My official JTM45 kit build thread. Pics & CLIPS ADDED

mushmouth · Post by **mushmouth** » Sun Aug 26, 2007 8:53 pm

Wow it's quiet in here lately...

Step 13 is complete -- Wiring the front side of the chassis to the board.

Let me know if anything I've done with the routing here is going to cause me noise problems. I tried to isolate everything from each other, but if that's wrong and certain things SHOULD be forced to cross or come in contact with each other that I haven't already done, let me know. I've tried to provide enough pics to see what's going on...

Pics:

franc · Post by **franc** » Mon Aug 27, 2007 4:45 am

mushmouth wrote:Wow it's quiet in here lately...

We're still watching

It's looking very good, you should be okay with the wires going to the pots like that.

Wallace · Post by **Wallace** » Mon Aug 27, 2007 5:40 am

Wallace.

wdelaney72 · Post by **wdelaney72** » Mon Aug 27, 2007 8:54 am

This is REALLY looking nice!

mushmouth · Post by **mushmouth** » Mon Aug 27, 2007 10:15 am

Thanks guys, I couldn't have done this so quickly without the help of the people on this board! This is beyond addictive. I'm bummed I'm coming to the end of the build...

I've posted a question in the JTM45 board about resistor choices here:
http://forum.metroamp.com/viewtopic.php?t=13290

I want to solve where I should be using the Allen Bradley Carbon Comps for vintage accuracy as opposed the beige carbon film variety. I posted the board layout there, if someone could circle which resistors they'd replace with Allen Bradley's I'd be all set. I'm planning to do the board tonight!

mushmouth · Post by **mushmouth** » Tue Aug 28, 2007 3:50 pm

Several nights straight of staying up until 2 or 2:30 am on worknights and over the weekend to work on this amp finally hit me yesterday. I got home from work at 6pm, passed out on the couch, and didn't wake up until 7 am this morning! I should be getting to work on the circuit board tonight. I'm going to get everything onto the board, take a pic and post it here before doing any soldering. Just want to make sure it's right.

Thanks all...

Wicksy · Post by **Wicksy** » Tue Aug 28, 2007 5:17 pm

Beautiful wiring there! That should be nice and quiet

You need to hurry up and get it finished so we can hear how it sounds

mushmouth · Post by **mushmouth** » Wed Aug 29, 2007 1:06 am

Ok. I have all the components in place on the board, not soldered. I've replaced everything recommended with Allen Bradley's, with the exception of a few I'm missing. I'll have George send me what I need. Those are temporarily filled with Carbon Film resistors. It's also missing the bias resistor you add in a later step.

Here is what was recommended in another thread, regarding which to swap out for the ABs:

Then I spoke with George who also recommended the 820 and the 100 on the 2nd tube cathodes, in addition to that 27K over on the right. I swapped the 820 and 27k.

Lemme know if you spot anything out of place. The orange stripe on 3 of the AB 68k's looks brownish, so I measured them. All of my AB 68k's come in at about 80k, except one comes in at 72k. Odd ducks, those.

Pics:

mushmouth · Post by **mushmouth** » Wed Aug 29, 2007 1:37 am

The ABs in the positions where they're replacing the grey 2 watters... Aren't those little ABs the wrong watt rating to be using in those positions??

toner · Post by **toner** » Wed Aug 29, 2007 2:25 pm

mushmouth wrote:The ABs in the positions where they're replacing the grey 2 watters... Aren't those little ABs the wrong watt rating to be using in those positions??

1/2 watt AB's are fine for those V2 cathode positions (820 and 100k). The gray 2 watts are only used there for their lead length.

Great job on the board. Looks very nice!

mushmouth · Post by **mushmouth** » Wed Aug 29, 2007 2:35 pm

So using your advice and George's advice on the ABs, I'm only missing one 100k and one 270 AB, correct? Everything look correct otherwise?

toner · Post by **toner** » Wed Aug 29, 2007 2:43 pm

mushmouth wrote:So using your advice and George's advice on the ABs, I'm only missing one 100k and one 270 AB, correct? Everything look correct otherwise?

First of all, ALWAYS trust George before me!

Yes, those two resistors will complete it. I checked everything on your board and it's all correct (unless I missed something, but I don't think so).

mushmouth · Post by **mushmouth** » Wed Aug 29, 2007 2:45 pm

toner wrote:
mushmouth wrote:So using your advice and George's advice on the ABs, I'm only missing one 100k and one 270 AB, correct? Everything look correct otherwise?
First of all, ALWAYS trust George before me!

Yes, those two resistors will complete it. I checked everything on your board and it's all correct (unless I missed something, but I don't think so).

What's the deal with the different color of orange on those 68k ABs? Is that pretty normal? I'm not thrilled about the 80+k readings on those, but I'm guessing with break-in they'll settle down?

toner · Post by **toner** » Wed Aug 29, 2007 2:53 pm

mushmouth wrote:What's the deal with the different color of orange on those 68k ABs? Is that pretty normal? I'm not thrilled about the 80+k readings on those, but I'm guessing with break-in they'll settle down?

I'm sure their age and how they were stored may affect the coloring. A few of mine had slightly different color brightness too.

Have you confirmed that your meter is accurate? Measure the CF's and see if they read high also. Just a thought.

I think CC's have a tendency to drift UP in value but I don't have first-hand experience with this. Ask George, Flames or Larry to confirm this.

mushmouth · Post by **mushmouth** » Wed Aug 29, 2007 2:59 pm

toner wrote:
mushmouth wrote:What's the deal with the different color of orange on those 68k ABs? Is that pretty normal? I'm not thrilled about the 80+k readings on those, but I'm guessing with break-in they'll settle down?
I'm sure their age and how they were stored may affect the coloring. A few of mine had slightly different color brightness too.

Have you confirmed that your meter is accurate? Measure the CF's and see if they read high also. Just a thought.

I think CC's have a tendency to drift UP in value but I don't have first-hand experience with this. Ask George, Flames or Larry to confirm this.

Yeah, the 68K Carbon Fibers I have all measure at about 67.5...