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    Mark 3 Transformers

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    jwb474

    Posts : 15
    Join date : 2014-07-13

    Mark 3 Transformers

    Post by jwb474 on Tue May 22, 2018 5:32 am

    I am getting ready for some future Mark 3 work. Going thru the manual folder I notice I had 2 different manuals.

    The output transformer from one manual identifies the transformer "Z-216" and the other manual has "A-431" Does anyone know what the difference is?
    DynakitParts lists the transformer as A-431.

    Moving on to the input transformer: The schematic of one manual has 117VAC input and the DC voltage on the 2nd cap is 480VDC. The transformer is labeled "P-782".
    The other schematic has 120VAC input and voltage on the 2nd cap is also 480VDC. The transformer is also labeled "P-782" Now with the same DC voltage and 2 different AC inputs,
    the transformer has to be different, but is labeled the same. Does anyone have any info on the difference?
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    WLT

    Posts : 25
    Join date : 2013-07-13
    Location : Rochester NY

    Re: Mark 3 Transformers

    Post by WLT on Tue May 22, 2018 9:34 am

    More info but no real answer for you. I have four manuals from different vintages. Here is the info from them

    North 43 Street, Serial number 3743002, 117 V AC, 480 V DC, A431
    Powelton ave, Serial number 3052064, 117 V AC, 480 V DC, A431
    Jefferson Street, Serial number 3409086, 120 V AC, 480 V DC, Z216
    Jefferson Street, Serial number 3409101, 120 V AC, 480 V DC, Z216

    I purchased the last two amps as new kits in the spring of 1974. From date codes I have seen on many Z216 I believe they are the later version with PVC wiring. My two Mark II manuals list 117 VAC and A431/430 but 465 VDC as the rectifier and choke are different.

    The question about the P 782 power transformer is a little difficult to track down. Hopefully others have some good info.
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    tubes4hifi
    Admin

    Posts : 1471
    Join date : 2008-11-30

    Re: Mark 3 Transformers

    Post by tubes4hifi on Wed May 23, 2018 5:30 pm

    Dynaco transformers starting with a Z were made in Japan rather than USA, otherwise identical (at least that's what I remember from 25 years ago . . . )
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    j beede

    Posts : 458
    Join date : 2011-02-07
    Location : California

    Re: Mark 3 Transformers

    Post by j beede on Wed May 23, 2018 10:58 pm

    tubes4hifi wrote:Dynaco transformers starting with a Z were made in Japan rather than USA, otherwise identical (at least that's what I remember from 25 years ago . . . )

    Maybe you meant to say electrically identical. I know that with the Mark VI the Japanese transformers certainly look much different than their domestic counterparts. This may not be the case with the Mk III. I have owned and worked on many Mk III and have not seen one personally with a transformer marked with a Z.
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    PeterCapo

    Posts : 511
    Join date : 2008-12-05

    Re: Mark 3 Transformers

    Post by PeterCapo on Thu May 24, 2018 11:45 pm

    jwb474 wrote:I am getting ready for some future Mark 3 work. Going thru the manual folder I notice I had 2 different manuals.

    The output transformer from one manual identifies the transformer "Z-216" and the other manual has "A-431" Does anyone know what the difference is?
    DynakitParts lists the transformer as A-431.

    Moving on to the input transformer: The schematic of one manual has 117VAC input and the DC voltage on the 2nd cap is 480VDC. The transformer is labeled "P-782".
    The other schematic has 120VAC input and voltage on the 2nd cap is also 480VDC. The transformer is also labeled "P-782" Now with the same DC voltage and 2 different AC inputs,
    the transformer has to be different, but is labeled the same. Does anyone have any info on the difference?

    A-431 was the earlier designation.  As Roy mentioned, I believe the A-431 was made in the USA and the later Z-216 was made in Japan.  They should both have been made to the same specs.

    For the power transformers, what you see on the different schematics is whatever level of AC mains the primary winding was intended for, in order to achieve the specified DC voltage levels along the different nodes of the B+ circuit.  The difference is in the primary winding.  If the primary is wound for 117VAC, then you need 117VAC across it to get the specified DC voltages after the secondary, such as the 480VDC node you mentioned.  If your AC mains is 120VAC, then with the PT having the 120VAC primary winding, you also get 480VDC on that same node.  The practical issue is how high the AC mains can go with either PT before you run into problems.  With a 117VAC primary winding, the maximum level of AC mains is specified at 124VAC in the original Dynaco manual.  With a 120VAC primary winding, logically, it should be okay up to a 127VAC primary.
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    WLT

    Posts : 25
    Join date : 2013-07-13
    Location : Rochester NY

    Re: Mark 3 Transformers

    Post by WLT on Sat May 26, 2018 9:47 am

    To follow up on J Beede comment. From what I have seen. The A430 and A431 transformers all seem to have their number stamped into the end bell. The Z series does not have the Z216 label anywhere on the end bells. What I do see is a ZTOXXX designation that is stenciled on. Just below that is the date code. Not stamped. Attached is one of my MK III with ZTO195.

    Have others found different results?

    jwb474

    Posts : 15
    Join date : 2014-07-13

    Re: Mark 3 Transformers

    Post by jwb474 on Sun May 27, 2018 2:40 pm

    WLT wrote:To follow up on J Beede comment. From what I have seen. The A430 and A431 transformers all seem to have their number stamped into the end bell. The Z series does not have the Z216 label anywhere on the end bells. What I do see is a ZTOXXX designation that is stenciled on. Just below that is the date code. Not stamped. Attached is one of my MK III with ZTO195.

    Have others found different results?

    I have verified I have the same markings on the gray bell transformers along with the same silk screening on the chassis showing 117VAC. These also have the brown cages. I do have a couple of MK3s with black cages and the silkscreen does not show any of the input ratings, but the color of the bells are gray. When I get industrious, I will open them up and see what markings there are.

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