Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12, 2025) x

Thread Closed

Model 70 air cap ground strap.
#15

Radioroslyn, I have been hitting the calculators. I still have not figured out which side of the am band for the osc. to create the spec'd 260KHZ if. Almost seems like it is a mistake.
From what I currently see I need .26 mh to het to 260, right now I am at .23 which I plugged in the calcs and was at around 230 KHZ or so, thus I IF'd it at that with the signal generator, and it dialed right in. I am comparing the sound of this unit to many other old vintage radios I have had, and at times it amazes me, but it is sensitive to every adjustment. The original OSC. wire measures most like 32AWG by my mic, .02 off. The way it is coupled back to the det coil may have something to with it, series. It tracks well, 1100 am on the spot, 600 hits high around 620.

'Now unfortunately I’ve never acquired an inductance meter, so I cant help there on that osc coil. The coil is original. I did ohm it out a while ago and it is 6.8 ohms total (5.2 ohms and 1.6 ohms where its tapped with a 50K.) So I’m assuming the coil is OK.' - Instailled I get around 7-8 ohms top primary .23 mh and 1.8 feedback .03 mh (milli henry) on the osc. coil. Seems like if my RF coil winding is off, it still would be passing the correct frequencies to hit the osc, I can zero beat correctly to a station. I can say this though, hearing the original with the bad coil, I am close but not there yet. Could the the 'power detector' causing distortions, might look into some tweaks there, maybe a diode or cap combination to solve it. Grid leak to try. 1500 into the grid, 1 meg to ground see what happens.


Messages In This Thread
Model 70 air cap ground strap. - by radio1 - 06-10-2020, 08:43 PM
RE: Model 70 air cap ground strap. - by rfeenstra - 06-11-2020, 08:38 AM
RE: Model 70 air cap ground strap. - by radio1 - 06-11-2020, 09:39 AM
RE: Model 70 air cap ground strap. - by radio1 - 06-12-2020, 05:17 PM
RE: Model 70 air cap ground strap. - by radio1 - 06-12-2020, 07:01 PM
RE: Model 70 air cap ground strap. - by rfeenstra - 06-12-2020, 11:20 PM
RE: Model 70 air cap ground strap. - by radio1 - 06-13-2020, 07:39 PM
RE: Model 70 air cap ground strap. - by radio1 - 07-02-2020, 08:21 PM
RE: Model 70 air cap ground strap. - by radio1 - 07-03-2020, 06:25 PM
RE: Model 70 air cap ground strap. - by radio1 - 07-03-2020, 06:42 PM
RE: Model 70 air cap ground strap. - by radio1 - 07-03-2020, 09:19 PM
RE: Model 70 air cap ground strap. - by radio1 - 07-04-2020, 07:11 AM
RE: Model 70 air cap ground strap. - by rfeenstra - 07-04-2020, 09:06 AM
RE: Model 70 air cap ground strap. - by radio1 - 08-13-2020, 06:13 PM



Users browsing this thread: 3 Guest(s)
[-]
Recent Posts
HiFi (Chifi) tube amp build - but my own design.
It's the other forum. I'm also in DIY, but mostly read there. Honestly, I kinda jumped into this without much thought to...TV MAN — 10:43 AM
Philco 71 Code 125
Hello,  I am in need of a schematic for this radio. Mine has the three separate circular tube shields and a shadow me...dconant — 08:06 AM
Stromberg Carlson 1500 Squeal
And life just keeps getting more complicated.dconant — 07:57 AM
54C Complete Teardown/Rebuild
Hello Roy, here is this one sincerely Richardradiorich — 12:45 AM
54C Complete Teardown/Rebuild
Richard, Had grabbed it already but thank you just the same.  I find myself wanting to find some way to block out the...glyphmon — 12:03 AM
54C Complete Teardown/Rebuild
Hello roy, here is a link to the schematic . Sincerely Richardradiorich — 11:54 PM
54C Complete Teardown/Rebuild
Richard, The Silvertone 2014 also is a transformerless set, so I am incorporating a 1:1 600 ohm audio isolation transfo...glyphmon — 11:37 PM
Preliminary work on wife's Silvertone 2014
Did an alignment today which was interesting.  IF alignment went great, almost all was already spot-on.  Adjusting on th...glyphmon — 11:35 PM
54C Complete Teardown/Rebuild
The main problem with adding a Bluetooth input is that this set lacks a traditional power transformer to isolate it from...radiorich — 11:19 PM
54C Cabinet Refinish
I started stripping this cabinet before it got super chilly out because I knew I wasn't going to be able to work on ...glyphmon — 11:18 PM

[-]
Who's Online
There are currently 1809 online users. [Complete List]
» 1 Member(s) | 1808 Guest(s)
Avatar

>