My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf

Brian

That's an unusual transformer with a single tapped secondary. You will need to make changes but available power transformers are here:

http://www.oldradioparts.com/2a23efl.txt

Be sure a replacement transformer fits on the chassis.

Norm

:My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
:I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
:http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf
:
:

Norm,

It is kinda an odd duck. It looks like the tube filaments are in series and have to be supplied with around 25 volts from the secondary.

Clifton

:Brian
:
: That's an unusual transformer with a single tapped secondary. You will need to make changes but available power transformers are here:
:
:http://www.oldradioparts.com/2a23efl.txt
:
: Be sure a replacement transformer fits on the chassis.
:
:Norm
:
::My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
::I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
::http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf
::
::
:
:

Filaments could be rewired to parallel. Then all would be needed is a transformer with two secondaries. One 300 volts @ about 50 ma and the other 6.3 volts @ 2 amps.

I agree, very difficult to find the exact transformer.

Norm

:Norm,
:
:It is kinda an odd duck. It looks like the tube filaments are in series and have to be supplied with around 25 volts from the secondary.
:
:Clifton
:
:
::Brian
::
:: That's an unusual transformer with a single tapped secondary. You will need to make changes but available power transformers are here:
::
::http://www.oldradioparts.com/2a23efl.txt
::
:: Be sure a replacement transformer fits on the chassis.
::
::Norm
::
:::My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
:::I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
:::http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf
:::
:::
::
::
:
:

I just found a transformer in my junkpile that is almost physically the same size (the lamination section is slightly 'thinner' than the RCA100), and it would mount easy....Trouble is, I need some help to figure out what the leads are (I know there is a code for tranny wires, but these are faded and don't seem to match the standard code). Looks like I found the primary side (still had a piece of the power cord attached)...There are 8 other leads coming out, of which 6 were taped over (as if they weren't used), the other 2 wires go to some sort of a 2 round prong plug as if it went into a female socket on a chassis.
Any ideas here to de-code this? It has the code 'E-1041' stamped on it, and the number '17' also.

Brian

Generally black is AC input, red - high voltage with a centertap, green - 6.3 volts, yellow - 5 volts.

Since you may not be able to tell with faded colors next best is using an ohm meter. AC input, which you found, will most likely read in 10 - 30 ohm range. Filaments both 6.3 and 5 volts almost zero ohms. Red - high voltage - a couple hundred ohms with center tap about half way between the two.

Any extra wires may be filament center taps?

Norm

:I just found a transformer in my junkpile that is almost physically the same size (the lamination section is slightly 'thinner' than the RCA100), and it would mount easy....Trouble is, I need some help to figure out what the leads are (I know there is a code for tranny wires, but these are faded and don't seem to match the standard code). Looks like I found the primary side (still had a piece of the power cord attached)...There are 8 other leads coming out, of which 6 were taped over (as if they weren't used), the other 2 wires go to some sort of a 2 round prong plug as if it went into a female socket on a chassis.
:Any ideas here to de-code this? It has the code 'E-1041' stamped on it, and the number '17' also.
:

Thanks for the info Norm...Is there any advantage of hooking the tranny's 120vac primary leads up to a Variac, and then measuring the voltages on the unknown wires, or isn't that practical?

Brian

That's a good idea. It will also show if the transformer is shorted. Prevent blowing a breaker...

Norm

:Thanks for the info Norm...Is there any advantage of hooking the tranny's 120vac primary leads up to a Variac, and then measuring the voltages on the unknown wires, or isn't that practical?
:

Right. If you don't find a 340 volt tranny with a 25 volt tap, you could rewire the heaters, I think, so they are in parallel. Then any tranny with a 6.3 filament winding will work.

The restriction then, as Norm mentioned, will be size.
I am too far away in Canada to send you a used transformer. You would have to pay the bomb squad at customs on top of the shipping. Good luck.

:Norm,
:
:It is kinda an odd duck. It looks like the tube filaments are in series and have to be supplied with around 25 volts from the secondary.
:
:Clifton
:
:
::Brian
::
:: That's an unusual transformer with a single tapped secondary. You will need to make changes but available power transformers are here:
::
::http://www.oldradioparts.com/2a23efl.txt
::
:: Be sure a replacement transformer fits on the chassis.
::
::Norm
::
:::My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
:::I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
:::http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf
:::
:::
::
::
:
:

Sorry, Norm, for stepping on your more elegant response.

I wonder if sometimes the design of the radio was matched to parts that were readily available at the time? Maybe that was a cheap transformer so they drew up a circuit that could utilize it? Just speculating.

:My friend has an RCA-100 radio (the schematic is here on a thread I started about a few days ago)...The power tranny is bad, starts getting hot, even without the rectifier plugged in. There is also that black 'tar' stuff underneath that oozed out. So I'm assuming its bad.
:I am trying to help him find a tranny (used, not new due to cost). Does anyone have something that would work, in their boneyard, for this set?
:http://www.nostalgiaair.org/PagesByModel/764/M0015764.pdf
:
This odd-ball transformer was most likely used cut $ from the radio. Where do you live? I have a chassis with good transformer (other parts missing) that I might trade for something. I have no idea what to sell it for, and then there are shipping costs. I have another working radio; not a bad performer for a simple superhet. EdM

EdM---The transformer/chassis you mention, is it from the same model as I need RCA100, or is it just one from your boneyard?

:EdM---The transformer/chassis you mention, is it from the same model as I need RCA100, or is it just one from your boneyard?
:
I will check when I go home from work for exact model number that I have, and get back with you Monday. I am very familiar with this type of set - RCA sold a number of them. They use 1-V rectifier, and other tubes are in a series string. Made under contract for RCA by a small company near Lynchburg Virginia, not too far from where I grew up. I had a great uncle who was an engineer there, and could tell some interesting stories about discussions about target customers, pricing, performance, reliability, and planned obsolence, that went on within the ranks of RCA. I now live in Texas. EdM

::EdM---The transformer/chassis you mention, is it from the same model as I need RCA100, or is it just one from your boneyard?
::
:I will check when I go home from work for exact model number that I have, and get back with you Monday. I am very familiar with this type of set - RCA sold a number of them. They use 1-V rectifier, and other tubes are in a series string. Made under contract for RCA by a small company near Lynchburg Virginia, not too far from where I grew up. I had a great uncle who was an engineer there, and could tell some interesting stories about discussions about target customers, pricing, performance, reliability, and planned obsolence, that went on within the ranks of RCA. I now live in Texas. EdM
:
Looks like there are several things RCA called a Model 100. Is your's like the Model 101 / 100, using 1-V rectifier tube, or the RCA 100 using 80 or UX 80 tube? I have the ones with the 1-V tube. One of the IF cans is unshieded, and under the chassis. Ed M

Ed, I have the one with the 1-V rectifier...Thanks for helping, let me know what you have, when you get the chance....