Slew of power transformer options - questions

[seven]

Hello,

I am thinking about building a 5E3 clone and see various options for power trannies. One famous vendor has about a dozen different 5E3 PTs e.g., 290, 335, 350 and 380 secondary voltages, and various types of fluxes, gaps and cores. So what are the differences with all these? I have a friend with a Jan '57 Deluxe and measured 385 on the PT secondary with the 5Y3 pulled (running 120-121 VAC on the primary). His amp sounds great as it is. So maybe I would go with the 380 VAC version. But what about the flux/gap/core options? Staggered gap? Standard/lower flux? Tuned core? Also, would going lower on the B+ secondary give me a browner sound at lower volumes? If not, why would one go 290 on the secondary vs. 380? Maybe running with 6K6 instead of 6V6?

Chris

[Bruce / Mission Amps]

A dead stock 5E3 from the late 50's, plugged into modern wall outlets can slightly over voltage the amp and make those power tubes run in super high idle current.
Plugged into a modern day wall outlet, I think a power tranny with a high voltage secondary closer to 340vac-350vac, rated at around 100ma would probably be more period correct and more like what Fender was thinking when designing the 5e3 amps.
I mean comparing an old 5E3 running from wall outlet voltages at around 115vac-117vac during the early 50's to late 60's to now.... as I see line voltages around Denver in the 122vac to 126vac!!
That extra voltage on the primary can really poke the B+ level up pretty high, but with a real 5Y3GT (made in the USA), I've read others mentioning high 410vdc on their 5E3 amps but I don't think I've ever seen the B+ much over 380vdc-390vdc on any 5E3 I've worked on even with high wall outlet voltages.
They sound the best to me with the B+ at the first filter cap of around 355vdc-370vdc... but that's me.
They were very simple amps and when the tweed Deluxe amps first came out, they were made for a very cheap price, with very inexpensive parts ....and I think you might be over complicating the amp.
Just pick a decent power and output tranny ... my choice would be from any good American made winder.
So, if you are particular, stay away from budget or cheaply made Chinese iron (think low cost and you'll find them), use good tubes and you'll still end up with a great tone with just about any version of this amp.

[Tom Phillips]

...But what about the flux/gap/core options? Staggered gap? Standard/lower flux? Tuned core? ...
Chris

Wow. I'm really surprised that someone is offering all those options when selling a power transformer. A transformer design engineer would know what the advantages were (or may be) but the average consumer would be at the mercy of the salesman. The "Tuned Core" for a PT sounds like marketing hype to me.
Just my opinion.
Tom

[seven]

Wow. I'm really surprised that someone is offering all those options when selling a power transformer. A transformer design engineer would know what the advantages were (or may be) but the average consumer would be at the mercy of the salesman. The "Tuned Core" for a PT sounds like marketing hype to me.
Just my opinion.
Tom

Well, maybe not a dozen, but I count seven. Check out the link here.

Didn't think that company was into much hype...

[Bruce / Mission Amps]

Didn't think that company was into much hype...

Hmmm.... If you call and talk to them you might change your mind, regardless, MM is one of the most overly hyped up winders in the biz.
Possibly what you seeing there is a bunch of trannys that they built as customs for a few boutique builders and then decided to sell them as their standard fare too.
I have heard that many winders will not offer any exclusivity for custom work.
Heyboer has done this too and I have found a couple of mine (with a slightly part number) being sold as someone else's. Very disappointing, but the vacuum tube amp business is quite cut-throat.

[seven]

I have heard that many winders will not offer any exclusivity for custom work. Heyboer has done this too and I have found a couple of mine (with a slightly part number) being sold as someone else's. Very disappointing, but the vacuum tube amp business is quite cut-throat.

Bruce, that's unfortunate. I didn't know that Heyboer made your trannies.

If I may ask, what is the secondary on your 5E3 PT come in at?

[steve_rolfeca]

Perfect timing! I'm trying to tame the high internal voltages in my recently completed 5E3 kit.

The amp is much louder and cleaner than I expected. Nice tone with a Weber 12A125, but with a Strat in the normal channel, breakup doesn't really come in until the volume is up around 9. Also, the dynamic response is fairly "stiff", a bit like a Fender DR Reissue.

I suspect that this is related to the Mojo Export power transformer. With no tubes installed, and the line voltage off the wall at 121.7VAC, I measured a no-load AC output of 811 volts. With tubes installed, the heater voltage is spot-on, but I'm seeing around 388 VDC at the plates.

That's with a 300 ohm bias resistor and either an NOS Sylvania 5Y3GT, or a Weber Copper Cap. With Tung Sol reissue 6V6's, it biases at about 40ma per tube. If I re-install the Sovtek "5Y3" that came with the kit, it jumps up to 427-428VDC and 43ma (!!!).

I installed screen and grid resistors to protect the tubes, and it's operating reliably, but I'm thinking that the amp would be more responsive if I could get the voltages down to vintage levels.

My vendor disagrees, but when I pressed the point, he suggested adding another stage before the first filter (40uf 500v with a dropping resistor somewhere between 1K and 10K).

I don't want to this, nor do I want to add a diode, or an even larger bias resistor. I've never had the opportunity to spend quality time with a Tweed amp in good condition, and I'd like to spend some time with it in authentic 5E3 trim before I start tinkering.

Could someone suggest a source for a PT that will give me more-or-less authentic vintage plate voltages? My local line voltage runs around 122 to 124 VAC, depending on time of day.

[seven]

I suspect that this is related to the Mojo Export power transformer. With no tubes installed, and the line voltage off the wall at 121.7VAC, I measured a no-load AC output of 811 volts. With tubes installed, the heater voltage is spot-on, but I'm seeing around 388 VDC at the plates.

That's with a 300 ohm bias resistor and either an NOS Sylvania 5Y3GT, or a Weber Copper Cap. With Tung Sol reissue 6V6's, it biases at about 40ma per tube. If I re-install the Sovtek "5Y3" that came with the kit, it jumps up to 427-428VDC and 43ma (!!!).

I measured about 385-0-385 no load. Looks like you are seeing about 406, about 20 volts higher, but I was running at 120.8VAC... What are you seeing with load?

I think the originals used a 250 ohm bias resistor.

Could someone suggest a source for a PT that will give me more-or-less authentic vintage plate voltages? My local line voltage runs around 122 to 124 VAC, depending on time of day.

Yeah, no one else has chimed in with original 5E3 PT stock secondary voltages running on 120VAC, +/- a volt or so...

Still would love to know what Bruce's secondary is coming in at...

[teleamp]

Hmmm.... If you call and talk to them you might change your mind, regardless, MM is one of the most overly hyped up winders in the biz.
Possibly what you seeing there is a bunch of trannys that they built as customs for a few boutique builders and then decided to sell them as their standard fare too.
I have heard that many winders will not offer any exclusivity for custom work.
Heyboer has done this too and I have found a couple of mine (with a slightly part number) being sold as someone else's. Very disappointing, but the vacuum tube amp business is quite cut-throat.

The did the same thing to Bill Webb on a transformer he had them reverse.

MikeY

[Bruce / Mission Amps]

The did the same thing to Bill Webb on a transformer he had them reverse.

MikeY

Yup standard fare! I had an issue once with the winder adding another 25 pieces to my order so that a very famous, well known, .. tweed clone amp builder... you know who, ... could pile onto my order of my own custom spec'd and custom wound output trannies so they could get my 100 piece discount! Gads what back stabbing sluts.
Did you get my reply message about the Sylvania 12AY7

[teleamp]

.....Did you get my reply message about the Sylvania 12AY7

Yes, there is a Santa!!! Let me know when the chassis are ready. I have a 1961 Jensen P12N on the way. This 5E3 is for me.

Did you get a chace to read this thread: http://www.thegearpage.net/board/sho...d.php?t=314363

Anyway, whenever your chassis are ready so am i, looking forward to it Bruce.

MikeY

[Bruce / Mission Amps]

Yes, there is a Santa!!! Let me know when the chassis are ready. I have a 1961 Jensen P12N on the way. This 5E3 is for me.

Did you get a chace to read this thread: http://www.thegearpage.net/board/sho...d.php?t=314363

Anyway, whenever your chassis are ready so am i, looking forward to it Bruce.

MikeY

I met with the metal polishing guys Wednesday and fifty Mission 5E3 chassis are on their way across town to the chrome plater this morning!!
After that, it's a quick trip over to the silkscreener's shop and when those are screened, baked and all done, I can start shipping my back orders... jeeze ...this last 50 Deluxe chassis took a long time to get out of the metal finisher's shop for some reason. They are about 45 days behind schedule.
A bit embarrassing for me this time as usually I can ship the 5E3 kits out in just a few days.

[TD_Madden]

Bruce,

I have a couple Tweedies I built a few years ago before you had the "voltage-corrected" PTs....consequently, I've got the zeners installed to drop the voltage.

Do you sell the "corrected" PTs separately now?