Two Express Transformer Questions

[mumford]

I got a new heyboer output transformer for my express and will wire it up this weekend. I had 2 questions:

1. Does it matter which of the green and purple (6.6k) wires go to V4 and V5? I thought I saw something saying one way was better.

2. I'm still getting hum when I turn up. I'm wondering if I need to rotate my transformers 90 degrees. Currently, in relation to the chassis, my PT is oriented with the bells to the sides, and the OT is oriented with the bells front to back. Because of this orientation, my heater wires come into the chassis about 1/8" from the filter caps and run straight back (not under the power board, like everyone else's). I know the two of them need to be 90 degrees from each other, but I'm wondering if I installed them both the wrong way?

[Structo]

Can't answer the transformer question properly but yes, you generally should have the cores 90 degrees to each other.

The primaries on the OT should go to the proper power tube.

If you get them backwards you will get positive feedback and the amp will howl.

Leave the primaries long and just tack solder the leads to the tube pins temporarily to try it.

If it doesn't howl or squeal, then you have them right and can tailor the wires to fit better.

[mumford]

If it doesn't howl or squeal, then you have them right and can tailor the wires to fit better.

I suppose that would work. Thanks!

The same is possibly true of the PT, but I'm not sure if I'll need to drill out the chassis to do it. I suppose that's really what I'm asking with the other question--should the PT be bells front and back, or left and right?

[paulster]

An Express has the PT oriented with the endbells left-right and the OT endbells front-back.

Technically they would both be better at 90degrees to their current orientation, or with the OT moved to the side of the PT, as the magnetically quietest spots are on the endbell sides rather than the sides of the stack. Quite why Ken did it this way is a bit of a mystery, although he clearly wasn't worried about having an amp that was quiet at idle.

You can tell if your hum is from the PT/OT placement relationship if you still get the same hum with the amp in standby mode. If you do then it's purely magnetic coupling.

If the hum is only there in play mode then it's coming from somewhere within the chassis.

[mumford]

You can tell if your hum is from the PT/OT placement relationship if you still get the same hum with the amp in standby mode. If you do then it's purely magnetic coupling.

Yes, it's not coming from coupling. What I think the source is, is where the heater wires enter the chassis, but the only way to change that is to rotate the PT 90 degrees or 180 degrees. If I go 180 degrees, then I'll have the standby wires coming out of the same place the heaters are now.

I just don't know much about this stuff, I'm afraid.

[andrew_k]

Post some pics of inside the chassis before you go rerouting everything.

[M Fowler]

Express mounting guide.

Preferably without the wooden dowel

[M Fowler]

Also the Trainwreck files section has the Express builders guide showing all this.

The layout shows all the PT holes and OT holes where your wires should being coming into the chassis.

The picture is not my amp but clearly shows how it should look.

[mumford]

Thanks! I'm wondering if the ceriatone chassis or PT is a different size--because I don't have anywhere near that kind of clearance.

[M Fowler]

I had Nik A. at Ceriatone make my Express for me while I was building my own Liverpool using Allynmey chassis and toneslut transformers, joebob boards etc.

Here is a shot of the inside of that express, nice foot shoot huh

[M Fowler]

Mumford I took some more pictures for you since I have to Express out doing little changes to is about each week all for the better to me. Having said that some don't agree with my approach to just changing tone caps.

010 and 011 are ceriatone. The other is Allymeyer's chassis and his Pacific trannies.

I hope these photos help you out.

[mumford]

Fantastic! Thank you so much!

This shows me exactly what I was asking. Nik uses the same holes for the PT wires as I did, but his PT is rotated 180 degrees from mine. I was worried that I was going to have to drill new holes in the chassis in a weird spot to move the wires away from the filter caps. Apparently I don't need to be that extreme. You made my day.

[mumford]

Post some pics of inside the chassis before you go rerouting everything.

I will, and I'll probably double-post them.

[mumford]

Off topic message deleted

[M Fowler]

Glad that helped following the pictures and following Ron Worley's build guide and all should come together for you.