There Has to Be a Better Way.
 

Here's my Philco 645 after doing all of the essential rebuilding and replacing.

https://lh4.googleusercontent.com/-F...co%2520645.jpg

Between disassembling components and removing everything on top of the chassis pan, it needs almost total rewiring. I started rewiring a couple of days ago, but every time I move to a new component or circuit, then something I did before looks wrong. Then I spend an hour confirming that my wiring was actually correct (or is it?).

Is there a systematic way to do this project without spending most of my time running in circles?

Quote: "Is there a systematic way to do this project without spending most of my time running in circles?"

No, not really!

I re-wired a Philco 40-115 (and others) and I look at all the crumbling wiring as a roadmap. I basically started at one end of the chassis and worked my way across. I followed along by terminal to terminal. Do the filament wiring, the B+ and notice how it flows. You can't just do it by circuit to circuit as there are too many interconnects. Make drawings/notes as you go along and confirm things with the schematic before and after.

Simple but time consuming and figure in a stopping point so you can continue fresh the next day.

Agreed. Just be thankful that you're not doing a 37-650. There are caps in that thing that I swear were installed before the chassis metal bending was finished. Between rotted rubber wiring and bakelite block condensers, mid 30s to early 40s Philcos generally STINK to work on!

Agreed. You do it by "neighborhoods." Divide the chassis into small areas and take a close photo of each section before starting. Then finish wiring one area as photographed before moving to the next. Take loose one end of an old wire but leave the other end connected: solder in the new wire and then route it to the other terminal where you finally remove the other end of the old wire. Best way to avoid mistakes. Follow the original lead dress to avoid feedback or hum problems. On a transformer-operated chassis, I like to make up twisted pair from hookup wire for the heater circuit to run from one socket to another where possible, ditto on runs to the power switch, all of which reduces possible hum. Can't do this with series string heaters where it's best to follow the original routing, which tends to put the first audio heater in a spot where hum should be the least.

Gotcha, thanks. I have many 'before' photos, but should have taken even more when disassembling components.

Ditto on the rubber wiring being a pain in the neck. Though I've always liked the block caps. The Philco Repair Bench site has a good deal of info on what is inside them, and the tar filled ones are a snap to rebuild...Just unsolder everything, pry the tar out with a flat edge screw driver, and stick the new caps in. You don't even need to refill them with wax/tar because the open end buts up against the chassis preventing any view inside in most cases.

I've used the Repair Bench extensively. I couldn't have figured out the block caps without Service Bulletin 289. And here's something you don't need to know--that black stuff in the blocks is wax. That's why it's easy to take out. If the part number starts with the letter "O," then it's high-temperature wax which might be a little harder to remove.

My 9yr ol girl rewired a Mickey Mouse tube radio,told her to be careful as it has an auto transformer,chassis could be live,it looked good too,turned it on,no work it was the kind that had a solenoid driven by a 6V6 to move the ears almost together when the station was correctly tuned,turned out a winding from the third if trans was open circuit,she pulled every thing apart until her cat kept flicking his tail against the trans,then the penny dropped,2 turns off to locate the break,slight retune,everything ok,the cat likes to watch the ears move.

And again , In my best Mike Myers as "Dr Evil" accent ;

............ "RIIIGHT"

Cabin fever must've set in: gonna be a long, cold winter.

Combatting Cabin Fever with a Soldering Gun
 

Finished the chassis rewiring. But I'm left with two concerns before I proceed.

First, I'm over-thinking the instructions for one of the mid-model changes, and now I'm seeing two possible meanings.

"Beginning with run No. 3 resistor (16)…(51,000 ohms) was removed and a resistor…(32,000 ohms) was connected from the oscillator grid of the 6A7 to the suppressor grid of the 78 RF amplifier."

The question is, when I remove resistor (16) do I break the connection or do I leave the connection intact with just the resistance removed?

https://lh4.googleusercontent.com/-9...co%2520645.jpg

Next, I can't figure out what the connection (tap on the output transformer, yellow circle) represents. I have a four-pin speaker plug--two for the output transformer and two for the field coil (red circles). So, how does the fifth connection to the output transformer occur?

https://lh4.googleusercontent.com/-1...co%2520645.jpg

Thanks for looking. If I can get those issues resolved, then I can move forward with the restoration.

Remove means no connection - otherwise they would say replace with a wire.

Follow the wire from the top of the field coil and you will see it is the same wire that connects to the output transformer centre tap... only need a four pin plug here

Your 4 connections to the speaker are the two circled field coil connections, and the two output side connections (to the right of the two circled plate connections). In other words, the upper two red circles in your schematic are on the input side of the transformer and are not connected to the speaker coil. Your output transformer should have five connections - the two plates (red circled) and the center tap (yellow circled) - none of which should go to the speaker plug, plus the two output side connections (not circled) that do go to the speaker plug.

sorry I can't make a drawing right now, hope you get what I'm saying.

Just to simplify, a quickie sketch..

It took the written explanations AND the sketch to get through to me. Thanks, everyone.

How to Install a 3-section Tuner.
 

When I finished everything under the chassis, I mentioned to my wife that I was ready to reinstall the tuner. She usually doesn't show much interest, but this time she offered to help put the tuner on the chassis:

https://picasaweb.google.com/lh/phot...eat=directlink

Yeah--she's from Boston.

I did finish reassembling the chassis except for the "shadow meter." I tested the filament circuit with a 6-volt battery, putting the tubes in one at a time. Then I brought out the isolation transformer and the variac (Chinese knock-off). I gradually increased the power, but at 90 volts I didn't even get a glimmer from the pilot light. Arg-g-gh! I forgot to turn on the RADIO! I started again, got the tubes all aglow and the transformer outputs were all good, but absolutely no sound. Arg-g-gh! I forgot to plug in the speaker! Again, this time with the radio turned on and the speaker plugged in, I got up to 115 volts, and still got nothing but dead silence. Arg-g-gh! I forgot to put in the 80--the only tube that was missing when I bought the set.

Finally, I got some response. I can tune in a couple of AM stations, but get howling, growling, and squealing when I get close to tuning the other local stations. On the "police band" I get a lot of noise, and on the shortwave I get nothing. That may sound disappointing, but I'm delighted that I could get it to talk at all. I'm going to leave it alone for a couple of days and then try to make it work like a proper radio.

Thanks for the help I've received so far. Here are upper- and under-chassis before/after photos. You can download them, print and frame them. They make perfect Christmas gifts!

https://lh3.googleusercontent.com/-X...co%2520645.jpg

https://lh6.googleusercontent.com/-i...co%2520645.jpg

Happy holidays to all.

That was using her noodle to get that tunah in place. Nice work, all. Sounds like you've got some bad contacts or the thing out of alighnment. It'll straighten out.

That's quite the transformation you've accomplished there. :thmbsp: Would love to see more close up pictures of the detailing.

More Progress and Some Photos
 

I'm figuring out a few things myself.

The set came with an 89 replacing a 78 as an IF or RF amp. I replaced it with a good 78, and that eliminated a loud hum.

Most B-C voltages were 30% higher than Philco specs. Rectifier was putting out 410 volts instead of the specified 300v. Switched in different used 80 and the output went down to 330v most tube voltages are reasonable.

Made my first foray into alignment. Spent hours trying to make the signal generator give an audible output before I determined that the connecting cable was defective. I adjusted each capacitor to obtain max noise (AM band only).

So now I have a usable radio with fair-to-poor AM reception and some extraneous noises.

Now I'm stuck on a couple of B-C voltage issues. Here's the latest test results:

https://lh5.googleusercontent.com/-D...co%2520645.JPG

I can't figure out why the voltage to the plate on 85 is so low. All components test OK, and I've even tried replacing the resistors 48 and 49 with new ones. Would it be worthwhile (or risky?) trying a lower resistance for the 99K resistor?

https://lh5.googleusercontent.com/-q...co%2520645.jpg

Full schematic:

https://picasaweb.google.com/lh/phot...eat=directlink

If you're interested at all, here's a small album detailing replacement of missing condenser cans:

https://picasaweb.google.com/coldrb/...eat=directlink

What is the (plate) voltage with the 85 removed? Does it jump up to the full 267 volts? If it does, i would try this (with the tube re-installed):

Since the 99K is the plate load resistor, shunt the 32K that's in series with it. Try maybe a 22K, a 10K, then a full shunt. That'll raise the voltage without losing signal-voltage swing across the 99K. See if this improves volume any.
Which capacitors did you adjust? The ones in the IF cans, or the ones in the front end?
Link won't come up on my rig. But found the Riders on Nostalgiaair
http://www.nostalgiaair.org/PagesByM...2/M0013822.pdf

Thank you, Mr. Coot
 

The full voltage did show up with the 85 removed. I tried the series of shunts, but there was no discernible change in volume. I have pretty good volume already.

The alignment was to two caps each on 1st & 2nd IF transformers, then two caps each on the three RF transformers, then the single "oscillator series."

I checked the link to the schematic, and it seems OK. I'll put it here, anyway for easier reference even though the readability is marginal.

https://lh5.googleusercontent.com/--...co%2520645.jpg

I'm puzzled with the grid voltages--more often than not I get appropriate values, but negative instead of positive or vice versa, and it seems to work fine. On the 42s here, however, the value seems to be way off. But it still works.

check parts 43, 64, 66 and 67. They involve the grid bias
on the 85. Its conducting too much.

Thanks. I'll look at those tonight.
By the way, I went back and checked the voltage when shunting the 32K resistor to the 85 plate, and there was increase in voltage.

dtvmcdonald may be exactly right. Philco's yearly list of changes include a capacitor from part 64 (BC Resistor) to the junction of 66 and 67. I was ready to do that a month ago, but I put it off because I DON'T KNOW WHICH IS THE C- END OF THE BC RESISTOR. So can someone please tell me which of the three terminals on the BC Resistor is the "C- end."

Well, I put in the additional capacitor and rechecked all of the above-mentioned parts. Every part tests OK. Rechecked all the voltages and they were the same. I have a few other things to look at, but any advice will be appreciated.

3-in-One Oil
 

I didn't resolve the voltage issues, so I spent several days trying to align this set. For the first 20 attempts, I kept forgetting some step in the process. When I finally got it right, I had fairly good reception above 90 kHz, but much noise and very weak signals below 90. The last step in the alignment is adjusting the oscillator condenser for the lower frequencies, but every time I adjustment it, the output (audible) did not change. I would screw it down to a hard stop, back it out a half dozen turns, and there was no variation in the (barely audible) output.

I finally pulled out that condenser for a close look, but I found nothing amiss. When I was bolting it back in place I noticed a little rust on the adjusting screw, so I put a drop of 3-in-One on it.

When I had the condenser bolted in and rewired, I turned it on and tried the oscillator adjustment one more time. To my amazement, all the lower frequency stations came in strong, clear, and with no noise between stations. That tiny bit of rust had stopped the screw before it got to the right capacitance.

Now I'm sure the set can be aligned, but now the high end of the dial is problematic. I get pretty good reception, but excessive noise between stations. The tracking is perfect. The lower-end stations are very strong, but when you get down to 600 kHz the stations comes in over a range of 40 kilocycles. There should be a way of balancing this, but all I've tried so far hasn't worked. Is it likely that the IF frequency is the problem? Or should I back away from the peak oscillator low-frequency adjustment?

I expect that my cheapo signal generator isn't very accurate. In fact, it's not really an actual signal generator. It's a signal GEMERATOR!

https://lh6.googleusercontent.com/-f...co%2520645.JPG

I would greatly appreciate advice on which alignment parameters to address.

Never mind. I started reading some of the old radio repair stuff. When I began reading about antennas, I realized that all the noise is extraneous signal picked up by the antenna. I had it hooked up to 40 feet of inside wire. With just 8 inches of antenna lead, the noise was negligible. With no lead, it's even better.

Philco Has Me Stymied
 

I had the Philco 645 chassis complete and performing very well. For advice on some electronic details I went to Philco Phorum and got exactly what I needed to know about a mysterious stray wire and the shadowmeter.

Then, two nights ago the radio suddenly, for no apparent reason, went silent. All that I could hear was a couple of stations on top of each other if I hooked up the long antenna and turned the volume to the max.

I checked socket voltages and found a discrepancy in the 6A7--Zero volts at the oscillator grid and 90 volts at the oscillator plate. When the set was working, it had -22 volts and 138 volts. All the other voltages are the same as when the set was working, including the power transformer. All transformer coils show appropriate resistance and continuity. I've checked the continuity of practically every circuit. Also retested and swapped some tubes.

Does the sudden failure and loss of the oscillator voltages point to something I should look into? Any likely, or even possible, causes?

I did query the pholks at the Philco Phorum but haven't seen a reply yet. Maybe I phrustrated them with my questions.

If anyone can help, here's a link to a legible schematic.

https://picasaweb.google.com/lh/phot...eat=directlink

Merci Beaucoup,
Winky

Did you try another 6A7? It gets B+ via the primary of IF transformer: what's voltage on each side of that primary? Also gets B+ through the shadow meter, it appears. Does the meter have the proper continuity?

- I did try another 6A7.
- Shadow meter shows 2.5Kohms, which I believe is proper.
- I did hook up the signal meter and found max output at the IF frequency with no adjustment to transformers.

I will post the IF transformer voltages as soon as I can be sure I'm not posting spurious data--like mixing up primary and secondary.

Thanks
Winky

The final score is 245 Volts on both ends of 1st IF transformer primary (and -2.5 Volts on the secondary).

I must be a genius radio-fixer guy.
 

Reece, thanks for your attention to my issue. Tonight I started following circuits from the problem grids, pulling out components to test them out of the circuit, and looking closely at every solder joint.

Found a cap that may not have been grounded due to a rusty bolt. That fixed the voltage at the anode grid. Then, at 3:00 a.m., I found a resistor that tested OK out of the circuit but was apparently shorting under load. That fixed the oscillator grid.

The culprit:

https://lh3.googleusercontent.com/-w...co%2520645.JPG

Holy Porosity, Batman!
 

Curiosity overcame me this morning. The few carbon resistor failures that I've seen looked burned. Why would this normal-looking resistor fail? I assume this porosity wasn't part of the design, but was it a manufacturing defect or did it occur during use?

https://lh3.googleusercontent.com/-O...co%2520645.jpg

In that vein, here's a photo of something I found a few months ago when I started this project. When checking continuity, I couldn't get consistent readings on this coil. I think somebody at the factory forgot to solder this one.

https://lh5.googleusercontent.com/--...co%2520645.jpg

It's all just circuit tracing. Good for you. So is the radio working OK now? You might want to go back through and look at all chassis grounds: they might look OK but have hidden corrosion that will show up later as intermittence or silence. What some do is grind a bit on the chassis right next to the grounding lug and with a heavy iron or gun get solder from the lug right over and onto the chassis.

We were posting at the same time! Wow, take a pic of that unsoldered lug and send it back to the Philco factory in Philly. They'll take proper measures. :yes: