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 Post subject: Heathkit Output Transformers... manufacturers and quality?
PostPosted: Mar Sat 07, 2020 11:16 pm 
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Location: Thornhill, Ontario, Canada
Hi all,
I have several refurbished Heathkit (and other brand) tube amplifiers that (on a whim!) I rotate though my tube stereo system. The common component is a Yamaha C6 stereo pre-amp, so all of the tube amplifiers are configured as monoblocs in this use, i.e. any pre-amps bypassed.
I am interested to know the manufacturers and quality Heathkit used for the OPT's as it has a bearing on sound quality and, for Williamson designs, stability margins.
As we know, the best (and most expensive!) P-P OPTs have:
-- High primary inductance... well over 100 Henries, plate-to-plate
-- Low leakage reactance
-- Low inter-winding capacitance (sectionalized windings)
-- "Good" iron (high permeability, narrow hysteresis, high susceptibility but low retentivity.)
-- Large core... you may think of others...

Anyway, here are some of my Heathkit amplifiers with the OPT number and/or a note:
W-7M 51-36 549-6214 This a large OPT as the amplifier is rated at 55 watts. Likely Chicago Standard, based on the "5x-xx" first number.
W-4M No number or marking on my OPT, but likely Chicago Standard.
A-9 51-14 18850 Likely Chicago Standard.
UA-2 56-63 1036933 Likely Chicago Standard.
Not mine, but for general interest...
W-5M Manufacturer may be Peerless. One number seen is 16309.
A-8 ??
W-3M ??
W-6M ??
AA-100 ??
AA-121 ??

I'm thinking the Heathkit default was Chicago Standard. Can anyone fill in the blanks or correct my notes?
Thanks for all replies.
Cheers,
Roger
EDITS: typos.

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Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


Last edited by engineer on Mar Sun 08, 2020 9:09 pm, edited 2 times in total.

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 Post subject: Re: Heathkit Output Transformers... manufacturers and qualit
PostPosted: Mar Sun 08, 2020 2:45 am 
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Location: Spring Hill, FL 34608
In my notes on the W-5M, the 16309 transformer is one that was used and has a higher failure rate. The better one is the Peerless 16458. I understand that the one linked below is a good replacement, but I can't answer to how good they sound. It's also a standard looking transformer, instead of being in the rounded corner can. It's the TT-035 OT

https://www.transcendar.com/push-pull-t ... -watt-p-p/

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 Post subject: Re: Heathkit Output Transformers... manufacturers and qualit
PostPosted: Mar Sun 08, 2020 3:28 am 
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Posts: 26006
Location: Detroit, MI USA
You need various versions of the EIA/RMA manufacturers code list.


http://www.triodeel.com/eiacode.htm#xfmr

is one such list but there are other, better versions online if you can find one.


The 3 or 4 digits immediately in front of the date code indicate the part's manufacturer.

In this case, 549 is shown as Midwest Coil and Transformer.

Peerless is shown as 391, and Acrosound is 878.

I was under the impression that being right up the road, Heyboer was used as OEM for some Heathkit products as their transformers were OEM in some other brands.

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Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Heathkit Output Transformers... manufacturers and qualit
PostPosted: Mar Sun 08, 2020 8:34 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Rochester NY USA
Chicago Standard and Stancor merged in the mid-50s but maintained separate product lines, at least through the early '60s. 138 is the code for Stancor, who made many of Heath's transformers. Grand Transformer was the earlier name for Heyboer, same address.

Many EIA code lists on my web page, under "Technophool".

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 Post subject: Re: Heathkit Output Transformers... manufacturers and qualit
PostPosted: Mar Thu 12, 2020 6:10 pm 
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Joined: Nov Fri 10, 2006 12:24 am
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Location: Thornhill, Ontario, Canada
Thanks for the above on manufacturing... Does anyone have an opinion on the relative quality of these OPT's? (see my OP.) For example, the OPT in the W-5M is alleged to be of higher quality than that in the originally cheaper W-4M, yet at least one poster has noted a higher failure rate on former.
Cheers,
Roger

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Roger Jones,
Thornhill, Ontario
Ontario Vintage Radio Assoc. http://www.ovra.ca


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 Post subject: Re: Heathkit Output Transformers... manufacturers and qualit
PostPosted: Mar Thu 12, 2020 9:14 pm 
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Location: near ST Louis Mo 62002
The Larger one was more reliable , the smaller one had a nickel alloy core and had a better frequency response curve .

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