Wow, I just learned more in Doug's email than in 2 years of vocational-technical training way back in 80's high school. Thanks, Doug!
-r. ----- Original Message ----- From: "Doug" <[email protected]> To: "Antique Phonograph List" <[email protected]> Sent: Tuesday, July 26, 2005 5:26 PM Subject: Re: [Phono-L] Resistor for VE Victor 350 > Okey doke, I finally got off my dead duff and looked the thing up i the > Victor service booklet for the universal motor. The resistor for 100-130 > Volt operation is a tapped resistor. Its total resistance is 230 Ohms. The > taps are at 180,205, and 230 Ohms. . Those resistors can be replaced in > sections, simply connecting a new resistor of the proper resisance and > wattage across the open section. That's where we need to know the wattage of > the new resistor. > > Unfortunately, I've never had one of the universal motors in a Victrola, so > I can't measure the motor current. We do have enough information to > calculate the resistor and its ratings. > > So, from what we know, let's try this: The normal line voltages in the > twenties were 110 Volts. Victor says that the Victrolas were shipped with > the motor connected to the 205 Ohm tap on the resistor. That means that the > resistor drops 110-32=78 Volts. > > 78 Volts dropped across 205 Ohms means that the motor currnet .380 amperes. > Further, 78 Volts dropped across 205 Ohms means 29.6 watts. Now, since we > know motor current, let's check wattage for each section of the resistor. > For the 180 ohm section, wattage will be 25.992 watts For the next section > (205 Ohms minus 180 Ohms) the wattage will be 3.61 Watts. The last section > of the resistor will be 230-205 Ohms, or 25 Ohms. With ..38 Amps motor > current, this section willalso dissipate 3.61 watts. These wattages are the > actual dissipated values in operation. > > So, let's put it all together. When you design equipment and you calculate a > resistor's rating as we have done above, you always specify the resistror to > have double the calculated wattage rating. So, with the first (180 Ohm) > section, you will use a 180 Ohm (175 will do), resistor at 60 watts. The > next two sections of 25 Ohms each will be replaced with 25 Ohm resistors of > 10 watts each. Note that the 25 ohm resistors need only be about 7 watts > each, but 10 watts is a standard rating. None of the replacement resistors > will be as large as the original resistor. Probably the original resistor > was rated at 66 watts, or more probably 75 watts. those got to be big > resistors. > > In operation, you will probably use the entire resistor, Line voltages today > are away above those of the twenties. My Detroit Edison service is 124 > Volts. I'd like about 7 Volts less, but there's no change possible! > > I try not to be confusing, but it's so difficult! > > Doug. Houston > > > > ----- Original Message ----- > From: "Bruce Mercer" <[email protected]> > To: <[email protected]> > Sent: Tuesday, July 26, 2005 4:44 PM > Subject: [Phono-L] Resistor for VE Victor 350 > > > > > > > > > >> 6. Re: Resistor Search (Doug) > >> > >> > >> ---------------------------------------------------------------------- > > > >> Message: 6 > >> Date: Sun, 24 Jul 2005 13:22:10 -0400 > >> From: "Doug" <[email protected]> > >> Subject: Re: [Phono-L] Resistor Search > >> To: "Antique Phonograph List" <[email protected]> > >> Message-ID: <001001c59074$3b3a4dd0$0100a...@doug1> > >> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > >> reply-type=original > >> > >> I assume that this is one of the dropping resistors for the Victor > >> universal > >> motor..right? > >> > >> We'll need to know which resistor it is (most of those installations had > >> a > >> couple of resistors). From that, we can go to the Victor service notes > >> and > >> find out its resistance and wattage rating. You can probably come close > >> on > >> value, or possibly right on the money. But we'll have to know the > >> resistance. > >> > >> The big wire wound resistors are made, and the (very few left) electronic > >> supply houses can get them. > > > > > > That's right Doug, it's for one of the universal motors. Mark sent me a > > pic > > of the > > resistor, he told me that it had four taps but only two were used and > > looked > > to have > > always been that way. It's about six inches long and wirewound as I > > expected. In the > > Look for The Dog Book, in the motor service section, it says the resistor > > was placed > > in series to drop the voltage to an ideal of 32 volts. Not to exceed 36v. > > or > > drop below 30v. > > ("As measured with a DC voltmeter"). I'm sure Mouser would have what he > > needs but I do > > not know how to determine just what he does need. I'm glad you saw this > > thread, as I'm sure you > > do know what would need to be used. He didn't mention any other resistor > > being in the unit. > > My experience has been with the induction motors. Hope you can help him > > out. > > > > Bruce > > > > ps. I finally got through to him on his email. [email protected] > > > > > > > > > > > > _______________________________________________ > > Phono-L mailing list > > [email protected] > > > > Phono-L Archive > > http://www.oldcrank.org/pipermail/phono-l/ > > > > _______________________________________________ > Phono-L mailing list > [email protected] > > Phono-L Archive > http://www.oldcrank.org/pipermail/phono-l/ >
