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Post by frank1956 on Wed Dec 10, 2014 11:57 am

Wildcat445 wrote:You are measuring across each tube.  That's okay, but I would suggest that you measure across the entire heater string.  From one end to the other.  You could have an open component that is not a tube, like a switch or a break in a wire.   .5 ohms is essentially zero.  That would be good if it were across the heater string.  I am assuming here that the tubes are not lighting.  Correct?

WC

WC,
If I am reading the schematic correctly them the heater string would be pin #3 and # 4 on each tube socket?? If that is the case then I measured the resistance on each one. I am still trying to figure out if I took the measurements correctly. i.e. do both probes from the ohm meter go on one socket prong at the same time or one on #3 and one on #4???? Totally confusing to me, this is a first for me, did not have to do this on the other radio's I have messed with.


Thanks
Frank
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Post by Wildcat445 on Wed Dec 10, 2014 12:45 pm

Bill is absolutely right!  There is no connection to the other side of the line shown on the schematic!  I had not seen that, I just ASSUMED.  

The schematic is showing common negative to be the negative end of the filter caps.  But it does not show where that is EXACTLY.  There should be an indication of common negative on one side of the power switch.  The way it is drawn, it appears to have an open across the filament line.  Shocked

To confuse you even more, some schematics do not draw the filament circuit in at all. Others draw it out to the side of the drawing, apparently not connected to anything. I think that is what happened here. It would have been nice to have a connection to common negative, though. Rolling Eyes

Frank, I understand what Bill is suggesting that you do, and that is fine.  I was advising you to measure the entire string, then if it is open, measure each component.  The entire heater string is the circuit where all the tube filaments are connected in series, like Christmas tree bulbs.  Two different ways of doing the same job.  Schematics that are incomplete or proven incorrect are a pain for experienced radiomen, much more so for someone fairly new to the hobby.  One probe would go on pin #3 and the other probe on pin #4.  If this was easy, Frank, everybody would be doing it.  There is nothing simple about this at times, and it can get fairly frustrating.  You are doing fine.  Forge ahead.

WC

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Post by frank1956 on Wed Dec 10, 2014 1:00 pm

WC,
So I would be measuring the resistance by the prongs on the tube socket, and each probe regardless of neg or pos from the ohm meter would go on one prong while the other went on the other? This then would give me a reading of zero or a small ohm reading?


Before I posted this I went and did as suggested one probe on one tube socket prong and one on the other, with my analog meter set to 1X the needle does not move. This was done for each tube socket in the radio. Not sure if this is good or bad news???

Frank
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Post by frank1956 on Wed Dec 10, 2014 1:12 pm

Also since you and Bill mention how the schematic looks wrong, I did some searching and found this from another forum. I copy just a small portion of it below. Not sure this has any bearing on this problem or not??

But they neglected to show the important line connection to the "common." Nothing will work without that. Here's what it should look like. Compare to similar Crosley models, like the 58TA: http://www.nostalgiaair.org/Resources/490/M0003490.htm

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Post by jerryhawthorne on Wed Dec 10, 2014 2:37 pm

Thank you Bill and WC that error on the schematic is exactly what I was asking about one page earlier on this thread.  Now I don't feel like a TOTAL idiot! The suggested change was what I was thinking also.
Jerry

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Post by 75X11 on Wed Dec 10, 2014 2:42 pm

It looks like everyone is getting warm around this campfire. Very Happy
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Post by Wildcat445 on Wed Dec 10, 2014 8:16 pm

You have it right, Frank. That is the part of the drawing that was missing. Now it should make more sense.

WC

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Post by Bill Cahill on Thu Dec 11, 2014 11:52 am

But, all tube Must be in their sockets to do these measurements. You should not get an open reading. You should get a low resistance reading. If the needle doesn't move, it indicates an open.
You aren't trying to measure the sockets. It's the filament pins oof the tubes while in their sockets.

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Post by frank1956 on Thu Dec 11, 2014 3:07 pm

Bill,
Thanks that make a little more sense.I will re take reading and get back to the group.

Frank
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Post by frank1956 on Thu Dec 11, 2014 3:18 pm

Just took reading with analog meter set to ohm 1X,  across the heater string with tubes in i.e. pin # 3 & 4 each tube one probe on 3 and the other on 4. I got zero across the board. Did the same with the plug, probes across each end of the plug ( volume off zero, on zero). I hope this makes sense to yall.

Frank
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Post by 75X11 on Thu Dec 11, 2014 3:44 pm

Frank, do you have any loose, new resistors of a low value you could take a reading on? On some of these readings, I wonder if the low ranges on your meter is functioning correctly. This would be just to make sure it is working correctly and in spec's.
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Post by Bill Cahill on Thu Dec 11, 2014 7:35 pm

Sounds like your meter has an open connection. Might be your probes are bad.

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Post by Wildcat445 on Thu Dec 11, 2014 8:14 pm

I read Frank's last post three times, but I think I finally got it. I agree with Bill and 75. Methinks the meter is on the fritz.

WC




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Post by 75X11 on Thu Dec 11, 2014 8:28 pm

It would be good to know for sure.
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Post by frank1956 on Thu Dec 11, 2014 9:03 pm

I am now totally confused with everything at this point. I don't think my meter is messed up as it is fairly new 6 months. I was under the impression I supposed to get either zero or very low reading???


Frank
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Post by jerryhawthorne on Thu Dec 11, 2014 9:47 pm

Confused Frank, don't feel bad, so are the rest of us! Wink Resistance scales on meters are subject to instant destruction if subject to high voltages. Not saying that happened. We just need to make certain it is reading proper.
One observation you made was that measuring resistance across the A/C plug gave zero with the radio on/off switch moved from one mode to the other. Unless the switch is not working and locked in the on mode this does not make sense. In the off mode it should read infinity. In the on mode it should read a few ohms if all the heaters are good or infinity if one is open.
Jerry

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Post by Dr. Radio on Thu Dec 11, 2014 10:07 pm

Frank, Frank, Frank Smile

Be patient. I don't mean to leave you hanging on a cliff, I just have a difficult time finding time.

My intent was to draw you a game plan, saves me lots of typing. Smile

Not on a lap top to do that yet.

Bill Cahill hit the nail on the head. That is exactly what I wanted you to do. The "prongs" are on the radio's power cord, there are no PRONGS on the tube sockets.

You take your meter leads and touch each one to the prongs of the cord.

With the switch off (as stated above), you should read infinite ohms (open, no connection, no meter deflection or "OL" or blank read out on a digital meter).

With the switch "on", the cold heater resistance of a 5 miniature tube set is about 140 ohms.

Not sure about this ".4" business.

As stated earlier if there was a dead short in the radio like that (.4 ohms), the minute you plugged it back in after your "mishap" you would have blown a fuse or tripped a breaker in your house electrical panel.

Here's something to do in the mean time to put everyone on the same page; familiarize yourself with your meter....

Grab your resistors from your junk box and measure them. Does the meter "agree" with what the values are of the resistors?

In other words, if you have a 100 ohm resistor laying on the work bench and the meter reads ".4", that tells me your meter isn't working or you aren't operating it as intended.

Also, basic technician stuff--don't touch the meter probe metal tip portions or the component "legs" when doing tests. The meter can read your skin resistance in parallel with the part throwing the reading "off".

Good evening for now. Wink
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Post by frank1956 on Fri Dec 12, 2014 11:26 am

My meter is working. I used the same meter when I posted my resistor reading on page 10 of this thread. I doubled checked a few of my stock resistors prior to this post and it works fine.

Dr, Radio the .4 was taken with a digital meter set at 200 the lowest setting for this meter, with both probes across the radio power cord prongs, that is where that came from. I was informed to use an analog meter and place one lead on each of the power cord prongs vice placing them across the prongs at the same time. I have tried repeatedly with this teat using my analog meter vice the digital meter. The needle on the analog meter does not move at all, the meter is set at 10X .

Frank
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Post by jerryhawthorne on Fri Dec 12, 2014 8:47 pm

Frank, when the analog meter does not move the meter it is reading infinite on that scale not zero! Makes more sense now. With the analog meter across the prongs on the plug you are reading infinite with the switch off or on then you no doubt have an open filament on one of the tubes. Time to pull the tubes one by one and measure between pins 3 and 4, you should get a low resistance reading when good and infinite when bad.
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Post by frank1956 on Fri Dec 12, 2014 9:50 pm

Jerry,
Thanks Finally something right Very Happy

Just to make sure I am on the same page as everyone else this test is being done while the radio is "UNPLUGGED" corrected??
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Post by jerryhawthorne on Fri Dec 12, 2014 10:06 pm

Yes, unplugged PLEASE. Makes it easier to measure across the prongs! Very Happy When measuring each tube, remove the tube and measure between the 3 and 4 pins on the tube itself.
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Post by 75X11 on Fri Dec 12, 2014 11:17 pm

Unplugged.
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Post by frank1956 on Sat Dec 13, 2014 12:06 am

Just checking it has been the whole time!!

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Post by Dr. Radio on Sat Dec 13, 2014 10:30 pm

Okay Frank. I figured graphics is much easier. As with any resistance tests, the radio is unplugged!

Get out the analog meter. Set to the X10 resistance setting. Short the probes together, you want to see the needle swing to the far end of the scale. This is ZERO ohms, or a "short" or "continuity". As explained earlier, this is NOT infinity, which is an "open" and no movement of the needle.

Set up the meter just how I show it. This method not only tests the heaters in the tubes, but the heater wiring's integrity.

Always keep the red wire on the SAME prong of the electrical plug for every test.

The first test is to make sure the switch is good. Turn the switch ON and leave it ON for all tests! The black probe connects to the "load" side of the power switch. This is "B-" which connects to the the wires that feed into the radio.

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With the switch on, you should read a short-------do you? If you do, go to next step. If not STOP.



My new project - Page 8 Frank_power2_zps599203ca

Now's its time to start moving the black meter probe to see where the "break" in the circuit is. Where the meter needle doesn't swing, that's where the issue is. So let's take the above picture for example, no swing means the 12AT6 heater is open (burned out).

You keeping moving the probe checking for the break in the series circuit. Report back your findings

As the testing/pictures progress, the needle won't swing as far each time. This is because the resistance is INCREASING as the meter reads thru more and more heater filaments

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My new project - Page 8 Frank_power5_zps806cfc4c


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Post by frank1956 on Sun Dec 14, 2014 11:11 am

Dr Radio
                                                                                                                                                                                       
Thanks for the graphics  they are a big help . I took  my analog  meter an shorted it out by touching  the two probes together . I set it to 10X and proceeded  with the first test the needle  did move but not to zero  but rather to 10 on the meter scale. Since you stated a short was zero and I did not get that I  wanted to see where  I stood before moving  on to the next phase .

Frank
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