Hello All,
I just acquired a 41-290 console and have a few questions about the audio output circut, etc. Unfortunately, someone cut the wires between teh chassis and speaker, even though they could have just removed the speaker plug. It looks as if there was an output transformer mounted on the speaker that is missing.
I checked my Riders' manuals for this information (in section 12-7, if my memory serves me correctly) and can't find out any information on this.
Would someone be able to tell me if the output transformer was mounted on the speaker, and what replacement audio output transformer would work with a pair of 41's? Also, how can I figure out which wires from the chassis would go to their corresponding connectors on the speaker plug?
I'd like to get the audio section straightened out before I give the set a total recap.
Any information will be greatfully appreciated.
Very Best Regards,
Joe Cro N3IBX
Posts: 1,703
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Joined: Sep 2005
City: Evanston, IL
Info gleaned from Philco Service Bulletin #325.
The audio output transformer, pn/ 32-8120 in chassis mounted (underneath) and is next to the 37 tube by the power transformer.
The field coil on this 14" EM speaker is 1,100 ohms DC. The speaker is p/n 36-1523. The voice coil impedance is 5.1 ohms at 400 Hz. and has a hum-bucking coil to boot.
This speaker is also used on models 41-285 and 41-287.
Chuck,
Many thanks for the information! I'll pull the chassis out of the case to see if it has the audio transformer in it.
Any idea what I could use to sub the field coil and the 400hz humbucking choke? I have a goodly supply of chokes on hand I could possibly use, but would have to check their ratings.
Very Best Regards,
Joe Cro N3IBX
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
The hum-bucking coil is part if the speaker filed coil pot, which is missing. It's obviously only needed when the "magnet" for the speaker is the filed coil. If you're subbing a PM speaker, it's not needed.
BTW, it's not a 400 Hz hum-buck coil. The 400 Hz. refers to the test frequency that the VOICE COIL is rated at it's 5.1 ohms impedance. An 8-ohm PM speaker will work fine.
You should check Play Things Of Past at
http://www.oldradioparts.com for a NOS or pull speaker. Gary has lotsa stuff.
A large 1,100 ohm, 15 watt power resistor will sub for the field coil. Be sure you have plenty of clearance around it. It will get
HOT. I'd suggest an aluminum-clad unit that will heat-sink nicely to the chassis with some thermal grease - just like a power transistor. Mouser sells them. 284-HS15-1.5KF $2.39
Spec Sheet:
http://www.arcol.co.uk/uploads/products/hsseries-10.pdf
1.5K will be the closest and that will be ok, as the A/C line voltage is 120 instead of 115 so the B+ in the set should still be a nominal value.
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
The field coil is there - it's the big winding. Probably 4 wires from it - two for the main coil and two for the hum-buck winding (that ties in series with the voice coil). Looks like all is there, just pulled apart. Check continuity on the vc, hb and files coils. Also looks like the socket has been onscrewed from the speaker frame? Hopefully the vc wires have not been yanked out of the cone or spider.
Pull out the harness plug there in the speaker frame socket to be sure. Mark the socket and plug BEFORE you separate to be sure of correct connection when re-mating.
Usingyour schematic to trace the four wires from chassis and mark them - should be easy, once you id the connections and continuity on speaker elements to re-wire that harness plug.
The four wires from chassis would be two from sec of audio out transformer (to the vc) and the other two from the power supply (see schematic).
Chuck - Your information is VERY MUCH appreciated!
Best Regards,
Joe Cro N3IBX
