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/ >
