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

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.

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

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

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

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.

If you're in the office and have internet, you can look up the Sams on ETF.
At least, Sams drew the power supply correctly, regarding the cap polarities.

Ok that makes sense now, it's filtering a negative supply. Thanks again everyone! The advice is very much appreciated.