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Philco 37-116 question - Printable Version

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Philco 37-116 question - snowm00se - 04-21-2017

I am in the process of recapping a model 37-116 code 22. I have started on the left side of the chassis and rebuilt the can electrolyte’s and the two lower Bakelite blocks. I have moved on to the center section and started replacing the old paper caps. I have discovered 3 caps that are buried deep in the chassis inside the coil section. Two of which I cannot even see. They are per the schematic and parts list #28, #17, and #9. How important is it replace these three? Can they be left alone and if so what impact would they have on the set working correctly? If it’s necessary to replace them how does one get to them? Thanks

RE: Philco 37-116 question - Nathan Slingerland - 04-21-2017

Hi - you'll find that many people on the Phorum have run into this when servicing 1937 models. You are not alone!
Even though it's no picnic, you will almost certainly want to replace those capacitors for the set to perform well.

Here are some links to previous threads:
http://philcoradio.com/phorum/showthread.php?tid=15581
http://philcoradio.com/phorum/showthread.php?tid=10378
http://philcoradio.com/phorum/showthread.php?tid=5663

I'm sure there's lots more info on this set to be found. The search functionality built-into the Phorum doesn't always do as well as Google so you may want to google search limiting results to this site:

https://www.google.com/#q=site:philcoradio.com+37-116+bandswitch

Remember to go slow and take lots of pictures as you go.

RE: Philco 37-116 question - Radioroslyn - 04-21-2017

So #9 is part of the avc circuit for the rf amp, #17 is the cathode bypass for the mixer, and #28 is the rf ground return for the mixer input. If any of these where leaky it wouldn't be a show stopper. May not have the best performance but won't kill off the  signal.
Most will pull out the sub-chassis to gain better access to the hard to get at parts. There are abt 15 or so wires to mark and disconnect, some mechanicals and unbolt the  sub chassis.
It's also a good time to have a look at the sw band osc coils, especially on the police band.

GL

RE: Philco 37-116 question - morzh - 04-21-2017

I was able to change them without pulling the RF Chassis but boy was it....tedious, shall we say.
This said, it wasn't the wires that deterred me but the necessity to desolder pieces of chassis or something of that sort. Looked a bit too much to do and required a heavier iron than what I have​.

RE: Philco 37-116 question - Arran - 04-22-2017

This was why I started a campaign of collecting any high wattage soldering irons I could find at a reasonable price. For years I struggled with the same problem, how to undo things like grounding straps and ground leads of bypass caps, then after picking up the first 125 Watt iron I saw at a garage sale I had no more problem. So now I have a nice collection of "electric blowtorches" that will undo or redo just about any solder joint to a chassis, asbestos cords and all.
Regards
Arran

RE: Philco 37-116 question - morzh - 04-22-2017

Yep. Next time I see one at a reasonable price I'll pick it up too.

RE: Philco 37-116 question - Chris h - 05-05-2017

I just went thru my 37-116 code 122 this last winter.  I reluctantly chose to remove the RF sub-chassis, and in hind sight I am glad I did. There are several caps that are buried inside the band switch that even with removal of the sub-chassis are difficult to get to! I chose to cut one end free and leave them in place, placing the replacement outside the switch. Removal also allowed me to replace the rubber chassis mounts, and all interconnecting wiring. (Which was getting a little crispy.)  I did find a few connections that had never been soldered! The assembly quality left a little to be desired. Which surprised me a little. I was also able to get at, and replace a few OT resistors that I probably would not have found, otherwise. Checking and replacing components in the main chassis, directly behind the RF chassis, is also much easier with the sub-chassis removed.
I used my big Weller 100/250 watt soldering gun for the direct to chassis solder connections.  Much easier to handle and manipulate than my big "electric blowtorch" soldering iron, and made short work of the chassis connections. Especially with a new tip!
I took lots of pictures, printed them, and made notations on the prints, regarding where the wires and components were placed. I also labeled each interconnecting wire on both ends and noted them on the photos, along with the ROUTING! I won't pull anyone's leg and say it went off without a hitch. I did have one misswire, but was able to solve it without having to remove the sub-chassis again, thankfully!
Just take your time and don't rush it. Mine works well, and now sounds great. It was worth the effort. I might add that it was a dead chassis when I got it.

RE: Philco 37-116 question - Phlogiston - 05-05-2017

Since the osc coil for band 2 is more often than not open, having the sub-assembly removed is about the only way to get to it - and you can fix the caps too.