New build Liverpool finished

[M Fowler]

I thought I was having trouble with my new build since it blew a fuse on first powerup. But I went through the amp and did not find anything but a loose heater wire, fixed that and resoldered some things. Popped the JJ EL84s in and EH 12ax7s and fired it up again this time I had music.

I moved the amp to the jam room and plugged into my Gabkits 212 with Celestion 30s for a test run and it sound darn good without a bottom plate and head cab. This is my first bare chassis build. I have worked on amps my whole life but never built my own before.

I owe it all to ampgarage and its members for all the help, files and parts. Thank you to all. I used Allynmey chassis, joebobs loaded boards and BOM as well as from other suppliers. I have not gone through with voltage check and will get that done next. Thanks guys.

Mark

[Allynmey]

Nice Job! Love to hear some clips!

[M Fowler]

Thanks Allyn I will get some clips done and posted. I know I have some solder spit on the chasis and will blow it out tomorrow and clean it up.

This was fun and nerve wrecking at the same time.

I will have to order that Rocket chasis from you next Allyn.

Mark

[rooster]

I see you used the Bourns pots. I like these. One thing I see that you might want to correct is the input jack? When you hook up the 1 meg resistor, the thing to do is continue the lead off the resistor to attach to the 'center' lug of the jack - so that the ground lug and the center lug are connected by a straight wire. This way when you unplug the amp, the jack will short out, acting just like you turned the gtr volume down: silence. Sometimes this jack needs a little cleaning on the contacts, BTW.

Anyway, good job, Mark. Now have some fun playing gtr!!

[M Fowler]

Thanks Rooster

I originally did have that center lug wired but when going through the amp I thought that couldn't be right so I cliped it and you can still see the solder left on it. I will wire it back up if that is why that center is being used. I like the Bourns pots also. I forgot to mention Tonesluts Heyboer tranny set but then you can see that already.

Mark

[pureoldsound]

Very cool how does she sounds?

[M Fowler]

pureoldsound

It sounded good last night but all were sleeping so I kept it down, tonight I want to let it fly. But I really should be getting in there and do my voltage first.

Mark

[M Fowler]

Well I had more time to night to play through the amp and of course I started getting some intermittent weird crackles on low notes so I assumed the speakers were rattling the tubes and stopped to check the guts out. I found a bad solder joint on the bottom red wire from the filter cap to stand by switch and re-installed the wire to the center lug on the input jack and she sounded very good. There are some intermittent other sounds now but I figure without checking the voltages or bias yet that I should stop playing around and get serious about that part of the job. Also without a bottom plate and not stuck into a cab you are bound to get some interference or am I just a big newb on that issue?
I'm just so darn glad she works.

Mark

[Ron Worley]

Putting the bottom plate on it makes a great difference, I guess it's down to the inherent instability of the amp....

Ron

[Subjecttochange]

What material do you recommend for a bottom plate? I just finished my express and I did not include a bottom plate and it sounds like I have similar problems as Mark. I am also a newb... at all this but I guess everyone starts somewhere. I am assuming it's just for more thorough grounding, and if that's the case since I have aluminum chassis, would some aluminum roof flashing work?

[Ron Worley]

Check the BOM in the files section- it lists the Hammond cover plate that you need, it's only about $13 and makes a big difference to my ears....

Ron

[M Fowler]

Ron are most guys also using the stick on cork to help absorb the shock as well? I ran across some at Home Depot. I can't say that I have seen that used before but what the heck every little bit helps.

Mark

[skyboltone]

What material do you recommend for a bottom plate? I just finished my express and I did not include a bottom plate and it sounds like I have similar problems as Mark. I am also a newb... at all this but I guess everyone starts somewhere. I am assuming it's just for more thorough grounding, and if that's the case since I have aluminum chassis, would some aluminum roof flashing work?

It depends on how you're tooled up too. I buy scrap half and quarter sheets of .040 6061 from a salvage dealer and cut my own on a table saw. Considerably cheaper than the hammond plate.

[rooster]

I found that some hardware stores stock aluminum flatstock in various sizes. Its .040 and amazingly one of the sizes is 24" X 8". I use a packing knife to score it and with a little bending it snaps in half - leaving me with two pieces, 1@ 18"X 8" and another @ 6"X 8". I actually use the second piece to sheild the area in front of the PT, Komet style (although they cover the whole inside vertical face of the cabinet). I tie the two pieces together with some copper sheilding tape. Maybe sounds complicated but its pretty simple. (The cab by MuchasX/Eric has this little aluminum 1/2"x 1/2" piece of angle 'iron' holding the faceplate on. The copper tape has adhesive on one side so I stick it on the wood underneath this angle piece, contact cement the aluminum pieces in place - (keeping the glue off the face of the copper) - and complete the ground plane with the screws used to attach the faceplate. Very simple)

And all of this being said, I too, thought the sheilding on the bottom of the chassis would really improve/help things. Eh, you know what? I live in the most bombarded radio wave area in town and its not the sheilding on the bottom of the cabinet that makes a difference. I found that sheilding the leads going to pins 2 and 7 of V1 + using a 10K resistor at pin 2 (something Glen K always stresses, BTW) was the real help. I will always sheild the bottom of the chassis just because it is the right thing to do, but it doesn't need it if you sheild those leads. And yes, I sit the raw chassis right on top of a Marshall 4/12 for biasing all the time - not a problem.

[geetarpicker]

And all of this being said, I too, thought the sheilding on the bottom of the chassis would really improve/help things. Eh, you know what? I live in the most bombarded radio wave area in town and its not the sheilding on the bottom of the cabinet that makes a difference. I found that sheilding the leads going to pins 2 and 7 of V1 + using a 10K resistor at pin 2 (something Glen K always stresses, BTW) was the real help. I will always sheild the bottom of the chassis just because it is the right thing to do, but it doesn't need it if you sheild those leads. And yes, I sit the raw chassis right on top of a Marshall 4/12 for biasing all the time - not a problem.

Not sure where that was first mentioned but it's not what's in my amps. Sorry 'bout that.

My original Express, Liverpool, and my 2 Express clones I built only have shielded cable from the input jack to pin 7 of V1. The shielded cable is grounded only at the input jack. Also there is no resistor on pin 2 nor any other shielded cable in any of my amps. Not that I haven't heard of wrecks with the added resistor, just that my amps don't have it. Typically if I have radio pickup problems it's the cord. I don't think I've ever picked up radio since I started using Mogami "Gold" cables. I do run bottom plates on all my TW type amps.

Actually one time I had problems with my Express radiating radio waves! When I'd crank my Express at my old house, it would eminate radio waves of the same frequency of the RF remote control on the satellite dish in the family room. So, if I started to really crank the amp (even in my studio on the other side of the house) the TV would start to change channels and folks would get pissed! The satelite controller RF remote circuit would actually pick up the amps RF emissions and start turning the dish on the roof searching for Ken Fischer or who knows what ... I had to wrap the power tubes tightly with a single layer of aluminum foil and ground the foil to stop the interference problem. Half of my CD was probably recorded with the EL34s wrapped with aluminum foil... I guess those EL34s REALLY generate some upper harmonics.

Glen