[jrebman]

I know this is a real long shot, but I thought I'd give it a try because if I don't ask, I won't ever know.

I'm looking for a pair of Magnequest MQ565 pinstripe Dynaco ST-35 PP output transformers.

I'm building a tube rectified 15 watt EL84 PP amp and these transformers are at the top of my wish list, but they generally appear to be unobtanium.

I've been scouring eBay, agon, and AK for quite a while in search of a pair, but nothing ever shows up, so in desperation decided to post here.

Thanks,

Jim

[JoshK]

Good luck with your search.  I hear MQ periodically produces these and they go fast...

[JohnR]

I've seen original Dynaco Z-565s on EBay now and then.

[fortitudine]

Try www.magnequest.com -- Mike LaFevre owns the brand and manufactures new transformers better than the old. Have not used them myself but lots of folks say great things about them. Dynaco rebuilds are quite popular these days.

[jrebman]

Thanks everybody for your replies.  John R., the only issue with the originals is that there are apparently a lot of them that have age-related problems with things like the wax dielectric, etc.  I also think the nickel pinstripe could have some nice sonic benefits in this amp, especially if strapped for triode mode operation.

I may be on the path to a pair of these after all, but I probably won't know for a couple months yet.


BTW, Bottlehead is no longer a full range distributor for MQ -- they only represent the things they use themselves -- some of the parafeed transformers, some power transformers, and a couple of chokes.  I don't know who is handling US distribution now and there is no update on the MQ web site.

Thanks,

Jim

[jrebman]

Score!  Well, not exactly what I was looking for, but maybe even better in some ways.  Mike L. found, in a dusty corner, a pair of 565s with M3 laminations and solid brass bell ends (can you say non-magnetic?).  They're on the way to me now. 

Thanks to the mystery AC member who ran interference for me .

-- Jim

[JoshK]

Nice score!

[jrebman]

And now when Jack Elliano gets done with a PT I'm having him build to my specs, I should have some top notch iron to build the project around.  I'm a big believer in good iron -- why take a good, time-proven design, some appropriate modern components, construct a nice chassis and then put mediocre iron on it?

Magnequest owns all the original design documents for the 565s and the guy who winds them was the shop supervisor where the originals were all made.

-- Jim

[JohnR]

John R., the only issue with the originals is that there are apparently a lot of them that have age-related problems with things like the wax dielectric, etc.

Yikes I have four of them!

Very much looking forward to hearing about how your amp build goes. I was planning to build based on the boards from ... um... right, diytube.com

[jrebman]

John,

Yup, that's what I got -- the Revision D board purchased from Triode Electronics.  I checked it out with a friend and it appears to be a really well laid out and high quality board.

-- Jim

[jrebman]

The Electraprint custom PT arrived today, and what a monster!  It has to be 2 - 3 times the size of the standard ST-35 one.  About 5 tall, 4-1/2 wide, and maybe another 5 between bell ends, and just about 10 pounds of M6.  Very impressive, but it's a good thing I'm not trying to fit this on a standard ST-35 chassis .  In case anybody's interested, here are the specs:

Primary: 120 VAC, 60 Hz

Secondaries:


310-0-310 200 mA
5v 2A
6.3VCT 5A

The extra 10 volts or so on the HV secondary is to compensate for the 5AR4 rectifier I'll be using -- another deviation from the original.

Good iron, I got!

-- Jim

[JohnR]

Cool. What will you be using for a chassis?

[jrebman]

John,

I'll be making a wood box out of something like 3" x 3/4" hardwood of some kind.  I have a friend who has a nice stock of aged Walnut from a tree he felled on his property many years ago, or it might end up being some Maple burl, or maybe something more exotic like Koa.  Then a bottom of either aluminum or birch ply, and a top panel of again, either aluminum, or possibly brass or bronze depending on how insanely priced it is.

Then, just for kicks and to make it all a little more interesting I'm going to radius the face of the wood so that the three inch wide piece is 3/4" in the center and then radiused out to 1/2" at the edges (it's nice to have a friend with a CNC .)  All this once my hand heals and I have a bit more feeling in my thumb and first two fingers on my right hand -- hopefully before the end of the summer.

-- Jim