New member introduction and some Express build questions

[shaunf]

Hi gents,

My name is Shaun and I am from South Africa. I stumbled upon this forum a few months ago while I was rebuilding my old Marshall JMP 50 watter and was amazed by the wealth of knowledge and information shared so freely here. I am pretty much a novice when it comes to electronics and amps. I acquired some basic knowledge when I decided to rebuild my old Marshall, due to the old turret board becoming conductive as a result of moisture ingress over time. The amp spent many years very close to the seaside and I guess this is what caused it. Fortunately, I was very lucky in that the amp worked perfectly first time, with absolutely no startup issues and she now plays like a dream.

Reading many of the forum posts got me fascinated in the Trainwreck amps and I recently decided I am going to bite the bullet and build myself an Express clone.

I have been in contact with RJ thanks to this forum, and am busy putting together an order, and in my spare time I have been learning as much as I possibly can about the Express amp, and digesting all the info all of you have so kindly provided. I feel that this is a fairly ambitious project for me to take on, but I am looking forward to the learning experience and also hoping that you gents will guide me when I get stuck.

To talk a little bit about my build:

1.) We run 220v here in South Africa, so I am going to be using one of those multitap Heyboer power transformers.

2.) I want to fit the Hall VVR during the build phase.

Based on those 2 factors, RJ has advised that using the above tranny together with the traditional cap stack is a relatively tight squeeze, but can be done. This becomes even tighter when you factor in the VVR. He suggested possibly using the multi-cap cans instead, which I agree may be a better option, and I'd like your thoughts on this.

Secondly, I haven't seen a layout diagram illustrating the use of multi-cap cans. Is there anyone that could point me to one, if it exists, or possibly assist me with this?

Thirdly, in reading Ron's build guide (Thanks Ron, I can appreciate the amount of work that went into that document), I see in the biasing procedure it talks about installing the 1 ohm resistors in place of the ground on the power tubes, but then later removing them and reinstating the ground after biasing. I also see some guys building clever bias boxes so the resistors are housed externally, instead of having to physically install the resistors in the amp. My question is can the resistors not simply be left in the amp, and if not, why not? I installed them in my Marshall and simply left them installed as per the layouts I got from the Ceriatone website and the Metro Amp forum. Is this a bad idea?

Thanks in advance guys, and I look forward to being a part of this fantastic forum and the passionate community who inhabit it.

Regards,
Shaun

[sliberty]

Welcome Shaun.

My first Express build includes permanently installed 1 ohm, 1% resistors, and banana plugs to use as test points. leaving them in is negligible, so go for it.

Steve

[M Fowler]

Funny you should ask, rj has me building an experimental Rocket right now using 33/33 can cap and 40/20/20/20 can cap. Very tight but can be done.

Mark

[shaunf]

Thanks for the welcome guys.

I have a couple more dumb questions, relating to Ron's Layout diagram, just for me to check that I'm clear on it:

1.) Looking in the area of the PS board and the cap stacks, does the red lead from R28 actually connect to both C18 and C20?

2.) Does the red lead from SW3 connect to C15 and C16?

3.) Does the blue lead from R27 connect to the lefthand turrent before going on to C18?

In the Ceriatone layout diagram the above connections are different.

[M Fowler]

1.) Looking in the area of the PS board and the cap stacks, does the red lead from R28 actually connect to both C18 and C20?

R28 connects to C20 only/

2.) Does the red lead from SW3 connect to C15 and C16?

Yes these two caps are together.

3.) Does the blue lead from R27 connect to the left hand turrent before going on to C18?

No it connects to R27 only so it has 18K instead of 9k1 the other caps are seeing.

[prspastor]

I left the 1 ohm resistors in my Express clone as well, although I separately grounded pin 1 to the lug with standard wire. I used the 1 ohm from pin 8 to the ground lug. Works just fine.