Rogers Model 551 Chassis 706

[Jerry Tombari]

I am restoring a Rogers Model 551 Chassis 706 (1931) radio and need data on alignment as well as anything else that you can provide. The radio is in bad shape and needs lots of work which I am looking forward to. Unfortunately the IF transformer primary is open and I can’t find the break. The transformer has three winding and I don’t know how to sub it. If I cant find a replacement I may have to abort the project and I don’t want to do that. I have never re wound a IF before so I’m a bit nervous to try.
Hope someone can help

[phil]

I will let others with more experience chime in . I have a 29 rogers but it is a TRF so no IF coils. I think I have a 1933 and it has been a few years but if my memory serves me correctly it said 255K IF on the schematic ,, so a more common 455 one wouldn’t work. also it was a center tapped IF transformer. mine was blown and someone helpful from the US took pity and sent me one which was just a super nice gesture. Posting a picture of it might prove helpful in case someone who isn’t a technical wizard might have a chassis that he can take it from? there may be other workarounds from the more experienced troubleshooters?
Phil

[Jerry Tombari]

Hi Phil. This may sound silly but what’s a TRF. I’m assuming the coil that I’m working on is an IF coil, it is located between the RF output tube and the audio output tube but it doesn’t have any tuning slugs just three separate windings.This is the earliest model radio that I’ve worked on so I thought that it would be fun. The 255K sounds like the right frequency but without any alignment info it is going to be a challenge unless I get more help.

[John Greenland]

Jerry;
let us Assume that the Rogers 706 chassis schematic that I have is the one for your radio (it has 2 Rogers 551’s followed by a Rogers 224 as the 3 front end tubes). This appears to be a regenerative type radio circuit. The only coil showing 3 windings appears to be the coupling coil from the 2nd RF amp (the 551) to the oscillator/detector tube (the 224). Two of the windings would be interstage coupling and the third smaller winding probably for the oscillator circuit. I would imagine that getting this radio to work without the proper coil assembly is going to be quite difficult. There are a couple of work-arounds depending upon which coil of the 3 is open.

Please note: that I am offering this as a possibility as I am a long ways from an expert in this type radio.

Good luck with your restoration;
John G. VO1 CAT

[Jerry Tombari]

Thanks John. Your schematic is the right one. The primary coil of the coupling coil is open the other two appear to be OK. Do you have a work around that I can try? In the mean time I was able to get some tiny wire and I might try and rewind it. The coil is the outer one on the coil assembly. I might be able to change it out. Again thanks for your help

[John Greenland]

Jerry;
The work around is one that I found on the net ( where else in this day & age). It involves bypassing the damaged winding with a resistor or small choke and then coupling the signal with a capacitor.

I have attached my idea if the plate winding is open.

Here is one of the articles on doing just that :
https://www.antiqueradios.com/forums/viewtopic.php?t=165802

TTFN; John VO1 CAT

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[John Greenland]

Jerry;

Minor correction, make sure the cap is good for 400 volts. Just to be on the save side.

TTFN; John G. Vo1 CAT

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