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 Post subject: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W4
PostPosted: Sep Thu 23, 2021 6:02 pm 
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Location: NJ 08090
Someone got into the chassis of this RCA 45 player and did a bad job of whatever they were trying to do LOL...It's a simple 'one tube wonder', RCA 45 player, but has a 35W4 rectifier and 50L6 instead of the more common ones with the selenium rectifier and a 25L6. The chassis is RS-155C...different than a standard RS-155. I have it playing, but I want to get it back to stock for now. If anyone can share a schematic that shows the 35W4 and 50L6 tubes in it, let me know. Thanks in advance!


Last edited by Tbirdkid on Sep Fri 24, 2021 6:08 am, edited 1 time in total.

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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Thu 23, 2021 9:02 pm 
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You listed 2 tubes so it isn't a one tube wonder. How many does it actually have, 3 perhaps? A 12AV6 also maybe? Is the chassis marked RC-155C or RS-155C, you show both.

The only deviation from a standard RS-155 I have is for an RS-155A which is a 3 tube chassis used in the all plastic 45 player 7-EY-2 (12AV6, 35W4, 50C5).

Larry

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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Fri 24, 2021 6:13 am 
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The chassis is marked RS-155C..I corrected the typos in the first post.
It has 2 tubes...35W4 and a 50L6...They were still known as the one tube wonder, since only one tube amplified the sound.
These 2 tube versions exist, from what I've seen on old forum posts....but no schematic for the RS-155C found.


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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Fri 24, 2021 1:04 pm 
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Hmm, interesting, I've never come across a 2 tube version. OK, let me see what I can find in my books. By the way, the "JF" is the color ID, should be coral and grey?

EDIT: It looks like the schematic for chassis RS-155C is in Sam's 341-13. Maybe somebody here on the forum has a copy?

https://www.samswebsite.com/en/photofact/search/index/samsid/341_13

EDIT 2: Unless they added an addendum at some point, they fib. I have 341-13 and it is a single sheet for the standard 1 tube RS-155 chassis. Back to the drawing board. :(

Larry

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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Fri 24, 2021 2:54 pm 
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Thanks Larry....I'm starting to think they never did a fact sheet on the '2 tube' model of the 7-EY-1JF (BTW you are correct+--It is coral and grey). The motor is a 120 volt motor..and not in the filament string.... so they used a resistor to soak up the spare 30 volts..but that resistor was changed at some point, and is a 250 ohm one. Not sure if that was right, as there were other mistakes made in the circuit and I admit I'm not sure on the calculation for what that filament resistor should be. I guess the previous repair guy couldn't find a schematic back in the day, so he winged it without one...and it showed.


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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Fri 24, 2021 6:09 pm 
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50L6 and 35W4 have 150 mA heaters, and you need to drop from 122V (commonly-used) to 85 volts, so 37 volts. By Ohm's Law, you need a resistor of 37/.15 = 247 ohms. So 250 ohms is exactly correct. You will probably need to use 220 ohms which is today's standard value. Again by Ohm's Law, the resistor will dissipate I^2*R, .15^2*250 or 5.6 Watts. Use a 10W resistor. Make sure there is space around it -- it will get HOT.

-David


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 Post subject: Re: Looking For RCA Chassis Schem RS-155C For 7-EY-1JF w/35W
PostPosted: Sep Fri 24, 2021 6:27 pm 
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Location: NJ 08090
Quote:
Make sure there is space around it -- it will get HOT.

Yea...I noticed the plastic housing above the amp chassis has been distorted....Maybe that's why they didn't do much of a run with this version of the design.
Thanks for the calculation!!!


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