[ntsc525]

Hi, everyone:

I'm trying to restore the rusty innards of what was a decent looking 71B Cathedral I won at a recent radio club auction. It was advertised as an 18B, but since I just wanted a Philco cathedral and didn't care what model, I bid on it and won it at a decent price. Just because a radio "self identifies" as an 18B doesn't make it one, and it was born a 71B Code 125.

The cabinet looked like it was restored, but not perfectly, yet clean enough to display. Looking at the chassis and doing some digging I figured out this is a seemingly rare 71B Code 125 with the shadow meter when most of them did not have this.

It played (well, on the upper end of the dial anyway) but the shadow meter wasn't working. I finally decided, after doing my 70 (my first 30s Philco), it was time to pull out the chassis of this "restored" radio and see what's wrong with the shadow meter and touch up the IF alignment after successfully doing that on my 70. Oh, if only it was that simple, it would be back on the air now!

Well, wow, the things you see when you flip this chassis over are shocking, and aside from the rust, globs of RTV silicone everywhere, and wrong value capacitors just globbed onto the Bakelite units (with some lug clippage to add insult to injury). I'm going to have to just start on one end and clean up every problem I find, including the roll of old electrical tape that was used to turn the dial because the original string is long missing, and someone decided that electrical tape and a small piece of fuel hose would make a good tuning washer for someone with a strong tuning hand.

Anyway, I have a few questions:

The tuning capacitor is so nasty I'm amazed it picked up anything at all. I found one that looks the same out of a 70 on eBay. I know the Philco part numbers are different, but is there anything electrically different between a late 71 and a most-likely early (non AVC) 70 tuning condenser? The actual dial portion unbolts from the front with one screw, so I would hope the 71 style dial and shaft assembly will fit on the 70 condenser.

What about a dial stringing diagram? I've searched the web and found lots of dead links promising a cord stringing diagram, but delivering ads or 404s instead. The Sam's dial stringing guide doesn't show the 71 either.

As far as a schematic is concerned, the best I can find is the Philco 71 series, which at first glance looks like it matches except for the shadow meter. Since I see the leads (non-original) of my shadow meter are soldered across a jumper (shorted) and since the shadow meter appears to be open on top of that, I'm wondering how it was originally installed, and if Philco issued a revised schematic for this, or if there was a more common shadow meter radio with the same circuit I could use.

I would really like to find a better, less butchered and less rusty chassis to work on, but my research seems to suggest this will be difficult. I'm not talking about surface rust like you find on many of these. I'm seeing chunks of metal flaking off the sheet metal, making me think I'm going to have to go find some Bondo and silver paint to try to clean this thing up! Reminds me of an episode of Graveyard Cars.

Anyway, any help and advice from the members here would be appreciated.

And, a lesson I hope people have learned over the years is, please upload pictures and documents directly to this web site instead of relying on outside links. I've seen Photobucket links that return errors because whoever posted it didn't renew their account, and links to a variety of "404 Not Found" pages.

Thanks!

[Radioroslyn]

Hi,
Probably the best way to start off is to post some pics of your chassis. Just to make sure we're on the same page with model and parts. It's been a little while since I've worked on a 70 or 71 I think the last one was a 370 which the dial is different from the B models. I'm kinda thinking that it doesn't use a cord but is friction drive w/a little pinch roller.

Don't think that the 70/71 used a shadow meter. If your set has one it may not be a 70 style chassis. The cabinet for a set w/a sm is going to be different as the escutcheon is larger.

Sam's isn't going to have any info for the 70 or so they only cover post war sets after 1946.

[ntsc525]

Mine is marked "71B" and "Code 125". This is the one with individual tube shields and has the tube complement consistent with the 71 series. In 1933 they did make them with the shadow meter, and used the same escutcheon as the 91B.

I believe most of the 71 series was without the shadow meter, and I believe certain models had the same chassis but with the large single tube shield as seen on the 70 series before it.

Like I said, there are older posts out there referencing this model and a dial cord chart for the 71 (maybe it was only the B series that used string, but I don't know). Over the years, wherever the pictures were hosted turned into 404s.

I have confirmed that even though mine used an electrical tape and fuel hose based friction drive, the pulleys are present for a cord, but I'm not sure how it goes together. The main dial has a large pulley similar to newer dial radios. The tuning knob drives a shaft with a pulley, and there is a double pulley / idler below that. I suppose I could come up with something that will work, but I would like to see the original Philco design.

I imagine if there were later Philcos that used dial cords with the same style dials, it was probably similar, so if someone could point me to a mid-1930s Cathedral model that uses cords that would be great. (Pictures would be great.)

As for pictures, I'll post when I have a chance to take them, but I know someone on this forum knows what I'm talking about, but the 71B with shadow meter is a rare beast, so most people will think of the version that comes up most when you Google it.

So, in summary, the tube layout does match the 71 series, but this chassis has a shadow meter and individual tube shields (with the bases welded to the chassis) and is probably the latest version of the 71B made. Hopefully someone here has seen one recently enough to remember the details.

Sure, anyone can find a 70 with SN below B22000 but I found a 71B with a shadow meter!

Regards,

Dan

[klondike98]

Ron's gallery has some nice information on the 71 series including some sales tags and other good stuff added by Geoff.  He mentions the shadow meter was in later versions.

[ntsc525]

I've looked at everything Geoff has, but there is no help about stringing the tuner and no schematics showing the shadow meter. On the link you referenced above, I see the 71H which is shown with a shadow meter and the same escutcheon as mine.

Anyway, if anyone has a 71 series radio, I wonder if all the dials used a dial cord, or if that too was only on the later ones. If anyone has a picture or diagram, I'd appreciate it.

I answered my own question about the 70 vs 71 tuning condenser, and though they look the same, the number of plates is different (I think 9 on the 71 and 10 on the 70) so, I didn't get the 70 tuner.

One of these days when I get home early enough and have the time, I'll take pictures and post them here.

Thanks.

Regards,

Dan

[ntsc525]

I found what I was looking for, though I don't know where it is today.

I had to go to the Wayback Machine (archive.org) to find where Ron Ramirez once posted a great page about the dial cord: (The original page was referenced in a post from 2008 that I found by searching for Philco 71 dial cord.)

http://web.archive.org/web/2008040804332...string.htm

I don't know where that link is now, because it now gives "404 Not Found", but the page captured by the Wayback Machine has the info and the diagram.

Now all I have to do is figure out the shadow meter, but that can probably wait until I get the rest of the radio working its best.

I hope Mr. Ramirez is still around and can repost that page, or point it out to me if it's already here somewhere and I'm just too dense to find it. ;-)

[ntsc525]

And now, a little more digging and I've found the current link, no Wayback Machine needed!

http://philcoradio.com/phorum/showthread.php?tid=14971

I don't know why that was so difficult to find!

Just goes to show you what a phantastic phorum this is. I'll pheel phulphilled once I get my 71B running again! ;-)

[klondike98]

Now that you found it on the Wayback machine....here's the current link for it in the Tech Section:
http://www.philcoradio.com/phorum/showth...?tid=14971

I didn't remember that that was on the phorum...

[Ron Ramirez]

I'm here...yup, still around...life has been very busy of late so it appears that I am keeping a low profile when the fact of the matter is I'm just really busy lately!

Glad you found the info you needed. Yes, most of the old website is now in the Phorum. Again, that busy thing...I did not have the time to devote to giving the old website the facelift it badly needed, so I merged website and Phorum. One of our Phorum moderators, Nathan, rebuilt the Philco Gallery and did an outstanding job.

[ntsc525]

Thanks, Ron, for everything. A scant few years ago I didn't know a Hippo from a Baby Grand, but since I got into tube radios I got bitten by the Philco bug pretty quickly. After dipping my toes in and fixing a few 40s sets, I've moved to the harder stuff, accumulating several cathedral and tombstones.

Now I have your book and frequent the Phorum as often as I can.

I know about busy, though, so I'm hoping to get back to my 71B this weekend and get it to a state I can be proud of.

I wish someone would do as much for Zenith as you've done for Philco, especially the on line catalog!

Thanks again, Ron, for your gift and contributions to radio geekdom!

Dan

[ntsc525]

I know this is an old thread (I started it the first time I looked at this radio, which I bought in 2017).

Anyway, I know I've talked about this radio elsewhere, and now I realize it should have been on this thread.  This is the one with the shadow meter that I had to rewind (my first coil rewind, and I'm happy it works!), the rusted out chassis I had to sand, grind, wire brush and paint, and the tuner assembly I had to replace.  (A can of Rustoleum hides a multitude of sin!)

So, I've got it working now, except the audio stage howls, which I suspect is plate to plate interference between the first audio amp (39/44 tube) and power output (42 tube).  I can see the feedback on the grid of the 42 and the plate of the 39/44 but not on the grid of the 39/44, so the RF parts look good.  Placing my hand between the tubes affects the feedback, and sometimes I really have to mess with it to get it to howl, but even when it's not howling, the audio is distorted, and the scope shows very high peaks in the audio, seemingly at higher frequencies.  So, shield, right?

However: This is the newer chassis (Code 125) with individual shields over the RF / IF tubes, and there is no shield around the first audio, and no ring on the chassis where one would go, like you see on the Code 121 chassis.  Makes me think Philco decided not to shield the first audio.  So, what the heck did they do then?

So, I'm wondering how did Philco deal with feedback on the Code 125?  Or was there a different type of shield used that doesn't require the corresponding ring on the chassis?  If there was something different underneath the chassis, I'd like to see that also, since mine was far from original when I started, and all I have for reference is a Code 121 chassis, and my wire dress is like that one.

Here is a picture of the radio as I received it.
   

If anyone has a picture of an original 71 chassis with the individual shields, especially if it doesn't howl, I'd appreciate it.

[mikethedruid]

You may have a microphonic tube, or a tube socket problem in the audio stage. You may have a bad solder joint somewhere in the audio stage too. Have you checked these things?

[Steve Davis]

Dan, look closely at the rivets on either side of the 39/44, it looks to me like the heads are not all the way down on the chassis. I believe there originally was a shield. Temporarily place a shield over the tube making sure the shield is grounded and the grid wire is inside of the shield.


Steve

[Steve Davis]

Dan, look closely at the rivets on either side of the 39/44, it looks to me like the heads are not all the way down on the chassis. I believe there originally was a shield. Temporarily place a shield over the tube making sure the shield is grounded and the grid wire is inside of the shield.


Steve

[ntsc525]

The rivets are firm to the chassis, and the grid wire is run through one of the rivets, which is the same as the Code 121, which puts it inside the shield. I see no signs this chassis ever had a shield around that tube, especially since it would take a very deliberate action to remove the ring and reinstall rivets. People who would hack into a radio would not be expected to cover their tracks like that.

By the way, I've tried several different tubes in both positions, and in fact, both of those "balloon" tubes have been pulled to be saved for a more special radio. (The original Balloon 42 howled more than the Ken Rad shoulder tube that lives there now.)

No loose solder joints either. Experimentation indicates the howling is affected by the incoming signal (spikes in audio or loud volume can trigger it), and hand placement around or between the audio tubes.

I believe shielding is the needed solution based on that, but I would like to see how the original Code 125 chassis handled the issue if they eliminated the ring on the chassis side.

If anyone has another Code 125, 225, or similar 71 series chassis with individual shields around the RF tubes, I'd be very interested in seeing how it was done.

The picture you're looking at is how I got the radio, before I worked on it, and the grid wire has been replaced because the insulation frayed around the rivet hole, and I was losing audio altogether. (That problem, at least, is fixed.)

What I don't want is to bodge a shield that wasn't on the original radio, unless they all were known to howl without the shield around the 39/44 after Philco removed the original shield. What I do want is to discover if Philco used some different type of shield around that tube, or some other solution and see if I can find one just like it so my radio is more authentic.

I'm sure I could stick a non-correct Goat shield around my now ST type 39/44 and solve the problem, but that's not what I'm after. I really want to know how these Code 125s originally worked without howling.

Dan