06-09-2019, 08:25 PM
Thanks Ed. I'm going to go with 100 pF.
Well, I didn't get as much accomplished on the 70 as I had hoped to, but what I did accomplish should make much of the remaining work go a bit easier.
I restuffed and reinstalled tone control (48) and bakelite block (31). As for the additional .01 uF capacitor which connects from the 47 plate direct to ground, I mounted it in the tone control housing. The grounded end is soldered to the metal frame of the tone control. The .015 uF section is switched as indicated on the modified scehmatic.
I came up with a bakelite block to hold the two 100 pF capacitors which are located in between the added 100K resistor, and installed it as well as the 100K resistor. I decided to remove the single bakelite block (21) and replaced it with a dual bakelite block. The added .047 uF capacitor inside that dual block is an AVC filter at the first IF transformer.
The wires from points F and G have been shortened and re-routed to what will be the 35/51 1st audio amplifier tube. I also added the additional power resistors which are connected to the "B-C" resistor (37). I only installed one at the B-C resistor as you will see in the photo below. The other additional resistor I added from the cathode of the 1st audio amplifier to ground.
IF secondary trimmer condensers (19) and (22) have now been isolated from ground, using the nylon hardware I bought last weekend for this purpose. Wires have been attached from the formerly grounded ends of each trimmer into the circuitry as indicated on the modified schematic.
An under-chassis photo showing this weekend's progress:
[Image: https://philcoradio.com/images/phorum/70mod/70_022.jpg]
and a schematic, the yellow highlights indicating what has been done:
[Image: https://philcoradio.com/images/phorum/70mod/70_023.jpg]
We're getting there...slowly but surely.
Until next time!
Well, I didn't get as much accomplished on the 70 as I had hoped to, but what I did accomplish should make much of the remaining work go a bit easier.
I restuffed and reinstalled tone control (48) and bakelite block (31). As for the additional .01 uF capacitor which connects from the 47 plate direct to ground, I mounted it in the tone control housing. The grounded end is soldered to the metal frame of the tone control. The .015 uF section is switched as indicated on the modified scehmatic.
I came up with a bakelite block to hold the two 100 pF capacitors which are located in between the added 100K resistor, and installed it as well as the 100K resistor. I decided to remove the single bakelite block (21) and replaced it with a dual bakelite block. The added .047 uF capacitor inside that dual block is an AVC filter at the first IF transformer.
The wires from points F and G have been shortened and re-routed to what will be the 35/51 1st audio amplifier tube. I also added the additional power resistors which are connected to the "B-C" resistor (37). I only installed one at the B-C resistor as you will see in the photo below. The other additional resistor I added from the cathode of the 1st audio amplifier to ground.
IF secondary trimmer condensers (19) and (22) have now been isolated from ground, using the nylon hardware I bought last weekend for this purpose. Wires have been attached from the formerly grounded ends of each trimmer into the circuitry as indicated on the modified schematic.
An under-chassis photo showing this weekend's progress:
[Image: https://philcoradio.com/images/phorum/70mod/70_022.jpg]
and a schematic, the yellow highlights indicating what has been done:
[Image: https://philcoradio.com/images/phorum/70mod/70_023.jpg]
We're getting there...slowly but surely.
Until next time!
--
Ron Ramirez
Ferdinand IN
