Modulus JTM50

[Mcentee2]

Anyone got any tips for redoing those heat shrink ends without desoldering ?

Is there "thin" electrical tape or similar that stays put for ever ? The one I have is quite solid in comparison to the shrink tube, and to me has the potential to unwrap itself, or get gooey and brittle over time.

Maybe even a spray/liquid that sets or something that can be applied ?

Possibly the answer is "Hey, you don't need to cover those joins to spades/lugs anyway, they aren't going to move around!" In which case that's fine

 

[Pete Farrington]

I like to insulate mains live terminals, just in case. If I don’t, guess what’s going to happen
I use wide diameter heat shrink, and cover the whole fuseholder with a chunk of it.

 

[Mcentee2]

I like to insulate mains live terminals, just in case. If I don’t, guess what’s going to happen
I use wide diameter heat shrink, and cover the whole fuseholder with a chunk of it.

See, it's tips like that make the world a better place - obvious to some, that would never have crossed my mind, even with a bag of "too large to use" lengths of heat shrink staring me in the face in the bench.

 

[Mcentee2]

The more I look at the joins, I am resigned to unsoldering and trying again.

There again, after an hour's research on Google images I must say the vast vast majority of even just jtm45 builds don't use shrink on any lugs, not saying it's "right", but might just leave it rather than rehash existing soldered joints, next amp I'll see if I can improve.....

 

[Gene Ballzz]

The more I look at the joins, I am resigned to unsoldering and trying again.

There again, after an hour's research on Google images I must say the vast vast majority of even just jtm45 builds don't use shrink on any lugs, not saying it's "right", but might just leave it rather than rehash existing soldered joints, next amp I'll see if I can improve.....

Well there ya go and there's the spirit! It's nice to see that you've already resigned yourself to the fact that you are now a card carrying addict and there WILL be more amps built!

Warmly Embrace Your New Jones!
Gene

 

[Mcentee2]

Well there ya go and there's the spirit! It's nice to see that you've already resigned yourself to the fact that you are now a card carrying addict and there WILL be more amps built!

Warmly Embrace Your New Jones!
Gene

Well, I am definitely improving some things over the Supa build a few long weeks back - actual soldering is better, not burning wire coatings any more (well, as much anyway), stripping/tinning/bending the wires to the right length, and planning what goes where before committing to cutting and soldering, and the ordering of things.

Lots of opportunity still for that to change with the jtm, lol!!

 

[Timonew]

I’m following this build with interest as I’m hoping to build a Wrocket this year. Please cover up those naked thermistor legs - they’re making me nervous! All the best with the build.

 

[Gene Ballzz]

I’m following this build with interest as I’m hoping to build a Wrocket this year. Please cover up those naked thermistor legs - they’re making me nervous! All the best with the build.

I love the look of "naked legs!" Without 'em, many of us wouldn't even be here!
Oh, Wait! Carry On,
Gene

 

[EJstrat&JVM]

I like to insulate mains live terminals, just in case. If I don’t, guess what’s going to happen
I use wide diameter heat shrink, and cover the whole fuseholder with a chunk of it.

Pete, you mean you put heat shrink on the OFF side of the mains switch and to the center lug of the panel mounted fuse holder?

 

[Mcentee2]

I’m following this build with interest as I’m hoping to build a Wrocket this year. Please cover up those naked thermistor legs - they’re making me nervous! All the best with the build.

I tried with the green cast off insulator, any longer and I couldn't get the thermistor legs to bend cleanly and stay put

Even if I unsoldered them from the terminals I am struggling to work out how I could cover them more, maybe use overlapping shrink of differen diameters like a telescopic cover otherwise there is no room to actually do the soldering without the heat getting to the wrap?

 

[Mcentee2]

Pete, you mean you put heat shrink on the OFF side of the mains switch and to the center lug of the panel mounted fuse holder?

I know your question was for Pete, but I don't follow what you mean by "Off" ?

My wiring goes:

Mains Live lug via
Thermistor to rear of fuse, then
Side of fuse to one side of SPST toggle

The above is always "Live" or "On".

Then from the other lug of the toggle to the PT primary, this is the bit that is switchable On/Off.

I did manage to get shrink onto both the toggle lugs

 

[neikeel]

Personally I don't shrink all of those things as I might want a convenient point to clip a meter too at some stage. You should not be putting fingers is a live amp unless you know what you are doing and suitably careful. Of course where things might flop around is different!

 

[Mcentee2]

Personally I don't shrink all of those things as I might want a convenient point to clip a meter too at some stage. You should not be putting fingers is a live amp unless you know what you are doing and suitably careful. Of course where things might flop around is different!

Many thanks

I agree, if the *main* risk that is mitigated by shrink is to stop untoward human touch.

I can understand also that if anything else became loose in the chassis and moved to touch those points, that is a risk too.

I was wondering if it also is required to reduce/stop the risk of arcing even if everything is secure anyway?

Probably minimal even if it's a thing, but I can then understand why some people would strive to do it.

 

[Mcentee2]

I tried anyway, this is as good as I could get it. Any more messing about will probably ruin the thermistor.

 

[Mcentee2]

Been waiting for some components to be delivered, but put the board together today, not completely as still a couple of things to go on.

There is probably an improvement or two you folks could suggest I am sure!

My eye is on the 10k 3W right next to the big board cap, I can't stretch the leads any longer to give it more space.

The .68uF cap I bought for v1b bypass is quite large but looks fun I had to fly the 2.7k around it. I hope I have enough space between all those 4 v1 cathode bits!

I went with above board wiring for this one, I did under board with my previous build which worked fine, so thought I would try this. TBH looks a little more untidy, I spent a while redoing it over and over but couldn't get it elegant, but at least can see it!

There is a 56k tone slope still to get, and the trimmer is being kept off the board until soldering time, as is the NTC off the SS rectifier section.

 

[Pete Farrington]

I think that all looks fine. You could have used a twist splice to lengthen the resistor leads and so had the turrets in line, but whatever works.
As long as there’s a bit of free space around the resistor body, it should help to mitigate heat transfer to the cap.
I’m not sure, but the normal channel cathode cap looks backwards?

 

[Mcentee2]

I think that all looks fine. You could have used a twist splice to lengthen the resistor leads and so had the turrets in line, but whatever works.
As long as there’s a bit of free space around the resistor body, it should help to mitigate heat transfer to the cap.
I’m not sure, but the normal channel cathode cap looks backwards?

DOH!! Yes, that cap is the wrong way round, the last one on there, think I was tired just at the last.

Will think about how best to do that 10k again.

Thanks!

 

[Pete Farrington]

With regard to the film caps, have you checked / are you bothering, with the outer foil thing?

 

[Mcentee2]

With regard to the film caps, have you checked / are you bothering, with the outer foil thing?

I checked in my previous build and couldn't hear any difference re orientation with the same caps, so didn't bother checking this time.

I did make sure that all the writing was the same direction though, starting at positive side towards negative FWIW as each can be different I suppose!

 

[Mcentee2]

Ok, so still a few tidy up bits left on the board, but today I can crack on with sorting the fly leads that will go from board to pots/tubes etc

I see a lot of folks wire theirs under the board and pop up through one of the holes then back onto the turret.

Last build was on a smooth board with no extra holes so I chose over board fly wiring, not even to under the turret.

For this one I see I have already made a "mistake" in pre wiring my input jack wires already

Won't be easy to get these measured then cut/stripped to go through under board and back out again so will prob have to leave these over board anyway, so my "try to be elegant" head is telling me I might as well make all the others match.

Any views either way for electronic/safety/practice reasons ?

Or is it rather just a visual/ergonomic or vintage correct choice ?

The ones that connect to the middle of the board I'll try and go under and pop up/through.