JTM 45/100 - Build story

[BoogieEngineer]

The NFB wire ... he purple one going from the 27k to the 16 ohms tap ?
it's on my layout. Or were you talking about another one that i missed ?

Yeah that's the one. I prefer soldering it right to whatever tap you want while you do the impedance switch.

[Xplorer]

Ok, i'll do this.

I tried to solder a buss wire accross the back of the alpha pots but the solder couldn't stick..

i'm mixed up between a full larry's grounding( meaning i'd have to unsolder a few grounds i already did ? )
or having a partial larry's grounding, only for the pots with wires from the ground lugs of the pots to some lugs on the chassis,
and find a solution for the buss wire ( these aren't pec pots, so i can't really have a lug reserved for the buss wire, high enough to prevent it from touching the other connections ) .

What do you guys think ?

[Xplorer]

Hold on, i sanded a bit the back of a pot, out of the amp. And i waited to see the tin getting stuck to the pot in less than 30 seconds. Indeed, it works in the end.
i might simply do this, like a stock old jtm. And i'll probably use the larry's grounding technic for the next 45:100 and compare both.

[VintageCharlie]

Looking fantastic...! Will you populate the board while it is in chassis? I suppose it's easier while it is outside?
Looking forward to the compelted amp+ pics and clips! Good luck!

Charlie

[Xplorer]

Hi karlis ! Sure, i'll populate the boards outside the amp. Thanks

[shakti]

I actually prefer to load the board up with the boards mounted in the amp. Everything stays nicely put that way.

[BoogieEngineer]

I actually prefer to load the board up with the boards mounted in the amp. Everything stays nicely put that way.

I find you could spray the melted rosen core all over the interior of the amp.

[Xplorer]

I may install the wires with the boards first, and the components in the end, with the boards inside the amp. We'll see.

[Xplorer]

[VintageCharlie]

My tech let the wire through the turret and hooked it around the top, then soldered it to place together with the component with just one joint. Looking at vintage amps galleries - at the underside of boards, it seems like this is the way they did it at the Marshall assembly plant too, as i haven't seen any visible solder joints beneath the boards. Also, this way there's no risk that the joint under the board holding the wire could melt while you are putting components on the top-side.

[Xplorer]

i might do this. i didn't take a close look yet but usualy i'm following the pictures of the old ones.

[Xplorer]

soldering the back of the pots is really a pain in the ass ... now that it has some solder on it, it doesn't want to melt anymore, to let me solder the buss wire. i should buy a new solder gun, hotter i guess.

[ol foot]

I found putting a bit of flux on the pot first made it heat up much faster and was able to solder the buss wire on easily.

[Xplorer]

Thanks, but i'm nt sure to know what's flux. The solder gun seems hot enough to melt tin on the back of the pots, but not enough to melt it again when it's got cold, as it is a bigger piece of tin than a simple wire of tin. for now i'm stuck ..

[VintageCharlie]

Flux is the stuff that cleans out all the dirt, when you're soldering. There is flux in the core of the soldering wire and normally it is enough. If you work with dirty surfaces, oxidated surfaces, etc. it is recommended to use additional flux - it will help ou get the surface cleaner and get the solder flowing better. If you're using NOS stuff, i'd say, even after proper removal of all the dirt and gunk from the contact surfaces, additional flux would be quite mandatory. But i'm no expert - i'm sure other more knowledgeable guys will guide you through this.