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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.
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Looks like you can cut them in half if you have to. Was this unit inside a can or box?
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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?
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I think AVC voltage is after the R41, 1Mohm.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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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.
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Oh yeah...the new sch.
Either the junction, or the other end of 6X and 7X.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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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.
(This post was last modified: 11-15-2024, 05:38 PM by dconant.)
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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.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
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That's what we wanted to see!  Wow, what a trip.
Did it have any affect on the auto tuning?
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Have not messed with the auto tuning yet. I have to say this has been my most difficult radio so far.
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Hello dconant,
That is some nice work !
Sincerely Richard
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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.
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