First JTM45 build

rockstah · Post by **rockstah** » Sat Jan 21, 2006 2:28 pm

looking good!

BashCoder · Post by **BashCoder** » Sat Jan 21, 2006 6:50 pm

Thanks, rockstah -- I'm trying!

Day Four -- wiring and stuffing the board

The pictures came out phunky this time, so sorry about that. I was able to get most of the parts mounted on the board, and the rest of the wiring finished. I'm waiting on my caps to arrive from Sozo, so those were left out. In some cases, I didn't solder a turret because of that. I've now done everything I can until I get the OT and Sozos. Once I install them, I only need to install the AC cord, the fuses and the bias resistor and I should be ready for the legendary Golden Glow.

On the board, I'm missing one 100K resistor that was a casualty of the mistake I mentioned in another post. Also, you'll see that I had to jumper two turrets (top right, between the diode and the 10 uF cap), because a review of my work showed that I had missed that when I wired the underside of the board.

I like the way the pots turned out -- I hope this is an OK wire routing. It's as clean as I could get it while still allowing me to lift the board to install the OT later. I tried to keep the presence wire away from everything.

I noticed something funny today. Sometimes when I was soldering a component to a turret and there was a wire connected to that turrent underneath, the air between the two solder joints would expand quickly from the heat and cause my new solder to "pop" like a bubble. Makes sense but very odd nonetheless!

rockstah · Post by **rockstah** » Sat Jan 21, 2006 6:53 pm

i notice every builder does things alittle different. seems most guys put components on the baords after they mount them. with my first and even my second build i get my boards completely intact before they even go near the chassis - everyone has their own way though

BashCoder · Post by **BashCoder** » Sat Jan 21, 2006 7:17 pm

Billy Batz wrote:I dont know if everyone does this but when I do an amp I usually populate and complete the entire board before it goes in.

I'm definitely doing that next time, if only because it makes checking the underside easier after installing components. I had to check to see if I had caused any problems for the wires underneath, and that was harder with the board wired in.

Billy Batz wrote:I put at least 2 more inches to each of the wire lengths then I think Ill need. Thats why I usually get 2 full amp wire kits for one amp. Otherwise it would be cutting it close with 6' of each.

That's brilliant, Dan -- I'm buying two wiring kits for my next amp (would probably last me for 2 more amps). I was worried that I would run out of the right colors of wire. I had exactly 2" of green left at the end, but I had some of every other color left over.

And agreed on the 6" -- several of the wires to the pots today were *exactly* the right length. It worked, but that's a bit too close for comfort and I could have used another inch or two here and there. There are too many different ways someone can choose to twist and route wires.

I love this wire that George uses, by the way. Easy to work with, great stuff.

Billy Batz wrote:Hell Ive drilled em with drill bits and step bits. I think those panles are weak to certain kinds of stress but I dont think people need to be paranoid about drilling them. If your holes arent lined up perfectly with the chassis for instance, Id take a drill bit about the same size as the hole and drill it. The metal is hadrer to drill then the plastic by a huge degree so it pushes the drill to ream out the panels overlap.

Dang, I didn't even think of the stepper bit -- I have the perfect one to do the mod a lot quicker. I used a round file a just a little bit on most of the front panel holes to get the pots and switches to fit. My placement was just a bit off.

Billy Batz wrote:2 minutes of tweaking and somehow my workbench is a shithouse of tools and metal pieces and wire.

...which will henceforth be known as "Billy Batz's Law".
"Bash Coder's Law" is that no matter what you do, solder smoke will find your face.

BashCoder · Post by **BashCoder** » Sat Jan 21, 2006 7:21 pm

rockstah wrote:i notice every builder does things alittle different. seems most guys put components on the baords after they mount them. with my first and even my second build i get my boards completely intact before they even go near the chassis - everyone has their own way though

Yeah, that's cool. For this first build I stuck to the script pretty closely, following Metro's instructions to the letter. I was worried that if I strayed from that, I would be screwed later on. For some things that would have been the case. But now that I have some experience, next time I'll be more confident and try some different things. Getting folks' feedback throughout this process has been very educational for me.

Flames1950 · Post by **Flames1950** » Sat Jan 21, 2006 11:21 pm

I just prefer to have the components and wire both all attached before the board drops in, especially with the older-style amps where the wire comes up underneath the turret -- if you heat things too long and the wire falls out and you don't notice........aaaargggh.

Stankyfish · Post by **Stankyfish** » Tue Jan 24, 2006 2:04 pm

BashCoder wrote:
rockstah wrote:i notice every builder does things alittle different. seems most guys put components on the baords after they mount them. with my first and even my second build i get my boards completely intact before they even go near the chassis - everyone has their own way though
Yeah, that's cool. For this first build I stuck to the script pretty closely, following Metro's instructions to the letter. I was worried that if I strayed from that, I would be screwed later on. For some things that would have been the case. But now that I have some experience, next time I'll be more confident and try some different things. Getting folks' feedback throughout this process has been very educational for me.

This is hugely inspirational!

I'm very interested in building this kit, but it would be my first amp build and I'm worried it might be too difficult for a first build. I've built several pedals, but they're a harmless 9Vs and about $20 in parts. I can't say the same about this puppy.

Flames1950 · Post by **Flames1950** » Tue Jan 24, 2006 4:04 pm

Man, this is a great first amp to get started on. The instructions really do a much improved job of walking you through everything in detail compared to the earlier 100-watt instructions. Plus we all love pitching in around here just for the hell of it.

And when you're done, if you've had the patience to do it carefully, you've got a professional quality amp for gigging and the studio..........

Stankyfish · Post by **Stankyfish** » Tue Jan 24, 2006 4:30 pm

Flames1950 wrote:Man, this is a great first amp to get started on. The instructions really do a much improved job of walking you through everything in detail compared to the earlier 100-watt instructions. Plus we all love pitching in around here just for the hell of it. And when you're done, if you've had the patience to do it carefully, you've got a professional quality amp for gigging and the studio..........

That's very good to hear. I'd considered building a smaller, simpler amp for a first build, but it wouldn't be THE amp I want and this would be. Everytime I read about building amps, I read the obligatory "there are lethal voltages present in the amp so if you are not used to working around high voltages, don't build it" and it bums me out because I'm pretty interested in doing it. If I knew an amp tech, I'd enlist their help to show me what NOT to do and how to avoid anything dangerous, but alas, I don't -- and there's no substitute for experienced help, no matter how much I read about it.

I'd also considered picking up a used JTM-45 RI and swapping the PCB and OT with a PTP board and new OT, but it would be a) more expensive and b) not as satisfying as assembling the entire thing myself.

The pictures in this thread have really gotten my juices flowing and I really dig the quality, authenticity and tone of the kits George has put together.

sub · Post by **sub** » Tue Jan 24, 2006 10:37 pm

Get Metro JTM45 kit

BashCoder · Post by **BashCoder** » Tue Jan 24, 2006 11:15 pm

I agree with Sub!

I think this is the best kit out there, especially for a beginner.

BTW, I got my Sozo's yesterday, and the OT is just a few days away. So we're very close to the Golden Glow now. I've used the down time to go over the instructions and the circuit a few times to see if there are any more mistakes, so I feel confident in the testing phase.

Read all the instructions online here to get even more pumped about building the kit.

As to the high voltages, there are a handful of simple guidelines to make this a safe build for you. Those are in the instructions too. I think it's a very safe-and-sane testing process.

Stankyfish · Post by **Stankyfish** » Tue Jan 24, 2006 11:33 pm

BashCoder wrote:I agree with Sub!

I think this is the best kit out there, especially for a beginner.

BTW, I got my Sozo's yesterday, and the OT is just a few days away. So we're very close to the Golden Glow now. I've used the down time to go over the instructions and the circuit a few times to see if there are any more mistakes, so I feel confident in the testing phase.

Read all the instructions online here to get even more pumped about building the kit.

As to the high voltages, there are a handful of simple guidelines to make this a safe build for you. Those are in the instructions too. I think it's a very safe-and-sane testing process.

Now I'm REALLY getting excited for this...

Can I ask one question? When the amp is powered up and the large caps for the power supply are charged up, how does one safely work inside the amp? After the amp is turned off and the amp unplugged, those caps (and presumably others?) will still be holding significant charges. Is there some procedure for safely draining the components that could be holding a dangerous voltage -- before messing around inside?

Flames1950 · Post by **Flames1950** » Tue Jan 24, 2006 11:59 pm

Most guys use a jumper wire with clips at each end -- clip one wire to pin three of the first 12AX7 and the other end to ground (the chassis edge is fine.) Then the resistors that decouple the power supply also let the charge drain off slowly over a couple of minutes instead of making a dead short and lotsa sparks.....

Some amps may need the standby switch in the play position for this to work; the typical JTM45 circuit does not however.

BashCoder · Post by **BashCoder** » Fri Jan 27, 2006 3:51 pm

Whoohoo!!! The Sozos and the Heyboer OT have arrived, so I'll be doing the "smoke test" this weekend! Hopefully tomorrow I'll be rokken like Dokken.

Well, OK not exactly Dokken. More like Albert King... But I'll still be rokken.

sub · Post by **sub** » Fri Jan 27, 2006 5:26 pm

Hey BashCoder please post more pics!
Your JTM45 such a "appetizing"

Thanks