2nd Build-Rob's JTM45 Micro

pfarrell

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This is awesome. So you had stencils made for the panel graphics and then it looks like you inked them yourself—or you had them laser engraved and then you filled with black? I've been using Front Panel Express—not super cheap—and the white on black anodized alu printing is not as HQ as actual screen-printing (they do double hit the white though). Black ink (still digital) on natural anodized aluminum is VERY good.... I'm also doing all my layout stuff in Illustrator...The cool thing about FPE is they will also drill, and it barely adds to the cost.

I've been scratch-building all my guitar amps... It's nice to see this thread. Can't wait to see the final!!
 

willholt92

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This is awesome. So you had stencils made for the panel graphics and then it looks like you inked them yourself—or you had them laser engraved and then you filled with black? I've been using Front Panel Express—not super cheap—and the white on black anodized alu printing is not as HQ as actual screen-printing (they do double hit the white though). Black ink (still digital) on natural anodized aluminum is VERY good.... I'm also doing all my layout stuff in Illustrator...The cool thing about FPE is they will also drill, and it barely adds to the cost.

I've been scratch-building all my guitar amps... It's nice to see this thread. Can't wait to see the final!!

Ah thanks a lot. It’s starting to look real now.
The plates are rear etched and then painted in. I did the artwork in Illustrator and then sent to Tubetown, they do loads of custom faceplate finishes, and cut holes too. It was pretty well priced for custom work.

Thanks I’m looking forward to getting building it now.
 

willholt92

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Small Weekend update.

I had a Sunday to myself for once, my Mrs had stayed at her parents with our daughter and the dog so I had time and chance to set up on the kitchen table.

I finalised most of the drilling, Board mounts, Ground points, Screw holes for the IEC connector (which I had forgot to include on my back plate when it was laser cut) and the holes for the OT and Choke. Also the cable holes for the OT and Choke to fit the grommets.

I've ordered a set of Rivnuts and a gun so that I can have these underneath the board and can still remove the transformers with out taking the board out if I ever need to.
So when these arrive I just need to open the holes up to the right size and rivet them in place, and hopefully that's the last of the drilling so I can start fitting components permanently.

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I moved on and wired and soldered the pots connections outside the chassis, and the bright switch with @Bitsleftover suggestion.
I tried to make my wiring as neat as possible on this build.

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I've ordered a pack of M3 button head screws and nuts so I can mount the board standoffs and ground tags when these arrive.
 

willholt92

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Me and my family have finally been hit by Covid so over the weekend as we are isolating I had an hour or so spare and my Rivnuts and gun came so thought I'd mount them.

Drilled the holes out to 6mm, and fitted them.
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Got all 4 in and then added my board standoffs to make sure everything clears which it does.
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This is when I noticed a really annoying issue.
BOTH of my Hammond transformers, OT and Choke have mounting holes which are off on one side. The stamping clearly hasn't been manufactured correctly which means that while one M4 screw will fit and tighten properly, on the other side the head of the screw hits the body of the transformer and will not tighten.


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Piss poor to be honest, I'm not very happy about it, wouldn't expect this level of sloppy tolerance from a decent manufacturer, particularly one with dimensioned drawings on the data sheet.

So not really sure what to do about it now, either carefully drill the mounting holes on the trannys out on the side which is too close, or go for a smaller screw like M3. Neither is ideal.

Either way it means that I need to redrill and fit more rivnuts in a different place.

Annoying too because I did check the screws fitted before drilling the holes but I only checked one side and this was the one which is okay.

Moral of the story check eveything twice.
 

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smuc

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Well, that's a bummer. Why don't you do a warranty claim/exchange with TT?

Otherwise, a nice looking build!
 

lowatter

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Why not just grind the heads smaller on both the screws slightly to make it work? I don't think it would be very noticeable and it would be a far less hassle. Your design and execution is great and I'm sure it's going to be a great homebrew amp.
 

jman72

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Why not just grind the heads smaller on both the screws slightly to make it work? I don't think it would be very noticeable and it would be a far less hassle. Your design and execution is great and I'm sure it's going to be a great homebrew amp.
This is what I'd do. Building an amp (or anything) usually requires some "cheating", since nothing ever works out perfectly. Filing down one of the screw heads would be the easiest fix by far.

Another option would be to take a pair of pliers and bend the tab on the transformers out a bit to make it fit. Not sure how stiff the tabs are, though.
 

Lancer X

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Looking great. All your custom plates are going to look spectacular!

I just finished a Deluxe Micro Mod, and I'm certain that your careful planning will ease your build. I just decided to use a Vibro Champ cab and chassis, and just bashed through and somehow it all fit (by about a mm). Very tempted to do the Micro Bassman next. Well, maybe after I sell my full size 5E3 that is, so my wife won't leave me... 😄
 

willholt92

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Well, that's a bummer. Why don't you do a warranty claim/exchange with TT?

Otherwise, a nice looking build!
I know, such a pain. I did wonder about that, but to be honest I bought these probably nearly 2 years ago so don't know if I could get them exchanged under warranty. I'll try and modify my way out I think.
 

willholt92

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Why not just grind the heads smaller on both the screws slightly to make it work? I don't think it would be very noticeable and it would be a far less hassle. Your design and execution is great and I'm sure it's going to be a great homebrew amp.
Yeah that is an option I'll probably try, it just grates on my designers OCD. Thank you very much I think that's what's more annoying I've been trying to be super accurate a tidy on this build.
 

willholt92

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This is what I'd do. Building an amp (or anything) usually requires some "cheating", since nothing ever works out perfectly. Filing down one of the screw heads would be the easiest fix by far.

Another option would be to take a pair of pliers and bend the tab on the transformers out a bit to make it fit. Not sure how stiff the tabs are, though.
I tried bending the tabs as soon as I noticed but it makes it even worse with the hole being so close to the pivot point it puts them completely out of line with the Rivnuts. If I was using nuts and bolts it would probably just about work.

I've found some low profile socket head cap screws I'm going to try first, hopefully they'll allow me to sneak them in. Hex head screws are smaller head profiles compared to pozi or philips.

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If not it will have to be taking them to a grinding wheel for now.

Worst case scenario as I work in design and manufacturing I can have special fixings made in the far east to pretty much any spec I need so that might be the final fall back.
 
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willholt92

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Looking great. All your custom plates are going to look spectacular!

I just finished a Deluxe Micro Mod, and I'm certain that your careful planning will ease your build. I just decided to use a Vibro Champ cab and chassis, and just bashed through and somehow it all fit (by about a mm). Very tempted to do the Micro Bassman next. Well, maybe after I sell my full size 5E3 that is, so my wife won't leave me... 😄
Thanks very much
Yeah I've already got parts massing for my next 3 builds haha it get's very adictive this amp building lark.

My Mrs doesn't know about those yet so they'll be making their way into my friends' hands when they are built I think.
 

Bitsleftover

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Will, I’ve got a spare OT waiting on my next build. If it makes life easy, I’ll gladly swap you. (I’m only down the road near Doncaster Airport) I’ll just drill a smaller hole in my chassis when I eventually make a start so it won’t make any odds to me.
 

willholt92

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Will, I’ve got a spare OT waiting on my next build. If it makes life easy, I’ll gladly swap you. (I’m only down the road near Doncaster Airport) I’ll just drill a smaller hole in my chassis when I eventually make a start so it won’t make any odds to me.
Ah sugar. I've only just seen this Mick.
Thanks for the offer mate, my new screws came yesterday so I had a few hours on it last night and I noticed that one of the Rivnuts for the Choke went in on the piss some how, looked okay from the top but it was angled inside chassis.
I could get the screw in about 1/4 of the way and then the oh so familiar feel of cross threading, so I bit the bullet and just drilled a new hole and banged another Rivnut in.

Really appreciate the offer though. Good to have you so close in case of disaster.
 

willholt92

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New screws arrived yesterday so tried fitting my transformers. OT went in perfectly, amazing what difference 1mm makes. Choke unfortunately didn't but after I realised I've messed up on of the Rivnuts for the Choke, so I just drilled a new hole and added another Rivnut. Thankfully the board hides my mistake from inside the chassis.

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I need to decide what I'm going to do with the unused taps on the OT, I was going to leave them full length and just cap and tape them off but they do look quite a mess so I might just cut them down before I do.
Although I have been thinking that I might use the second output jack as a 16ohm and have both 8 & 16 to give me a bit more flexibility for cabs and speakers instead of a headphone. TBC for the moment.

I fitted the backplate and all the components which all wet smoothly.
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Then put all the valve sockets and ground points in too while I was there.
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Hoping I might get a few hours this weekend and get the inputs wired and in and maybe start running heaters.
Although that will depend on how a tiling job in my kitchen goes
 

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Lancer X

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Looking great, man!

If you've ever done a build with eyelets, let me know if you find the turrets much more challenging to solder. I have been considering a turret board for my (eventual) Bassman Micro.
 

willholt92

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Looking great, man!

If you've ever done a build with eyelets, let me know if you find the turrets much more challenging to solder. I have been considering a turret board for my (eventual) Bassman Micro.
Thank you, it's getting there now.

I haven't built an amp on eyelet board yet, this is only my second build.
I have built a couple of pedals on Eyelet boards though, and they are easier to solder to than turrets from my experience.
I am planning to use eyelet board for my next build which will be Rob's Tweed Deluxe.

Turrets definitely require more heat when soldering, so I'd advise getting a large flat tip for your iron which will hopefully help.
 

willholt92

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Bit of an update/ really angry episode

I had a go tonight to get a bit more done on the amp while my Mrs is out.

I've been steadily building the cabinet over the last few weeks, I couldn't be bothered with the finger jointing and ended up just glueing and screwing the head and then drilling and doweling the holes.

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I came to solder the input jack tonight and hopefully I have done it right.
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I thought I'd get the resistors and heaters done on the valve sockets what a nightmare this has turned out to be.
I bought a JTM45 wiring kit from Modulus here in the UK, and the wire is so thick, the plastic sleeving is awful.

I've just nearly smashed the entire amp up in anger at trying to get the heater wires on the sockets. Burnt myself so badly and I've given up.

What gauge of wire do the heaters need? I'm going to buy some good quality solidcore wire for it because I cannot get the wire I have to work at all.

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Any help would be much appreciated, I'm so f******g pissed off with it.
 

Paul-T

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I'm getting a glitch on this page and can't see all the photos; but I used #22 for heaters on my micro, and Marshall famously used that gauge for heaters in their heads.
 




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