[tbone]

Greetings, I hope you are all well!

I am restoring a 37-116 for Phorum Member Rich.

So far the Chassis work has gone well. I replaced all caps, re-stuffing the filter cans and bakelite blocks, and have completely dismantled, cleaned and repaired the sub chassis. There was a bad solder connection on one of the hidden oscillator section switch lugs. Must have been bad from the factory. I guess this is one reason we take them apart.

Besides a couple of self induced issues  I have the chassis playing on the bench. All is working well except the magnetic tuning, which I believe is a bad 80PF mica cap in transformer 81. With the 81S trimmer tight, I am close, but need more capacitance to get it right. I plan on tackling this next.

The rest of the set alignment went as expected. At first I was nervous since someone in the past connected a cap from the BC RF trimmer to antenna terminal 4. I was expecting an open coil, but that was not the case. It was just simply out of alignment. Now you start to hear a signal coming in between .5 and 1 uv at the antenna connection.

The set needs tube shields and other misc items. Rich was able to find another 37-116 in state for a reasonable price, and this is what I have questions about.

Both radios had a fused plug on the AC line. Was this a Philco supplied item?
The parts set had a bottom cover and the one I'm working on had no indication of one.
The speakers are different. One uses pins that push in, while the other one uses a socket and plug.
The wiring harness for the lighting is also built better on the parts set. It has a nice loomed harness with a plug so it can be removed.
The Magnetic Tuning transformer #81 is a square can which has a different 81S tuning cap. Could this be used in the set I'm repairing if needed?

I'm interested in what you can tell me about these clearly different versions of the 37-116. Also, if you have any tips on the Magnetic tuning that I may be missing other than the standard service information, I would appreciate the info.

Additionally, I will be installing an audio input jack. I have some questions on the best way to tackle this. How would you mute the radio audio while connecting an external source? What is the best location to connect to, volume control high? I was thinking of a simple switch along with a 3.5MM jack. All suggestions are welcome.

Attached is the schematic link from Riders which I am using, and a picture of the plug.

Thank you for looking.

37-116 Schematic

[Radioroslyn]

The different spkr connection is between the early 1st 6 months and late last 6 months. My standard has the push pins. They were poor sellers and were discontinued for the 2nd half of the season. The deluxe has the socket.
The ac plug w/dual fuses I doubt is original. I only place I've seen them is on Heathkit equipment. I would take a look in the Philco catalogs and see if they are listed.

[Ron Ramirez]

Both radios had a fused plug on the AC line. Was this a Philco supplied item?

From the number of 37/38-116s and 37/38-690s I have encountered in years past, I feel that the answer is - yes, they came with the fused plug from the factory.

New ones are being made, and you can find them at farm and home stores that sell electric fencing. The new ones are made in China (surprise, surprise) and have a "Dare" name on them instead of "El-Menco" but otherwise are identical to the originals.

The parts set had a bottom cover and the one I'm working on had no indication of one.

Since the 37-116 had an open back, the bottom cover is a safety feature. I seem to recall that the 37-116 chassis did not mount on a solid board but instead was supported at the front and back, with the rest of the area under the chassis being open. If that is indeed the case (and I honestly do not remember at present), then a bottom cover is highly recommended, in case there will be children - or dummies - in close proximity to the radio. The bottom cover will keep prying fingers out of the chassis.

The speakers are different. One uses pins that push in, while the other one uses a socket and plug.

Correct. Early models used five individual pins. Later models used the round socket at the end of the cable with matching plug on the speaker.

The wiring harness for the lighting is also built better on the parts set. It has a nice loomed harness with a plug so it can be removed.

No comment other than they made improvements as they went along.

The Magnetic Tuning transformer #81 is a square can which has a different 81S tuning cap. Could this be used in the set I'm repairing if needed?

Possibly, but study the Magnetic Tuning circuit of a 38-116 first to be sure they are the same.

[tbone]

Ron,

Thanks for the info. I actually have a good Elmenco fused plug which I will put on the radio. It's not cracked and looks to be solid.

As for the Magnetic Tuning transformer, both sets are 37-116, just different vintages as you pointed out. I may look into the square transformer from the parts set. I'll open it up to check the parts values inside. If they are the same, I might try it. I suppose Philco made a change for a reason.

I will wait and see if anyone has any ideas about adding an external audio input jack. The end user really wants this feature.

I know that some folks liked the simplified alignment process of the 38 models, but I found I like the 37 setup better. It allows you to peak both ends of the band and sensitivity seems more uniform across the band as compared to the 38 models I have worked on. Personal preference I guess.

Thank you again.

[RodB]

There might be a 3.5 mm jack that has a circuit interrupt when the plug is inserted. If so, you can use it to break the connection to the rf circuit when the external audio source is plugged in.

[rfeenstra]

I found a supply of the Elmenco plugs and have been using them on quite a few radios. that way I don't put a fuse holder under the chassis. Both of my 37-116's had them and yes, Ron, the bottom board is not solid on my 116's.

[tbone]

Thank you for the replies. I will be experimenting with the external audio connection this coming week.

I managed to repair the magnetic tuning today. I took apart the original can again to look at the coil. I had replaced the 110PF cap and the 490K resistors already and the primary was causing the required dip in audio. I tried replacing the 80PF mica that was in parallel with the secondary trimmer, thinking maybe it was bad. No dice. I could not get enough capacitance and the trimmer was down tight. I tried experimenting with extra fixed mica caps and still no change.

I decided to remove the transformer from the parts chassis. When I opened it to change the resistors, it was built completely different. The secondary had a big ole air variable cap and no fixed mica across it. The primary was identical to the old one. This transformer reminded me of the one in the 38-690.

After changing the resistors and installing it, the magnetic tuning worked perfectly! I had to tweak everything slightly, but that's it. Something must have been wrong with the coil in the old one. Philco must have had issues in the original design and went to this model. Hopefully this info will help someone working on one of these models.