I am trying to get my Roger's Batteryless radio going. the tube lineup is R30 , R30 , R30 , 27 , 27 , 45 , 45 , 80
I have found a transformer between the two 27 tubes that seems to be open. there is a red wire from the power suply going in ,through one winding, and it goes out to the plate of the first 27. it had about 70 or so volts in the red wire going in , and nothing coming out.
to confirm my findings I removed the transformer and hooked up about 20 volts to the red wire , and ther was nothing coming out of the yellow wire
there is also a wire from the grid of the second 27 through the other winding in the transformer , then to ground. I think it is ok.
now the question, would anyone know how I could find out the ratio of this transformer? Is it worth trying to find a rreplacement , or must I rewind it ?
AES sells a replacement for these, which is small enough to take apart your old potted can and hide the new one inside. But many times if the secondary of the old transformer is OK, you can make it work by using a resistor in the range of 15K up to about 47K across the open primary, then add a capacitor about .01 to .047 from the plate to the lead from the secondary that goes to the grid of the next tube. You lose a little gain this way but it is a lot less work. The turns ratio of most of these is on the order of 1:3 but is not all that critical.
mrhuntnpeck wrote: > I am trying to get my Roger's Batteryless radio going. > the tube lineup is R30 , R30 , R30 , 27 , 27 , 45 , 45 , 80
> I have found a transformer between the two 27 tubes that seems to be > open. > there is a red wire from the power suply going in ,through one > winding, and it goes out to the plate of the first 27. it had about > 70 or so volts in the red wire going in , and nothing coming out.
> to confirm my findings > I removed the transformer and hooked up about 20 volts to the red > wire , and ther was nothing coming out of the yellow wire
> there is also a wire from the grid of the second 27 through the other > winding in the transformer , then to ground. I think it is ok.
> now the question, would anyone know how I could find out the ratio of > this transformer? Is it worth trying to find a rreplacement , or must > I rewind it ?
> it is in a large metal can sealed with tar.
> Phil
-- I don't know Jack Schitt, but once I met Diddley Squatt !!
If "nospam" appears in email address, please remove it to reply
I melted all the tar away , and took apart the transformer today . I thougt I might try my hand at rewinding it. it doesen't look easy though , the wire is pretty fine.
I looked through AES's website . I don't know which one would make a good match though.
I measured the resistance through the ... secondary ?, and it is about 7.6 k ,, would this make sense?
I am assuming that the primary is the one with the yellow from the plate of the first 27 , and then going to the 70 volts power supply. , and the secondary being the one going from ground , through to the grid of the seond 27
and I am also assuming that this would step up the power, and signal from 70 , to about 200 volts?
I could use some advice on which one would make a comparable replacement . would anyone know ? I am a little lost trying to figure this out.
also the schematic seems to show a wire tap off the secondary , and it approaces, a ground terminal , but it shows it terminating there , as if it is not connected to ground , but as if could be ,, like a jumper? it says something that I can't read there .
there were only 4 wires coming out from the transformer.
is this an interstage transformer?
the next transformer, the one after the second 27 feeds the two 45 tubes, and it seems to use two similar transformers , but they are centre tapped.
On Sat, 04 May 2002 23:09:43 -0400, Bonita Lee Geniac
<b...@NOSPAMwdl.net> wrote: >AES sells a replacement for these, which is small enough to take apart >your old potted can and hide the new one inside. But many times if the >secondary of the old transformer is OK, you can make it work by using a >resistor in the range of 15K up to about 47K across the open primary, then >add a capacitor about .01 to .047 from the plate to the lead from the >secondary that goes to the grid of the next tube. You lose a little gain >this way but it is a lot less work. The turns ratio of most of these is >on the order of 1:3 but is not all that critical.
>mrhuntnpeck wrote:
>> I am trying to get my Roger's Batteryless radio going. >> the tube lineup is R30 , R30 , R30 , 27 , 27 , 45 , 45 , 80
>> I have found a transformer between the two 27 tubes that seems to be >> open. >> there is a red wire from the power suply going in ,through one >> winding, and it goes out to the plate of the first 27. it had about >> 70 or so volts in the red wire going in , and nothing coming out.
>> to confirm my findings >> I removed the transformer and hooked up about 20 volts to the red >> wire , and ther was nothing coming out of the yellow wire
>> there is also a wire from the grid of the second 27 through the other >> winding in the transformer , then to ground. I think it is ok.
>> now the question, would anyone know how I could find out the ratio of >> this transformer? Is it worth trying to find a rreplacement , or must >> I rewind it ?
The turns ratio of the transformer steps up the signal level, not the DC voltage of 70 volts that you are measuring. The actual AC signal level there measured with an oscilloscope might be only a couple of volts, and for instance if the transformer were a 1:3 step up, that would give you about 6 volts of AC signal to the grid of the next tube. Most of the time you can use the AES P-T156 to replace interstage and driver transformers. There should be only four wires used in that interstage circuit, Plate, B+, grid, and ground. Dont know what you see on the schematic without having it to look at. Once in a while they had a shield of some sort on transformers that would need to be connected to ground. The primary and the secondary resistances could be on the order of many thousand ohms depending upon the gauge of wire which the transformer was wound with.
mrhuntnpeck wrote: > I melted all the tar away , and took apart the transformer today . > I thougt I might try my hand at rewinding it. it doesen't look easy > though , the wire is pretty fine.
> I looked through AES's website . I don't know which one would make a > good match though.
> I measured the resistance through the ... secondary ?, and it is about > 7.6 k ,, would this make sense?
> I am assuming that the primary is the one with the yellow from the > plate of the first 27 , and then going to the 70 volts power supply. > , > and the secondary being the one going from ground , through to the > grid of the seond 27
> and I am also assuming that this would step up the power, and signal > from 70 , to about 200 volts?
> I could use some advice on which one would make a comparable > replacement . would anyone know ? I am a little lost trying to figure > this out.
> also the schematic seems to show a wire tap off the secondary , and it > approaces, a ground terminal , but it shows it terminating there , as > if it is not connected to ground , but as if could be ,, like a > jumper? > it says something that I can't read there .
> there were only 4 wires coming out from the transformer.
> is this an interstage transformer?
> the next transformer, the one after the second 27 feeds the two 45 > tubes, and it seems to use two similar transformers , but they are > centre tapped.
> On Sat, 04 May 2002 23:09:43 -0400, Bonita Lee Geniac > <b...@NOSPAMwdl.net> wrote:
> >AES sells a replacement for these, which is small enough to take apart > >your old potted can and hide the new one inside. But many times if the > >secondary of the old transformer is OK, you can make it work by using a > >resistor in the range of 15K up to about 47K across the open primary, then > >add a capacitor about .01 to .047 from the plate to the lead from the > >secondary that goes to the grid of the next tube. You lose a little gain > >this way but it is a lot less work. The turns ratio of most of these is > >on the order of 1:3 but is not all that critical.
> >mrhuntnpeck wrote:
> >> I am trying to get my Roger's Batteryless radio going. > >> the tube lineup is R30 , R30 , R30 , 27 , 27 , 45 , 45 , 80
> >> I have found a transformer between the two 27 tubes that seems to be > >> open. > >> there is a red wire from the power suply going in ,through one > >> winding, and it goes out to the plate of the first 27. it had about > >> 70 or so volts in the red wire going in , and nothing coming out.
> >> to confirm my findings > >> I removed the transformer and hooked up about 20 volts to the red > >> wire , and ther was nothing coming out of the yellow wire
> >> there is also a wire from the grid of the second 27 through the other > >> winding in the transformer , then to ground. I think it is ok.
> >> now the question, would anyone know how I could find out the ratio of > >> this transformer? Is it worth trying to find a rreplacement , or must > >> I rewind it ?
> >> it is in a large metal can sealed with tar.
> >> Phil
-- I don't know Jack Schitt, but once I met Diddley Squatt !!
If "nospam" appears in email address, please remove it to reply
mrhuntnpeck wrote: > I melted all the tar away , and took apart the transformer today . > I thougt I might try my hand at rewinding it. it doesen't look easy > though , the wire is pretty fine.
> I looked through AES's website . I don't know which one would make a > good match though.
> I measured the resistance through the ... secondary ?, and it is about > 7.6 k ,, would this make sense?
> I am assuming that the primary is the one with the yellow from the > plate of the first 27 , and then going to the 70 volts power supply. > , > and the secondary being the one going from ground , through to the > grid of the seond 27
> and I am also assuming that this would step up the power, and signal > from 70 , to about 200 volts?
> I could use some advice on which one would make a comparable > replacement . would anyone know ? I am a little lost trying to figure > this out.
> also the schematic seems to show a wire tap off the secondary , and it > approaces, a ground terminal , but it shows it terminating there , as > if it is not connected to ground , but as if could be ,, like a > jumper? > it says something that I can't read there .
> there were only 4 wires coming out from the transformer.
> is this an interstage transformer?
> the next transformer, the one after the second 27 feeds the two 45 > tubes, and it seems to use two similar transformers , but they are > centre tapped.
Be sure to inspect the windings where they connect to the terminals. That is a location that the wire can open up. If you find a break there you may be able to put a jumper over the broken section.
> I melted all the tar away , and took apart the transformer today . > I thougt I might try my hand at rewinding it. it doesen't look easy > though , the wire is pretty fine.
> I looked through AES's website . I don't know which one would make a > good match though.
> I measured the resistance through the ... secondary ?, and it is about > 7.6 k ,, would this make sense?
> I am assuming that the primary is the one with the yellow from the > plate of the first 27 , and then going to the 70 volts power supply. > , > and the secondary being the one going from ground , through to the > grid of the seond 27
> and I am also assuming that this would step up the power, and signal > from 70 , to about 200 volts?
Hi. If I may comment also?
I just went and measured the primary (input) winding of an old interstage transformer and it is 2300 ohms. So that means your 7,600 ohm secondary is probably in the right range, seeing as how it it is wound with many many turns of very, very fine wire! Gosh and I didn't know, until now, the secondary of mine was open!!!
I agree with Bonita; transformers don't step up (or down) DC voltages. They only work with AC voltages which vary up and down. OK?
The AC, in this instance is the 'audio sound component' of the signal. As you indicated in your earlier post the primary winding of your interstage trans. is open; therefore AC cannot be transformed into the grid circuit of the next tube.
The audio AC is what you get after the radio signal has gone through the detector circuit of the radio. When you tune the radio between stations there is no audio signal (well apart from some hiss and noise etc.) so there is nothing to pass along the next stage through that transformer.
As you pointed our, that there was not a positive potential on the plate of the preceding tube so no DC current flowed through the transformer winding to that tube and it was not being powered at all! So, no audio! Good fault finding on your part, indicating as you said, that that transformer primary winding was 'open'.
A further comment if I may, subject to correction if anyone wishes; the primary winding that you refer to may be wound with somewhat (slightly) heavier wire than the secondary because it has to carry the DC current through to the plate of that tube, even though it may only be a few milliamps! Whereas the secondary is required to carry no DC current at all (virtually so) to the grid circuit of the next tube.
Darn; now I've got to investigate that open secondary of my interstage trans! I'd always assumed it was good, intending to use it, one of these days, years, eons to construct a tube audio amp. Oh well.
Good luck with yours or one of the 'work around' ideas suggested..
This is an old post, but it took a while. I am sitting back listening to my 1929 rogers batteryless The problem was caused by not only one interstage transformer, but two. The other was centre tapped, for the grids of the 45 tubes.
I ordered the P-T156 from AES as Bonita suggested, and it was much smaller than the origional, but they both seem to work fine.
before I found that problem I had to find some open resistors, and as a matter of course, replaced the caps.
I still need to do the allignment, and plenty of cosmetics, but it is a great feeling to (finally) hear some sound come out. it actually tunes in the stations on one end really well , until the capacitor closes , and starts touching, but that is a straightforeward problem.
Thanks to all who helped with this
phil
On Mon, 06 May 2002 10:58:49 -0400, Bonita Lee Geniac
<b...@NOSPAMwdl.net> wrote: >The turns ratio of the transformer steps up the signal level, not the DC >voltage of 70 volts that you are measuring. The actual AC signal level there >measured with an oscilloscope might be only a couple of volts, and for instance >if the transformer were a 1:3 step up, that would give you about 6 volts of AC >signal to the grid of the next tube. Most of the time you can use the AES >P-T156 to replace interstage and driver transformers. There should be only >four wires used in that interstage circuit, Plate, B+, grid, and ground. Dont >know what you see on the schematic without having it to look at. Once in a >while they had a shield of some sort on transformers that would need to be >connected to ground. The primary and the secondary resistances could be on the >order of many thousand ohms depending upon the gauge of wire which the >transformer was wound with.
>mrhuntnpeck wrote:
>> I melted all the tar away , and took apart the transformer today . >> I thougt I might try my hand at rewinding it. it doesen't look easy >> though , the wire is pretty fine.
>> I looked through AES's website . I don't know which one would make a >> good match though.
>> I measured the resistance through the ... secondary ?, and it is about >> 7.6 k ,, would this make sense?
>> I am assuming that the primary is the one with the yellow from the >> plate of the first 27 , and then going to the 70 volts power supply. >> , >> and the secondary being the one going from ground , through to the >> grid of the seond 27
>> and I am also assuming that this would step up the power, and signal >> from 70 , to about 200 volts?
>> I could use some advice on which one would make a comparable >> replacement . would anyone know ? I am a little lost trying to figure >> this out.
>> also the schematic seems to show a wire tap off the secondary , and it >> approaces, a ground terminal , but it shows it terminating there , as >> if it is not connected to ground , but as if could be ,, like a >> jumper? >> it says something that I can't read there .
>> there were only 4 wires coming out from the transformer.
>> is this an interstage transformer?
>> the next transformer, the one after the second 27 feeds the two 45 >> tubes, and it seems to use two similar transformers , but they are >> centre tapped.
>> On Sat, 04 May 2002 23:09:43 -0400, Bonita Lee Geniac >> <b...@NOSPAMwdl.net> wrote:
>> >AES sells a replacement for these, which is small enough to take apart >> >your old potted can and hide the new one inside. But many times if the >> >secondary of the old transformer is OK, you can make it work by using a >> >resistor in the range of 15K up to about 47K across the open primary, then >> >add a capacitor about .01 to .047 from the plate to the lead from the >> >secondary that goes to the grid of the next tube. You lose a little gain >> >this way but it is a lot less work. The turns ratio of most of these is >> >on the order of 1:3 but is not all that critical.
>> >mrhuntnpeck wrote:
>> >> I am trying to get my Roger's Batteryless radio going. >> >> the tube lineup is R30 , R30 , R30 , 27 , 27 , 45 , 45 , 80
>> >> I have found a transformer between the two 27 tubes that seems to be >> >> open. >> >> there is a red wire from the power suply going in ,through one >> >> winding, and it goes out to the plate of the first 27. it had about >> >> 70 or so volts in the red wire going in , and nothing coming out.
>> >> to confirm my findings >> >> I removed the transformer and hooked up about 20 volts to the red >> >> wire , and ther was nothing coming out of the yellow wire
>> >> there is also a wire from the grid of the second 27 through the other >> >> winding in the transformer , then to ground. I think it is ok.
>> >> now the question, would anyone know how I could find out the ratio of >> >> this transformer? Is it worth trying to find a rreplacement , or must >> >> I rewind it ?
Glad to hear you got it working with the transformer. That is a good part to keep in stock if you plan on repairing any radios that use interstage transformers as they are often bad. Even though it is physically smaller than the originals, you cant really hear any difference in perfomance. And it sure beats trying to rewind one of the old ones.
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