Philco 38-2 Low Volume - Printable Version
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RE: Philco 38-2 Low Volume - RodB - 11-15-2024
Good find on that cap!! I think after an IF alignment now, your AVC will respond correctly since it is already having some effect. A good place to measure it is near the source where the blue wire (if it's still blue) comes out of the 2nd IF and connects to the two 4 Meg and two 1meg resistors. Now your meter won't load down the circuit as much.
RE: Philco 38-2 Low Volume - dconant - 11-15-2024
I have already determined what I needed and aligned the IF have all three compansators peaking. The volume is now what I consider normal. I have included pictures of my IF2 with the 110pf cap tacked in to replace the one in 2XA. Note the 110 on what looks like two caps together. These would be for 2XA and 2XB. I am assuming the 110 is the value of those two caps and that is why I choose 110pf for my 2XA replacement. I will be doing the same for 2XB. 2XC show a 160 so I assume that would be 160pf. The second new mica cap is 2XD that I replaced when I first started on the restore. If you look closely at the bottom picture you can see black specs in the wax where the caps are, I'm thinking might be some kind of corrosion. I need to figure out some way to get the old caps out of the circuit so I can use their terminals for new cap. Hope these pictures help explain what I have.
RE: Philco 38-2 Low Volume - RodB - 11-15-2024
Looks like you can cut them in half if you have to. Was this unit inside a can or box?
RE: Philco 38-2 Low Volume - dconant - 11-15-2024
Round metal can.
RE: Philco 38-2 Low Volume - dconant - 11-15-2024
If I may I would like to test if I still have an AVC problem. Using the run 2 schematic where is the best place to see if AVC voltage is changing?
RE: Philco 38-2 Low Volume - morzh - 11-15-2024
I think AVC voltage is after the R41, 1Mohm.
RE: Philco 38-2 Low Volume - RodB - 11-15-2024
I think Mike means at the junction of R7 and R7X. He was looking in the other schematic. Try that and see if you get a nice voltage swing when tuning a strong station. This is a complicated AVC due to the discriminator for the tuning.
RE: Philco 38-2 Low Volume - morzh - 11-15-2024
Oh yeah...the new sch.
Either the junction, or the other end of 6X and 7X.
RE: Philco 38-2 Low Volume - dconant - 11-15-2024
AVC changes from -2.5 to -11. How is that. I don't get the best reception here. Looks like I may be all set now (I hope).
Thank you all for the help.
RE: Philco 38-2 Low Volume - MrFixr55 - 11-15-2024
Hi DConnect
Yes, sounds like the AVC is working well. One clue is that the grid voltage on the 6A8 changed, but that is not the best place to measure.
Bottom line is that you nailed it!
And learned a lot in the process. Now, make that aux in mod so you can enjoy the radio both ways.
RE: Philco 38-2 Low Volume - RodB - 11-15-2024
That's what we wanted to see!
Wow, what a trip. Did it have any affect on the auto tuning?
RE: Philco 38-2 Low Volume - dconant - 11-16-2024
Have not messed with the auto tuning yet. I have to say this has been my most difficult radio so far.
RE: Philco 38-2 Low Volume - radiorich - 11-16-2024
Hello dconant,
That is some nice work !
Sincerely Richard
RE: Philco 38-2 Low Volume - dconant - 11-17-2024
Thank you Richard.
RE: Philco 38-2 Low Volume - dconant - 11-21-2024
I have been playing my 38-2 for a while now and it is doing very well. I did have to replace the 6A8 (osc) as it developed a short that killed off the screen voltage to some tubes. I got a new one of the ST type. Mine was a GT, ugly in a radio full of ST tubes. I'm wondering since this is the oscillator tube in my radio does this need a tube shield? The 6A8 that was in there had a metal base. Now that I noted that I see there probably was a shield raised base on the tube socket. The rivets are loose leading me to believe the raised shield base was there and therefore a tube shield. So I guess I need to find that raised shield or get a metal based 6A8.
I got my new dial, now I can do the magnetic and RF alignment.