Saturday, January 31, 2009

The missing piece(s)

Turns out these amp kits are a little more shoddy than I would have originally guessed. I'll admit I'm a bit more of a novice than I should be when starting a project like this, but the 'kit' certainly isn't helping.

A: It didn't come with step-by-step instructions. Lame but I'm sure I'll feel more accomplished with doing something worth while if I can make the thing work.

B: There are at least three MAJOR holes that have to be drilled in both the chassis and the cabinet. I'm really worried about the cabinet holes because the tweed looks so nice. I'm afraid I'm gonna screw it up by drilling. The two holes are absolutely necessary, so I'm baffled as to why these holes don't come pre-drilled. If I had to build the cabinet from scratch I'd understand, but it's like buying a case for a desktop computer with no drive bays cut into it.

C: The hardware that came in the kit is all over the place. By that I mean the bolts for mounting the tube sockets are too big to fit in the socket bolt holes, there are a lot of loose nuts that didn't come with matching bolts, there are several odd sized and non-paired bolts, the RCA jack is for a blackface amp and not a tweed amp, and the RCA male plug is 'vintage' and I can't figure out how to solder anything to it.

I was wrong about the tube socket bolts. They are a tight fit, but they do fit. The pre-amp tube shield bracket took a bit of prying and molding to screw in. All of the tube sockets are now installed.
***End Update***

There are some other smaller issues as well that I won't innumerate here. I did buy a few things from Mojo and Tube Depot to help out the cause. I got a nice blue jewel for the power light. I bought some speaker wire (to replace the speaker wire I quite stupidly screwed up). I bought the correct tweed RCA female jack and a workable RCA male jack. It's not 'vintage' but at end of the day if the RCA jack isn't vintage I don't really give a shit. I bought some safety glasses so that if a cap explodes it won't take my eyes with it. I also got a pre-amp tube shield. It came with a shield receiving socket base but no shield. Lame.

Today I'm gonna start soldering things to the fiber board. I might be getting a bit ahead of myself, but I'm chomping at the bit to get this thing put together.

***Another Update***
Everything is soldered (including one thing I didn't want to solder that I'll have to un-solder and then re-solder.) Also Yuengling Black & Tan is excellent.

Friday, January 23, 2009

It Begins

My call time today isn't until 12:00pm, so I took the extra time to sit down and start planning the layout for the Tweed Champ. There are still quite a few things I'm not sure about. The biggest question floating around is how to ground the whole thing.

Here is a picture of this morning's work.

With a few exceptions everything laid out fairly nicely. The orange drop caps' leads come out at strange angles (i.e. not from the edges), so they sit up off the board a little more than the other components.

The circled components are the ones with more major problems. Starting from the right, the bias resistor for the 12AX7 tube has leads that are too short to reach the eyelets on the fiberboard. This is a carbon comp resistors so I can't just head over to Radio Shack to get another one. I'm trying to decide if I will make a solder bridge to the leads or solder in a bit of wire to bridge the gap. I'm leaning towards a solder bridge.

The 470 1W resistor circled in the middle of the board (which serves as a bias for 6V6GT tube) also has leads which are slightly too short. It does reach the eyelets but just barely.

The 10K 2W resistor in the bottom left is the only metal film resistor in the circuit making it the only non-carbon comp resistor. I'm not 100% sure of the significance of this type of resistor in this position. I'll look into it. The problem with this resistor is that the component is actually longer than the distance between the eyelets laid out for it. The leads are bent in under the component.

Here is a photo of the Chassis:

The circled bit on the Chassis is a rubber gromit which protects the OT (output transformer) wires from the sharp metal edge of the cut hole. There was only one grommet included in the kit. I guess that means I need to track down another one. Hopefully Home Depot can help in this department.

That's all the time I have this morning. This weekend I'm going to see Rascal Flatts with the TV show I work on. My slit wrists might make it more difficult to work in the future, but I'm sure I'll find a way.

Wednesday, January 21, 2009

Everyday I learn there are 10 more things I don't know

I haven't been doing much more than reading and studying lately. The more I look into this project the more I realize I know just enough to kill myself. As an example I found articles about how to drain the filter caps which hold, even at rest, upwards of 320 VDC. Scary.

I did find a website that has a pictorial step by step construction of the 5F1 circuit. It's not a huge help, but seeing the different connections at least gives me an idea of how the whole thing is suppose to come out. Being the visual person that I am it's nice to have a picture to go along with the wiring diagram which, by the way, is the only piece of instruction that came with the amp kit.

Yesterday I wrote the company where I got the kit to ask them, among other things, about how to mount the Fiberboard and Insulation Board (pictures to come later). As it stands I think I have to drill two holes. It would seem to me that if you HAVE to drill these two holes that the boards would come pre-drilled as all the other necessary holes have been drilled on the board.

Other issues include the color coding on the AC power line not matching the schematic (also pictures to come later), and general lack of understand on how to properly ground everything. I still have a lot to learn.

*update* So the folks at home can learn along with me: I found a few handy articles in reference to the AC power wiring problem mentioned above.

Saturday, January 3, 2009

Signs of progress

Today I got tired of watching the Penguins lose. With Melissa gone and TV production on hiatus I have a lot of free time on my hands so I sat down to finally build a working version of a small solid state amp from a schematic in Make Magazine. The amp is centered around the LM386 chip readily and cheaply available at Radio Shack.

I built one of these about a year ago that worked to a limited degree. Looking back at that project I had mistakenly swapped the polarity on one of the caps causing unwanted yet interesting intermittent operation.

I thought that if I'm going to try and put together a more expensive project like the Fender Champ then I should probably practice soldering and schematic reading on a smaller project. Here are some pictures of the successful completion of the amp.

As you can see it's a pretty simple amp involving just a couple of components. The reason I failed at building it properly so many times can be chalked up to stupid mistakes. As an example on the working version, before it was working I thought I was finished and just about bashed my head through the wall when it didn't work. I then realized I had yet to solder the chip to voltage. Stupid.

Also forgive the soft focus of these pictures. My digital camera has no macro capabilities. Also, when not working I tend not to care too much about image quality as long as you can see the image well enough.

There aren't very many solder points thanks to the design of the PCB which has long connective rows. That made it a lot easier to tie everything to 'ground' which in this case is the negative terminal of the 9V power supply.

That's a shot of my 'workbench.' It's frustratingly small but gets the job done most of the time. Also note the rockin' Penguins rug adorning the floor.

My computer is woefully unable to record audio right now. When I fix that issue I will put up some audio from the amp.

This project was more about the 'making of'' than the final product, but the final product doesn't sound that bad at all. I could wire in a pot to control the gain if I really wanted to (which I don't). I was thinking that you could build another of these and couple them. You could get a bit more power out of the extra speakers, and you could have different gain settings for each amp. I've always liked mixing a bit of distorted in with any clean signal.

I've read online about people powering a 4x12 cab with this amp. I've got a cable wired to plug it into my 4x12, but my 4x12 is wired to be a 1x12 right now. I'm wanted a bit less volume when I play for my neighbors sake.

As a side note this amp was constructed while listening to the latest Big D and the Kids Table album 'Strictly Rude'