Calling all jtm45 kit experts..cuz I ain’t one...

[neikeel]

Was it not in this thread that we said the noisiest places to have carbon comps in the amp are the 1meg and 68k on the input?

[Tcaradonna]

Yes indeed it was. Oops! Once again I’ve fallen into the trap of following directions. I’ll rework these now as I can tell it will be challenging later on.

Out of curiosity, are there any opinions about which of my 2 turret boards to use? I have the old metro amp plain turret board as well as the double turret version. I plan to do my jumpers on the back of the board so I’m not sure what advantages the double turret offers other than looking cooler.

[Tcaradonna]

Progress note:
Dry fitting parts onto the turret board.

I used the CF 68k resistors here even though I have AB NOS CC type. Hoping for less extraneous noise (the non-musical kind). The synergy (rebadged Sozo) are big, so it’s a bit tough to make components around the fit neatly. I hope everything is in the right place...I triple checked it but things happen. This part took a lot more time than I thought.

I’m a bit unclear how best to wire leads behind and flipping over and soldering a component without causing the backside to come loose. How about taping a card board support to the back to hold things in place. I suppose one could dry fit the back, hold it in place with a cardboard sheet, flip it over, dry fit the components then solder from above once and all the way thru. That seems it would work.

Pics:
https://ibb.co/ygPfRzM

Cheers!

[neikeel]

Board looks great

You use bus wire on the back with insulated tubing.

Bring the wire up from the back and bend a hook over the turret, both ends. That way they cannot slip back. There is sufficient space for the wire and comonents (tight if x4 into 1 tho').

I personally use vintage split turrets for my builds and for those new to the game recommend the post 68 Marshall technique of using boards with a hole in board of the turret to loop the wire through and solder around the turret, putting the bus wire on top.

You can use the other under board technique as the finished build is much cleane,r but you will need to take photographs of the under side of the board to trouble shoot later (hope not) check and double check the connections and stick to Marshall wire colours (esp around the PI and screens connections as there are two ways of wiring the under board connections.

[Tcaradonna]

Progress note:
I struggled with a “best way” to do a front and back turret board, but the results came out ok. It’s been a learning experience for sure and I thank you for your suggestions!

I wasn’t able to shove all the wires thru the top from the bottom, too many places there just wasn’t room. Mostly because it ended up shifting an already tight board in certain areas out of an eye pleaseing placement—a big consideration for me. It looks most clean to have the wires on the bottom, but the most reliable and serviceable is probably all on the top and loops around the double turret. In the end, I actually found it best to tack solder the components on top, wire up the back, and then go back to the top to finish and dome solder the turrets.

I left a couple of areas unsoldered where it will connect to other wires on the board. I also pre wired the an up angle on the long white, yellow, orange and green wires because that is the ultimate direction for these wire. I double checked all my placements, and think I got it right.

Pics!
https://ibb.co/ssbwqq1
https://ibb.co/rG8hsz2

Cheers!

[AJW]

"dome solder the turrets"? The solder fillet on top of a turret should never be a dome. It should be concave as it recedes into the joint when cooling. A dome could mean that there is a void (bubble) within the solder joint. I know Marshall's had domes too, but trust me that is not good solder technique.

I spent a decade being recertified every year to solder for a military contractor, and I had to have an example of a perfectly soldered turret kept on file before I could go back to my job. Check this section on soldering turrets out: https://workmanship.nasa.gov/lib/insp/2 ... inals.html

Note that top mounted components are not acceptable in that document We all build our amps that way since Marshall did, but please stop short at replicating the dome. You'll have a more reliable circuit.

[Tcaradonna]

That’s very interesting.

Not having done turrets before I can’t say I know much about this. I know there is a mil spec that definitely seems to focus on the wrap soldering. I think that has the advantage of being able to visually verify and check someone else’s work, where as top loading components into a hole takes a leap of faith. Only having done the joint yourself or seen it done would you know if it was good or not, afterwards, there is no way to prove it. I can say I’m very confident of my connections having a good electrical and mechanical connection, because I watched very carefully how the solder wicked into these joints and the shear quantity of solder the turrets were taking, it was quite impressive! Anyone else would have to trust me. .

Some other boards mentioned this doming technique I referred to as the right way (whatever that means) or perhaps better to say more true to vintage. It actually was difficult to get the domes because as you said the solder wants to retract into a concave meniscus rather than bubble on top of the turret.

I think this and other solder techniques would be an interesting and educational discussion to have. I would love to hear opinions. Clearly the military and NASA has an opinion.

Just one point of reference, here are some gut shots of my genuine Marshall JTM45 handwired reissue (head version of combo with tremolo), very dome—y!
https://ibb.co/1MspGJC
https://ibb.co/XFbxJ3y
https://ibb.co/gdSZDx7
https://ibb.co/NsfDN2P
https://ibb.co/gWCPz5G
https://ibb.co/MhCd42V

Cheers

[Tcaradonna]

Mini progress note:
I cut and dry fit the socket wires from the board. The instructions made mention of a couple of routing considerations to minimize noise, but there were only a couple. Mostly the direction was, “refer to the picture”. Trouble is, there are probably important subtleties I’m missing. They did make specific mention that on V1 blue wires should go straight down and along the floor of the chassis, while green wires to V1 should travel along the bottom side of the turret board(kept high and away from the chassis).

Here’s how things look. I haven’t soldered them down yet.
https://ibb.co/RBFthNf
https://ibb.co/mDPv4tD

Cheers

[Tcaradonna]

Mini progress note #2:

I pressed on with wiring up pots. I tried my best to make it neat, but not sure if neat=best performance. I squared off many of the bends, I just like the look of that, I hope that’s ok.

I tried to keep the presence purple wire away from other tone wires as suggested. The example photos don’t get much further than mine, so I think I’m ok here.

What confuses me, and what’s been a beef I’ve had with the metroamp directions is all the wires length suggestions seem to run short. I tried to account for this in wiring up the board and added an extra inch plus alpha to all lengths. For the most part that worked great.

However...the black ground lead in the corner of the board has no home! The directions say leave 4”. I left over 5”. It says it should be grounded to the bus wire on the pots. Really? There is no way on God’s green earth that could happen! Even mine doesn’t reach. 4” must use some true voodoo plexi sorcery to be grounded there. A skill I tragically do not possess.

There is one other possibility. I noticed in all the pictures I’ve seen, I don’t see that ground wire hooking up on the pot bus wire. Does that mean there is another place to ground it??? (I didn’t plan to implement Larry grounding...)
Thank you!

Pics
https://ibb.co/MnxCFcK
https://ibb.co/G753Gmw

Cheers!

[neikeel]

Looks good BUT...............

See your black wires to the heaters - too long.

Shorten the loop so that your socket wires so that they curl around the nuts relatively closely
only cross the wires at 90, you will get ac coupling and noise.

[Tcaradonna]

Mini progress note #3
The wiring continues...
IEC plug holes drilled, plug mounted. A beefy power cable was sacrificed, yielding white, black and green awg16 stranded copper wires for use. I wanted to ensure a good ground. I also double shrinktubed the black line voltage for added stiffness and insulation because it had a long way to go and the stranded wire was kinda flexible.

I still haven’t dealt with my dangling ground from the board. I think I’ll drill a hole at the inputs near where Larry grounding goes and place it there with a spare grounding lug. I’m still puzzled by that wire.

Ok, now for the whining... can I just say that the Genuine Marshall knobs are absolute garbage? They are unbelievably poor quality. The set screw goes into tapped plastic and the knobs just wouldn’t fit on the CTS pots without some serious muscle, I only got one on and even with some wax I couldn’t get it on. Good thing I also got the generic knobs with the valvestorm kit. They are so much better! Brass sleeves, and fit right on. Nice! See picture below for comparison.

Pics!
https://ibb.co/wrgHnFx
https://ibb.co/gzsjnbF
https://ibb.co/0nqKzcX

Cheers!

[Tcaradonna]

I definitely have some excess on the black loops. Looks like a job for tomorrow...

[neikeel]

I try to use the Scott knobs, but even those are drilled out

Difference between 6mm and 1/4" usually.

[Tcaradonna]

I looked up the Scott knobs. They look nice, (but 8 bucks a piece... are there any 1 knob Marshall’s?)

I trimmed the heater wires and soldered up the sockets. I think this is better.
https://ibb.co/w0zzb7s

Cheers

[Tcaradonna]

Soldering complete! (Maybe). I added a ground lug for the ground wire on the corner of the board. I placed it approximately where a Larry ground would go, and I drilled the hole in line with the 2 standoffs above so on the top side, a brass screw is in line. Hopefully this works, I hate ground problems.

https://ibb.co/mX5s0pH

Moving on to testing phase...
Cheers!