Edcor vs. Heyboer

[Structo]

Even though the laydown PT takes a bit of room away from the interior of the amp, it is the best design for strength.
Sort of like a unibody car, it becomes part of the chassis and having the four corners attached to the chassis floor, adds a lot of resistance to the twisting of the chassis, as well as not having any tabs to bend.

I see the Marshall style stand up trannies but the appear to have some pretty beefy/ heavy gauge brackets on them.

[Rattler66]

thanks for all the input guys

[krash]

The main thing you get with a laydown transformer is a reduced torque on the chassis because the center of mass of the transformer is much closer to the center of rotation when the transformer is being torqued. Also, since there is no mounting tab but the transformer is directly mounted through the corners of the core, there is no chance of the transformer bending.

I have seen the chassis itself bend with a laydown transformer. This was a JTM45 (ish) amp from Ceriatone that bent in shipping and parallelogramed the whole chassis, twisted it where the transformer was mounted, and sheared off a bunch of solder connections. Yes, this was an amp I was working on for a customer. FedEx paid for it, but it's a word to the wise: the way they built amps in 1970 may not be up to the rigors of shipment common in today's world. Laydown PTs are better, but not perfect. Best is to not ship amps built on the template of a vintage tube amp.

You want to see the right kind of mounting for a standup transformer, take a look at the Peavey Classic 30 transformers. That's a study in strength. Take it from an outfit that ships hundreds of thousands of these things... they go with a heavy steel chassis and ungodly thick mounting for transformers half the size of the Radiospares-type 18W OTs. Kind of the Peavey way... it may not sound good, but at least it'll last forever.

[RJ Guitars]

Krash,

I am definitely listening to you and respect your history on this. I am not from Missouri but I have something in common with those folks. In addition to that I have been in materials and science research for all of my career and I have a real tendency to go test and measure things that other folks have seen and reported on before me. In this case as in most cases I found some truth that aligns with you and some additional information that should prove useful to anybody interested in using any of these trannies.

I did go back and look at the tranny mounting tab designs and then took measurements of the tab thickness on several 300 volt high amperage transformers.... all of them just about the right technical specs for a Trainwreck style amp.

.032 - Heyboer
.032 - Edcor
.032 - Hammond
.045 - Pacific

The easy winner is Pacific. Both the Pacific and the Heyboer use a wider tab than the Edcor or Hammond and that is no doubt better. The Pacific is even a cut above the Heyboer in robustness of the end bell.

If a transformer lost an anchor screw the Heyboer or Pacific would probably fare better but still lose to any of the others with all the screws secure. With secure (locktite them) screws I'd look for the chassis to bend long before the tranny give way if the amp took some serious abuse.

There is a lot of good math and science that suggests it is the combination of the four screws and the strength of the mounting surface that is key to the strength of the final tranny mount. With a solid platform to mount our tranny on we can quickly get to the point of diminishing return by adding more steel to the endbell tabs.

This is a bit ironic for the Trainwreck builders since the original Trainwreck chassis used very flimsy .031 soft aluminum as the chassis material.

rj

[krash]

I'm going to be rounding up my dead old Edcor and I'll get the model # and measure the mounting tab thickness.

[Zippy]

The main thing you get with a laydown transformer is a reduced torque on the chassis because the center of mass of the transformer is much closer to the center of rotation when the transformer is being torqued. Also, since there is no mounting tab but the transformer is directly mounted through the corners of the core, there is no chance of the transformer bending.

"Torque" depends on which way the abuse to the chassis is delivered. If you whack the cabinet on end, yes, the laydown might fare better. If you drop the cabinet on its bottom or top, there remains the issue of shearing the aluminum chassis at the mounting bolts. The steel tabs will fare better than the chassis in this instance. Best to spread the force and reduce the stress by appropriate backing plates or fender washers.

I don't see how a transformer bends - tabs, yes; bells dented, yes; but cores bending, no. Maybe you were talking "tabs".

[M Fowler]

I will agree with Krash on one thing the Edcor are heavy big beasts and I do find the mounting to be not as thick as the other transformers but I did not think it was such a problem that I would refuse to use that brand.

But.....if your in commercial amp building you do want your product to be the best for your clients so I understand the switch or lack of use of the Edcors. For the hobbist and many of the Ampgarage builders the Edcor is a great value and should not be overlooked because of this complaint.

Mark (hobby builder)

[Richie]

I have to somewhat disagree with krash, i've seen steel chassis caved in or pulled out from the weight of the transformers from shipping. But ..yes the laydown will fair better, and yes the steel will fair better in the outcome.
But if people like to use the aluminum chassis,they won't switch
to steel.
The mounting feet, don't know if it helps, but for may years, i used the much larger fender washers on the chassis underside for more support. not that it will help in a tranny mounting leg bending.
Also the marshall amps have a clamp they use to help support,like on the older 2203s JCMs etc.. they also used a mounting ring. Both of these are good things to add to help keep a transformer from being damaged.

I guess it boils down to, if an amp is dropped, depending on what you use, and how its dropped, and weight of the trannys,and mounting position,plus ,type chassis metal used.. something has to give,one or the other is going to bend.

[krash]

the bent tabs on my amps' transformers were from shipping the amp, when it would find itself in a "laying flat" position (combo amps). Unpack the amp at the destination and the transformer mounting is bent.

never had such a problem with laydown transformers, but I also quit shipping combo amps, and in fact quit building them for anyone but myself and friends whose amps I can hand-deliver. Packing method for a small Marshall-type head (like a 18W/20W head cab) is such that the amp would remain upright at all times and shear force would not get regularly applied to the transformer during transportation anyway, but a standup transformer in this power range will not fit in one of these little cabinets I use.

[Richie]

the little L brackets, these also work, may have to get a longer transformer bolt, but you can add the L brackets for support on the standups. I've also seen transfomers lams shift, meaning the transformer itself looks like the leaning tower of pizza

[Phil_S]

IMO, if you've seen the lams shift, that transformer wasn't properly varnished. As I understand it, the transformer is baked and the hot tranny is dropped into a bath when it's complete. The varnish gets sucked into the lams as it cools. I can't imagine what it would take to break that loose from being dropped.

[David Root]

I have seen more than one old transformer with not quite square laminations. In fact the 1967 Bassman OT I am planning on using in my next amp is not quite square. This is a Schumacher (EIA code 606741) not some cheapo piece.

Perhaps they just "slump" that way with age and use??

[dartanion]

I would bet that the lams weren't quite square when varnished if they are leaning to one side and not bent tabs. I have seen this in "new" transformers and haven't really worried about it too much. If the transformer doesn't work right and has skewed lams, then it would be sent back.

On the vintage stuff, I have seen lots of leaning transformers, but mostly tabs or tweaked chassis around the transformer.

[RJ Guitars]

I took a photo of the four large trannies that I had in the shop. You can see the better tab design on the Heyboer and Pacific. The Hammond is this picture is pretty beat up because of some funky packaging and shipping from the guy who sent it to me.

The Edcor is a slightly smaller tranny than the other three but still would benefit from the wider tab design.

One difference that is also apparent is that Edcor, Hammond, and Pacific are using thinner lams than the Heyboer. Does anybody understand what impact that might have on things?

rj

[M Fowler]

rj, good post.

See how pretty those blue trannies look compared to the others, nice. The mounting tabs need to be wider and heavier material send Phyllis a note.