[Nathan Slingerland]

Thanks Ron - that's a big help.

[Radioroslyn]

That 10mf cap in 152 should be a 100v. On most of the smaller Philco chassis that use the triple 42 tube combination 50v is fine as they only require -20 or 30v. The set w/the larger triode output tubes (6A3 and 6B4) require abt -60v bias which this cap is directly connected to.

Looks like fun, wish I was there. [Image: http://philcoradio.com/phorum/images/smi...n_razz.gif]

[Nathan Slingerland]

Thanks Terry - I wish you could be here too!

I ended up using a 10uF 200V electrolytic for it since that was what I had.

[Nathan Slingerland]

Tonight I finished restuffing all of the electrolytics except for part #153 (3uF/2uF/1uF) - Part No. 30-2159. I'm waiting on parts for that one.

I tried out the technique Chuck describes for retaining the internal positive stud of wet electrolytics as a connecting point.

As mentioned the stud is pure aluminum and somewhat brittle. The first can I tried it on I broke the stud and ended up falling back to the previous method of passing a wire out through the rivet hole.

On the second try I got it. Note the second solder lug that I riveted to the stud. I drilled a 7/64" hole and used a 5/32" x 1/8" aluminum rivet to mount the #4 solder lug (RadioDaze LUG4A-10).

[Image: https://farm2.staticflickr.com/1833/4420...6fd5_z.jpg]
[Image: https://farm2.staticflickr.com/1842/4240...9e20_z.jpg]

Not having that exterior wire go to the stud is a really nice cosmetic improvement.

[Image: https://farm2.staticflickr.com/1834/4240...9bba_z.jpg]

[Nathan Slingerland]

It's been a few days and even though Mike doesn't like non-electronic things happening I thought I'd give an update on the de-rusting effort.

Chassis

Evaporust gel works really slowly - but it is getting the job done. Here's a progression of applications over several days (a few hours each day):

[Image: https://farm2.staticflickr.com/1838/4406...7813_z.jpg]

[Image: https://farm2.staticflickr.com/1894/4231...eda0_z.jpg]

[Image: https://farm2.staticflickr.com/1832/4233...9fbd_z.jpg]

[Image: https://farm2.staticflickr.com/1848/4328...671b_z.jpg]

[Image: https://farm2.staticflickr.com/1882/4328...717c_z.jpg]

[Image: https://farm2.staticflickr.com/1856/4330...90aa_z.jpg]

Transformers / Chokes

After soaking in regular Evaporust overnight most of the paint had come off of the top of the power transformer shells.
Interestingly, none of the paint on the inside of either shell came off.

[Image: https://farm2.staticflickr.com/1874/2920...f536_z.jpg]

Here's what the other items looked like after de-rusting with naval jelly:

[Image: https://farm2.staticflickr.com/1891/4342...60aa_z.jpg]
[Image: https://farm2.staticflickr.com/1864/4414...a2ed_z.jpg]
[Image: https://farm2.staticflickr.com/1849/4409...c532_z.jpg]

At this point I've applied four coats of paint, lightly sanding between coats to even out the rough spots.

[Image: https://farm2.staticflickr.com/1884/4240...5eea_z.jpg]
[Image: https://farm2.staticflickr.com/1877/4240...b8d0_z.jpg]

Once the chassis is done being derusted I'll reinstall the power transformer top shells, mask off everything else and paint their sides.

[morzh]

Great result, Nathan!

[Nathan Slingerland]

Today I got up early and worked all day on the 37-690.

Finished with Derusting
I used naval jelly on the few remaining stubborn spots on the chassis.
Removing the rust left behind some pitting where the rust was (expected). I don't really like to paint chassis - so I applied Boeshield to seal up the raw metal and let it dry for a couple of hours.

This is what the chassis looks like now:
[Image: https://farm2.staticflickr.com/1899/4245...d11c_z.jpg]

Grid Cap Clips
As you might recall from the eBay listing - whoever the seller bought this from had tossed the tube shields and clipped off a bunch of the grid clip connectors in their zeal to scrap it. I have no idea if the backstory is true - but whatever the case the clips are missing. While I was waiting for the Boeshield to dry I patched some new ones onto the main chassis. In all 6 clips were missing. I raided a junker 37-630 and 37-650 chassis for the clips.

One of the nuts is frozen solid on the IF cans - so for now I just patched on the clips. Hopefully I'll be able to replace the grid cap wire entirely once I start work on the main chassis in earnest.

Before;
[Image: https://farm2.staticflickr.com/1899/4245...ec8f_z.jpg]

After:
[Image: https://farm2.staticflickr.com/1871/4421...ef64_z.jpg]

Reinstall Transformers and Electrolytics
Once the chassis was sealed I remounted the chokes, output transformer and electrolytic capacitors.

[Image: https://farm2.staticflickr.com/1879/2932...4471_z.jpg]
[Image: https://farm2.staticflickr.com/1874/4421...ceea_z.jpg]

Reconnect Everything

Next I re-connected all of the parts I had previously removed.

[Image: https://farm2.staticflickr.com/1873/4245...3762_z.jpg]

Replace Candohm
The 2.2K and 3K 50W resistors arrived from Mouser. So the next step was to mount them.
Space is tight so I didn't really have much option except to mount them directly on the chassis. I applied some lithium grease underneath to help with heat transfer.

Old candohm:
[Image: https://farm2.staticflickr.com/1841/4421...2ede_n.jpg]

Replacements installed:
[Image: https://farm2.staticflickr.com/1846/4421...14fa_z.jpg]

Recap
Normally I would bring up a radio on the variac after replacing the filter capacitors. The 37-690 is such a big set that I decided it was safer to recap the amp chassis ahead of applying power.

Over the course of the afternoon I worked through the bakelite blocks and restuffed the two paper caps.

A few resistors were out of spec and were replaced.

After:
[Image: https://farm2.staticflickr.com/1870/4336...6384_z.jpg]

Clean Tube Sockets,

I used a small brush with deoxit on it to clean the socket pins on both the amp and main chassis. I don't always do this but some of the tubes had some sort of oxidation on them - so I figured it would be on the socket pins as well.

Install Tubes and Tube Shields

All of the tube shields were missing. On a 20 tube set... well that's a lot of tube shields! I had just enough shields in reasonable enough shape to use.

I had previously gone through and tested all of the tubes (replacing a few weak ones).

Ready for Bring Up
[Image: https://farm2.staticflickr.com/1854/4355...f539_z.jpg]

Well.... almost ready for bringup.

Woofer Problems

Now to tell you guys about something that I noticed last week. There's an issue with the woofer: the voice coil and connecting wires are damaged. I saw what looked like a dangling wire in the eBay photos so this wasn't a total surprise. Once I took a closer look after I had everything apart I confirmed the bad news:

[Image: https://farm2.staticflickr.com/1890/4338...1d69_z.jpg] [Image: https://farm2.staticflickr.com/1833/4319...7b86_z.jpg]

At first I thought I might be able to patch it (delicate!) but measuring the remaining bits of wire with the multimeter I couldn't get any resistance.

I had to decide between sending the speaker for repair (I don't want to learn voice coil repair on this set!) - and finding a replacement. Believe it or not, Gary from oldradioparts.com had a 37-690 woofer in good condition.
Gary's prices are very reasonable - cheaper than it would be to have a professional repair it even including shipping. So the new speaker is on it's way (arriving Tuesday).

----

I still plan to bring it up on the variac and check voltages since it's only the voice coil that's disconnected. The field coil and output transformer measures good - and the tweeters are intact.

How much volume is there out of the tweeters? Should I be able to get something out of them if things are more or less working?

[Arran]

Quote: "Arran - thank you for the suggestion on electrolysis rust stripping. That sounds more ambitious than I'd like to get into with such a complex set, but I'm sure the result would be excellent."

It's actually very easy, you just need a DC power supply, even a car battery charger will work, some scrap steel, a plastic container, and either washing or baking soda (lye too if you want to really strip paint in a hurry). There are videos about how to do it all over You Tube, and it's also a method our own Russ uses to strip rusty parts.
Regards
Arran

[Ron Ramirez]

How much volume is there out of the tweeters? Should I be able to get something out of them if things are more or less working?

As I recall, the 37-690's tweeters are louder and more pronounced than the 38-690's tweeters, so yes, you should get something out of them in a test.

[Nathan Slingerland]

After a week and a half of traveling I'm ready to get back in the saddle with the 37-690!

Here's the state of things:

Variac Test

I brought the set up on the variac as a quick test. I did hear some small amount of clicks when adjusting the controls but no signal.

I tried listening for the local oscillator with another AM radio but didn't pick anything up.

Replacement Woofer

I received the replacement speaker from Gary at oldradioparts.com.

I repeated the same test. The volume control adjusted the (small) amount of hum in the speaker but of course still no signal.

Main Chassis - Start of Recap

Here's what the underside of the main chassis looks like:

[Image: https://farm2.staticflickr.com/1850/4424...9b9d_h.jpg]

My first priority was to replace Part 99 Electrolytic Condenser (2, 2, 1 mfd). Doing that was easier said than done since it's not directly accessible.
I carefully labeled and desoldered the wires connecting the phenolic board.

[Image: https://farm2.staticflickr.com/1841/2935...d3d5_z.jpg]

[Image: https://farm2.staticflickr.com/1883/4424...2403_z.jpg]

I restuffed Part 99 as with the previous ones. This one is a dry electrolytic and required a lot of help from the heat gun in order to get the original capacitor out.

[Image: https://farm2.staticflickr.com/1894/2935...d788_z.jpg]

I also restuffed the connected tubular caps as well as Part 134 Condenser (.1, .1, .8 mfd).

[Image: https://farm2.staticflickr.com/1847/4250...fac1_z.jpg] [Image: https://farm2.staticflickr.com/1845/4250...97de_z.jpg]

Next up: lots more recap!

[klondike98]

[GarySP]

Looking good so far, Nathan!  Thanks for the ongoing lesson of patience !!  Take care, Gary

[Nathan Slingerland]

Yesterday I finished recapping the remaining left and right sides of the main chassis:

Left side

[Image: https://farm2.staticflickr.com/1895/2963...1681_b.jpg]

Right Side

[Image: https://farm2.staticflickr.com/1893/4450...a374_b.jpg]

Part No. 82 on the schematic - a 30-4201 (P) cap was marked with a 1200 volt working voltage:

[Image: https://farm2.staticflickr.com/1846/4366...e56d_z.jpg]

It's a 0.001uF capacitor so I used two 630V 0.002uF caps to come up with an equivalent that should meet that rating.

[Image: https://farm2.staticflickr.com/1888/4274...cdb5_z.jpg]

As with many of the paper caps on this radio the paper label is peeling off. I've been regluing those with rubber cement after restuffing.

When I remove the old cap I try to retain the wax on one end - then use low temperature brown hot glue to fill the other end.

[Nathan Slingerland]

Next up is everybody's favorite part about these 37-XXX radios - the RF subchassis.  

Disconnect RF Subchassis

I went through and labeled each of the connection points to the RF subchassis and labeled each wire after desoldering it.
With my trusty letter wire markers I made it to letter T!

[Image: https://farm2.staticflickr.com/1865/4366...1296_z.jpg] [Image: https://farm2.staticflickr.com/1868/4385...d5ff_z.jpg]

[Image: https://farm2.staticflickr.com/1864/4385...58ec_z.jpg] [Image: https://farm2.staticflickr.com/1858/4366...f8e4_z.jpg]

[Image: https://farm2.staticflickr.com/1858/4385...d5f5_z.jpg] [Image: https://farm2.staticflickr.com/1875/4366...4c0d_z.jpg]

[Image: https://farm2.staticflickr.com/1890/2963...6177_z.jpg] [Image: https://farm2.staticflickr.com/1871/2963...dd9b_z.jpg]

RF Subchassis Removal

[Image: https://farm2.staticflickr.com/1870/4385...2b99_c.jpg]

[Image: https://farm2.staticflickr.com/1871/4276...f225_c.jpg]

[Image: https://farm2.staticflickr.com/1860/4276...0a04_c.jpg]

[Image: https://farm2.staticflickr.com/1861/4366...8d29_c.jpg]

Freedom

I believe that I've read that the 37-116 and 37-690 share the RF subchassis. Note that the tuning condenser is actually stamped 37-116 on mine.

[Image: https://farm2.staticflickr.com/1879/4457...1eaa_c.jpg]

[Image: https://farm2.staticflickr.com/1846/4452...130e_c.jpg]

Finally, here it is with one of the sides removed to facilitate recapping:

[Image: https://farm2.staticflickr.com/1852/2963...a434_c.jpg]

[Image: https://farm2.staticflickr.com/1891/4366...d280_c.jpg]

Like they say in the Staples ads...
[Image: https://media.giphy.com/media/Rl9Yqavfj2Ula/giphy.gif]

[Nathan Slingerland]

RF Subchassis Recap

Most of the capacitors are more or less accessible without taking the sections completely apart. Unfortunately there are two capacitors buried in the antenna and RF sections that are entirely inaccessible.
I didn't see a way to replace them otherwise.

[Image: https://farm2.staticflickr.com/1870/4452...89bd_c.jpg]

[Image: https://farm2.staticflickr.com/1893/4457...7935_c.jpg]

So here we go!

[Image: https://farm2.staticflickr.com/1855/4452...caf8_c.jpg]

[Image: https://farm2.staticflickr.com/1896/4457...9c83_c.jpg]

In order to lift a given section out it's necessary to first desolder it from the tuning capacitor:

[Image: https://farm2.staticflickr.com/1849/4386...3b76_c.jpg]

Here's a sense of how deep these things are inside of the wafer band switch. Ugh.

[Image: https://farm2.staticflickr.com/1881/4276...3376_c.jpg]

[Image: https://farm2.staticflickr.com/1891/4276...7cb1_c.jpg]

The end of the capacitor has very little lead and there's almost no room to get a soldering iron in (and mind the very fragile wires coming from the coils!).

I finally managed to replace the buried capacitor in both sections.

[Image: https://farm2.staticflickr.com/1883/3070...4e42_c.jpg]

Range 2 Antenna Coil

Unfortunately I did notice this broken wire on the Range 2 Antenna coil as I was buttoning things back up.  

[Image: https://farm2.staticflickr.com/1867/4276...2f72_c.jpg]

At first I was sure that I must've broken it - but I noticed something else - the screw holding that coil in place was missing.
You can see the new screw that I put there in the picture below:

[Image: https://farm2.staticflickr.com/1892/3070...b7c6_c.jpg]

Maybe it shook loose and the wire was already broken?
Maybe it was broken long ago by someone else?
I'd like to believe that anyway.  

The remaining wire was very fine and fairly brittle. It's also has a cloth covering near the coil which I tried - but ultimately failed - to strip and solder a new wire to.  

Oh well - not much I can do about it now. And let's face it - band 2 is often dead on these models due to the oscillator coil failing.  I just hope the broadcast band coils are intact.
I marked where the connection should be below. Unless someone has a clever idea for how to salvage it I'll just leave it be.

[Image: https://farm2.staticflickr.com/1873/4276...192a_c.jpg]