I'm working on a 1949 Stromberg-Carlson AM/FM radio, and I suspect that the filter choke in the power supply is bad. I have two questions:

1. Is it correct that if I don't get a continuity reading through the two leads of the choke that it is bad?

2. Assuming that I have to replace it, the schematic calls for .028 amps dc current; 320 ohms dc resistance; 5 henries inductance. The choke is relatively small, like a 1.5-inch cube. I don't see anything like it in the antique electronic supply catalogue. Can someone tell me how critical those ratings are? Which ones might be flexible? Thanks.

Hi Mike

You are correct, no continuity on a choke means it's open. Value isn't critical. Higher the henery the better filtering.

AES P-T155H is rated 5 henry, .050 amps & 270 ohms. This one will work. (page 28 in catalog)

Do you have any small transformers in your junk? Primary of an output transformer will also do the job.

Norm

:I'm working on a 1949 Stromberg-Carlson AM/FM radio, and I suspect that the filter choke in the power supply is bad. I have two questions:
:
:1. Is it correct that if I don't get a continuity reading through the two leads of the choke that it is bad?
:
:2. Assuming that I have to replace it, the schematic calls for .028 amps dc current; 320 ohms dc resistance; 5 henries inductance. The choke is relatively small, like a 1.5-inch cube. I don't see anything like it in the antique electronic supply catalogue. Can someone tell me how critical those ratings are? Which ones might be flexible? Thanks.

OK, Thanks again, Norm.

:Hi Mike
:
: You are correct, no continuity on a choke means it's open. Value isn't critical. Higher the henery the better filtering.
:
: AES P-T155H is rated 5 henry, .050 amps & 270 ohms. This one will work. (page 28 in catalog)
:
: Do you have any small transformers in your junk? Primary of an output transformer will also do the job.
:
:Norm
:
::I'm working on a 1949 Stromberg-Carlson AM/FM radio, and I suspect that the filter choke in the power supply is bad. I have two questions:
::
::1. Is it correct that if I don't get a continuity reading through the two leads of the choke that it is bad?
::
::2. Assuming that I have to replace it, the schematic calls for .028 amps dc current; 320 ohms dc resistance; 5 henries inductance. The choke is relatively small, like a 1.5-inch cube. I don't see anything like it in the antique electronic supply catalogue. Can someone tell me how critical those ratings are? Which ones might be flexible? Thanks.

The choke abouve costs about $10 plus shipping.
I agree as far a sticking to oroginal-looking parts, replacing the choke is the best but if you want to save money and improve things too...
check out this.
Radiodoc suggested this link in another related thread:
http://www.antiquewireless.org/otb/resto0504.htm

It is an "active choke" or better described as an active circuit for use as a choke replacement.

I ordered up the parts and built it. Great! Cheap too. less than $3 for the whole thing (I used a varible pot for r2) .... and what beautiful smooth DC you'll get. Ripple is virtually zero.

The last "used" choke I bought was $4 plus shipping.

:The choke abouve costs about $10 plus shipping.
:I agree as far a sticking to oroginal-looking parts, replacing the choke is the best but if you want to save money and improve things too...
:check out this.
:Radiodoc suggested this link in another related thread:
:http://www.antiquewireless.org/otb/resto0504.htm
:
:It is an "active choke" or better described as an active circuit for use as a choke replacement.
:
:I ordered up the parts and built it. Great! Cheap too. less than $3 for the whole thing (I used a varible pot for r2) .... and what beautiful smooth DC you'll get. Ripple is virtually zero.
:
:The last "used" choke I bought was $4 plus shipping.

Hi Peter,

If the original choke is on the chassis, the circuit can be made on a piece of perf board small enough to hide under the chassis keeping everything on top looking original.

Radiodoc

Hi Radiodoc:
Yes certainly I could do that. Chokes often are under the chassis... ( although not the last one I replaced... no room at all... the substitute perhaps was over sized... I had to ty-wrap it to the dynamic speaker off the chassis)
But even if I put it under the chassis, ...I still wanted to do something that will 'pot' the whole thing perhaps in a plastic lump like a 'potted-module" so only 3 leads stick out. in / out and ground. This way it wouldn't look so conspicuous and possibly intimidating to the next guy working on the set.
I built this 1st one on a very small ( single ic socket pc board) but if I decide not to 'pot' it I could also probably easily build it on a 5-6 terminal phenolic strip and mount it under the chassis neatly. I just hate leaving a mystery for the next guy and I'd want somehow to include the schematic... lol

Maybe I could hide the whole thing by slipping it into an old style fat cardboard capactitor tube or similar thing and stick a mini schematic on the side or inside.

I don't want to go too far... but just to make it nice.

:Hi Radiodoc:
:Yes certainly I could do that. Chokes often are under the chassis... ( although not the last one I replaced... no room at all... the substitute perhaps was over sized... I had to ty-wrap it to the dynamic speaker off the chassis)
:But even if I put it under the chassis, ...I still wanted to do something that will 'pot' the whole thing perhaps in a plastic lump like a 'potted-module" so only 3 leads stick out. in / out and ground. This way it wouldn't look so conspicuous and possibly intimidating to the next guy working on the set.
:I built this 1st one on a very small ( single ic socket pc board) but if I decide not to 'pot' it I could also probably easily build it on a 5-6 terminal phenolic strip and mount it under the chassis neatly. I just hate leaving a mystery for the next guy and I'd want somehow to include the schematic... lol
:
:Maybe I could hide the whole thing by slipping it into an old style fat cardboard capactitor tube or similar thing and stick a mini schematic on the side or inside.
:
:I don't want to go too far... but just to make it nice.
:
Peter,

You may want to (if you haven't already) check out http://www.antiquewireless.org/. Just click on sample our quarterly publication and then click on past articles. AES has had some articles on restoring old radios.

Radiodoc

Yeah, you could do something like coat it with tar or J-B weld if you're good at molding a neat looking globule. You could also build one of those nifty tin boxes if you are good with tin. Then it'd look like a Philco condenser bank. That'd really throw people. I hope that you are leaving the old choke in place so that the radio looks original on top.

Thomas