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Hi everyone
After a lengthy battle with the British Post Office I finally got my Plexi kit last week and it seems to be the first one to be built on here.

The differences between this and the normal sIII are the coupling caps of which there are 6 0.022uf Sozos on the board and a 500uf bright cap over the volume pot.

This will be my first amp build. I've built a few BYOC pedals which have given me a grounding in how to solder which has been invaluable so far.

I've been lucky enough to scrounge a set of Mullard EL84s and a Mullard 12AU7 which I might try and use in the phase inverter.

I got these untested and exposed to the elements for the last two decades or so so it shall be interesting to see if they work.

No rectifier valve as yet. I'm interested in the use of an old octal base with diodes soldered in although I have heard this can raise the B+ higher than the caps will go. Hopefully it may get the sound closer to the 1987 that the amp takes its inspiration from. Has anyone tried a solid state rectifier with the kits?

Hopefully I shall get the chassis and transformers up and running in the next few days and put a few more updates on!
cheers
Dom

Lucky to scrounge ... I'll say. The board looks good.

I've built two plexi 18s and lbet modded his sIII . Stick with the tube rectifier vs the diodes. Voltages could be too high and the EZ81 does not have much sag anyway. I was going to build that into one of the models I made but it sounded too good to mess with.


And yes, you are the first plexi 18 kit builder!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Wow have fun!

I've been thinking about plexi lol... i wonder if i should just use my current recto and swap out the caps - just to try it... i'd have a saggy plexi lol...

Edit - Like Stephen said i wouldn't use the cap can... i think the sag on that recto is really low like only 10v or so...plus you are much cooler with the real deal under the hood. Tubes all the way bro.

Ill see about finding an EZ81. None up for scrounging unfortunately!
The valves came from my dad's shed. I've got a box full of stuff unfortunately nothing else seems the right stuff for guitar. Lots of old Mullard and Brimar though
Right got the hardware on - well most of it anyway



Has anyone used a 12AU7 in their amp? I've heard its too low gain for the Marshall sound but seems worth a try seeing as I have one lying around

"The valves came from my dad's shed."

That's so awesome. I picture a garden shed with lots of Second World War-era bits and pieces laying about.

Like a mini Bletchley Park.

Havent tried that one but read this about swapping tubes:

http://www.thetubestore.com/gainfactor.html

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Heater wiring and v1 are done hopefully ill get some pics up tomorrow.
Stephen can you give any advice on wiring up the 120v lamp for using with 240v? Im pretty sure the diagram shows it being wired up between the 240v and 120v taps but just want to confirm.
Im also hoping to start building a head cab and 1x12 speaker cabinet. Pine is pretty plentiful and cheap here and I already have all the gear to cut and make joints etc so that is what ill most likely use.

That's the way you do it .... [money for nothin' & your chix for free...]

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

After a week not working on it (mainly due to Black Sabbath at the weekend) I've finally got the power supply and heater sorted



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I know its a bit messy however it seems to work.

hey; good start! it's not looking bad at all; the heaters look wired up nicely. Maybe twist the 6.3v green heater wires as they get close to the terminal and route them to the bottom of the chassis and it will look alot cleaner. Also I would install the ground terminal and route all the grounds from the PT to it right now(just to get them out of the way)

What i have found is that if you take one wire at a time and route it in a clean way it makes it harder to make mistakes (because you can see everything better) Also; it makes the project feel like it's going faster because everything goes from messy to clean.

Have fun!

Yes, short, tiwsted leads on all AC, routed away from low level signal side (pre amp, PI) is good practice.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I've finally finished although I'm still not sure I've got the power transformer wiring right for 240v.


However the rest is all finished and should be correct




If the transformer wiring is correct all that remains is to start it up and see if it works!

Trinity 240V wiring

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Cheers Stephen
All finished now. Testing hopefully tomorrow!

Happy New Year!
Just finished testing the plexi. The TMB channel worked fine and sounded brilliant through my Les Paul and rangemaster clone. There was a slight problem with mains hum but that may be due to the lack of cabinet. The other channel works on the low impedance input but the high impedance does not work and makes a loud buzzing sound which looks likely to be due to a dry joint.

All problems now sorted. It works amazingly well and is near dead quiet. Next is the head cab and a 2x12 speaker cab

Great news. What was the problem in the end?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

It was a poor joint where the resistor met the input jack. Sorted it immediately and it all worked

Congratulations since this was your first amp build. One solder joint is excellent!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps