciated.

Thanks,
Steve

CRT filament mod 2213 S/N range; B010100-B029389,200001-203411

Modded scopes should have a Tektronix ID Number label on the rear
somewhere;M50226 is the Mod number.

S/N's B027000-B030000,202500-203411 should be checked for prior
modification BEFORE implementing the mod.

IIRC,inverter xfmr's with an -01 suffix will already have the mod.

from my schematic peniclled-in notes,CRT fil voltage ;

**measure disconnected from PCB!!** (true-RMS meter)

unmodded 7-7.3 VRMS
modded 6.1-6.4 VRMS
2X mod 4.4-4.6 VRMS (2X= mod mistakenly done twice)

 

[Steve]

Thanks so much, that's exactly the info I was looking for.

Best regards,
Steve