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 Post subject: TC 15 rookie build
PostPosted: Mon Nov 12, 2018 2:46 pm 
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This is my first amplifier build. One of the reasons I ordered from Trinity was their reputation for excellent documentation and support - which I have found to be well-deserved, and essential for a first time builder like me.

The Brown Truck of Happiness arrives with an oblong, surprisingly heavy box.
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Installing hardware
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Check the BOM and organize the semiconductors. I think it was on this forum I saw someone putting all the caps and resistors into a chunk of styrofoam. Makes it easy to find them later.
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I odered a VRM with this kit because being able to get nice tones without breaking the windows is probably the most important feature of an amp for me.
I found the VRM to be a bit of a tight fit over the power transformer.
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I could have installed the VRM upside down or sideways and had plenty of room, but just being stubborn, I got some nylon spacers to raise the power transformer just a touch higher and create some breathing room for the VRM. You can just see the off-white spacers under the PT in this picture. Also soldered leads on the VRM's mosfet, to make placement of the mosfet more flexible.
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Last edited by alathIN on Mon Nov 12, 2018 2:53 pm, edited 1 time in total.

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 Post subject: Re: TC 15 rookie build
PostPosted: Mon Nov 12, 2018 2:51 pm 
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Heater wiring.
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Power side wiring done.
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I had gotten myself confused about the VRM. Mr Cohrs at Trinity devised this test. Attach the pos of a 9V battery to the VRM's B+ in tab and the battery's neg to ground. Measure voltage from the VRM's B+ out while adjusting the VRM - I was able to dial up to about 6 volts and back down to zero, so it looks like the VRM works.
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 Post subject: Re: TC 15 rookie build
PostPosted: Mon Nov 12, 2018 3:01 pm 
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Turret board back
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Front and work area. BTW, I do not like that brand of soldering flux (the little squeeze bottle). It's supposed to be the kind you don't have to clean off after soldering, but it's messy so you want to clean it off anyway. And I'm not sure it works as well as rosin flux.
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My wife was astonished. "You built that? It looks so professional!" She always has encouraging things to say ;-)
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A modification: I added a turret to the board. You can tell, it's just about the middle of the picture, and it's the wrong size (smaller than the original turrets).
The reason I did this is that this is the location for the effects loop, and I wanted the cap and the resistor to both be secured on both ends instead of something "hanging in space." This required putting in an extra jumper for now, but it will be easy to take that out and replace it with the loop send and loop return leads.
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If you want to add turrets you can get ones that secure to the board with screws. This is the traditional crimp-on kind, and I had to improvise a crimping tool which worked out OK for one turret but I wouldn't want to do a whole turret board without the correct tool.


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 Post subject: Re: TC 15 rookie build
PostPosted: Mon Nov 19, 2018 12:54 am 
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Had some busy work days and no time to work on my amp. Today got back to it, so it's a good day.
Tube circuitry is addictive. I'm already planning my next project. (Gear Building Syndrome?)

Spent the most time attaching leads to the turret board. I know there are different ways to do this. With the idea it would help me keep things neat, I decided to solder my connecting leads to the bottoms of the turrets. I'm not sure I'd do it again this way, but no major problems. It was an opportunity to double-check the turret board wiring (found two errors - misplaced jumpers). Then installed the turret board. With all those leads connected to the turret board, the satisfying neatness feeling is long gone. Should get better as I start connecting things.
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Then had some time for a few odd tasks.

One of the oddest is the Tone Contour Switch. It's a six-position rotary switch for tone control on the EF-86 channel, which is supposedly modeled after an older era AC-15. I have never heard of an old Vox with this tone control, but I don't know much about old Voxes. I did see a YouTube demo of the tones from this channel when I was deciding what to build, and it sounded really good clean, crunchy, and in-between. That - plus the outright bizarreness of how this switch is wired - helped convince me to try building a TC-15. I've seen pictures of them that came out more neatly than this, but I think it will be functional (cross fingers)

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Last was making the Hi - Lo input jacks - one set for each channel.
I imagine probably everyone knows about this already - I'm new, and happened to see it on a video from Boot Hills amplifiers - but I really like this idea of making a chassis face template for wiring things that would be a hassle to wire inside the chassis. My kids had left a piece of poster board on the laundry room floor, despite numerous requests to pick it up, so I decided it was fair game to borrow a chunk off the corner.
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 Post subject: Re: TC 15 rookie build
PostPosted: Thu Nov 22, 2018 9:39 pm 
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UPDATE

I don't remember what site I saw this, but dude had a different way of doing his shielded jumpers. I thought I'd give it a try and I like how it turned out. Start out the usual way, then solder a short lead on to the shielding.
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Bend the lead around and throw some heat shrink on it.
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So I installed the jumpers and, in theory, the amp is done.

Face plate, channel 2, master, and power. Channel 2 is modeled after the classic Vox Top Boost.
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Channel 1 - EF86 preamp and 6 position tone switch. Apparently this is typical of an earlier generation Vox AC15.

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The whole shebang

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Power section

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Output section: phase inverter tube socket, power tube sockets, impedance selector, output jacks.

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Channel 1 volume and tone

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Channel 2 volume, bass, treble

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So, I said it's done in theory.

Next time I get back to this, it will be time to double-check the circuit paths, power up, and test voltages.


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 Post subject: Re: TC 15 rookie build
PostPosted: Sat Nov 24, 2018 11:52 pm 
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Went through the Trinity start-up procedure. Overall no real problems, just a enough oddball occurrences to keep me on my toes. At one point I was measuring voltages and my phone rang, vibrating a box of parts on my desk, and I almost needed to change my pants ;-)

I used the light-bulb-in-series power limiter trick, which I hadn't done before, and the bulb started glowing a creepy dim reddish-brown, just like in a basement in a Stephen King movie. And then (duh) I couldn't figure out why all my voltages were off when I was plugged into a voltage-limiting power cord (duh).

Once I replaced the light bulb thing with a normal power cord, everything fell pretty closely in line with what Trinity says is correct.

measured number (Trinity's spec)
V1
p1 72 (85)
p3 2.0 (1.9)
p6 109 (131)
p8 2.0 (1.9)

V2
p1 145 (137)
p3 1.36 (1.46)
p6 145 (137)
p8 1.36 (1.46)

V3
p1 174 (169)
p3 1.2 (1.3)
p6 275 (279)
p8 173 (160)

V4 (PI)
p1 260 (256)
p2 46 (47)
p3 69.6 (69)
p6 256 (254)
p7 47 (47)
p8 69 (69.7)

V5 EL 84 1
p3 8.4 (8.3)
p7 381 (384)
p9 219 (242)

V6 EL 84 2
p3 84 (8.2)
p7 381 (384)
p9 218 (242)

V7 5AR4
P8 391 (380)

Next step in the procedure was plug in and play.
First impressions:
the EF86 channel is LOUD and has a really nice crunch
the Top Boost channel isn't shrill at all - I actually had to turn up the treble to 6ish and the master cut to zero to get in the right range
Both channels: the low end is punchy as all get out. Reminiscent of a Fender Twin (one of the speakers in my 2x12 cabinet is a BBQ reproduction of a vintage Fender speaker; that might be part of it).
I play fingerstyle and this amp is very touch sensitive. I felt like I could hear my fingerprints.

Too late to play much or really get into it, lest I wake all the kids instead of just one ;-)

More detailed report to come.
But initial impression is extremely pleased.

Could not be more delighted with Trinity customer service. I went into this with no idea what I was doing or getting into, and it came out great. Having the nice detailed illustrated instructions, as well as direct Q&A support from The Holy Ghost notched my stress level down quite a ways.

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Next project will be building a cabinet. It will probably look a lot like that speaker cabinet it's sitting on, because I have a lot of those materials laying around 8)


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 Post subject: Re: TC 15 rookie build
PostPosted: Thu Dec 20, 2018 11:42 pm 
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Nice build! I love my TC15; has been my #1 since early 2016. Use it constantly. Early on only loved the Top Boost channel, but then this year discovered the EF86 channel in all its glory, and it is all I use live. It is an amazing circuit and so great for a live band.


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 Post subject: Re: TC 15 rookie build
PostPosted: Sun Dec 23, 2018 1:33 pm 
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Joined: Sat Dec 04, 2010 3:42 pm
Posts: 517
Location: Qualicum Beach, BC
Congratulations! Your build looks great! It's a great amp, too. I'm sure you will have lots of fun with it.


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 Post subject: Re: TC 15 rookie build
PostPosted: Sun Jan 19, 2020 7:02 pm 
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Posts: 4
Did you decide against the effects loop? I saw your question at the Metro loop forum and found you here. I just built a tramp and was wondering about adding the zero loss loop to that.


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