[madghost]

I have a Philco 37-690 20 tube monster. I have the chassis out and I am trying to use my limited knowledge to get this thing to work.
-First time I turned it on and all the tubes lit up, but no joy on any sound, not even static out of speaker.
-Tested all tubes, found nine bad ones.
-Replaced all bad tubes except one 5X4G (tested at 50%, the other tested at 65%).
-Turned set on and I picked up a station. I think on BC AM. A lot of scratchy static when turning tuning knob. Also, hum coming out of main speaker that stayed at same volume. Seemed to be typical of electrolytic hum. Little to any volume control.
-Set to work to replace electrolytic caps. All e caps are on power sub chasis. Initial inspection of sub chassis showed that some rewiring had taken place wrt to e-caps. Rewiring looked professionally done using same type of cloth covered wire as rest of sub chassis. Because of this, I have replaced the caps in question exactly as I have found them. The original e-caps were all in cans. Some have already been replaced with cans of an aftermarket brand. Again, wired with same type of cloth covered wire as original. Replacement cans have a higher mfd rating than schematic calls for.
- So far, I have replaced the e-caps with schematic rated Mfd. or with rating I found on replacement caps. I still have a hum out of the main speaker. Also I have no sound at all from the two "tweeter" speakers.
I still have two e-caps to go. One is part number 168 and the other is 165. Problem with 165 is that with two red wires coming out of the bottom of the can and one black, I dont know how to wire in a new axal cap. For the part number 168, there is a single junction coming out of the can (this appears to be one of two original cans left). Both wires connected appear to be the same color and one goes to another e-cap (166). How do I wire this one?
-I have not replaced any regular caps on the audio chassis

Additional Questions
-Would the lower producing 5X4G be a problem? What percent of tube value is ok?
-Should I continue with the way I found the subchassis wired or should I try to wire it back to original schematic? I know they did some mods to the Philco 690, but the bulletins don't seem to indicate this type of mod.
-Why won't the two additional speakers work at all? I get nada out of them. Both are linked to the sub chassis, so you would think I would get something if the main speaker was operational.
-Does radio shack sell TV Tuner/cleaner. I would imagine this is a reason for static/scratchiness when moving the tuning knob? Would cleaner work on the variable (tuning) condenser?
-Can somebody tell me what a magnetic tuning knob does? Unfortunately, with out an owners manual, I have no idea how to properly operate this radio, whch bands are for what, etc.

Any and all help would be appreciated. PS, I picked up this radio for 100 dollars at a garage sale. I have already spent more money on tubes and caps than I payed for it. I understand the sound that comes out of this thing should make it worth it. True? Anybody else out there have one of these?
Thanks, MG

[AI2V]

I had a 38-690 for 40 yrs until I sold it a couple of months ago. $1432!!!

Not many suggestions but yes, you must have good 5X4's plugged into your transformers. They supply the high voltage to the the entire radio. A check for the proper B+ on the audio output amp plates is sufficient at this point to verify that the rectifiers are doing their job. (50% on the tester is pretty crappy but it still should work).

As for the tweeters, look at the pins that insert into them; there are two thick and two thin ones- audio and field current. The "sockets" are mated for these two sizes but they can be forced in backwards yielding no audio. The tweeters are NOT loud so don't look for ear-splitting sound from them.

There is also a modification on phasing these tweeters- don't do that mod until you can hear audio. Better yet, don't attempt it.

For the time being, don't put your interstage power cable trough the cabinet hole- it will just chafe. Also, use some spray switch cleaner/lube on the 10 (?) pin power connector; you will be inserting/removing it many times so save wear on the irrepaceable connector.

Just things learned from the 38-690.....

[Frank]

Before you can play this radio, you have to replace all of the wax paper capacitors, and replace the capacitors within the bakelite blocks. All electrolytics need to be replaced as well.

This is a very complex radio, and will require a lot of time. The components are packed into a tight space. I am doing mine now. My lower chassis is done, and I am now working on the upper chassis, with about 60% of it done.

The RF deck will be a challenge, as there are several wax capacitors that are placed in an inconvenient place. I got lucky and was able to replace mine without removing that sub-chassis. There are holes on top to cut the ground wires to two of the toughest capacitors to replace. I was able to cut and resolder new ones through the holes.

First, you should contact Chuck Schwark of this forum to get all of the service data for that model. He will also send you a copy of the owners manual for it. You need this information to repair this radio. Don't try to figure it out through trial and error. It is much to valuable a radio to experiment with.

Go to Chuck's site and read about rebuilding the block capacitors. They are not hard to do, but it is important that they get rebuilt, or the radio will never work. All of the data for this process is there.

He also has an explanation for what magnetic tuning is. It's sort of a drift control that was used when tuning with the station selection mechanism. The mechanism is not perfect, so this helped lock in a station.

I would guess that you will spend less than $75 in parts to rebuild this radio, but you will have many hours of your time invested in it. But, this was Phico's answer to the Zenith Stratosphere, so it is well worth the effort.

Frank.