Have a 6 tube chassis that was put in a model 38 battery set cabinet.
Now I just have to figure out which chassis I have.
Don't think the tubes in it are correct.
Has an 80,41,6K8,6SQ7,78 and one missing tube.
Tried to post a couple pics, but I guess they are too large.
I could send to someone if they would like to post them for me?
Number stamped in the chassis is C89328. Number inked in under the chassis is 38-1078
murf
(This post was last modified: 12-17-2023, 03:28 PM by murf.)
Looks like a model 38 that was converted to an ac set.
So it's a 5 tube set. Model 38. Drat!
Now I just need to figure out the proper tube line up for a converted model 38.
Do have audio, but does not pick up any stations.
Maybe a wrong tube installed?
Tried swapping the 78 with a 6D6G and swapped the 6K8 with a 6A8 with no change.
Now what?
murf
I'd leave the 78 and the 6K8 alone as they may not be too compatible with the 6D6 and 6A8. The 6D6's inter electrode capacitance is is different so they don't like to play nice when swapped for 78's. The 6K8 is different type of mixer tube, triode/hexode which is different from the pentagrid converter that the 6A8 is.
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!
Plan B. Use the diagram from the model 60 to check the wiring and signal path of this set. Pretend (look up the tube's basing info to see what needs to go where) that the 42 is a 41. If you try a 42 in this set there a good chance that you could damage the opt from too much current flow. Since you have a 6A8 I wound check the mixer socket wiring and see what it's wired for. Use the 6A7 circuit from the 60 as a guide to sort the mixer. 6A7 and 6A8 are electrically the same but one uses a standard base and the other a self centering base. The power supply is going to be a little different as the 38 uses a pm spkr which has no fc. So there's probably going to be a resistor between the two larger value filter caps. Not sure how the bias is developed for the 41. It may have a resistor from pin 5 the the chassis (cathode bias). Or in Philco style there would be a resistor in the center tap of the hv winding to the chassis like the 60 (fixed bias).
Have fun chasing electrons!
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: 12-18-2023, 09:26 AM by Radioroslyn.)
I am wondering if a model 60 would fit in this model 38 cabinet?
Would make more sense than trying to resurrect this boat anchor.
Otherwise it will have to be a shelf queen.
Thanks for all the help!
A 60 or 66 should slip right in. You'll need the spkr too. Geez I thought you liked a good challenge!!
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: 12-18-2023, 09:53 AM by Radioroslyn.)
The two things to look at are the plate load resistance and the plate current. The 19 can haul down 50ma where the 42 is at 34ma/250v. This is good the primary should be able to handle the current from the 42's plate.
The plate load resistance of the 19 is going to be high because it's configured as a push/pull output stage. Each plate requires a load of 10,000 ohms, totaling 20,000 across the primary of the transformer. Remember this is ac impedance not dc resistance. The 42 is looking for about 7,000 ohm load.
And you still need a some sort of a inductor to replace the fc.
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: 12-19-2023, 10:04 AM by Radioroslyn.)
