SVT transformer dims request

[Jelle]

At the moment I'm drawing out a chassis for an amp that I plan to use ampeg SVT power and output transformers but I cannot find info about the dimensions of the holes that have to be made in the chassis to accommodate these transformers.

Does anybody know the dimensions of the holes that are needed in the chassis?

Thanks,

Jelle

[Enzo]

Don't know, but won't you also need the filament transformer?

[bob p]

mercury makes reproductions. they have the physical dimensions if yoiu ask for them.

[Jelle]

Good points!!! I did not realize the separation of the heaters to an another transformer....

Thanks guys! You rock!

Jelle

[Jelle]

Hi guys,

I contacted Mercury but they did not have the drawing as of this time....

I know that the best way is to order the transformers before the chassis but this way saves me a lot of time.

Is there anyone with a 6550 SVT on the bench who is willing to send me the dims to draw up a chassis?

I'd appreciate it.

Thanks,

Jelle

[bob p]

sounds like they blew you off. i've gotten measurements out of them by email a number of times, but then i have an account and i buy stuff from them. it couldn't be too inconvenient for somebody at mercury to take a ruler over to the shelf and measure it for you. they probably dismissed you as a tire kicker that wasn't really interested in buying something.

[Tom Phillips]

Jelle,
If you are building an SVT from scratch maybe you should consider using off-the-shelf transformers from a company like Hammond. They won't be the same form factor as the original SVT transformers but you won't be paying for reproductions of vintage drop in replacements which come with a premium price.
Just a thought,
Tom

[Jelle]

I also thought it was strange that a respected company that is very proud of it's products was not able to give this information... They are not encouraging me to order their products which do have a good reputation.

Tom, thank you for the suggestion! I have found SVT PT and OT trannies for about 125 USD each at Fliptops.net and they did give out the info.

If I would want to build an amp with 4x6550 with the screens at ca 350-400v and the plates at ca 600-700v like the fender PS, what would be the ratings for the PT for the HV section?

I'm building a guitar amp from scratch BTW...and I like the way the Fender PS and SVT's have their power supply to the 6550's.

Thanks,

Jelle

[Tom Phillips]

Originally Posted by Jelle

...Tom, thank you for the suggestion! I have found SVT PT and OT trannies for about 125 USD each at Fliptops.net ...

I'd go with that if you can get them but that price sounds too good to be true. I would expect about twice that price plus the heater transformer. Is there a special deal going on? Or...better check again.

[bob p]

Originally Posted by Jelle

If I would want to build an amp with 4x6550 with the screens at ca 350-400v and the plates at ca 600-700v like the fender PS, what would be the ratings for the PT for the HV section?

That sounds an awful lot like the standard 200W, fixed-bias, 600 plate voltage, 5K load, 3% THD setup that's listed in the GE 6550 data sheet. Top of Page 3, right side. Add it up. For 2 pairs running full tilt: 2 * ( 270 + 33) = 606 mA @600 VDC, just for the power tubes.

You won't have a lot of options available for transformer iron at that voltage and current rating. There are some threads where we've already covered this exact application if you're interested.

[Steve Conner]

I saw the title "SVT Transformer Dims..." on the new posts page and expected the next word to be "Lights"

I've been looking for PTs for a similar amp project using an old Fender 300PS OT. I just asked around my junk collecting friends and hunted on eBay. So far I came up with:

a 240V:240V isolation transformer (we have 240V line here) which could be hooked to a voltage doubler, just like the 300PS did. Of course there is no heater winding, but the SVT didn't have one either. If you got a toroidal one you could easily add a heater winding using some fence wire or similar However, I'm wary of this approach because any current you draw from the half-voltage node of the doubler (where the 300PS connects its screens and preamp) will appear as a DC imbalance on the PT, which could upset a toroidal.

A PT from a 300 watt tube ham radio transmitter that used paralleled TV sweep tubes. This has loads of extra windings for heaters, bias and screen supplies, etc. It's maybe a little undersized, but I plan to try it anyway.

[Jelle]

Originally Posted by Jelle
...Tom, thank you for the suggestion! I have found SVT PT and OT trannies for about 125 USD each at Fliptops.net ...
I'd go with that if you can get them but that price sounds too good to be true. I would expect about twice that price plus the heater transformer. Is there a special deal going on? Or...better check again.

Tom,

I have made an error here! I apologize for this. Sorry! The price is indeed about twice.

Bob,

I'll check the threads you mentioned, Thanks!

Jelle