i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
I've had a few NOS tubes blow out the pilot lamp instantly.
Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
I later tracked this problem to the 35z5 of course..
I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
I replaced with a Hytron that fit much more snug.
That Radio sounds a lot better!

My question is: I have many that are used...
Nearly every one of them show the shorts light on the
pilot heater,shorts tests switch 1-5 on a TV-7 DU..
except for sw point #2..
the filaments do light on these tubes.
What gives here?
Many Thanks for any discussion of this tube..

: i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: I've had a few NOS tubes blow out the pilot lamp instantly.
: Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: I later tracked this problem to the 35z5 of course..
: I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: I replaced with a Hytron that fit much more snug.
: That Radio sounds a lot better!

: My question is: I have many that are used...
: Nearly every one of them show the shorts light on the
: pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: except for sw point #2..
: the filaments do light on these tubes.
: What gives here?
: Many Thanks for any discussion of this tube..

I suppose i could check this with one known to be working, but the handfull i checked yesterday had the same results...The manual states for BALST,,shorts 1-5
they failed all except for sw#2.
I'm afraid to try these in a circuit..

: i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: I've had a few NOS tubes blow out the pilot lamp instantly.
: Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: I later tracked this problem to the 35z5 of course..
: I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: I replaced with a Hytron that fit much more snug.
: That Radio sounds a lot better!

: My question is: I have many that are used...
: Nearly every one of them show the shorts light on the
: pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: except for sw point #2..
: the filaments do light on these tubes.
: What gives here?
: Many Thanks for any discussion of this tube..

Hi Dave

The 35Z5 does have a heater tap, pin #3. The pilot light is connected between pin #2 and #3. If on turn on the light flashes and burns out the section of the filiment between 2 and 3 is already open or the pilot light socket may be shorted to chassis. This will blow both the tube and light in a radio with chassis ground.

Some tube testers do not check 35Z5's properly, only using the tap to one side of the filament. I have no idea why your tester shows a short from pin #1 to pin #5. Pin #1 isn't used on a 35Z5. Use an ohm meter to verify continuity between pins #2 and #7 on the 35Z5's.

If the light & tube burn out after the 35Z5 is heated it's caused by a short on the B+ line or filter caps. However if your socket has a bad connection on pin #8, cathode, or pin #5, plate, you could get surges that can blow both tube and light. Try tightening these connections with a pliers.

Norm

: : i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: : I've had a few NOS tubes blow out the pilot lamp instantly.
: : Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: : I later tracked this problem to the 35z5 of course..
: : I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: : I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: : I replaced with a Hytron that fit much more snug.
: : That Radio sounds a lot better!

: : My question is: I have many that are used...
: : Nearly every one of them show the shorts light on the
: : pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: : except for sw point #2..
: : the filaments do light on these tubes.
: : What gives here?
: : Many Thanks for any discussion of this tube..

: Hi Dave

: The 35Z5 does have a heater tap, pin #3. The pilot light is connected between pin #2 and #3. If on turn on the light flashes and burns out the section of the filiment between 2 and 3 is already open or the pilot light socket may be shorted to chassis. This will blow both the tube and light in a radio with chassis ground.

: Some tube testers do not check 35Z5's properly, only using the tap to one side of the filament. I have no idea why your tester shows a short from pin #1 to pin #5. Pin #1 isn't used on a 35Z5. Use an ohm meter to verify continuity between pins #2 and #7 on the 35Z5's.

: If the light & tube burn out after the 35Z5 is heated it's caused by a short on the B+ line or filter caps. However if your socket has a bad connection on pin #8, cathode, or pin #5, plate, you could get surges that can blow both tube and light. Try tightening these connections with a pliers.

: Norm

Thanks Norm..yes, i didnt think to check it with an ohm-meter..i guess if pins #2 and #3 show a connection it's ok then!...

The TV 7 does both checks...it just said in the manual to perform shorts tests settings 1-5..? :D
They show good other wise and still have plenty of life.

thanks again.

: : : i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: : : I've had a few NOS tubes blow out the pilot lamp instantly.
: : : Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: : : I later tracked this problem to the 35z5 of course..
: : : I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: : : I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: : : I replaced with a Hytron that fit much more snug.
: : : That Radio sounds a lot better!

: : : My question is: I have many that are used...
: : : Nearly every one of them show the shorts light on the
: : : pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: : : except for sw point #2..
: : : the filaments do light on these tubes.
: : : What gives here?
: : : Many Thanks for any discussion of this tube..

: : Hi Dave

: : The 35Z5 does have a heater tap, pin #3. The pilot light is connected between pin #2 and #3. If on turn on the light flashes and burns out the section of the filiment between 2 and 3 is already open or the pilot light socket may be shorted to chassis. This will blow both the tube and light in a radio with chassis ground.

: : Some tube testers do not check 35Z5's properly, only using the tap to one side of the filament. I have no idea why your tester shows a short from pin #1 to pin #5. Pin #1 isn't used on a 35Z5. Use an ohm meter to verify continuity between pins #2 and #7 on the 35Z5's.

: : If the light & tube burn out after the 35Z5 is heated it's caused by a short on the B+ line or filter caps. However if your socket has a bad connection on pin #8, cathode, or pin #5, plate, you could get surges that can blow both tube and light. Try tightening these connections with a pliers.

: : Norm

: Thanks Norm..yes, i didnt think to check it with an ohm-meter..i guess if pins #2 and #3 show a connection it's ok then!...

: The TV 7 does both checks...it just said in the manual to perform shorts tests settings 1-5..? :D
: They show good other wise and still have plenty of life.

: thanks again.

Dave

The continuity test is ok for checking the filament. Actually checking pins #2 to #7 will test to pin #3 also. Pin #3 is a tap between the others. You are right the section between 2 and 3 will usually go open. You could make a plug in solid state replacement for testing if you are working on a lot of radios with 35Z5's. Use a 200 ohm 5 watt or greater resistor from pins 3 to 7 and a 50 ohm resistor 2 watt resistor between pins 2 and 3. Use a 1N4004 or similar diode from the plate, pin 5, to cathode, pin 8, with a 100 ohm resistor in series. You can always add a small fuse. This would make a nice test unit and you will not burn up 35Z5's.

Norm

: : : : i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: : : : I've had a few NOS tubes blow out the pilot lamp instantly.
: : : : Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: : : : I later tracked this problem to the 35z5 of course..
: : : : I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: : : : I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: : : : I replaced with a Hytron that fit much more snug.
: : : : That Radio sounds a lot better!

: : : : My question is: I have many that are used...
: : : : Nearly every one of them show the shorts light on the
: : : : pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: : : : except for sw point #2..
: : : : the filaments do light on these tubes.
: : : : What gives here?
: : : : Many Thanks for any discussion of this tube..

: : : Hi Dave

: : : The 35Z5 does have a heater tap, pin #3. The pilot light is connected between pin #2 and #3. If on turn on the light flashes and burns out the section of the filiment between 2 and 3 is already open or the pilot light socket may be shorted to chassis. This will blow both the tube and light in a radio with chassis ground.

: : : Some tube testers do not check 35Z5's properly, only using the tap to one side of the filament. I have no idea why your tester shows a short from pin #1 to pin #5. Pin #1 isn't used on a 35Z5. Use an ohm meter to verify continuity between pins #2 and #7 on the 35Z5's.

: : : If the light & tube burn out after the 35Z5 is heated it's caused by a short on the B+ line or filter caps. However if your socket has a bad connection on pin #8, cathode, or pin #5, plate, you could get surges that can blow both tube and light. Try tightening these connections with a pliers.

: : : Norm

: : Thanks Norm..yes, i didnt think to check it with an ohm-meter..i guess if pins #2 and #3 show a connection it's ok then!...

: : The TV 7 does both checks...it just said in the manual to perform shorts tests settings 1-5..? :D
: : They show good other wise and still have plenty of life.

: : thanks again.

: Dave

: The continuity test is ok for checking the filament. Actually checking pins #2 to #7 will test to pin #3 also. Pin #3 is a tap between the others. You are right the section between 2 and 3 will usually go open. You could make a plug in solid state replacement for testing if you are working on a lot of radios with 35Z5's. Use a 200 ohm 5 watt or greater resistor from pins 3 to 7 and a 50 ohm resistor 2 watt resistor between pins 2 and 3. Use a 1N4004 or similar diode from the plate, pin 5, to cathode, pin 8, with a 100 ohm resistor in series. You can always add a small fuse. This would make a nice test unit and you will not burn up 35Z5's.

: Norm

Thanks for the values, that's a great tip.!
will do..I found an Rca with the Thin base. You can get a clear view with a magnifer of the 2 tiny wires connected to a post at pin 3 and the single wires to 2 and 7..They appear to have a coating that stops just at connection..the actual wires are really very thin..

what a tricky old tube...
just did a hallicrafters S-38 that also has one.. i love my new s-38!

: : i've found these to be very troublesome. There is a third heater tap (ballast or pilot lamp tap), that i think causes a lot of problems with this tube.
: : I've had a few NOS tubes blow out the pilot lamp instantly.
: : Yesterday after a power supply workup on a Sentinal (249-w,1940,i think)..it worked fine, except trash and noise when at volume..
: : I later tracked this problem to the 35z5 of course..
: : I was tipped off when i touched the tube and the pilot lamp glow increased quite a bit.
: : I'm not sure if the noise was internal arcing or caused by the lack of a snug fit..(raytheon)..
: : I replaced with a Hytron that fit much more snug.
: : That Radio sounds a lot better!

: : My question is: I have many that are used...
: : Nearly every one of them show the shorts light on the
: : pilot heater,shorts tests switch 1-5 on a TV-7 DU..
: : except for sw point #2..
: : the filaments do light on these tubes.
: : What gives here?
: : Many Thanks for any discussion of this tube..

: Hi Dave

: The 35Z5 does have a heater tap, pin #3. The pilot light is connected between pin #2 and #3. If on turn on the light flashes and burns out the section of the filiment between 2 and 3 is already open or the pilot light socket may be shorted to chassis. This will blow both the tube and light in a radio with chassis ground.

: Some tube testers do not check 35Z5's properly, only using the tap to one side of the filament. I have no idea why your tester shows a short from pin #1 to pin #5. Pin #1 isn't used on a 35Z5. Use an ohm meter to verify continuity between pins #2 and #7 on the 35Z5's.

: If the light & tube burn out after the 35Z5 is heated it's caused by a short on the B+ line or filter caps. However if your socket has a bad connection on pin #8, cathode, or pin #5, plate, you could get surges that can blow both tube and light. Try tightening these connections with a pliers.

: Norm

Hi,
I have a Heathkit tester that tests 35Z5s as good after the heater is blown. I remember several years ago I worked on a Firestone Fire Chief that had a jumper from pin 2 to pin 3. I was pretty green at the time and let a working jumper stay in place, but now that I have 2 radios on the bench with the same problem described in your messages, I wonder if my tube tester is testing from pin 3 to pin 7. Any advice before I create a fire hazard and try jumping pin 2 to pin 3?
-db