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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Wed 14, 2018 4:56 am 
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Copiertech wrote:
Google translate will automatically translate the forum threads...

Wow...I'm so behind all this technology. I'll join that forum and see if anyone can help. Thanks again.

AJJ wrote:
...the T573 is sufficient for servicing the T574 (schematic downloaded from radiomuseum)


I do have that schematic. But there are two problems. The download from RadioMuseum is very low rez and certain sections are unclear (most of the component values are unreadable). Also, the T573 did not have the 4 switches in question. So that schematic won't that.

However, I made up a schematic of the 4 tone switches.

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Sorry I don't have all resistor values, yet. I believe the red line is signal input and the other 3 colors must be outputs, but as of yet I don't know exactly how they are wired back to the chassis. Only one switch at a time cna be pressed in (upwards on the schematic) and the 1st switch is not wired, just mechanically disengaging any other witches when pressed.

AJJ wrote:
The "heat" problem you noted appears to be an issue with the placement of storage space, not impacting performance of electronics. Maybe there's a way to put a thin sheet of styrofoam under the plastic tray?


Tefifon did not fabricate their own chassis. They purchased those and just assembled them into their own radios. That's why the placement of the tubes was not ideal. Although they did move one tube away, onto a mounted bracket, there is still one rectifier tube under the cassette tray. I have one cassette with the melted tape and I wonder if it was caused by this problem.

Is the concern that any fan might interfere with radio?




One more question. I already did most of the recap work, but am missing a couple of caps. Since I need to order more.... Are there any caps, that might need to be replaced, inside the typical metal enclosure that I believe is the radio receiver? I didn't open that cause this is my first time and didn't want to mess with that part. But since I'm ordering caps I wanted to know if there are any caps in that place.

Thanks...


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Wed 14, 2018 5:25 pm 
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Adinol wrote:
.... Are there any caps, that might need to be replaced, inside the typical metal enclosure that I believe is the radio receiver? I didn't open that cause this is my first time and didn't want to mess with that part. But since I'm ordering caps I wanted to know if there are any caps in that place.


Based on the way the schematic is drawn, I'm assuming you mean the portion of the radio that has the pair of ECC85 tubes. Regardless, the only way to know for sure is to look inside.


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Wed 14, 2018 7:21 pm 
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ONE ECC85---2 sections

I always open up these enclosures....for inspection, cleaning, check resistors, etc. do you have the parts list?....that should tell you if there are any electrolytic or paper caps.

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Wed 14, 2018 10:42 pm 
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Adinol wrote:
AJJ wrote:
They do make direct LED bulb for replacements these existing incandescent lamps.


Are those some kid of LED's with the same light bulb sockets? I have not seen any such LED's on the sites I've been studying. Is there a link? Or a technical name I can Google? Thanks.

https://www.pinballlife.com/index.php?p=product&id=2561

https://www.pinballlife.com/index.php?p=product&id=3108

Here's my Zenith 6S254 with one on each side of the dial;


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Thu 15, 2018 3:45 pm 
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Thanks for posting the photo of your Zenith, fifties. An LED upgrade is definitely in the works for me. However, since my radios all have a those long dial glasses, I wonder if an LED strip would be a better option (with a separate 12V power supply). Anyway, the illumination is not at the top of the list of priorities, so....

This thread is not specific to servicing one unit. I am working on 4 radios at once, so following is a mix.

First, my Tefifon T754.

I opened the enclosure, inspected the components, all was good, did a little bit of cleaning, took the opportunity to clean the shell of the enclosure and put it all back together. There were no electrolytic or film caps in there and noting looked overheated. The photos:

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Next is a picture from a Loewe Opta stereo. I found a smashed radio on the street a year ago, so I removed the chassis and the speaker. I will be building my own cabinet for that one. The enclosure is easy to open from the bottom, but too much additional dismantling is needed to remove the PCB. However, when the bottom cover is off I can peek at the sides and I see no electrolytic or film caps in there. So, I think I'll just leave it alone. Here's the photo:

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Last is a photo from a third enclosure. As you can see this one is soldered (in 5 spots). As you know the whole enclosure is a massive heat sink for a soldering iron and I didn't get anywhere melting the solder off of the first solder spot. I am also assuming some of the solder must be trapped in the thin crack where the two plates overlap. It's probably a nightmare trying to desolder this thing. Unless you guys have some tricks and techniques that might help me.

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I have a feeling that the odds of finding electrolytic caps in there are slim (and perhaps the same for film caps). But I wonder if there's a way to open it.

Thanks....


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Thu 15, 2018 7:09 pm 
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Unless you know there is a problem or they are easy to open I wouldn't open those tuner boxes. You are right they almost never have electrolytics. The caps are also usually small value mica and ceramic. A resistor might drift but usually because there isn't much power used the resistors usually are OK.
Otherwise a large wattage iron, solder sucker and de-soldering wick. More likely to do more harm tan good.

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Fri 16, 2018 3:41 pm 
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In spite of what I said earlier, I agree with Notime*.

I am a card-carrying OCD case, and---when it is reasonable---I open things for cleaning and inspection----especially when the overall chassis comes to me with a 1" layer of dirt.

RF cans do sometimes have P/W caps, and they also can have stuck trimmers or spots that need a drop of oil.

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Fri 16, 2018 5:59 pm 
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Sorry for mis-identifying the single ECC85 as a pair earlier; I should've waited until I finished my morning coffee.

Some of us have learned to inspect everything and leave nothing to chance. But another lesson many have learned (sometimes repeatedly) is not to go beyond our ability and touch/adjust/open/tighten/move/clean/modify/fix things we don't fully understand. It's heartbreaking when you break or "mess up" an item that's expensive or not replaceable.

You're a self-identified "newbie" and are working on multiple complex sets. It's wise not to take on an uncomfortable task. You can always come back to refine your work and open the RF/converter section later.


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Fri 16, 2018 6:25 pm 
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AJJ wrote:
...another lesson many have learned (sometimes repeatedly) is not to go beyond our ability...

...You can always come back to refine your work... ...later...


That's precisely the lesson I learned, already 2 times, since I've started servicing my sets.

1st time - I used welding tip cleaners (like little files) to clean the tube sockets and in the process removed the plating.

2nd time - I straightened the blades on the tuning capacitor, thinking someone was in there and bent them by accident.

I wasn't going to make a 3rd mistake without asking first. But I think a 3rd mistake is inevitable at some point in my future.


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Fri 16, 2018 7:41 pm 
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AJJ wrote:
But another lesson many have learned (sometimes repeatedly) is not to go beyond our ability and touch/adjust/open/tighten/move/clean/modify/fix things we don't fully understand.

Eh eh, reminds me of a line from a Clint Eastwood flick (can't remember which), where he said, "a man's got to know his limitations"... :wink:

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Fri 16, 2018 9:08 pm 
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Adinol wrote:
But I think a 3rd mistake is inevitable at some point in my future.
We all learn from our mistakes.

That's why I'm a genius.

- Leigh

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Mon 19, 2018 10:17 pm 
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Capacitor polarity / black line

the unpolarised caps normally have a black line at one end. They are not a reliable indicator unfortunately.
these " unpolarised " caps have a " shield " , the exterior part of the cap , the outer layer. this can be put to advantage in rf and af circuits where we want to have all the shielding we can get. ex in the cathode circuit where we have a resistor/ cap parallel combination going to ground , well we'd install the cap with the shield end at the ground. To find which is which , check manufacturer data sheet or build yourself a small setup with a scope.

https://youtu.be/BnR_DLd1PDI this is a good video .

Hope this helps you.


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Mon 19, 2018 11:38 pm 
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No offense, FuzztBear, but that one 'expert's videos do not prove he is right. They just prove he can differentiate the outer shell of a capacitor from the inner layers, and so what?

At the frequencies that an AM radio operates, the polarity of a film cap amounts to a gnat's fart of difference in frequency response or dB or milliWatts of output or whatever.
In other words, a self-confessed newbie can just focus on making good solder joints, keeping his components isolated from their surroundings, and keeping all leads short as possible. Just doing that will give results that can be measured by the human ear. :lol:

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Tue 20, 2018 12:40 am 
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I was actually asking about that same video in my initial post, in this thread. Right here:

Adinol wrote:
I read on http://www.justradios.com that new film caps do not have a polarity. However, in this video https://www.youtube.com/watch?v=BnR_DLd1PDI&t=2335s the host says that new film caps do in fact have a polarity and should be installed with outer shield on the negative.


Members already replied that this issue is not relevant for these radios.

There is one detail that I am unclear about, though.

As I was recapping I noticed that all the old paper caps have a black band, which was always connected to ground. So, the old factories did mount their paper caps as explained in that YouTube video.

So, if this issue is not relevant for old tube radios, why did the old factories install their paper caps that way?

I just want to make sure there is no misunderstanding. I am not disputing anyone. I am simply trying to understand.

Thanks...


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Tue 20, 2018 1:47 am 
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The old rolled paper caps were a different animal than the modern film caps, number one. Number 2, no, they are not all marked or polarized. And number 3, are you sure they were always oriented with the outer shell more negative when they left the factory?

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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Tue 20, 2018 2:08 am 
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I also have to admit that there is one detail in that YouTube video that I could not make sense of.

The host shows on the scope that the cap produces more noise when he is holding the cap by the body. So, the antenna is the human body, not the cap itself. Or perhaps, in theory the cap is also an antenna, but picks up a signal that is not even showing up on the scope.

In practice, one would not be holding the caps by their bodies when the radio is running. Also, in a radio most of those caps are inside the chassis, which is ground.

So, I have to admit that I was also struggling to make sense of that video.

Of course, as a self described newbie I can't say that I know from experience that all the paper caps have a band at the negative end. All I can say is that the 4 radios I am currently working on (and I also bought a 5th one) do have paper caps with the marked side all soldered to ground. Although that makes up 100% of my personal experience it is clearly not real experience in the world of radio repair.

It would still be interesting to know why some factories followed this practice with paper caps.


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 Post subject: Re: Need Newbie Clarifications on Tube Radio Restoration
PostPosted: Feb Tue 20, 2018 2:12 am 
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If we can stand some "over-clarification"......
The old-time outer-foil thing was never about "polarity"---that means the correct orientation of a device that has properties dependent on whether voltage or current is positive or negative.

If I may be allowed a "parochial moment"---be wary of trying to learn this stuff on Youtube. There is no quality control there. Here, there is some informal quality control, if only because the membership will quite quickly challenge statements that are misleading or outright wrong. To be sure, you might have to witness some little ego contests, but the correct answer almost always bubbles to the top.

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