I have been working on a model 116b for the last few months and up to now thing have been going well. It have finished the recapping process and have had the radio playing. The chassis was as dirty as any I have seen. Covered in a black oily sooty substance that is very hard to remove. I scrubed and cleaned using 409 cleaner and was able to get most of the grime off. I let the unit sit for a couple of days to dry and when I turned it on everything seemed ok in fact the shadowmeter that had not worked before now did. I came back to the project the next day and when I powered up the radio I had lots of popping and crackling from the speaker and smoke from the band switch area, also the 2000ohm resistor in the shadowmeter circut was so hot it began to smoke. The radio does still get weak reception but still lots of smoke and an occasional spark from the contacts on the band switch. I did try to dry the unit in the oven to no avail. The resistor is number 75 in the schematic. The shadowmeter no longer works. I was hoping some one could give me some suggestions on where to go from here. I received lots of help from members of the forum on last years project which was a 201x. It turned out great. Thanks, Gary
Hmmmm Doesn't sound good. I would disconnect the shadow graph and check the resistance of the coil. It may be open (not good) You could add a jumper across the the graph and see if that helps the performance. Check #47 for shorts and the #76 tube for shorts.
Sparking form the bandswitch is bad! You will need to take a close look at it and find out whats arcing. Clean well make sure that there aren't any carbon traces. If you don't you can burn up the phenolic part of the switch then the terminals will come apart.Sometimes you can use a bit of epoxy to repair the wafer. Double check any parts of the switch that has B+ on it. Those would be the ones connected to the plate circuits of the RF amp and the LO.
Good luck
Terry
Also note that if a carbon track has burned into the phenolic of the band switch (which is very likely your problem in this instance), that carbon must be removed. That may include digging into the phenolic. You will have to operate very carefully to keep from breaking the phenolic if you have to scrape the carbon out. Fill the resulting groove with epoxy after making sure all carbon is gone. Been there, done that, and have another such problem switch waiting for me - a 37-650.
I cleaned the carbon as well as I could and applied some epoxy around the effected terminal. So far it Is holding but I must say it makes me nervous that it could fall out at a later time and cause a problem. This repair also took care of the over heating resister. Still no shadowmeter although I do get some slight movement of the vane when tuning in a strong signal but mostly it stays at its narrowest as though it was tuned to a strong signal. Attempted to realign the set last night hoping that may help the shadowmeter problem, this seemed to help the performance accross all bands with the exception of lower end of the broadcast band say below 800 kz. Everything seems to go dead below that point. Thanks for your help I will keep you posted. Gary
Shadow Meters have a permanent magnet in there to "bias" the vane to the neutral position and it's likely weakened over time and the current thru the coil is not enough to cause enough swing. Also very important is the accurate IF and RF alignment to maximize the resulting AVC voltage (and RF tube plate/screen current draw thru meter coil and vane movement) to make the set perform to it design max. If possible, a better aerial and ground system will also help to bring in more signal.
Chucl
You may want to check the resistance of the over heated resistor to see if it has lowered in value this will cause current flow though the sg coil. Also check the sg coil for shorted turns.
Good luck
Terry
Glad to hear you got it back working again! These things at times can be very frustrating!!!
If your Shadow Meter coil is partially shorted and has less thatn the nominal resistance, you can re-wind the coil.
See my Service Tip No.1 on my site:
http://www.philcorepairbench.com/tips/svctip01.htm
The newer type meter coil should have approx. 10 ma. of current thru it to properly swing the vane and that's about
A 10 V. drop, so Georg Simon Ohm's law says the coil resistance should be approx. 1000 ohms. If your coil is appreciably
less, then I'd suspect shorted turns. That's about 900 turns od AWG 40 wire.
Chuck
I have been reviewing the work I have done on this radio and remembered that a did not replace the caps inside the block identified as #63. It shows that it should contain twin .00011 value condensers. I dont find this value listed from any supplier. Any suggestions on where I might find them?
What you are looking for is two 110mmfd, uuf ,or pf caps. Mica.
Terry
I researched this after I posted the question and came up with what I needed. Sorry for the unneccessary post.