RS clone OT - correct primary wiring?

[novosibir]

It's the first time, that I'm building a MetroAmp JTM45 kit with a Marstran RS clone OT.
I've wired the secondary for 16 ohms, as seen on the attached diagram, means blue-yellow together, black-green together, to run the brown to the speaker jack's shield (ground) and the red to the tip (hot).

But which of the primaries have to run to V4's control grid and which to V5's control grid?

On the diagram it seems, that the secondaries are inverted connected, because the hot is taken from the bottom of the winding, the ground from top of the winding - as opposed to all other OT's diagrams.

So after my logic the primaries w/ the stripes must go to V4's grid and the primaries w/o stripes to V5's grid...

... but who of you knows it concretely?

TIA

Larry

[Athlord]

So after my logic the primaries w/ the stripes must go to V4's grid and the primaries w/o stripes to V5's grid...

... but who of you knows it concretely?

TIA

Larry

Hello Larry,
yes that´s right.
Gruss
Jürgen

Ps.: Wenn es Pfeift - dann wars doch nicht richtig....

[novosibir]

Hello Larry,
yes that´s right.

Thanks Jürgen! Seems that my logic was right

Ps.: Wenn es Pfeift - dann wars doch nicht richtig....

This is what I want to avoid right from the beginning, a possible squealing or motorboating...
... and I hate to unsolder again, because desoldered and soldered again cables never look as neat as at the first take - the insulation was melting, the cable itself became stiff due to soldering at its end, aso.

It's also, because I run the greens and the browns to a DPDT switch first, to switch between 6.6K and 8K - and when I have to swap 4 cables later due to possible problems, two then are too short

Larry

[Athlord]

Hello Larry,
your work is verry accurat and clean - therefor i understand that you ask for the right wiring.
Cheers
Jürgen

[novosibir]

your work is verry accurat and clean - therefor i understand that you ask for the right wiring.

Thanks Jürgen!

But nonetheless now I'm confused!

Just got a OEI sheet from Brian Wallace in an email and he told me, that he's using the same color code as it's been used by OEI - but by reading this sheet it seems, that it's quite the opposite

So once again - are you absolutely sure and have you tried it yourself with a Marstran RS clone?
Or was your opinion just by looking at the diagram I've posted above?

Larry

[Athlord]

Hi (Moin Moin) Larry,
i am confused too.
Look what you can see on the Marstran Site:
http://www.marstran.com/RS%20OT%20wiring%20diagram.gif
These Pictures confirmed this.....

"The fault almost always is sitting in front of the amp " - in this case it´s true...

Cheers
Jürgen

[novosibir]

Look what you can see on the Marstran Site:
http://www.marstran.com/RS%20OT%20wiring%20diagram.gif

Yep I've seen it, Brian has added the tube numbers after my inquiry and after starting a topic on his forum:

http://forum.marstran.com/viewtopic.php?f=2&t=257" onclick="window.open(this.href);return false;

In a few days I'll know, what was right, but have wired it now after the new insight.

Larry

[RockingJTM]

I finished my JTM45 2 weeks ago. I installed the Marstran RS OT, the Marstran 20H choke and the Marstran 1202-55 PT.
The amp sounds really great now!! such a tone. I love it!!! Here are some pics. I'm sorry for the wiring mess.

http://img23.imageshack.us/img23/264/img7841m.jpg
http://img42.imageshack.us/img42/8431/img7805.jpg

[paulster]

My quick technique that I use for all new transformers to determine winding polarities is to use the 1kHz square wave test signal on my scope on the primaries and into channel 1 and then take each of the secondaries into channel 2.

The square wave doesn't look so hot being terminated like that but it's still perfectly effective for identifying which way round the primary and secondary should be to guarantee no horrible squeals or having to extend wires after installation.

It saves having to hook up a signal generator too.

[novosibir]

... to use the 1kHz square wave test signal on my scope on the primaries and into channel 1 and then take each of the secondaries into channel 2.

That's a good idea! Why didn't it come from me

I'll try it, before I fire the amp up first time

Thanks Paul!

Larry

[paulster]

That's a good idea! Why didn't it come from me

There's clearly a first for everything!

Let me know what you think of the tranny once you've finished with the build. I'm really tempted to add a JTM45 to my stable for some nice tube rectified squish, and Brian's RS OT was top of my list.

[Twistingcrow]

Yes Larry, tell us what you think of this tranny, I don't know what to choose between the stock Metro tranny and the RS deluxe... Telling us what differences separate them would greatly help...

[novosibir]

Yes Larry, tell us what you think of this tranny, I don't know what to choose between the stock Metro tranny and the RS deluxe... Telling us what differences separate them would greatly help...

Sorry, but I think, that I must disappoint you!

I haven't compared the Metro tranny to the RS deluxe and I don't intend to still do it.
I've simply choosen the RS clone for this build after hearing this tranny in another amp 2 years ago, what simply was overwhelming

And this RS clone in the amp, I've finished 3 days ago again is nothing else than simply overwhelming, though it's still not broken in and also the SoZo Vintage's aren't - I have a hard time, to stop playing at all and it's a sound, what none of my amps can obtain - neither my DINO, nor my British Purist - this sound is particular!

Larry

[paulster]

You're really not helping with the GAS, Larry!

Glad to hear the tranny is that good though.

[HTH]

The RS OT has an amazing tone - its a very special transformer indeed. I put one in an AC30CC and it transformed the amp.

I'm planning on building a 2x12 combo (with 6L6s or EL34s) around this OT and have the amp's tone fall somewhere between an AC30 and a Fender Twin.