Bad Magic Eye Tube?

[Jeff Tranter]

I have a Canadian-made Rogers-Majestic (Philips) RG5050A AM/SW/FM
radio with a 6FG6/EM84 tuning indicator tube. The tube only shows a
very small green dot when tuned to a strong AM station. The heater and
plate voltages look good. The voltage on the grid varies from about
-0.5V to -8V when tuning from no station to a strong station
(presumably tied to the AVC line). According to the tube info -8V
should be about 1/3 deflection of the full 21mm shadow. All other
radio functions appear okay. Should I assume the tube is bad? The
strange thing is that when the radio is powered up from cold, I
briefly see the tuning indicator tube display a nice rectangular
shadow and then it goes away.

The relevant portion of the circuit can be seen
Loading Image...

[Michael Jenkins]

I don't know if this applies to the 6FG6 but I had a problem with a 6E5 that
sounds very similar. The AVC voltage was changing but there was no change
in the magic eye tube.

The magic eye tube is mounted horizontally and is visible through a hole
behind the glass dial in my radio and was connected to the radio through a
pig-tail socket at the base of the tube.

I found this reference on the internet to magic eye tubes at
http://www.gbronline.com/radioguy/tuneye.htm. Under the section trouble
shooting it talks about the problem I was having with the magic eye tube.

Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.

The problem is of course the socket is enclosed so you can't easily test the
voltage on pins 2 and 4. You have to remove the enclosure around the socket
to expose the resistor.

I hope this helps.

Michael Jenkins

Post by Jeff Tranter
I have a Canadian-made Rogers-Majestic (Philips) RG5050A AM/SW/FM
radio with a 6FG6/EM84 tuning indicator tube. The tube only shows a
very small green dot when tuned to a strong AM station. The heater and
plate voltages look good. The voltage on the grid varies from about
-0.5V to -8V when tuning from no station to a strong station
(presumably tied to the AVC line). According to the tube info -8V
should be about 1/3 deflection of the full 21mm shadow. All other
radio functions appear okay. Should I assume the tube is bad? The
strange thing is that when the radio is powered up from cold, I
briefly see the tuning indicator tube display a nice rectangular
shadow and then it goes away.
The relevant portion of the circuit can be seen
http://members.rogers.com/jefftranter/radios/rogers-rg5050a/dscn2182.jpg

[Jeff Tranter]

This circuit has a 470K resistor and it is easy to get at. It tests fine
with an ohmmeter.

Post by Michael Jenkins
I don't know if this applies to the 6FG6 but I had a problem with a 6E5 that
sounds very similar. The AVC voltage was changing but there was no change
in the magic eye tube.
The magic eye tube is mounted horizontally and is visible through a hole
behind the glass dial in my radio and was connected to the radio through a
pig-tail socket at the base of the tube.
I found this reference on the internet to magic eye tubes at
http://www.gbronline.com/radioguy/tuneye.htm. Under the section trouble
shooting it talks about the problem I was having with the magic eye tube.
Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.
The problem is of course the socket is enclosed so you can't easily test the
voltage on pins 2 and 4. You have to remove the enclosure around the socket
to expose the resistor.

[Jeff Tranter]

This circuit has a 470K resistor and it is easy to get at. It tests fine
with an ohmmeter.

Post by Michael Jenkins
...
Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.

[Ken]

Post by Jeff Tranter
This circuit has a 470K resistor and it is easy to get at. It tests fine
with an ohmmeter.

Post by Michael Jenkins
...
Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.

I have a radio with same tube. I bought a spare cause The one i had didn't
work (or so i thought) In my case it was a problem on the board. My guess is
that you are having an issue somewhere else. The fact you are getting an
image on startup suggests that the tube itself is working . If you want I can
test the tube for you. I had to build a little jumper with a 470k resistor
the test it. Email me privately

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[Jeff Tranter]

Post by Ken
I have a radio with same tube. I bought a spare cause The one i had didn't
work (or so i thought) In my case it was a problem on the board. My guess is
that you are having an issue somewhere else. The fact you are getting an
image on startup suggests that the tube itself is working . If you want I can
test the tube for you. I had to build a little jumper with a 470k resistor
the test it. Email me privately

[Ken]

Post by Ken
I have a radio with same tube. I bought a spare cause The one i had didn't
work (or so i thought) In my case it was a problem on the board. My guess is
that you are having an issue somewhere else. The fact you are getting an
image on startup suggests that the tube itself is working . If you want I can
test the tube for you. I had to build a little jumper with a 470k resistor
the test it. Email me privately

That's because I am a moron! I for to take you to remove the transistor from
the address. Sorry,

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==============================================================

[Michael Jenkins]

Jeff,

I don't know if this applies to the 6FG6 but I had a problem with a 6E5 that
sounds very similar. The AVC voltage was changing but there was no change
in the magic eye tube.

The magic eye tube is mounted horizontally and is visible through a hole
behind the glass dial in my radio and was connected to the radio through a
pig-tail socket at the base of the tube.

I found this reference on the internet to magic eye tubes at
http://www.gbronline.com/radioguy/tuneye.htm. Under the section trouble
shooting it talks about the problem I was having with the magic eye tube.

Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.

The problem is of course the socket is enclosed so you can't easily test the
voltage on pins 2 and 4. You have to remove the enclosure around the socket
to expose the resistor.

I hope this helps.

Michael Jenkins

Post by Jeff Tranter
I have a Canadian-made Rogers-Majestic (Philips) RG5050A AM/SW/FM
radio with a 6FG6/EM84 tuning indicator tube. The tube only shows a
very small green dot when tuned to a strong AM station. The heater and
plate voltages look good. The voltage on the grid varies from about
-0.5V to -8V when tuning from no station to a strong station
(presumably tied to the AVC line). According to the tube info -8V
should be about 1/3 deflection of the full 21mm shadow. All other
radio functions appear okay. Should I assume the tube is bad? The
strange thing is that when the radio is powered up from cold, I
briefly see the tuning indicator tube display a nice rectangular
shadow and then it goes away.
The relevant portion of the circuit can be seen
http://members.rogers.com/jefftranter/radios/rogers-rg5050a/dscn2182.jpg

[J M Noeding]

On Sat, 5 Jun 2004 15:46:42 -0400, "Michael Jenkins"

Post by Michael Jenkins
Jeff,
I don't know if this applies to the 6FG6 but I had a problem with a 6E5 that
sounds very similar. The AVC voltage was changing but there was no change
in the magic eye tube.
Sure enough, I opened the back of the socket the tube plugs into on the
pig-tail (this was a struggle without breaking) and there was a open
circuit 1 meg resistor between pins 2 and 4. I replaced it and it works
perfectly.

perhaps not so easy to open the socket of a miniature type tube, but
it might be more interesting for 6U5, EM34, EM4 types.....