National SW-54 Thoughts

[jr_tech]

I would ohm check the 35Z5 heater... guessing it is open between pins 2 and 3.

jr

[dieseljeep]

Originally Posted by jr_tech

I would ohm check the 35Z5 heater... guessing it is open between pins 2 and 3.

jr

Jumper pins 2&3 for now, to finish trouble shooting. That's a trick, I learned over 60 years ago, by an old time radio tech.

[Dubis7]

Quick check confirmed it, pins 2 and 3 were open on that tube. I swapped a new resistor in and swapped in another 35Z5. I'm back to testing, though I'm still waiting on the parts for my station before moving forward much more.

Are there any solutions for injecting signals without a signal generator? I have a signal generator, a Heathkit SG-8, but I haven't restored it yet. I'm trying to decide whether I should step back and get that work so I can start injecting signals, or if there's something else I could use.

I have one of those AM radio transmitter kits, tested and working. Do you think I could clip in a lead from the antenna output via a coupling capacitor and start injecting along the grids of each tube?

[Dubis7]

I need a crash course in signal tracing or something.

I rebuilt (or think I did) my Heathkit SG-8 signal generator. New electrolytics, replaced the paper caps, and I swapped in a 1N4004 for the selenium.

I tested that by placing it along the antenna of an AM radio and was able to pick up some warbling along the B band when I moved the dial around. It moved with the dial, and went away when I switched off the generator. So I think I have that working. This thing has RF out and AF in and out.

From what I understand, I need to connect the ground clip to the chassis through a capacitor, then connect the other end about 450 KHZ on the B band to the input of the grids on the tubes. So I started at Pin 5 of the 50C5, no dice. Just that humming.

Help? Any suggestions? I'm really at a loss on this at this point. I've tested components multiple times and can't seem to find any more that are out of spec. I'm reaching a point where I'm tempted to just replace everything and hope that gets me something.

[jr_tech]

Use the audio output for testing the audo stages, 455 khz for testing the IF circuits and 550 khz and up to test whatever frequency the radio is tuned to.

jr

[Dubis7]

Mine has an AF and RF output. Which should I be using?

Should I be hearing the signal come through the speaker on the radio?