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#1
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electrolytic cap question
Hey everyone, I'm working on a set where someone has done some prior work. They bridged the selenium rectifier with silicon diodes. I got some great advice from the group on the fact that the old rectifiers were still left in circuit. Anyway I had noticed that a resistor was never added in circuit to compensate for the voltage difference. But now as I'm working through the electrolytic's I see that 2 of the electrolytic's have been grounded out of circuit? Wires to the respective positive leads have been clipped , a wire was contnected to each lead and grounded to the chasis. Is this another way to do this instead of adding a resistor? I'm trying to make some sense of this. Thanks
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#2
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Are you saying that the circuitry that was connected to the positive part of the lytic has been clipped from the cap and then wired directly to chassis?!?...That would be a B+ short (sabotage!) and should fry the rectifiers, burn up the power transformer or trip the breaker if it is a transformerless PS.
Get the schematic (avoid sam's if possible) and check every PS component and it's wiring against the PS section of the schematic. Correct any discrepencies.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#3
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Is this the 1949 Emerson that you mentioned in the selenium rectifier thread? If you give the model number, perhaps the folks here could look up the schematic (at http://earlytelevision.org/tv_schema...s_postwar.html ) and give more specific advice.
Regards, Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html |
#4
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Electrolytic continued
It's an Emerson 611, these are C-7 & C-8 on Sam's. I'm in my office and do not have the schematic in front of me I believe they are both 80 300 in each can. I managed to get a good pic attached. The 2 white square caps above are also part of a prior restoration. Thanks
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#5
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Quote:
At least, Sams drew the power supply correctly, regarding the cap polarities. |
Audiokarma |
#6
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If you trace the leads from the cans back to the diodes they should be connected to the neg. term. of the diode. this set has 2 power supplies, one + and one -. That gives them 400 volts that is needed for the sweep circuits to work. It saves on the cost of a big transformer. In the day this was not a pricey set. All the best, Tom
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#7
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That looks correct. As mentioned, these caps are set up to filter a negative supply.
Note that they are mounted on those brown insulators ... that's sign that they are not an "ordinary" filter cap. The schematic agrees. |
#8
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Ok that makes sense now, it's filtering a negative supply. Thanks again everyone! The advice is very much appreciated.
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