Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ALBATROS1234 on April 02, 2019, 05:12:28 pm
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i picked up a 1946 stromberg carlson 1121 pf console stereo and its just too cool and must be properly restored. when making a list of parts to order i came across what they call on the parts list a "filter choke resonating capacitor" it has a value of 1uf @ 200v in the chassis it is a huge paper and wax job so its gotta go since this thing is 73 years old. i did some digging and it seems this is and old school way of filtering whereas a smaller choke than normal could be made to resonate at a certain frequency to improve filtering when a certain size cap it connected in parallel with the choke. my main question is what type of cap do i used. it doesnt seem to need to be polarized as it spans between the first 2 main filter caps where a choke can normally be seen but parallel to this choke( see below schematic capcitor #13) i want to replace this cap because i got a feeling it is a crucial part of this design and will hum if i dont put the correct type and value of cap in this place. thanks for looking gents
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Any 1µF @ 200v will work.
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thats what i thought just wanted to see if it needed to be a certain type cap, thanks slucky.
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Perhaps check with PSUD2 if the choke voltage can reverse polarity. I'd use a poly cap for safety and possibly ripple current. lt may be tricky to work out the nominal resonant frequency as you need to measure the choke inductance at the operating voltage and dc current. The aim is to significantly lower 100/120 Hz ripple harmonic.
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I ordered a Dayton polypropylene cap. I used the value from the schematic because it was available online for free as well as a service manual for the webcor record changer. That plus the cap can and a few other odds and ends should be at my house when i get off work .Thanks for the reply.