New Transformer not what I expected

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New Transformer not what I expected

Postby joeztech » Fri Sep 05, 2014 11:46 am

Today I received a new Heyboer Dynaco 470, NTS-8093 (their part number for it) that is intended as a replacement for a Dynaco A470 output transformer. Unfortunately it is not. The Dynaco A470 is an ultra-linear transformer with a primary winding equipped with a center tap, two screen grid taps and two plate leads. Instead the Heyboer transformer I received has a primary winding with only a center tap and two plate leads - a Williamson type transformer. (666) Yes, I could rewire the amplifier to use a Williamson type transformer, but I refuse to compromise on the original design. I consider a Williamson design a step backward. I immediately wrote an e-mail to Heyboer asking about returning it for credit against my account.

This is bad in multiple ways. I will have to get return authorization, pay for shipping to return, wait for the credit back to my account, order from another company and wait again to receive one. =:o Plus Heyboer gets attention for not supplying the correct design part in the market. I have already waited about two weeks since my original order was placed. My next order will be from Triode Electronics.

Joe
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Re: New Transformer not what I expected

Postby HiFiGuy » Sun Oct 04, 2015 9:33 pm

I have used Triode upgraded power transformer on my ST70 and I am very happy with it. When I need to replace my original Output transformers I will probably go with the Transcendar units. They are made locally and I have experience with his iron, it is VERY good.
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Re: New Transformer not what I expected

Postby joeztech » Mon Oct 05, 2015 11:38 am

After the initial false start, I contacted Heyboer and they sent the correct transformer at not additional charge and told me to just keep the other transformer. I understand that it is OK for guitar amplifier service as that was what it was originally manufactured for. I may be able to find a buyer for that transformer. The correct replacement is in my ST-70 and doing a great job for me.

The Transcendar transformers are also a good choice for replacement of Fisher equipment audio output transformers. Several members of the Fisher group on AudioKarma.org have used them and are happy with the results. Transcendar does have a good reputation.

I am currently restoring a Fisher 500C and will be adding Dave Gillespie's EFB modification and also the IBAM modification for individual signal grid bias of each output tube. Fortunately the unit I acquired has good output transformers. Dave's EFB modification permits higher power output with less distortion and less heat dissipation in the output tubes - a win - win situation. I ordered a set of the new Tung-Sol tubes which can be set for 34mA each and generate about 34 watts output with low distortion.

Joe
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Re: New Transformer not what I expected

Postby dcriner » Wed Oct 07, 2015 5:23 pm

Heyboer is a very respected custom xfmr manufacturer. But, I wouldn't use them for ST-70 replacement xfmrs that are readily available, off the shelf, from several sources.
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Re: New Transformer not what I expected

Postby joeztech » Wed Oct 07, 2015 5:43 pm

The transformer that Heyboer sent was correct and well made in every respect and was an off the shelf transformer of their manufacture, delivered promptly. It was somewhat less expensive than some other brands at the time and the only thing I did after I received the correct transformer was to use the original end bells from the OEM transformer. The build quality and results are identical with other brand replacements for the OEM Dynaco transformers. I have been enjoying it ever since.

Joe
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