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Post by frank1956 on Thu Jul 03, 2014 4:31 am

Reading taken, meter zero out, set to R X 100. Set unplugged. On pin # 6 & 7 on the couplate got just above zero. Pic's attached.

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Post by 35Z5 on Thu Jul 03, 2014 5:23 am

Frank you're not following instructions, if you don't set meter correctly(Rx100K scale, not Rx100) and measure from correct points(pins 6 & 7 of couplate), the reading is useless, as this one most certainly is... You are measuring nothing more than a straight piece of wire, which is supposed to have zero ohms... Using wrong scale and measuring from correct points, there won't be any reading at all even if the 470K resistor inside the couplate were good... On the Rx100K scale reading should be around the 5 if the resistor is good... If its bad will read higher resistance, meaning less meter deflection...

BTW if this meter doesn't have a scale of at least Rx10K, it will be useless for this test...

Tom
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Post by frank1956 on Thu Jul 03, 2014 5:54 am

Tom,
I have two meter's. One analog with the following scale X1K,X100 and X10. One digital has the following scale 2000K, 200K,20K and 2000. So wish mester and at what scale would you suggest I use.
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Post by 75X11 on Thu Jul 03, 2014 6:23 am

Try your digital in the 20K scale and post the reading for 35Z5. It looks like you have had a late night of it and it might be good to let it sit awhile. I'm only here because I have just started work and the trf site is notifiying me of posts again. after very long at a session, one gets burned out and it pays to rest and get a fresh start. That cares for the most important piece of test equipment you have. The one between your ears.  Very Happy 
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Post by frank1956 on Thu Jul 03, 2014 10:45 am

Thanks you are right 75X11.
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Post by Wildcat445 on Thu Jul 03, 2014 11:13 am

I'm confused. 75, do you mean 20K or 2000K? He can't measure 470K on the 20K scale. I'm not sure about your reference to the 35Z5. I understood that our concern was with the 12AV6. I got in on the tail end of the conversation, admittedly.

Perhaps if Frank would measure from pin 4 of the 50L6 to pin 7 of the 12AV6, it would be easier. Sometimes pin markings are hard to read on a couplet. Will this not get him to the same place as reading across the couplet? He is looking to measure R6, a 470K ohm resistor in that couplet.

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Post by 75X11 on Thu Jul 03, 2014 12:37 pm

You're correct. I read the last line of 35Z5's last post and thought 20 k would be more than 10 k. I didn't read enough. That's what I get for posting while writing service orders. One thing though, I think the digital might be a good choice for this stage of the game. The interpretive measurments could serve as confirmation. It might also be good to confirm the actual pin layout on the radio to insure there are no reversals. Stepping back now. Embarassed 
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Post by 35Z5 on Thu Jul 03, 2014 1:30 pm

75X11 wrote: I think the digital might be a good choice for this stage of the game.  

Agreed, that inadequate analog meter is just confusing the issues... Plus we don't know what it's impedance is, it could well be dragging down voltage readings in high resistance circuits... If meter is only 1000 ohm per volt, the 470K may well be OK... A digital will have a very high input resistance so there is no danger of loading the circuit...

The digital meter 2000K scale will read up to 1,999,999 ohms, will be fine to measure a resistor that's 470,000 ohms...  Note there are usually a couple resistor in these radios of 3-10 meg, so 2000K won't read those... Better meters will read to 20 meg or 19,999,999 ohms...

EDIT the GE meter is only 2K ohm per volt, there's part of the problem with that 12AV6 reading...

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Post by frank1956 on Thu Jul 03, 2014 3:13 pm

I am back and ready for some more. I measured the ohms from pin 4 on 50L6 to pin 7 on 12AV6 using 2000K and got between 459 & 450
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Post by 35Z5 on Thu Jul 03, 2014 3:31 pm

Close enough, for grins lets measure the voltage on pin 7 of 12AV6 again to see what this meter says... Use the 200v scale...
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Post by frank1956 on Thu Jul 03, 2014 3:40 pm

Voltage on pin 7 of 12AV6 was between 22.7 & 22.9 set on 200v scale
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Post by 35Z5 on Thu Jul 03, 2014 4:14 pm

Umm  470K OK, 12AV6 plate voltage approx half what it should be.. You can measure pin 1 on 12AV6, should be maybe .1 to .3v at most, use 2v scale...

Got another 12AV6 or 12AT6 we can try???

Any suggestions guys???
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Post by frank1956 on Thu Jul 03, 2014 4:33 pm

I do not have a replacement tube. I took the reading using 20V do not have 2V scale, got -0.02. Should I order one?????
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Post by Wildcat445 on Thu Jul 03, 2014 4:41 pm

We should have working audio. Everything checks good, except low plate voltage on the 12AV6. I would think that it should work, even if it was weak. I can't figure it for being dead. If Frank has another 12 AV- or 12AT6 on hand, it would not hurt to sub it for grins, I guess. I would not ask him to go buy one on the basis of my guessing.

Something in the back of my mind tells me that we missed an opportunity to learn something in the soldering iron on the volume control test. Frank, please do not misunderstand my question. Are you sure the soldering iron was on the CENTER terminal of the volume control, and that the soldering iron you used was plugged in and working? And that the radio was on and the volume turned up full? Redoing that test is the only thing I know to try other than subbing the 12AV6 at this point. If C5, the coupling cap for the output stage, was leaky, what would that do for B+ on the 12AV6? C5 couples the 12AV6 to the grid of the 50L6, pin 5. Do we have positive voltage on that pin? Whadda ya think?

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Post by frank1956 on Thu Jul 03, 2014 4:50 pm

WC,
I take no offense here. I am trying to get the radio to work just as much as you and the rest of the team are trying to help. To answer you questions.
(1) Soldering iron on center terminal of volume control. Yes
(2) Soldering iron plugged in and in working condition. Yes
(3) Was volume turned up full? Yes

Test was redone to ensure quality control and results were still the same  Sad

Re did pin # 1 on 12AV6 get -0.23v
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Post by 35Z5 on Thu Jul 03, 2014 4:57 pm

Now that you have a meter you can be friends with, go back and check pins 5 & 8 on 50L6... Pin 5 should be zero & 8 approx 7v...
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Post by frank1956 on Thu Jul 03, 2014 5:01 pm

Checked pin's 5 & 8. Pin 5 zero pin 8 7.2-7.3
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Post by 75X11 on Thu Jul 03, 2014 5:18 pm

I am having a time trying to find the drawings for this model, Could one of you give me the volume and or index number for either the Riders or Beitmans references to this model? A hard copy is nice to keep track with.
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Post by frank1956 on Thu Jul 03, 2014 5:28 pm

http://www.nostalgiaair.org/Resources/941/M0016941.htm
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Post by 35Z5 on Thu Jul 03, 2014 5:48 pm

So what's going on in this pict??? There isn't supposed to ba a cap connected to pin 2 of the 50L6... Are Pins 2 & 3 connected together??? Again not supposed to be... What's the purpose of the loose wire???


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Post by frank1956 on Thu Jul 03, 2014 6:18 pm

I ask myself the same question in regards to the cap. Was an old one there when I replaced it, went step by step when I replaced them. The reason I was wondering is I saw one re-capped like this one, and there was not one were this one is. Since I replaced it with an original I did not question it. The loose wire was loose like that when I got it, looks to go to some sort of external plug??? You might be able to see were the old solder was, did not re-connect as it made no difference in the speaker.


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Post by Wildcat445 on Thu Jul 03, 2014 6:32 pm

75, try Riders 23, Page 36 for the schematic drawing. Pin 2 is a filament, right? Why not lift one side of that cap to see what happens?

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Post by 35Z5 on Thu Jul 03, 2014 6:46 pm

Get rid of the wire and make sure pins 2 & 3 aren't connected together, it'll never work if they are... Also that cap should be connected between pin 3 on 50L6 & pin 7 of 35W4, or positive end of C10A, same point as they are connected together or at least suppose to be...

Study the schematic I posted back on page five, not much different than looking at a road map... There are no dead end streets connected to pin 3(loose wire)... The jack isn't pictured, this radio has been monkeyed with in the past...

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Post by frank1956 on Thu Jul 03, 2014 7:03 pm

Wire removed, pins 2 & 3 no longer connected. Cap is not long enough to reach between pin 3 on 50L6 and pin 7 on 35W4. It calls for a .01 600 v. Can I use a .047 630v this is long enough to make connection???
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Post by 35Z5 on Thu Jul 03, 2014 7:09 pm

Connect cap to wherever it will reach on the circuit I colored in red, includes red wire from output transformer...I that doesn't work add the piece of wire you just removed to the loose cap leg it won't care... The cap will effect tone, so larger value .047 will reduce high freq response...
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