Philco 48-461 radio restoration

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

Post by Sherman »

Rocky told me how to do the grille cloth and I did it! Gonna put radio 2 together today and then post a pic for you.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Rocky wants me to install an X2 safety capacitor across the line instead of the film capacitor. So I have to do that before putting radio 2 together. It "should/may" reduce interference coming in the AC line. I suppose. Orange drop caps are stylish. Really? I only pimp for demonstrable performance advantages.

For fun while waiting for caps to arrive, I started looking for noise sources here at DG land. The worst, I mean it kicks your ass, is the under-counter LED lighting in the kitchen. So I ordered a new low-noise LED driver for it.

I saw a utube about some LED lights on a church's cross. The local hams were distraught. One of them traced it to the cross and all he had to do was replace the LED driver, so YMBDN.

Then I tested all the 5Vdc wall warts, because one is used for powering the differential probe. I found one pretty good one on hand, although most of them suck. But I can't use it unless I cobble up a USB adapter from USB C to normal USB. Why bother? I am going to power the probe from a 6Vdc lantern battery in series with two 1N4004 diodes. What idiot would want to inject all that USB power supply switching noise into a differential probe? Don't people think any more? I've got the 6Vdc lantern battery but the diodes come in tomorrow.

:shock: S&A = shock and awe. :shock:
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Decided to take a chance guys. Connected the differential probe directly to the lantern battery. It worked just fine.

Now, using it I can detect 1-2 mv p-p of line hum at the speaker. We were shooting for 0. Should we bump the B+ lytics to 1000uF? Bullwinkle says yes because he can still hear it.
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Curly
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Philco 48-461 radio restoration

Post by Curly »

Honestly, how many mooses listen to the radio?

Too, I noticed that the differential probe black lead is 0 ohms to the mains ground. You have to open the probe and break that connection. It's coming through the output coax to the scope. You can float the scope but that leaves it vulnerable to static, etc., so they say.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Found the church video. Check it out.

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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Curly wrote:
Sat Apr 02, 2022 5:40 pm
I noticed that the differential probe black lead is 0 ohms to the mains ground.
No way. Check it again.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Guys, the safety/anti-interference filters arrived and I installed one in radio 2. This radio is sounding so good now, almost HiFi!

Poor radio 1 has the repaired speaker and, honestly, it sounds terrible now compared to radio 2. For a while it was winning but now it is just pathetic. So I ordered a replacement speaker intended for old cars. Did you know that the old cars had tube radios not unlike the classic AA5/6s? The stupid speakers you get at Worst Buy have dumb tweeters and cross-over networks. They're designed for high-power audio amplifiers. They do not sound good with a low-power radio output.

Guys, don't forget when you are doing breadboarding, always turn off the power when you want to change the circuit.

The new scope probe is on order.

I put the halogen lamps in the track light. Super quiet.

The AM transmitter that Rocky ordered is stuck in US customs for God knows how long. Don't worry, I'm on it.

Balti told me to be more modest. From now on, you will get the modest Sherman. Just remember, it wasn't my idea.
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Rocky
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Philco 48-461 radio restoration

Post by Rocky »

Bravo Sherman. Such a great job you are doing.

Much amusement here:

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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

We have a new kitchen radio! Radio 2 is all finished and serving admirably as we make our morning coffee and eggs. You can see the new grille cloth installed. I don't plan to do anything significant with the cabinet other than touch up two scratches on the top. It may not be stunning in the looks department, but it sure plays sweetly. Now radio 1 is back on the bench for caps upgrade and better alignment. Also, will most likely replace the speaker, although that is a big job, because the whole dial mechanism is mounted to the top of the speaker. Re-stringing dials is not for the faint-of-heart, I am told.

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DG
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Philco 48-461 radio restoration

Post by DG »

Sherman. Want to do me a favor? Put the original chassis's back in the original cabinets, return to normal bulb operation with power from the filament string, not the B+. Replace defective speakers as needed. Repair dial diffusers as needed. Keep us updated.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Gulp.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

OK, Mr DG, I put the chassis's back in their original cabinets. So now we can say that radio 1 is the one with the refinished cabinet and radio 2 is the unrefinished cabinet. I replaced the grille cloth on radio 1 as nobody liked it. It's now the same as radio 2, which we replaced previously. I fixed the diffuser on radio 2. For both radios I wired the dial led lamps to the filament string as designed, so now they light up immediately when the radio is turned on.

Changing the speaker on radio 2 was a challenge. You can see below on the right the old speaker and one of the new ones. The challenge was to somehow reproduce the mounting structure of the old speaker on the new speaker. I did it by making a wooden block in the right shape, cutting a hole in it for the magnet, and then gluing it to the speaker (JB Weld QuikWeld steel epoxy -- works great). Then the speaker could be screwed to the chassis from below, just as for the original speaker. Had to bend down the terminal strip to stop it from hitting a tube. It's a tight fit but I got it done. The audio transformer is glued to the top of the block. Metal tape coats the wood to stop hot tubes from cooking it. On the left of the photo you can see the new speaker installed, with the dial assembly screwed to the top and re-strung. Everything works fine.

BTW, you can also see a dial lamp reflector I kludged up. The underside of the cardboard has metal tape on it to make a poor man's mirror.

Time for a confession. That speaker got destroyed because I used one of those air blaster cans to try to remove debris. Not cool! That happened a week or so ago and then just yesterday I saw a Mr Carlson video warning not to do that. Too late, lesson learned the hard way. I tore off all the damaged cone to open things up and learn how speakers are constructed.

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DG
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Philco 48-461 radio restoration

Post by DG »

That's highly creative thinking and great execution, Sherman. Bravo and thank you!

Please save the old speaker in case we ever decide to get it re-coned.
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Natasha
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Philco 48-461 radio restoration

Post by Natasha »

Not too bad a job for a 6-year old. Next time, though, please get a non-butt-ugly radio to work on. Then I can have it in my kitchen!
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

I hear ya, Nattie. We wanted to make our mistakes on a not-so-important radio. I'm already looking for the next project...maybe a TV. I wanna build Mr Carlson's capacitor leakage tester too. And our Spitfire AM transmitter is in, so need to get that fired up with some oldies streams. Rocky would say whee!
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Rocky
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Philco 48-461 radio restoration

Post by Rocky »

Whee!
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Hello peeps, time for an update!

First, DG was not happy with the residual hum that could be heard on radio 2. Remember the re-capping on radio 1 had reduced hum at the speaker to less than 2 mV? Well, on radio 2 it was 60 mV -- definitely audible. I have been fruitlessly searching for the reason for weeks. I even went so far as to disassemble the 2nd IF transformer to check it out. Nothing made any sense. But now I'm happy to report that this morning I found the cause. I was checking for cold solder joints as a possible cause and so was wiggling wires and pushing them around and such. As I pushed one wire suddenly the hum went away. But it wasn't a bad joint! The wire was a filament line. It was running very close to the main audio input capacitor to the output stage and inducing hum. Just separating them by an inch or two solved it. I should have known this, as I now recall Mr Carlson talking about it. Oh well, no matter how we got there, it's all good.

Now, I am going to make two changes to radio 2:

1. Add a jack for an external speaker. I patched in one from a stereo system (4 ohms) and it sounded so good! The jack will have a switchover that cuts out the internal speaker. Pretty standard stuff.

2. Add bluetooth support. I have already patched in a receiver and streamed from my laptop. There are some challenges. For example, even when the audio input to the volume pot is switched to the bluetooth, the radio broadcast can still be faintly heard. I'm going to switch off the B+ to the 2nd IF stage when switched to bluetooth. Already tested that and it works. Apparently some factory radios do that. Without that, people were just tuning the radio off stations, but that is lame (stupid and still hisses a little).

Still trying to decide if the bluetooth receiver should be integrated into the radio, or whether I should add an aux jack to which an external bluetooth receiver can be connected. Probably going with the aux jack idea, so other things could also be connected if desired.

Finally, about the AM transmitter stuff. Sadly, the Part 15 regulations simply do not allow enough RF energy to be emitted to overcome all the EMI in a typical modern home. The Spitfire turned out to be big disappointment. It picked up all the EMI and re-radiated it. Stated simply, it hummed like a hummingbird. I could not find a solution for that. So forget AM transmission. That's why I headed toward bluetooth.

I asked Albert why I can't seem to ever reach my 7th birthday. Believe me, it bothers me a lot. He said it depends on the reference frame and that I must be accelerating. Of course. :facepalm:

Hope I didn't bore you too much.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Greetings R&B fans! Update time...

Guys, I bought the 3rd 48-461 for parts because it was so cheap. $25. You know at that price it will be in sad shape, and it was. At least I got tubes and various important parts like the oscillator coil, IF transformers, volume potentiometer, audio transformer, etc. It was horribly hacked by know-nothing technicians over the years. Jeez, the audio output tube socket was replaced by a non-loctal one so they could sub a different tube. Even Curly would agree that is insane. The enclosure is pretty good mechanically with a very clean dial glass. Sadly, the speaker appeared to have been eaten by mice and there were droppings inside! Maybe I'll post some pictures. Not worth trying to resurrect it. Don't worry, I won't be buying anymore of these 48-461s. I'm in arrears on my allowance anyway.

Radio 2 is finished now. The external speaker jack and aux input work great. I am currently listening to the 40s stream from XMSirius via a bluetooth receiver plugged into the aux jack. The audio amplifier stage is remarkably good on this AA6 radio. Lots of brass back then compared to the strings (aka guitar) emphasis today. I find it refreshing. And Etta James. Don't get me started. I only destroyed one bluetooth receiver and one audio isolator while figuring it out. I would say YMBDN but Balti would have a heart attack. ;)

Oh, I've got a correction for Rocky. He posted earlier that I would use a dropping resistor to convert the 240Vac to 110Vac and burn down the house. Cute, but wrong. We would have to boost the voltage, not drop it (probably by replacing the power transformer). Maybe he should stick to software. :lol:

DG wants me to get going on the feature requests, so gonna start looking into BM3D.

Thank you for your support during the 48-461 days!
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Bullwinkle
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Philco 48-461 radio restoration

Post by Bullwinkle »

Thank you Sherman. It does indeed sound sweet on bluetooth with a good external speaker. You forgot to mention a couple other things you destroyed, but we'll let it go. The ends justify the means, right?

Marking resolved.
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Levi
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Philco 48-461 radio restoration

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Post by Britney »

Always wished that Etta James song was twice as long!

And now, the true founder of Rock and Roll:


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DG
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Philco 48-461 radio restoration

Post by DG »

Hi Sherman. Great job on radio 2 but I'm not quite ready to sign off on it. Can you take care of these things please?

1. Your aux input is not isolated, so B- (AC line neutral!) appears on the connector. You need to add an audio isolation transformer. The transformer can also have step-up to raise the audio level a bit. I have ordered some appropriate transformers and they will be in shortly.

2. You used a large phone plug for the external speaker jack. It is so long that the radio is forced too far away from the wall behind it. Please change that to a mono 3.5mm plug/jack. Again, I ordered them for you and they are already here.

3. You replaced the led dial bulb with a type 47 bulb. Not sure why you did that but it is simply too dim. Please put the led bulb back.

Thank you, and please keep us updated.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

OK, DG, will do. I replaced the bulb because I was worried about the rectifier tube filament. I'll add a resistor if needed with the led bulb.
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Rocky
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Post by Rocky »

Sherman, can you please add the aux input and speaker jack to radio 1 also? That's great stuff.
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Sherman
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Philco 48-461 radio restoration

Post by Sherman »

Sure, Rocky, I would be honored.
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