Replacing a missing speaker - Printable Version
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+--- Thread: Replacing a missing speaker (/showthread.php?tid=18524)
RE: Replacing a missing speaker - Eric - 06-18-2018
RE: Replacing a missing speaker - KCMike - 06-18-2018
That is a tie point. I remember trying to figure that out.
Did you get the speaker hooked up?
Do you know how to read the schematic in regards to the numbers that are all over?
It took me a couple days before I realized how the numbering worked.
Let me know if you need it explained.
RE: Replacing a missing speaker - Radioroslyn - 06-18-2018
It looks to be a one lug terminal strip. The resistor goes over to the choke in the p/s and feed the hv to the audio output stage. The little brown thingy is C -27 a hv mica cap that is part of the tone compensation circuit. All those parts have hv on them. That schematic is really hard to read as the connections that cross over and ones that join are noted poorly.
GL
RE: Replacing a missing speaker - Eric - 06-18-2018
Good info about about the tie point just looked weird.
yes I figured out about that the # goes to the bundle then look for the color marking (weird)at the other end.
I did hook it up per your print but couldn't get anything but I'm drawing .6a at 100v (just keeping it low)
The Output ckt appears to be wrong on my radio per the print as C27 is there but not R16 (30k) and they should be in parallel with the output xformer?
Also other wires on the 41's seem to be wrong? Will post a drawing.
RE: Replacing a missing speaker - Eric - 06-18-2018
Here is a diagram I made sorry if it hard to make out, now something that just jumped out at me is that one of the 41's was missing is it possible that who worked on this rewired this for one 41 operation? I labeled the 41's as A & B
RE: Replacing a missing speaker - KCMike - 06-18-2018
Yea that is kind of hard to figure, for me anyhow... If the wiring has been altered could be a challenge to put back to original but doable.
Did you check the audio transformer for continuity? L-17 & L-18
Maybe also ck. if you have plate voltage on to output tube.
I think you should get some sound with one output tube.
RE: Replacing a missing speaker - Eric - 06-19-2018
Mike
Yes L 17, 18 are good, checked most of the coils and they are good.
unfortunately I have to leave it for a week going to KY to visit the grand kids.
I think I will give it a try with the one tube one of the things I didn't have is the jumper in place and to make sure the choke and FC are connected. Started tracing all the leads and marking them on the print to see what was changed. Seems like a lot of work for one tube.
Thanks for all the help
Eric
RE: Replacing a missing speaker - KCMike - 06-19-2018
Have a good trip. Always good to see the grand kiddies.
When you get back to the radio you have to have the jumper in place or you won't have any B+
RE: Replacing a missing speaker - Eric - 06-19-2018
Yes one lead should come off of the pin marked 80 not sure about the other as I've not verified all the leads, it still looks screwy! I'm going to take all my info and try to sort it out on paper then check it to the chassis when we get back in a week.
Eric
RE: Replacing a missing speaker - Eric - 06-28-2018
So this is where I'm at.
1 replaced the most of the caps (except those in the molded block) and resistors that were out of spec.
2 I'm using the one 41 as it was set up.
3 wired the speaker socket per your print.
4 the set powers up and for the most part I get good voltages,
5 On the 37 # 3pin I get feed back through the speaker as well as the Vol and Tone pot
6 tried to put a signal through the ant but nothing.
here is the voltage chart I see a problem with the 6A7 pin 5
RE: Replacing a missing speaker - Radioroslyn - 06-28-2018
I take it that the top voltage is should be and the bottom is what you got??
RE: Replacing a missing speaker - Eric - 06-28-2018
Yes the green is what the schematic says should be.
More info 6A7 pin 5 goes -2 to -14 in turning the tuner.
also hooked up my signal gen at the ant terminal through a .05mf cap, I do get a tone which I can follow up and down the dial but no stations?
Question, I have located the IF's on top, should the gang be open or closed to peak them at 370kc I get the loudest signal with the gang closed.
RE: Replacing a missing speaker - Radioroslyn - 06-29-2018
Ok.
A couple of things stick out to me. Pin 4 of the 41 should read - 16vdc. Having +10vdc on it will cause the tube to draw excessive plate current. This maybe why pin 2 only has 112v. If it's a typo your output transformer is trashed, replace it.
The IF adjustments it doesn't really matter where the tuning dial is set. Inject a 370kc signal into the cap on the 6A7 and adjust the four trimmers inside the IF cans for max sound from the spkr w/the generator set @ minimum output. Note two of the four little screws have HV on them so insulate your tuning tool if it's not plastic.
It's not unusual for the grid 1 voltage to vary w/oscillator frequency (as you tune the dial). Typically it's abt -2 or 3 vdc so the .2 would indicate that the oscillator isn't working but since you have a few volts - it would seem to be ok. If you suspect it you can listen for it @ 370kc above the dial reading on another receiver.
GL
RE: Replacing a missing speaker - Eric - 06-30-2018
Terry
Ok I did some poking around and went back over the paper work. The dial has to be set at 1500 kc and that corrected the .2 on the 6A7 pin 5 now -17
I rechecked the opt and it is new and the resistances were good but that got me to thinking so I swapped the center tap per Mike's print to the other side of the FC coil and the numbers came in as you can see. Still no stations but I have to leave it for now Heading to my sisters for a Birthday for Mom she turned 97 boy I wish I had her mind!
RE: Replacing a missing speaker - Radioroslyn - 06-30-2018
Happy Birthday to your mom! Later this afternoon I'm headed out to my granddaughter's birthday party she's 4.
Good seem like you got the output stage sorted. Does you chassis have two #41 tubes?
If you measure the voltage on pin 5 of the 6a7 as you tune the dial is there a point where the voltage drops off sharply? If so you may have a bend plate on the oscillator side of the tuning cap.
Would go ahead and align the IF stage to get that out of the way as a trouble source. If it's misaligned that can cause poor sensitivity (no stations).
Just for grins try connecting your ant to the grid cap on the 6a7. This will bypass the rf amp stage, if it's not working this can cause poor sensitivity too.