18 whatt - “paint by numbers”

2 years ago, I bought a bunch of parts from ubuyguitars.com. Included in my haul was basically all the parts to a VHT Standard 18. Total cash outlay for the collection of parts, including shipping... about a hundred bucks. Finally getting around to assembling the amp.

First step is chassis conversion. The chassis is actually for their 36 watt combo, but I am going with an 18 watt head so I will need to make a bunch of new holes in the top for tubes and move the circuit board a little bit. The faceplate is fine as-is. The power and standby switches will be upside down but that’s OK.

I don’t have a Greenlee hole punch so I made due with the tools available.

 

The grade aluminum used in amp chassis is wonderful for bending, forming, punching and welding but is awful for machining. It doesn’t really cut, it just sort of smears but with some chamfering after the fact, it comes out OK. At least all the holes are exactly where I wanted them to be.

 

The new hole for the rectifier socket wanted to be a little offset from where an existing hole was. This is where my “ hole punch” really shines.

 

As long as I had it in the machine, I thought I may as well put on a personal touch. It didn’t turn out very good because the metal is not perfectly flat. The lettering was dialed in to be cut 0.005” deep (a standard sheet of paper is 0.003” thick). It’s really deep in one spot and quite shallow in another. I spent some time “truing” the surface with a straight edge and a dead blow hammer but this was as good as I could get it.

 

One of the components I bought was a “partially loaded chassis”. It looked like it had been used as a test bed for components and then run over by a truck. It contained all the pots, jacks and switches on the front panel as well as the OT. I was able to move all the front panel stuff to the new chassis pre-wired!

 

I will be making a cover plate for the back to hide all those holes. It will have the speaker jack, fuse and IEC power plug.

 

Here’s why I’m calling this “paint by numbers”... most of the work is done. This is the “18watt handwired el84 circuit board loaded” from ubuyguitars.com. With the faceplate components prewired and the board with all the leads attached, all I have to do is wire them together according to the color coded layout included with the circuit board.

 

Thanks, SacDAve, Just went back and re-read your build post...I’m sure I will be visiting it again as my work continues.

Thought I had the necessary wires for the heaters but turns out my stash was heavier gauge than I thought. I think I have another stash that I pulled from an organ donor that I can check in the morning. Also, going through the layout and schematic, I discovered that I’m missing 3 resistors. I have a buddy in town who builds amps...I’ll have to go rummage through his parts bin.

 

What does everyone think about this crazy idea...??? Rather than daisy chained heater wires, run individual twisted pairs to each tube and gang them together with the PT on a tag strip? It's a bit tight in the chassis with this layout and it would make it less of a micro wrestling match to wire the heaters and still keep things neat and tidy inside.

 

Well, this thing kicked my backside all day but I finally prevailed!

I found some suitable heater wire and ended up doing it the twisted wire, daisy chain way. Then I spent the last two evenings “painting by numbers” hooking the board up to the pots, jacks and tube sockets and connecting the transformers. Then I hooked it up to the light bulb limiter and could not get the damn light to go dim after installing the pre-amp tubes. After 5 hours I discovered a heater wire creeping against pin #3 on V4...fixed that and all is well.

Still need to make the rear plate and after playing it for an hour or so tonight, I can say that all the pots and jacks need to be upgraded.

It sounds pretty cool though. I was running it through my unfinished 5e3 as a speaker cabinet loaded with a vintage organ speaker (a 12” Rola from 1951!) and it gets pretty flabby when you hit it with much gain but clean it sounds very nice. The tone controls are not very drastic throughout their range, I wonder if new pots would help that also. I wish the high/low input channel was not affected by the master volume... for me, that would make it more versitile.