Another 2204 Build

[Bjorn]

Hello,

I am going to be building a 2204 for my senior project and I think I'll document it here. I have bought the 2204 Version B* kit from Triode Electronics and have attached the components to the turret board. I'll post a pic before I solder it up so I can double check my work, but right now I have a question about the chassis.

My plan is to build a chassis from sheet metal stock and so I bought a 2' x 1' x .063" aluminum sheet from Amazon. But after doing some more thinking, I'm wondering if that would be small for future expansion. After bending it, the size will come out to be about 18" x 7" x 2.5". I would like a lot of room inside to work with because this will be my first build and I don't want to be cramped, but also because I would like to add things in the future (a clean channel, an effects loop, etc). Also, .063" feels a bit thin. When I put the power transformer on top of the sheet it bends it quite a bit. So I'm considering buying a bigger, thicker sheet from Metal Depot (probably 28" x 12" x .08").

Any thoughts on how much space you feel is comfortable to work with as well as chassis thickness? Also, will it be particularly hard to add things like a clean channel after I have finished building the kit? My thinking was that I just wanted to build the kit to spec so that I can troubleshoot things easier, then add my own things later.

Thank you,
Bjorn

Edit: Version 2

[DummyLoad]

consider a 2204 ver. 2 chassis from triode. plenty of room in that chassis. big plus is it allows for use of carling type switches (.5"dia.) that are easier to source than square switches. 


--pete


http://www.triodeelectronics.com/2204achassis.html

[Bjorn]

Hi Pete,

The reason I was staying away from a pre-drilled chassis was because I wanted to add another tube for a clean stage. I also wanted to add a few pots (mid-shift for the tone stack, gain and volume for the clean stage). Do you think think I would have enough room inside of the Triode chassis to drill these holes? It would certainly make it easier to not have to drill all the other ones.

Also, I accidentally snipped one of the 1M resistor's leads in the phase inverter. Would a 1/4W resistor be sufficient to replace it? My fast napkin math shows that it wouldn't ever dissipate much power, but I'd like to double check that.

Thanks for the help,
Bjorn

[Bjorn]

So I've decided to get a bigger metal stock sheet and then bend and cut it manually.

Here are some pictures of the turret board. Some of the components are just about touching, is that ok?

I clipped on what's left of the 1M resistor's lead onto the capacitor right now but I think I might just order a set of 1/2W resistors from Amazon. The more the merrier right?

[sluckey]

You're missing out on the biggest benefit of using turrets... bending component leads and poking them into the holes on top. Makes changing components a joy. Wrap your wires around the turrets since you will rarely change wires. It will be a real PITA to change a component as you have them. At least give it some thought. I realize you may have a valid reason for doing it that way.

[Bjorn]

Oh, I thought that was against the rules. I think I'll go and do that for some of the components I'm think of swapping in the future.

Thanks!

[sluckey]

Hey, we are a wild unruly bunch!   

[Bjorn]

Alright, I made a box out of the sheet metal. I suppose it worked out all right for me not having any prior experience with metal work. I'll have to grind down one of the edges so that the tabs lay flat, and I might try and bend back one of the sides I over-bended, but besides that it is quite definitely a box. I've attached picture of it as well as my current plan for the layout. I also put the turret board in the picture just for reference.

My next step will be to drill all the holes. I think I'll buy one of those kits of step drill bits to get most of the holes done. It seems like people use chassis punch's instead of step drill bits for the bigger holes, will the step drill bit still do the job? I'm also not quite sure how I'll do the hole for the power socket. I can't find a manual nibbler that can nibble the gauge of aluminum I have and I don't want to buy anything big. I guess I can just drill a hole and then file away.

-Bjorn

[purpletele]

Alright, I made a box out of the sheet metal. I suppose it worked out all right for me not having any prior experience with metal work. I'll have to grind down one of the edges so that the tabs lay flat, and I might try and bend back one of the sides I over-bended, but besides that it is quite definitely a box. I've attached picture of it as well as my current plan for the layout. I also put the turret board in the picture just for reference.

My next step will be to drill all the holes. I think I'll buy one of those kits of step drill bits to get most of the holes done. It seems like people use chassis punch's instead of step drill bits for the bigger holes, will the step drill bit still do the job? I'm also not quite sure how I'll do the hole for the power socket. I can't find a manual nibbler that can nibble the gauge of aluminum I have and I don't want to buy anything big. I guess I can just drill a hole and then file away.

-Bjorn

Bjorn,

I use a step bit for most everything that I drill on a chassis.  I have a whole set of punches but I only use the punch for a multi-cap which is 1 5/8" or something just bigger than the step bit.

The IEC socket is a PIA.  I suggest drilling four corners and try to get enough room for a Dremel drill with a saw wheel or something similar.

1. Be careful with the corners of your chassis so they don't rattle.

2. If you are going to fit the chassis in a cabinet try to do it now before it is loaded with components.

3. Make sure you get the rubber grommets for the penetrations through the chassis.

Your chassis looks good so far!

[Bjorn]

I procrastinated hard this week and have only actually done anything in the past couple days. I had this week off school as well.  . Oh well.

Thank you for the info purpletele. A couple things:

1. The gap between the corners is pretty big so they won't rattle against themselves, but do you think they might rattle in air if they aren't connected?

2. My current plan is to build a head cabinet later, so I'll dimension things then.

I got the stepper bits and have drilled almost all the holes. It's worked out well, but I'm using a hand drill so my wrist is taking a lot of force. I think all that's left now are the holes to mount the tube sockets. For the IEC socket I drilled a bunch of holes and will try and grind the rest away using an angle grinder that I just got. I also added more preamp tubes and pot holes to allow for future renovations. I've attached a couple pictures of the chassis so far.

I went shopping for screws yesterday, and I while I don't want to jinx it, I think that will be the single hardest part of this whole process. Because while it was a bit funny how long it was taking the first hour I was in the hardware store, it wasn't so much the second, and that wasn't even the first store I had been to. I'm not entirely sure why it was so hard, I suppose a mix of little sleep, trying to make educated guesses about the parts I had at home, and having to switch back and forth between metric and imperial because why bother stocking machine screws smaller than #6 when you don't have to, had something to do with it. Still alive though.

I also soldered the turret board.

-Bjorn

[Bjorn]

Alright, I mounted most of the components, wired the power supply (not the capacitors), wired the heaters, and powered it on (first with a light bulb limiter, then without)

power transformer voltages:
750vac
7.2vac

mains: 125vac

Those voltages are a bit higher than the datasheet's 690 and 6.3, but I think it is still within the limits (right?).

I took some pictures of the glowing filaments last night. I have also attached a picture of the current wiring. Please excuse the lamp's wiring, it's temporary until I get some heat shrink wrap. The CT leads are also a little longer than necessary, I haven't decided if that will be the ground point.

Next up is the capacitors. I was reading the chapter on grounding in Blencowe's book on preamp design, and he says how it is bad design to have your caps to be far away from the tubes that they supply. My amp will have them on polar opposite ends of the chassis. Hopefully this won't pose too much a problem.

-Bjorn

[PRR]

> power transformer voltages: 750vac 7.2vac
> a bit higher than the datasheet's 690 and 6.3

Transformers sag. 10% is a quick guess. Your NO-load voltages are 8% and 14% high. Under load they will sag. I don't see a problem.

I would re-check the 6.3V when everything is working. 6.5V is not a real problem, but if higher you may want to deal with it.

[Ugly Distortion]

You're missing out on the biggest benefit of using turrets... bending component leads and poking them into the holes on top. Makes changing components a joy. Wrap your wires around the turrets since you will rarely change wires. It will be a real PITA to change a component as you have them. At least give it some thought. I realize you may have a valid reason for doing it that way.

I need to get this resolved once and for all so I'm gonna pry Sluckey on this and rest of posters too, I also thought this was against the rules, not sure where but I learned that first you must have a solid mechanical connection and that solder isn't glue it's just there to keep the connection from moving and oxidising. Despite knowing that Fender and Marshall and others just stuck leads in a rivet or turret hole and were good to go for decades of road worthy use I try and stick to a good wrap first, and yes it's a big PITA especially as I make mistakes and don't even mention unwrapping a lead from around a terminal strip lug, I throw out a lot of resistors and small caps. Should I just stop bothering completely with the solid mechanical connection thing? Solder is glue?

[sluckey]

Should I just stop bothering completely with the solid mechanical connection thing?

No. A good mechanical connection before solder is applied equals a good reliable joint. But the bent lead in the turret hole can be a good mechanical joint too. I bend my leads with a slight angle off of 90° so the lead will put some mechanical tension against the inside wall of the turret. My leads will extend down into the turret about 5/16". Then fill the turret with solder. For a finishing touch I come back and add a small dome of solder on top of the turret just for looks. All this provides a good reliable joint.

Fender did not just stick the leads in a eyelet. Every lead was bent over on the bottom of the eyelet then trimmed to length. This provides the mechanical connection. Ever notice that you have to give a tug to unsolder an original component from a Fender eyelet board?

[nandrewjackson]

Looks like a good project,  Bjorn, keep up the good work