I just finished recapping a 40-150. I replaced all the caps except 3 micas, almost all the resistors, and almost all the rubber-covered wire. There were a few wires that still had very rubbery insulation, and by coincidence those wires were exceptionally hard to get to, so I put left them as is.
I have not done any alignment. The radio fired up and plays fairly well. The problem is that when tuning, there is a loud whistle when you approach any station from either side. As you get closer to the station, the pitch drops until it goes away altogether when the station is perfectly tuned. This happens with all stations across the dial, weak or strong.
Does anyone know what causes this?
I had the same problems with a different set. It was due to oscillation in the IF amplifiers. In my case, it was a poor ground connection to a tube socket holding a tube shield. But in your case, it looks like the set uses loctals, so it would have no shields.
I would check for any bad tube socket or other riveted ground connections.
Another possible cause is LEAD DRESS. In some cases, it is critical. You might try using the set with under-chassis exposed, tune so you get a good whistle, and move around wiring and components with a insulated probe. If the whistle changes, that may provide a clue.
I always take a digital photo of the chassis before starting restoration, and attempt to put everything back where it was.
Good luck,
Dave
The problem may correct itself after you do the alignment.
Dave, thanks for the advice (and you, too, cwtravis.) I'll move some wires around and see what I can make happen.
The previous "restorer" had installed new filter capacitors, cutting the old cans out of the circuit. He basically hung the new filters, some other caps, and a couple of resistors in mid-air, connected with stiff bus wire and some sleeving, all in a bundle in the vicinity of the first AF tube. The result was a dreadful hum that increased at each end of the volume control and came to a minimum when the volume was at the mid-point.
Unfortunately, all this is under the push-button coils, so the photos I've seen don't show the wires very well. I restuffed the capacitor cans and then had to make up my own routing for most of the power supply wires.
All the other wires that I replaced I soldered the new wire to one end of the old and then pulled the new wire through the exact routing of the old.
I did make one mistake in not noting the exact routing of the B+ wire to the 2nd IF transformer. That wire weaves over and under several of the wires going to the IF tube on its way to a B+ terminal but I forgot to note exactly how. That area might be a good one to start with moving wires around.