Finally got the .1 caps and installed them. Still no reception, so I poked around with the antenna wire and got 2 local stations with ant hooked to the 3rd RF at the tuning condenser. See photo. I guess that means the problem in between there and the ant connection Suspect the rewind on 2nd RF was not good enough. Any test to isolate it any closer?
Thanks for your help.
George
Are those capacitors shoved up inside the first two RF coils? And what is that wire roughly wound around the three capacitors above the RF coils in the photo above?
Measure the hv on pin 2 of the 26 tubes (from the chassis). Should see about 90vdc or better on all of them. Touch pin 3 of the 27. Sound hear a loud buzz. Pin 2 has hv on it. If that looks good connect your ant wire to each one of the tuning cap's stator one at a time (the part that doesn't move) and see if you can hear a station while tuning around. Or you can use your generator.
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
(This post was last modified: 12-23-2021, 12:36 AM by Radioroslyn.)
Never mind, Mike. I was rather ill yesterday and the photo gave me an optical illusion of having a large film cap inside two of the RF coils. This morning, after some sleep, I can see that isn't so. However, the windings around the caps still look like they are either coming loose or have been crudely rewound.
I am well aware of how to rebuild those cap/resistor combinations, having most recently done that work on a model 87 only a few months ago.
Thanks yall,
The voltages on the 26 tubes pin 2 to chassis were: 1st 32V, 2nd 66V, 3rd 28V, and 1st AF 66V. I do get a buzz on pin 3 of the 27. Went back and measured voltages on filter caps to 6 (gnd) and they were #1 170 V, #2 148V, #3 67V, #4 29V, #5 26V.
One other thing is the resistance on the primary of 2nd RF coil I rewound was 5 ohms, checked the other two coils and it measured 20-30 Meg ohms. The BC resistor was open so I installed 2 watt resistors on it, checked them again and they were ok. I'm trying to give you all the info I can and I appreciate everything yall do. Also the 100 ohm resistors on the coils read 108 to 111 ohms so I think they are ok. I think I am at the point where I cant see the forest from the trees.
Thanks,
George
What voltages do you have across the .1 cap you just put in? You should see about the same the voltage at the cosponsoring 26's plate. Unless your rf coil is rotting... It's important that the 100 ohm series resistor are good if not they will drop the hv going to each of the 26's
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
(This post was last modified: 12-23-2021, 03:54 PM by Radioroslyn.)
Finally had some time to work on the radio. (I have kids and grandkids home for the holidays) Rewound the rest of the rf transformers and the antenna coil. Picked up a few stations but it was like it wasn't totally tuned in. Did the alignment with the sig gen with a 250pF (don't have a 200) per the instructions. Hooked antenna back up and don't receive anything. I will try the alignment again as time allows.
Well, got back on the radio and aligned and went thru the neutralizeing procedure to no avail. Did everything several times with no improvement. Went back to voltage checks and still low voltage on the 26 plates (52-55V), same reading across the 100ohm resistors. I was thinking the filter coil could be bad so checked the resistance in circuit it was 408ohms. I dont know where to turn, does anyone have the correct voltage measurement for points on the schematic such as F,G etc? What should I do now?
The Field coil is 3100 ohms so it's pretty high as fc's go. You might removing the 71A's and see if the plate goes up to a more normal level. This may indicate that there is an issue with bias getting to the 71A's. Would check 35 & 33 that their ok and have a good ground connection. For what it's worth here's a voltage chart http://www.nostalgiaair.org/PagesByModel...029653.pdf Beware sometimes they don't measure the voltage from the chassis but from odd places like the B- rail or one the plates of the 80 over to one of the dc voltages. I find it confusing. This one doesn't say so maybe from 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!
Thanks Radioroslyn,
What I refered to the filter coil is item 34 which is the filter choke coil. After I posted I found the chart and for that part number it should be 400 ohms so I guess its good. The resistance on the field coil from point F to point G is 3.28 kohms. The voltage readings I go for those two points to chassis is point F to gnd is 118 V and point G to gnd is 50 V. On the filter caps, cap 1 gnd is 147 V and cap 3 to gnd is 52 V. So I dont know, the PT seems to be good. What now. Thanks again for your reply you and Morz and Ron are a great help.
George
So F should be up to about 150v so overall there's about 35v missing. Would check the AC voltage at pins 1&4 of the 80 tube. Should see 5Vac. Be careful as there's almost a couple of hundred volts DC there too between either pin and the chassis. If you have 5V you may have a weak 80 tube that can't deliver the current needed for the HV in the set.
If you have hi/low sw in hi put it in low if your 5V is below 5V to see if that helps.
If the cap between pins 1&6 is smaller than 2mf that will cause the HV to be low. As a last resort you could add another 2mf in parallel to in = 4mf. That's about as high as you would want to go.
Check resistors in #35, 157 ohm 1545 and 2240. Originally I was thinking the 1000 ohm resistor as it is the filament bias for the 71A. The 157 ohm the filament bias for the 26's. The others are a voltage divider for the hv. With either of these bias resistors off it can cause the tube to draw excessive current and lower the hv line.
As for your choke it's 12.5 Henries @ 80ma 400 ohm pn 3269. The power transformer has a hv winding that is 575vac end to end pn 3271.
GL
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!