Home Forums Electronics Restoration Need Transformer data for De Forest Crosley type 7D732

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  • #24237
    Matt Newman
    Forum Participant

    Question: What is AC centre tapped high voltage and current between the two red leads? Operating at 115 vac, 60 Hz, line drain should be 67 Watts, 0.56 Amps as indicated on attached schematic. Type 7D732 pertains to Rogers 12-70, 12-75; Majestic 770, 775; De Forest Dufferin, Welland, and Victoria. Thanks for your help! Matt

    #24239
    Ralph Spracklin
    Forum Participant

    Morning Matt
    Rogers Majestic and Deforest Crosley used these tubes in over 120 Models during the years 1937-1941′ Both these tubes were of the octal type base. The 2X3 is/was a 1/2 wave rectifier, which was the equivalent of just one half of that of the 5Y3, a full wave rectifiter. In other words the 5Y3 contained two 2X3s in one envelope. That is why the 7D732 (and others) uses two rectifier tubes. Maximum plate voltage is recommended at 350 volts RMS from Plate to Center Tap on Power Transformer, or 700 Volts RMS across both plates. Which is about normal for the era we are talking about. As for the Current, maybe someone else can answer that for you.

    Ralph

    #24240
    Ralph Spracklin
    Forum Participant

    Sorry Guys, I feel like I am hogging the forum here.

    Further checking tells me that,the data/specs, barring the Htr. Specs at 2.5 Volts for the 2X3 and 5Volts for the 5Y3, both of those two tubes are alike. They both draw 2 Amps. and safe operating voltages (higher than I first thought) are also identical. However, as I said on my first post above, 350 volts, Plate(s) to Centre-Tap on Transformer would be about the normal operating voltage on your set. Which at the input to your filter choke/field coil, would be around 250-270 volts DC. So use the Data supplied at Frank’s Site, or any manual for that matter, for the 5Y3 as your reference. and you will be in save water.

    Ralph

    #24241
    Matt Newman
    Forum Participant

    Ralph, perfect and thank you. Good advice. I will use the 5Y3 as a reference. I am new to CVR and am not familiar with Frank’s site. Would you be able to point me in that direction? Agian, thanks. 73, Matt

    #24242
    Ralph Spracklin
    Forum Participant

    Hello Again Matt

    Two ways to access the site seen below.

    < https://frank.pocnet.net/ >
    or as do, Just Google tube number, such as ” 5Y3 Vacum Tube Data ” and a number of sites with Tube Data will come up, including Frank’s. I usually go for this second choice, as it takes me directly to the particlar Vacuum Tube in question.

    Regarsd

    Ralph

    #24261
    Matt Newman
    Forum Participant

    From advice on this thread and infomration obtained from Hammond, I’ve attached three possible candidates for the transformer replacemet on my 7D732. See Atch PDF. Notes from Hammond suggest the center tapped 6.3V should be 4A to be safe. The 5V would need 3A for the 5Y3.

    #24263
    Matt Newman
    Forum Participant

    From advice on this thread and infomration obtained from Hammond, I’ve attached three possible candidates for the transformer replacemet on my 7D732. See Atch PDF. Notes from Hammond suggest the center tapped 6.3V should be 4A to be safe. The 5V would need 3A for the 5Y3. Your views on this and any feedback would be greatly appreciated. Thanks! Matt

    #24265
    Ralph Spracklin
    Forum Participant

    Having looked over your stated options, and the fact that you are leaning towards one of those three options, I would choose the first option, the 273BX. My reasoning is that this option gives you a little extra ‘current’ leaway in regards to the total amperage draw from the two 2X3s. This option wil allow P/Tnsformer to run cooler should a short in some other part of the radio circuit cause overloading of the Power Transformer, causing it to overheat. I never checked all theoptions offered by Hammond, However, do Hammond not have a fourth option that would give you 5 Volts at 4 Amps, along with 6.3 Volts at 5 Amps. I know cost can enter in to the decision to purchase. Also whatever you purchase, make certain that the footprint of the new Transformer will match/fit the original mounting hole/s on the chassis itself.

    Ralph

    #24279
    Matt Newman
    Forum Participant

    Unforunately Hammond does not offer a forth option. Other sources will be checked for 5 volts at 4 amps. BTW, I wil be using the 5Y3 instead of the two 2X3s. A new socket has been installed for the 5Y3 due to the need for pin 6. In the event a transformer with 5 volts and 4 amps cannot be found, will the Hammond 273BX (5 volts and 3 amps) be okay as next best availabe?

    For your information and other readers, the speaker socket on my 7D732 had to be replaced. I thought this was “unobtainium”, but found a replcement at Surplus Sales of Nebraska. Also, for pilot lamps, I found two LED replacements, 6.5 volts with a BA15S base on Amazon.

    Thanks for your help and advce on this project.

    Matt

    #24291
    John Greenland
    CVRS Member

    Matt,
    There is a 4th option. Replace the 5Y3 with a solid state version and save the 5 volt requirement altogether.

    Check here — https://www.tubesandmore.com/search/node/solid%20state%20rect

    Regards , John G. VO1 CAT

    #24292
    Matt Newman
    Forum Participant

    John,

    Many thanks for this suggestion. I am assuming the solid state rectifier (SSR) contains the for diodes for full wave rectification. Is this correct? Are the pin designations the same as they are for the 5Y3? If so, then the SSR would be a true drop-in replacement not requiring pin wiring changes. Correct? Do you know if the the SSR has been used to replace a 5Y3, or two 2X3s, in radios similar to the De Forest Crosley 7D732 I am working on? Lastly, I am assuming my questions could apply equally to either the P:-YJR, or the T-SSR01. If I go for this option, then the Hammond 273BX would simply not use the 5 volt @ 3 amp secondary.

    73, Matt, VA3MGN/AA1VN
    Richmond Hill ON

    #24293
    John Greenland
    CVRS Member

    Hi Matt,

    Your best bet is to look on the site that sells them. They will have all the info that you need.

    Regards John G.

    #24294
    Matt Newman
    Forum Participant

    John, good advice. Thanks for your help and advice.

    #24295
    Ralph Spracklin
    Forum Participant

    Morning Guys
    I have been off site for a few days, ended up in hospital for a whle, But am now back home and responding well to treatment. Mat, yes John is correct and some individuals like to swap out for soilid state. My own thoughts on this is the instant applicaton of high voltage in a system that has not had the time for the other tubes in that system to warm up. There are other pros and cons here, some of moreconcern to the individual than to others. Go to the Blueglow Site for a great explanation of those pros andd cons. See Below!
    Regars
    Ralph

    https://www.google.ca/search?q=Any+cons+to+using+a+solid+state+rctifier+instead+of+5y3+tube&sxsrf=AJOqlzX8T971Mj4h6hV2v8Mg1rUKmNz7iA%3A1678468415426&source=hp&ei=P2ULZMTcF_q50PEP7oepoAY&iflsig=AK50M_UAAAAAZAtzTzXMlfdtfDr2K4EV5GpaZ6lIvOGO&ved=0ahUKEwiE-KmN7tH9AhX6HDQIHe5DCmQQ4dUDCAo&uact=5&oq=Any+cons+to+using+a+solid+state+rctifier+instead+of+5y3+tube&gs_lcp=Cgdnd3Mtd2l6EAMyBQgAEKIEMgUIABCiBDIHCAAQHhCiBDIFCAAQogQ6BAgjECc6EQguEIAEELEDEIMBEMcBENEDOgsIABCABBCxAxCDAToICC4Q1AIQgAQ6CAgAELEDEIMBOggILhCABBCxAzoLCC4QgAQQsQMQ1AI6CAgAEIAEELEDOgsILhCABBCxAxCDAToICC4QsQMQgwE6CwguEIAEEMcBEK8BOggILhCxAxCABDoFCAAQgAQ6BwgAEIAEEAo6BQguEIAEOgUIABCxAzoGCAAQFhAeOgUIABCGAzoFCCEQoAE6CAghEBYQHhAdOgcIIRCgARAKOgQIIRAVOgoIIRAWEB4QDxAdOgQIIRAKOgYIIRAVEApQAFjNzAJg-9ACaAFwAHgAgAHRAogBoEWSAQkxMC40MS44LjKYAQCgAQE&sclient=gws-wiz#fpstate=ive&vld=cid:367ba343,vid:AnDvj3Arr5U

    #24297
    Matt Newman
    Forum Participant

    Ralph and John,

    Congratulations Ralph on your return home. I trust your recovery goes well. I am 82 and I have no idea how I made it this far. The pros and cons of SS vs. tube rectification are very interesting. Thanks for the BlueGlow URL. It’s a keeper. And, thanks, John, for introducing me to the SSR. The Crosley 7D732 came with two sockets for the 2X3s. I changed out one of of those sockets for a 5Y3 to accommodate for the need for pin #6. Unless there is a transformer available without a 5 volt filament secondary, I’ll likely stay with the Hammond 273BX as best available option (up to now). Would not use the 5 volt secondary. I’ll see how that goes first with an eye on a solid state rectifier for the future. I just hope 5 volt @ 3 amps is okay instead of 5 volts @ 4 amps (does not seem to be available). I will check out the transformer question at the upcoming OVRA meeting on March 19. There may be an off chance someone knows of a used replacement (???).

    All the best for now,

    73, Matt

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