Philco 48-461 radio restoration

Anything related to video and my tools that is not a support request.
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Curly
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Philco 48-461 radio restoration

Post by Curly »

Transformers are always going to hum, Rocky. Resistors rule!
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Philco 48-461 radio restoration

Post by Guest »

The older type line dimmers throw out a lot of EMF (that is why some LED bulbs pulse at low levels, induced noise)
Newer, rated line voltage dimmers tend to not throw out that much EMF
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

It's not rocket science guys. We have to dissipate 4W. So here's a simple 100 ohm 25W power resistor in the neutral line. Mount to chassis and Boris is your uncle. This is bucking about 15 Vac, sending 109Vac to the radio. Common in the era was 110Vac. Undervolting at 100 Vac could lead to cathode poisoning. Respect tube specs!

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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Reached a good milestone as the major electrical restoration is complete. In the photo below you can see that a lot of re-capping has been done. We decided to recap in the RF section only if a failure(s) occurs. Don't want to risk detuning anything. You can see the dropping resistor mounted to the outside of the chassis on the right (not enough room inside the chassis). It is in the neutral line and the AC plug is polarized. Also it will be buttoned up inside the cabinet. Still I may add a cover to it.

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In the next photo you can see that I moved the B+ dropping resistor (drops the high B+ to the second level B+) from the tube sockets to the electrolytic caps area. Conveniently, it has a 6Vdc drop across it so I got some 6Vdc led strips and connected one. I plan to use part of it to light the dial better than the type 47 dial lamp. BTW, the dial lamp must be present as without it half the rectifier tube filament gets overvolted. Hopefully, if I do things right we'll still be able to see if and when the bulb burns out, even though there are also a couple leds. Maybe it can be replaced with a resistor? Finally, in the photo you can see the Philco decals, one of which will be applied to the refinished cabinet.

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Here is the remaining work:

1. Re-flow solder on one of the rectifier tube terminals as it has a coldish joint and when you wiggle it a certain way the audio gets hummy. Gonna use our new desoldering tool (it's an iron with a hole in the end and a powered vacuum sucker) for the first time. People say they don't know how they lived without it. Way better and more thorough than solder wick.

2. Run the led power lines up through the chassis and install the leds in an appropriate location.

3. Decide what final capacitor value to use for audio output bypass to cut the highs a bit (anti-hiss). That only appears to boost the bass, of course. DG said no tone pot.

4. Complete the cabinet refinishing and re-assemble everything.

Then we can get our energy back to coding. Meanwhile, Cook County removed their vaccine mandates and we will be able to swim again after several months. We are all pure-bloods here at DG tools. 8-)
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Darn it, DG doesn't want any leds. He says the external appearance must be as original, and dial illumination is definitely an external appearance. He said he would consider allowing a high cutoff filter but only after hearing how the original sounds when installed in the cabinet. Got the intermittent connection fixed so it's time to start the cabinet refinishing. Oh, and we have to align the radio too, though it seems pretty close already.

Meanwhile, Rocky found another 48-461 on ebay and bought it for (at a minimum) spare parts. The vacuum tubes alone are worth what he paid. Pretty soon, we'll be the world-wide experts on the 48-461. :lol:
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Finished the first staining. It's paste stain so on the second coat I'll hit the lighter areas harder to eliminate any blotching and unevenness. Looking for a nice dark brown mahogany effect, aged and distressed looking. Of course, the varnish top coat will make it shiny. Maybe lacquer is better? Polyurethane is a no-no for restorations. Will do second staining this afternoon, after my nap.

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Also, I ordered replacement Philco-style speaker grille cloth, as the original is tattered and dirty. Debated trying to save it, but I think not. I had to restore the cardboard backer too as it was disintegrating. I'll show you that when I get ready to put it all together. Did you know this radio originally sold for $35 and there were about 44,000 of them made? You may bow down now.

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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Some little factoids for you. For radios without line transformers the safety strategy was to enclose everything in the cabinet so that no metal parts are exposed to touching. OK, seems reasonable. But then I thought, aren't there three screws that hold the chassis in place from the bottom? What if junior lifts up the radio and touches one of them while holding a water pipe or other ground? Horrors. So I looked and those guys were smart. The screws holes are recessed so as to be very difficult to touch them. Coulda put little wooden caps on them but these radios were intended to be CHEAP, so Philco was saving pennies everywhere, as the post-war competition was stiff back then. Finally, this radio has a floating chassis that cannot be energized unless one specific capacitor fails shorted. So I guess if it doesn't fall into the bathtub it's OK.
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Curly
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Philco 48-461 radio restoration

Post by Curly »

Hope DG keeps an open mind about the led solution. C'mon, think about the original design. The dial lamp burns out and you go that's too bad. A week/month/year or two later the rectifier tube filament burns out and you're like what? Screwed. Who is going to take the back off and chassis out to replace a bulb? Balti said any smart person would replace the dial lamp with a single warm white led. Who wants a simple bulb burnout to be a pie in the face? Two fingers for you buddy, and don't you forget it.
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Bullwinkle
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Philco 48-461 radio restoration

Post by Bullwinkle »

Feelin ya Curl. Show us what it looks like with one led and we'll decide. No sweat, nobody is going to be holding up a color temperature meter. We do have to solve the bulb issue.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

OK guys, don't worry. I have it under control.
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DG
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Philco 48-461 radio restoration

Post by DG »

Sherman, the only way we will have an LED dial lamp is this way:

https://www.pinballbulbs.com/products/c ... warm-white

Please find an appropriate one (there are many options) and get rid of the wires you ran up through the chassis. When you design this, make sure the right amount of current flows to keep the rectifier tube happy.

For your line resistor, add thermal compound and use correct hardware. The screws/nuts are different. Really?

We're not installing fans! Are you kidding?

And Curly, you do need to remove the back to replace the bulb, but you don't have to remove the chassis. The bulb holder slides off its mount and gives good access.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Yes sir, Mr DG. I didn't know those things existed. You may be 69 but I am only 6.
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DG
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Philco 48-461 radio restoration

Post by DG »

You're doing great, Sherman! You know what they say, live and learn. Living is enough for me at this point. You keep on learning.

The second staining looks good and I like the idea of not going for a perfect spotless finish, and seeking an aged distressed look. Grimy hands, cigarette tar, dust, and who knows what have been all over it for 75 years, right? Great judgement for such a young'un. ;)
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

:bow:

:agree: :agree: :agree: :agree: :agree:

Can I be DG approved?
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Curly
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Philco 48-461 radio restoration

Post by Curly »

Rocky deserves it more.

The bayonet base led is brilliant. I was just about to think of that.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Well then maybe Curly approved?
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Curly
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Philco 48-461 radio restoration

Post by Curly »

Don't make me laugh, kiddo.

DG, point taken, but a user shouldn't have to remove the back to change a light bulb. Think about radios as household appliances. Apply science to the appliances.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Guys, I replaced the dropping resistor hardware with matching screws and lock-washer nuts. And I applied Artic Silver thermal paste. I ordered several different types of led bulbs. Here's one of them:

https://www.pinballlife.com/ablaze-prem ... leads.html

Honestly, I want to replace the type 47 bulb with a resistor (47 ohms 1W) hidden in the chassis. That will keep the rectifier tube happy. Then run the led bulb off the 6Vdc I tapped off the B+ dropping resistor. I can use the same wires that were previously used to supply the type 47 bulb. Let's see if DG will go for it.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Here is the cabinet after second staining (before varnish topcoat). The other cabinet shows the factory look. I think it is dark enough; any darker and the grain begins to disappear. Honestly, that factory finish looks plasticy, like bakelite to me. I want it to look like wood! After the stain dries good and hard I'll start the topcoat. BTW, wait til you see the chassis on the second unit. Unbelievable some of the repairs, e.g., components and wires just twisted together without solder. Attempts to solder to the chassis, which are stupid and always fail. I'll show y'all that stuff after the first unit is done. DG said he could live with my last lighting idea, but he wants to see how it looks first.

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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

OMG, B- is shorted to chassis on the second unit. That should be fun to track down. :roll:
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Natasha
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Philco 48-461 radio restoration

Post by Natasha »

Radio is butt-ugly?
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Boris
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Philco 48-461 radio restoration

Post by Boris »

Is charm, dear. History.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

So guys, how do you track down a B- to chassis short? Signs showed that someone was desperately searching for it, as many lines were opened to isolate things and then re-closed. But they didn't find it and the patient was declared deceased. Bless his soul and may he rest in peace. But we are going to resurrect him from the dead. You watch!

OK, so here's how you find the short. You pick one point on the B- distribution. You determine the number of connections to that point and start opening them all one-by-one until the point no longer shows continuity to chassis. Then you follow that shorted connection back and continue in this manner until you find the short. It's a recursive thing so can take time. If your starting point isn't too bad you can find it faster.

Imagine my surprise when I isolated all 6 connections to my chosen point and the short was still there. That is Twilight Zone stuff. :wow: My chosen point was one lug of the detector tube. So I thought, aha the tube is shorted. But removal of the tube changed nothing. Should I give up, hell no! So now I was thinking, the tube socket must be bad, by a process of elimination. So, determined to replace the socket, I started clearing the lugs. When I had cleared off the first lug (pin 7) and pushed the disconnected wires out of the way, lo and behold, I spotted the previously hidden short. Honestly, you'd have to be as smart as me to have found this, so I'm not surprised nobody did. 8-)

Alright, so here is the spoiler. The lead of a resistor wrapped around the pin 8 lug was not trimmed and it was touching the loctal tube metal clip. Note that lugs 7 and 8 are joined and the common of the two was my chosen B- point; here I have cleared lug 7, and lug 8 has the shocking short. Hard to believe it wasn't bad on manufacture but it could be that dimensions changed over time and finally it touched. Or maybe it was intermittent. Is that crazy or what? Here is a photo of it. You may bow down now.

Image

Got some parts on order and then we'll see if we can get a heartbeat on this one.

BTW, one of the idiots that tried to fix this replaced the lytics. But for one of them he connected the negative side to chassis (wrong! should be B-). But he made that connection by soldering it to the chassis (always guaranteed to fail). When I first pulled the chassis, that connection was broken off and the lytic was flying in the wind. When the parts arrive, I'll do things the right way! :salute:
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Britney
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Philco 48-461 radio restoration

Post by Britney »

:bravo:
Sherman, you're my hero.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Ya think this cap may be in distress (the paper one, not the lytic at the top)?

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