tube question

[radio nut]

My current project uses a 6af6 tuning indicator eye tube. The tube has two sides but only one side is active. Should both sides move when the set is tuned?

[Reece]

The 6AF6 has separate grids for each side of the pattern. If the two grids (pins 3 & 4) are connected together, both sides of the pattern should move unless the tube is defective.

In some cases the two grids may go to separate circuits as the design was to better indicate FM vs. AM tuning.

[radio nut]

each side is wired differently so maybe its a resistor that is out of tolerance. But I have bigger fish to fry, the fm sounds out of tune no matter what I do. I did read on a capehart site that resistors in the fm circuit are fairly critical as far as tolerances are concerned so I'd better get busy!

[radio nut]

The diagram that I have been using is from nostalgiaair. Its does not have watt ratings for resistors. So what do I do for replacements?

[radio nut]

I checked a few resistors and I looked for replacements and can't seem to find the high resistance ones. Can anyone tell me where to find as an ex. 33m resistors.

[wa2ise]

Originally Posted by radio nut

... high resistance ones. Can anyone tell me where to find as an ex. 33m resistors.

Be aware that some really old schematics used "M" for "thousand" Like as in "millennium" for "1000 years". See if the diagram has any resistors marked with "K", if not, then this could be the case. So that could be a 33K resistor.

[bandersen]

Originally Posted by radio nut

The diagram that I have been using is from nostalgiaair. Its does not have watt ratings for resistors. So what do I do for replacements?

You can usually estimate the wattage based on the size of the original resistors. 1/2 watt should be fine for most. Bigger ones are likely 1 or 2 watts.

[Reece]

The pictures on this site will give you an idea of wattage ratings:

http://www.philcorepairbench.com/resistcompare.htm

[radio nut]

Ok, thanks for the resistor info. I have yet to get resistors but will order them soon. Now I have a new problem I have never seen. the am band has been running well so I use this radio frequently. After its been on awhile it gets a ringing noise in the speaker. when this happens if i tap the amplifier chassis the ringing gets louder as I'm tapping. What in the world causes this? I rechecked my solder joints and all paper/electrolytics have been replaced. This also happens on aux. input so I am saying it has to be the amp/rectifier chassis only. This issue takes about 20 minutes to show up

[47'Plymouth]

hi Radionutt
got a new 6AF6 in a Cornell-Dubellier model BN Capacitor tester thats used to test for shorts..has a 12AX7 for a rectifier/amp tube...trying to redo it also

[old_coot88]

Originally Posted by radio nut

... it gets a ringing noise in the speaker. when this happens if i tap the amplifier chassis the ringing gets louder as I'm tapping. What in the world causes this?

Almost certainly a microphonic tube.

[Reece]

Coot has it. Tap each tube in turn and you should localize it. The answer is a new tube, but you can often silence a microphonic tube with extra weight attached to it, which modifies its mechanical point of resonance. A way old timers did it (thank you, thank you) was to wind a number of turns of heavy solder around the tube envelope. Then slide it off, tighten up the turns a bit, and slip back on so it stays by its own pressure. Looks funky but usually works.

[old_coot88]

Originally Posted by Reece

...A way old timers did it (thank you, thank you) was to wind a number of turns of heavy solder around the tube envelope. Then slide it off, tighten up the turns a bit, and slip back on so it stays by its own pressure. Looks funky but usually works.

Some early TV tuners used a lead shield on the mixer/osc. tube to quiet down the microphonics. Without it the oscillator tended to "FM" like crazy with every click of the detent.

[radio nut]

well, I replaced the bad tube,found an out of tolerance resistor and a dead resistor in the tuning eye circuit. Tuning eye is good now. I still think the fm sounds slightly out of tune. The rider's info says that the discriminator transfomer has a calibration to it. The picture of the chassis does not show a transfomer for it and neither does the electrical diagram. The 6h6 disc. tube is good and the resistors and caps around it check fine.If I hook a cd player to the phono input it is extremely clear and sounds great. Is the circuitry just not able to get the fidelity I am thinking I should get?

[radio nut]

This set is a capehart panamuse with two chassis's and 23 tubes. It has seperate am and fm circuits up to the audio amp.model 21n2