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 Post subject: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 4:16 am 
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Joined: May Thu 18, 2017 4:09 am
Posts: 23
Location: Eastern Washington
I have this old TRF I pulled out to finally restore. It is battery powered and appears to be a home built system. Is there something​ out there I can read on how to build an actual tubed dual knobbed TRF? I feel like I'm going at this blind. I thought it wouldn't be harder than my RCA Victor, but that has a schematic in the back.
I can upload and post images, if needed, or go read whatever manuals or articles or sites you guys think I should.

Album of some pics I took. I'm not sure what pics are needed most:
http://imgur.com/a/o4P87


Last edited by Isky on May Thu 18, 2017 5:15 pm, edited 1 time in total.

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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 3:54 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Livermore, CA
Hi and welcome

If your radio is a 5 tube type made in 1920's may be able to use the following schematics? Most radios built at the time were very similar.

http://www.nostalgiaair.org/pagesbymode ... 029794.pdf

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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 5:03 pm 
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Joined: May Thu 18, 2017 4:09 am
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Location: Eastern Washington
That does look like it could help a lot! Thank you!


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 10:09 pm 
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Joined: Jan Mon 30, 2012 2:03 am
Posts: 254
Location: Port Orchard, Wa
Are you sure its not a neutrodyne? A vast number of 5 tube neutrodynes were built using the Fada booklet

"How to Build Hazeltine's Neutrodyne Circuit Radio Receiver",And Fada RF coils. There are usually one or

two of these an Ebay at any given time. http://www.ebay.com/itm/Antique-Neutrod ... 0400030917 And the booklet is always available in PDF or CD-ROM form

http://www.ebay.com/itm/How-to-Build-Ha ... SwxYxUwYLz


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 10:21 pm 
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Joined: May Thu 18, 2017 4:09 am
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Location: Eastern Washington
It very well could be. I'll research. Thank you for responding.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 10:49 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: S. Dartmouth MA 02748-1225 USA
That radio does not appear to be a Neutrodyne...

It looks like a regenerative set with replaceable coils, for possibly shortwave. It has a resistance coupled 3 stage amplifier and most of the filament controls are using Amperite cartridge ballasts. A clue to being a regenerative detector is the RF choke.

Someone has added an RCA phono jack to the front panel in "modern" times. Built probably from a magazine or plans. They certainly did not spare on the parts :o

There may be neutralization for the RF amp, there is not enough detail to determine if there is or what it is. Often, it is just a metal plate in vicinity of the antenna coil but it may be a 3 plate trimmer.

IMHO, draw out the schematic that will detail how it all works...

YMMV

Chas

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There Are None So Blind As Those Who Will Not See: John Heywood, 1546


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Thu 18, 2017 10:53 pm 
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I added to my notes, before I read the last message: just draw a diagram and replace parts until it works?
That might be the plan. I don't really want a short wave, but some of my friends might be interested in it once I have it working.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 12:05 am 
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Isky wrote:
I added to my notes, before I read the last message: just draw a diagram and replace parts until it works?
That might be the plan. I don't really want a short wave, but some of my friends might be interested in it once I have it working.
One needs to know how it works, then test parts for failure. All of the parts are unique to the early '20's. They cannot be bought as drop in replacements NOS. Certain parts can be gutted and new internal component installed. That is if one wants an undetectable repair...
The coils installed are more than likely for BC band.

GL

Chas

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There Are None So Blind As Those Who Will Not See: John Heywood, 1546


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 12:14 am 
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I'm not terribly worried about undetectable repair. I'll keep photos and all the old parts in a bag or container labeled for where they go inside the radio in case someone else cares, later.

I was just thinking replace all the caps and build battery banks before I power it up. Then check to make sure all wires are intact. (or do that first) Then make sure everything has power actually getting to it. Then resistors, right? The same way I did for my RCA Victor. It worked until I moved. (I need to replace a few more wires in it that I didn't get to before I moved. They were just "good enough" at the time.

I don't need to understand how THIS circuit works, just tubed radio circuits in general, right? Or are they really that specific?


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 2:01 am 
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I'm sorry, I totally missed the link and never saw the pictures. I agree with Chaz. Definitely not a neutrodyne.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 9:05 pm 
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It's okay. I still liked reading the book.

I am going to work on a diagram of what I have right now. I've forgotten some of the symbols, so I'm starting there. Then, I'll make sure I understand what each part does... and replace all the capacitors before I power it up.

Trying to decide between building a battery pack and making a transformer right now.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 9:34 pm 
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Do not change any capacitors or resistors until the entire radio is documented. There are some components missing, the drawings will determine what is missing. Do not disturb any variable capacitor that does not have a front panel adjustment. Such a cap is probably for neutralizing. To reset such a variable capacitor requires a specific process.

There are many "Fans" of homemade 20's receivers on ARF. The restoration process is both fun and educational.

https://www.tubesandmore.com/products/kit-power-supply will economically power this radio.

Here is a recent topic that may be of interest:

viewtopic.php?f=6&t=319885

GL

Chas

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There Are None So Blind As Those Who Will Not See: John Heywood, 1546


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 10:56 pm 
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Location: Eastern Washington
Chas wrote:
Do not change any capacitors or resistors until the entire radio is documented.



I did just say that. :P And that'd I'd make sure I understand what each part does before I mess with it. I promise not to break it worse than it already is.

Thanks for the links. The power supply kit looks very simple to put together, and easier than doing all of it myself.

What I've been looking for is really what it should look like, to be able to know what might be missing. I haven't ever worked on a radio older than about 1945. This thing has some similarities, but not enough for me to be sure what I'm doing. I do know messing with variable capacitors is over my head and outside of the testing equipment I'm willing to buy, though. I just have to hope those aren't bad. I meant to replace the "paper" ones. (I'm not sure the accurate term for those, but they look like paper tubes to me.)


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Fri 19, 2017 11:49 pm 
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So what your looking for is an example schematic approximate to what you have?

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There Are None So Blind As Those Who Will Not See: John Heywood, 1546


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Sat 20, 2017 12:27 am 
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Yes, and more understanding of how they work. I'm now learning a lot from a guy at work about radios and amplification.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Sat 20, 2017 5:02 am 
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I have a part that's not even connected to anything. Sigh

But, I did find the missing two resistors floating around in the cabinet. :/


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Mon 22, 2017 1:33 am 
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Joined: Mar Sat 08, 2008 3:21 am
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Location: hillsborough, nc
It looks like a very nice set to restore and use, especially if it is a regen.
In fact, I'd probably make it a regen even if it's not!
I don't see a feedback winding, but it may be there...
The A and B bats would likely be way too big for the cabinet, or it ran on AC.
Once you get it going, there's room for a power supply inside, which would make it very practical for setup and use.
The Bradley shiny thingies are rheostats, used to control filament voltage on tubes, a way to control gain of amplifiers.
Let's see that schematic, just a few hours work!
WL


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Mon 22, 2017 3:32 pm 
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I've made a drawing, but it's so messy it's not exactly helpful. I have two components I can't identify. I did notice the rheostats said they were once I cleaned the dust off. I also found the two missing resistors floating around loose, but I'm not sure which one goes where... Though I suspect the hand labeled one goes on the spot by the added RCA jack. Photos incoming after I clean up the diagram. I've learned quite a bit along the way. I didn't know condensers were capacitors, so I thought the receiver only had one capacitor, and was trying to figure out how that could work. The feedback winding appears to be inside the coils. I don't even know what one of the switches does. Glass resistors are a new thing for me. That's cool! It does have a battery, but also has maybe AC power? I'm off to work at the job that pays me. I'll shrink and poet pics on break.


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Mon 22, 2017 4:01 pm 
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Joined: Mar Sat 08, 2008 3:21 am
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Location: hillsborough, nc
Feedback winding will be just a few turns.
The old resistors were glass to obtain the very high resistance needed and stay stable.
The diagram will take several iterations of cleanup/verification, been there.
Once you get it to "standard" layout, the functions will be pretty clear.
Study the diagrams of simple regens and you'll similar circuitry, if it is in fact a regen.

Having only one coil is a very good sign!
WL


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 Post subject: Re: Antique Homebrew or Kit - need help bringing her alive
PostPosted: May Mon 22, 2017 4:07 pm 
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Location: Eastern Washington
It has two coils that look more modern than I would expect for the age of the rest of the radio. Inside each is a much smaller winding in wire tinted green. Those are a small amount of windings, maybe 10. I'll have to count them. They are not wrapped around anything and just tucked into the larger coils.


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