[Greg]

Hmm... I just noticed that on mine the spring pulling the bottom coil towards the top coil rubs against the bottom coil. That can't be good. Looks like some of the wax is off the bottom coil at that point the spring contacts it.

[dconant]

Looks like maybe both are. It will eventually cut into the coil. Can you move the bottom of the spring out a little on that post? Wonder if I should open mine up and have a look. I was thinking of not opening mine up but just put shrink tube over the grid cap wires.

[dconant]

I have found a 2 meg resistor in the chassis that is not on the schematic. There is no 2 meg resistor in the parts list either.  It is between ground and the junction of the 70K resistor(#103) and the .008 cap (#104). It is pretty well hidden under that 9 pin terminal block. Has anyone else seen this?

[462ron]

Hi Dan, it’s been 10 years since I restored my 37-116 but I seem to remember something about a 2 meg resistor being added to reduce or eliminate a loud pop when changing switch positions. I tried going through the Philco Radio Library section for changes or updates but couldn’t find anything!

Ron

[dconant]

Thanks Ron for taking the time.

Dan

[morzh]

Does it eliminate the pop?
I am not sure I've understood how it helps much.

The charging circuit is the parallel of the two lalves of the potentiometer before and after the tap, in series with the 10K resistor, charging to the voltage that is at the tap.
Now you connect 2M resistor to form a Thevenin with that charging circuit, which does not divide it too much as it is 2M vs possibly a 200K (do not know what the pot is and what the tap is at), so Gosh willing, it reduces the voltage by 10% or so.
And switching to the same or close voltage level will still create the same pop.

[462ron]

Mike I don’t remember where exactly the 2 Meg connects to. Possibly C104 and C105 on the 3 position tone switch takes in some DC voltage and when switching, the wiper grounds out one or the other cap. The 2 meg resistor could soften the discharge. A discharge going into the volume control probably makes the pop noise. I don’t have the full schematic handy to see if there’s any path for a DC voltage buildup. Anyway, it’s been years since I saw that change and just remember it had something to do with that popping noise. Not sure now where I even saw it!

Ron

[morzh]

I honestly did not pay attention as it is so very not important. But as long as we are discussing it, and there is a claimed function, I'd like to understand it.
So far I understood the 2M goes from that denoted by red circle point to GND.

[MrFixr55]

Hi DConant,

Sorry, I missed your question regarding 500WV caps in an AC-DC AA5.

Unless the technology changed, the electrolyte had to be exposed to voltage near the designed "WV" (working Voltage), otherwise the cap would not "form" correctly and the capacity would be much lower than the listed value. I can't remember exactly where I learned this, but it may have been either in the 1940s NRI Radio course or in the US Navy "Basic Electronics" Ca 1953.

In some cases, this may not have been mush of an issue as these caps, back in the 30s to the 60s or so were rated +100% / -20%. In other words, a 40 uF cap could have an actual capacity between 32 and 80 uF!

I think that the specs are tighter now.

[dconant]

Thank you MrFixr55. Now I understand why you said what you did.

Dan

[dconant]

I managed to open up the Expander Unit and replace the grid cap wires. Tested the connections found they looked good and got it all back together. Pretty touchy work there. The springs in my unit were not touching the coils. 

I have started on the power supply section but have found my notes and pictures are lacking. Yeah I got sloppy here and I told myself be diligent. The part I am having trouble with is the Mag Tuning switch. I took it out to clean the contacts but messed up doing documentation. I failed to document 2 wires and now questioning the rest of it. I see the mag switch is two switches where when one section is on the other is off. I believe one section controls the flood lights and the other controls the mag tuning. From what I am noting when the flood lights are on the mag tuning side is open. Or the other way around. Is this correct? I look at the schematic and see three separate switches. One for mag tuning (#93), one for the floods (#94) and the other for pilot light (#135). There are only 4 contacts on that mag switch assembly. So I don't see where 135 comes from. I'm wondering if 135 is that contact behind the dial assembly? I'm thinking the switch contacts on the back of the mag switch are for the floods and the contacts around the switch are for the mag tuning. The picture below are my notes of the switch. RF9 and RF10 are the 6.3 volts going to the RF section. RF11 connects to a 99K resistor in the RF section. RF12 connects to another 99K resistor in the RF section. What I have labeled as Light Plug is the plug to the flood lights. As you can see I failed to document where the second wire of the light plug went. Tuner switch label is that switch behind the tuner assembly. I have included the section of the schematic I am referring to. So long story short I need some expert help here to determine where the wires go.

[dconant]

Hello, I finally got brave enough to take the cans off the Expander Unit. Got the grid cap wires replaced and back together. I then began work on the RF unit. I took the unit out and replaced all resistors and paper caps. I left the mica caps in there. Doing all that required me to remove the three sections so I could get at the resistors and caps. I don't see how anyone can possibly replace the paper caps without doing so. As it stands right now the radio is play quite well since the initial power up just to see what I was up against. I spent about 30 hours on that RF unit. What a congested piece of work that is.

My B plus is about 300 volts vs 370 on the 127 ecap. Schematic shows 370 from B plus to B minus.  300 volts is what I had before I started the restore. I tried another 5U4 with same results. Any idea why 70 volts low?

I need to replace the filter choke (#120) as the one in the radio is a replacement measuring around 3K. Currently I am using a 400 ohm 5 watt resistor (maybe that is good enough?). Can some one tell me what Hammond choke I would need to buy? The picture with outlined in red is what should be in there. This is the link to the Hammond chokes. https://www.hammfg.com/electronics/trans...ke/153-159

Thanks,
Dan

[morzh]

Are you measuring relative to the centertap or the GND?

[dconant]

Measuring from center tap like the tube voltages show. Cap 127 is isolated from ground. Cap 127 shown in upper left of picture.