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38-116 Code 121 Powering Up Help
#16

Good tubes should not distort the xfmr DC measurements, they are as good as open.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#17

Ok it's looking much better but we need to find what happened to the -20vdc on pin 5. Lets take a look at the junction of  134 and 135, between there and chassis ground should see the -20v or so. If not go to 140 (the backwards one) do you have -20v across it? Testing can be done with the 6L6's out. If you do have the -20v around it would seem that your interstage transformer isn't wired it properly and we can go over that too. The 6L6 that had the high + voltage on pin 5 would appear to be a goner. OBTW Why don't you replace that backwards cap, if it had a high + voltage across it it's going to be shorted. Just a thought.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#18

Thanks for the pointers Terry! I checked where 140 positive goes to ground this morning and found 0 vdc there. I will also check resistors 135 and 135 too. I have a order into Bob Dobush @ findatube for 2 6L6G tubes.

Andy Sorrell
Palmyra, Virginia
#19

If you can easley disconnect one end of 140 disconnect it and measure for the -20v. If by chance it magically appears that indicates 140 is bad /shorted. Not having the -20v will cause the 6L6's to draw excessive plate current thus loading down the HV. Could very well be why your HV is low.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#20

did some more measuring this am. I have 0 vdc at the juncture of resistors 134 and 135. I also have 0 vdc at the ground point where the 10 mfd e cap (140a) positive is connected. I also checked the 6 vertical pins on the bottom of the audio interstage transformer - the three on the left should be -21 vdc and they are all 0. the top on on the right should be 21 vdc and it is also 0. the bottom two on the right should be ~260 vdc and I get 260 vdc. I have not disconnected 140 yet but will do that next.

Andy Sorrell
Palmyra, Virginia
#21

If you disconnected 140 and you still don't have your - voltage check - side of your 2-8mf filter caps they are NOT suppose to be grounded. Did you restuff the originals? Pretty sure they had cardboard insulators around the base so the metal portion of the can wouldn't short to the chassis.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#22

Okay i think I am getting close to the issue. for the 8 mfd filter caps 141 and 142, I have connected both the positives together. They connect to one of the pins (top pin) on the filter choke (136) which itself has a connection to the 5 vac coming from the power transformer that supplies the rectifier plates. The bottom pin on 136 connects to a 0.3 cap (139) that connects back to the above positive connection from 141, 142. The bottom pin also has a connection to the positive end of the 8 mfd e cap (140).

I have the negative of filter cap 141 connected to the yellow/green high voltage center tap. I then have the 141 negative connected to the negative of 142. The negative of 142 (and 141) is then connected to the negative of the e cap of 140- this is also connected to a wire going to the field coil.

I have the positive end of the 10 mfd 50v ecap (140A) going to a ground lug. When I rebuilt the filter can that holds 140 and 140A I tied the two negative leads together - so there are three wires coming out of the 140 140A filter can - the positive end of the 10 mfd and the positive end of the 8 mfd and the tied together negative end. The positive of the 8 mfd goes to the bottom pin of the filter choke 136 described above. The positive of the 10 mfd goes to ground lug described above and the negative connects to the negatives of the 141 and 142 also described above.

I think my error may be that in the negative connections for 141 and 142, I used the existing negative lead on the filter can as my connection point for the above negative connections. It may very well be that the cardboard insulating rings are not working properly and the negative is shorting to ground at one or both of those points. I will check those this weekend and make a new tie point for the negative leads!

Andy Sorrell
Palmyra, Virginia
#23

If you want to do quick check just measure the resistance from filters - to the chassis. Should see a few hundred ohms and not 0.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#24

I think i am really getting close to my issue(s) now - I disconnected the negative connections I made to the tabs on filter cans 141 and 142 and connected them all to an empty terminal post (that is not grounded). With all the tubes back in (even the questionable 6L6s) I am now getting -47 vdc when connecting the positive lead of my tester to new connection points for the negatives and the negative lead of the chassis connected to the ground post where the positive of 140a goes. For the positive connection of the filter caps 141 and 142 I now get 305 vdc (should be 385) from positive to the filter cap negative. I get 255 vdc from the positive to chassis ground (should be 315 vdc). I also now get -19 vdc at pin 5 of both the 6L6s and at the junction of resistors 134 and 135. And best part is I now get an audible "click" from the speaker when I turn the magnetic tuning switch in and out. I didnt get that before!!

Andy Sorrell
Palmyra, Virginia
#25

And I can also confirm that I have a short in one of my 6L6 tubes (the metal one). Now will await my replacement 6L6s that are in the mail.

Andy Sorrell
Palmyra, Virginia
#26

Hi folks- so I received my 2 6L6 tubes and put them in. My filament volts ac is at 5.9 vac on pins 2 of both 6l6 tubes. Pin 3 on both tubes in 250 vdc and pin 4 on both tubes in 255 vdc. Pin 5 in -19 vdc on both tubes. I also get -19 vdc at the junction of resistors 134 and 135 and -47 vdc where 140 positive goes to ground. From positive to negative for electro cap 141 I get 295 (should be 385 vdc) and i get 250 vdc from positive to ground (should be 315 vdc). i checked the candolm (part 137) and the original checks right for the resistances - 1k and 4 k. the interesting thing is that I do not get any voltage ac for the filament volts past the 6 l6 tubes - CORRECTED - I do get 5.9 vac but it on pin 7 on all tubes past the 6L6 s- the 6j5 driver at pin 2 shows no volts ac on the meter but the tube filament glows. i do hear some humming from the speaker - when the volume is all the way up and I turn my signal generator to about 600 kc I can hear it on band A which is good - and when I push the lever in on the dial it is muting (and unmuting when i release it) - but i do not get any stations. Any ideas?? -- Andy

Andy Sorrell
Palmyra, Virginia
#27

You may have a tired rectifier tube. HV seems a little low.

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#28

Thanks terry - have a new 5x4 rectifier - but swapped it out with another good one i have and same result. Might be time for phone a friend!

Andy Sorrell
Palmyra, Virginia
#29

So since I am still have issues in reception, I thought it may be helpful to layout the changes I made in the power supply in case I screwed something up along the way. So coming into the radio the ac line cord hot lead goes directly into a new 2 amp slow blow fuse.  From there it goes to one leg of the on/off tone switch. The other leg of the on/off switch goes to an ungrounded pin on the a new terminal strip I added that is connected to a cL-90 inrush limiter (the CL-90 gets very hot by the way,  would burn my finger if I touched it more than a second) the other end of the CL-90 continues to take the hot back to the bakelite block (145) where it is connected to a primary from the transformer. Connected to this is a new .01 x1/y2 safety capacitor that is connected to the other primary from the transformer which is connected to the ac line cord neutral. The ground connection of the bakelite block 145 connects to the ground connection from the power transformer and the ground on pins 7 and 8 of the furthers left (from the bottom) 6L6 tube and connects to the ground connection of the aerial lead-in screw terminal on the back of the chassis. Attached is a photo of the above description:


Attached Files Image(s)
   

Andy Sorrell
Palmyra, Virginia
#30

Two things, you have miss wired the line bypass cap. Should be 2X .015mf one wire of each connected to the gnd terminal and the other two wires go to the other two terminals. This isn't a deal breaker but that's how it's connected on the schematic.
After you pass thru the fuse and CL-90 do you have 120vac across the power transformer's primary??

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry




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