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Post by Resistance is Futile on Sun Jun 22, 2014 5:14 pm

Wildcat445 wrote:Frank, I will be happy to fix your radio, if you will teach me how to post pictures as good as yours.  Get a meter and run some voltage measurements that have been suggested.  We are here to help.  Good luck.

WC

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Post by frank1956 on Mon Jun 23, 2014 1:21 pm

Well I got my tubes tested today and they are all good except the 12BA6, dead as a door nail. Have one on the way  cheers One more thing should be in today. Hopefully by ends weeks I will have voltage measurements. Got the volt meter yesterday.
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Post by frank1956 on Mon Jun 23, 2014 3:17 pm

Here are my voltage measurements. Tube 12BA6 114 12BE6 133. Does that sound right. No neg reading.
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Post by 35Z5 on Mon Jun 23, 2014 6:50 pm

frank1956 wrote:Here are my voltage measurements. Tube 12BA6 114 12BE6 133. Does that sound right. No neg reading.
Nope...

If you go back and look at the schematic link I posted on first page, the 12BE6 & 12BA6 is listed as having 94v on pins 5(plate) & 6(screen) of both tubes...  While not shown, pins 7 & 1 on 12BE6 should have a small negative voltage as well as pin 1 on the 12BA6...

If the 12BA6 is dead, then it isn't drawing any current so voltages would be high on it but not 20v high... Accurate measurements depend on operating tubes that draw current... If the 12BA6 is burned out, there should not be any B+ voltage as the 35W4 rectifer can't light(or any of the other tubes for that matter)...

Also the 12BE6 is almost 40v high, sumpthin's up... What are you using for negative meter connection? Should be neg end of filter cap...

Tom
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Post by frank1956 on Mon Jun 23, 2014 11:01 pm

I do see what you are talking about on the schematic 94V. I am using the neg on the filter cap. Either I do not have a clue as to what I am doing or the radio is messed up, I'll go with the first. The tube pin's are not marked on the socket, but I assume the go clockwise. I have attached some pic's as to what I am doing and the reading I am getting.Help!!! - Page 2 100_3686_zpsb2bf3be4
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Post by 35Z5 on Mon Jun 23, 2014 11:48 pm

Ummm OK it's high...

Do this, measure pins 3 & 4 of the 50L6, thinkin we need to establish wiring is correct and there is voltage drop across R9... Should be approx a 20v difference in the two pins...
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Post by frank1956 on Tue Jun 24, 2014 9:09 am

Took the measurements on both pin 3 & 4 several times and got nothing -000.
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Post by Wildcat445 on Tue Jun 24, 2014 10:53 am

Pins 3 &4 are the plate and screen on the 50L6. Zero voltage would not be good. Did you measure voltage at C108, the output filter cap? Then after R9? If you have B+ at those points, and not at the plate of the 50L6, that places suspicion on the output transformer. You have no voltage on the screen, so that makes that scenario not as likely. What is voltage at the cathode of the rectifier, pin 7 and at the input filter cap? BTW, not to be critical, since anything is better than nothing, but I hate digital volt meters for old radio work.

WC

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Post by 35Z5 on Tue Jun 24, 2014 12:31 pm

Are the tubes lighting??? If not you're wasting time reading voltages till the heater string is operational...


Wildcat445 wrote: I hate digital volt meters for old radio work.  

WC
Let him learn on digital, are by far easier to read for the beginner... After using them at work for 20+ years, I've learned to like digital better than analog...


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Post by Wildcat445 on Tue Jun 24, 2014 1:59 pm

The OP reported voltage on the 12BA6 and the 12BE6, so the tubes must be lighting. He also reported static from the speaker, further evidence that tubes are lighting. Also voltage on those two tubes would indicate that there is B+ at least in part of the radio. No voltage on the 50L6 would indicate, to me at least, that something is amiss between the rectifier and the 50L6.

We have a legitimate difference of opinion on the preferred meter. I learned to use, and prefer still to use analog meters for most applications in working on tube equipment. Measuring resistance is somtimes easier with digital, and I like digital for working on automotive equipment. The accuracy of digital meters is not necessary for tube radios. Solid state equipment may be a different matter, where a tenth of a volt can make the difference between working and not. I also like to use a VTVM. I do not have a digital VTVM. And I recommend analog meters for beginners for the reasons I cited.

WC

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Post by 35Z5 on Tue Jun 24, 2014 6:13 pm

Well I'm bettin' fifty cents there are no filaments...    Very Happy  No unless it's wired wrong I can't explain how there was voltage on the 12BE & BA6, screen(pin 4) of the 50L6 should be the tie point for B+ feed to the small signal tubes...

For work I used a good old Simpson 260 from 1969 to approx 1988 when we were issued 467 LCD, thought I'd moved up to the penthouse... That 260 is still around here someplace, haven't used it or my VTVMs in years...
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Post by frank1956 on Tue Jun 24, 2014 8:53 pm

C108 Measures about 22-23. I am looking at the schematic and it show's a blue wire going to pin 3 on 5OL6 tube, that shows 122-123 measurment.
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Post by 35Z5 on Tue Jun 24, 2014 11:00 pm

What about pin #4??

OK scratch that, pin 4 is connected to C108, I assume Pin 4 is also low? By schematic should be 94v...

What are voltages on either side of R9?
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Post by frank1956 on Wed Jun 25, 2014 11:11 am

R9 has between 7-8 on one side a -000 on the other
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Post by 35Z5 on Wed Jun 25, 2014 11:29 am

If R9 isn't overheating due to a B+ short then it must be open... If there are normal-ish voltages on the red & blue wires of output xfomer and little or none on the yellow wire, the transformer is suspect...


Properly operating if there is 115v on the end connected to yellow wire, should be approx 95v on the end that connects to pin 4 of 50L6... With set UNPLUGGED, measure resistance of R9... Set meter to R x 2K... If no reading try R x 20K...

Toss a pict up of the 50L6 & 35W4 connections...
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Post by Wildcat445 on Wed Jun 25, 2014 3:08 pm

You guys are using a digital meter, so my comment made no sense. Forge ahead.

WC

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Post by frank1956 on Wed Jun 25, 2014 6:09 pm

R9 reading set UNPLUGGED 2.27 and 4.33. Per your request pics of 50L6 & 35W4. 50L6 first pic.

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Post by 35Z5 on Wed Jun 25, 2014 9:13 pm

If that's the 35W4 by the osc coil, it's in the wrong socket, should be in the socket that had the blown cap...

For resistance on R9 I should have said across it(end to end), measuring from ground would show a short but not give a accurate reading of the resistor...
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Post by Wildcat445 on Wed Jun 25, 2014 9:31 pm

The resistor on pin 4 of the 50L6 appears to be 2500 ohms, red, green, red. The value of that resistor (R9) is given as 1500 ohms. That may be enough to make a difference. The 35W4 does not look right to me, either. I expected to see one side of the power line connected to that tube somewhere. According to the schematic, that should be thru R10, a 22 ohm resistor to pin 5. Are all the tubes in the correct socket?

WC

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Post by frank1956 on Wed Jun 25, 2014 10:24 pm

Sorry about that I posted the wrong socket. Here is the update. I took the R9 reading from end to end, not sure what reading I am looking for as it is all over the place i.e. 7.43, 19.53 etc.

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Post by 35Z5 on Wed Jun 25, 2014 10:47 pm

Wildcat445 wrote:The resistor on pin 4 of the 50L6 appears to be 2500 ohms, red, green, red.
WC

It's brown, green red so is 1500, looks fairly new, def not orig as film resistors didn't exist in 1954...
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Post by 35Z5 on Wed Jun 25, 2014 10:52 pm

frank1956 wrote:Sorry about that I posted the wrong socket. Here is the update. I took the R9 reading from end to end, not sure what reading I am looking for as it is all over the place i.e. 7.43, 19.53 etc.

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Be sure meter is on R x 2K scale... A wondering reading usually means the ground lead isn't making connection and/or the resistance scale selected is too high...

If you can't get something on the order of 1.5K on R9 it's probably open... If you have some loose resistors would be a good idea to practice reading a few...
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Post by frank1956 on Thu Jun 26, 2014 8:46 am

My digital meter does not have an R X 2K scale, so I have one that only has a  1 x. Here is a pic of that reading.

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Post by 75X11 on Thu Jun 26, 2014 9:22 am

If that is an x1 scale, it looks like 25 ohms to me. I'll defer to Warco as it will keep the number of cooks to a minimum.
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Post by Wildcat445 on Thu Jun 26, 2014 9:48 am

Okay, maybe that first stripe IS brown. Sorry for my bad eyesight.

Do I see an analog meter? I'll go away now.

WC

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