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Frank, It happens to the best of us. I have difficulty when my head is upside down & backwards too. Cant you just recut the holes with the correct orientation?

Makes a case for prefab chassis/panels and even kits!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

That's exactly what I did...I just recut the holes on the other side...and the new faceplate will cover it.

It certainly makes a good case for precut stuff. combine the cost of a new faceplate and the time I'm putting into cutting these holes, I'm defintely feeling like I should have just sucked it up and ordered a precut chassis...

-F

Just glad you could recover. I hate reworking chassis but sometimes you have to, liek on the 30W Lightning I just shipped. A lot of fiddly work.

Now, focus - on with the build!

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I have started using the faceplates as my template after making a few similar mistakes. I have kept my first ever chassis as a momento, it looks like a piece of Swiss cheese.

You know, it's not the end of the world. There'll be a square hole near V1 that no one will ever see, unless they yank the chassis...

OK I have a grounding question I have posted on 18Watt but I will elaborate here. I finally built a 2 X 10" 16 Ohm cabinet but was having a bit of problems with the 16 Ohm output from the sIII so I changed the output jacks to insulated type and then found that the 16 Ohm output squealed. I grounded that jack common and the squeal went away but then I got to thinking about the 125E OT that I am using for this build, it has various combinations of tags depending on your load impedance e.g. for an 8K primary the following tags are used:

4 Ohm 3 & 5
8 Ohm 2 & 5
16 Ohm 2 & 6

From what I can make out of the schematic for the OT tags 2 and 3 are the commons however if I have both grounded at the jacks I will never be able to get the combination of 2 with anything as 3 would take precedence. Any clues/theories?
Nigel

Nigel, I'm not sure I follow you...in other words, you can't get a common ground among all the speaker taps on the 125E?

If I remember correctly, the hammond didn't have a common ground with an 8K primary.

If you wired it as a 5K primary, you could get a common ground.


The solution to this problem is to use one of the speaker switches with 4 lugs....Jersey Aaron over at 18watt uses these and he's spoken nice things about em...they're sold through mouser. I've used one on one of my amps with no problems, although I feel the switch feels flimsy...

here's the part number 10WA156 it's made by Lorlin...

cheap too....only about 3 bucks, compared to hoffman's 9 dollar switch...however, I *like* hoffman's 9 dollar switch.

That's correct Frank and 8K primary has a possibility of 2 or 3 as commons, a 5.6K primary has 1 as the common. Perhaps I should use 5.6K as the primary, thoughts anyone?

I am not a fan of the speaker switches myself, I like having three output jacks 4 8 and 16 Ohm.

Nigel,

I posted this over at 18watt, I used a selector switch that has multiple poles, like the Alpha Rotary Switch or Lorlin Nylon Rotary Switch, that way you can use one for the + and one for the common. I generally don’t ground my OT output to the chassis, but you could after the switch.

Eddie

Ooohhh....you want to do this without a switch?

well, then that's easy. Simply route the intended leads to the apropriate jacks for hot and ground....for each particular ohm rating.

The one catch is that you can not wire the output jacks to close to ground when empty. The jacks all have to remain open...

-Frank

Thanks guys, I went with the 5.6K primary solution, grounded the common and now I have all outputs working as intended. As it is an EL84 amp 5.6K is cool however if I went 6V6 I think I would want an 8K primary according to what I have read.

Dunno...

I've got a 6v6 amp here running on a 4K primary....no problems what so ever....

You may well be right Frank, I just read somewhere on 18Watt that for 6V6's 8K was preferred and 15K for 6L6's but it's all a bit black magical to me
Nigel

s2 told me recently that the el84 can go as low as 4k but the 6v6 prefers 8k....

However, this lightning build has been *so* much of a PITA, with respect to stability, that I'm not going to worry one bit. It's currently stable with 6v6's and a 4k primary....

so if I have to live with 6v6s pumping through 4k, I'll live with it. The tone is something to die for (finally ) so I'm going to leave it as is and not touch it...

Every tube has it's impedance sweet spot where the max amount of power will be transferred. If you're not on it (either higher orl ower), you will have less power available. Same applies when you use 'incorrect' ohmage speakers e.g. using 4 ohm speakers on an 8 ohm transformer or tap.

They all work, it's just how well and how it sounds and performs.

Sounds like you found a sweet spot.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hey gang,

an sIII progress report is in order!

After my setback with drilling my chassis, I've regrouped and I'm forging ahead with some serious mojo. Since completing the chassis holes (including my screw up) I've:

1- Installed tube sockets and wired up 6.3v heater run.
2- Installed Power transformer and...
a) soldered up 6.3v rectifier filament
b) soldered ac secondaries to recto socket
c) soldered 6.3v taps to already established filament run
3- Attached the front faceplate and proceeded with the following:
a) wired up all input jacks from jack to socket with shielded wire
b) just to be done with shielded wire, completed run from tmb volume to v2
c) Soldered up lamp, Power and Standby switches.
4- Installed OT and soldered all primary connections.
5- Since my el84s are under the output jacks and impedance switch, I wired up all remaining leads from el84s and left enough room to trim to the board.
6- Installed rear faceplate and all mounted connection components.
7- Wired all secondary connections from OT to impedence switch.
8- Wired up output jacks hi-watt style and connected to switch.


Well that about does it. I was going to install the board and keep going tonight, but it turns out that I lost one of the 4 mounting screws I need for the board....and I don't have any more in the length I need. So I decided it was a good quiting time.

I strongly suspect I'll be done with the amp before my tubes arrive early next week (I had to order myself an ez81 and a few more preamp tubes)...

-Frank

p.s. I've been very diligent in photographing the entire build from start to finish....I plan to post a photo essay of the build after I'm done...so stay tuned...

I'd really like to see a good series of pics on this build. I always take pics, but not as diligent as you are being. More importantly, looking for a success story for your amp.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Well, I got some more progess done during my son's afternoon nap:

1) Mounted the board and all frontside pots.

2) Grounded all frontside ground points from all pots to bus bar.

3) Completed 2-3 lead runs on the pots.

4) Grounded el84 cathode point to star ground at PT side.

4) Completed all leads from tubes to board.


At this stage, the only thing I really have to do to complete the amp is complete leads from board to pots and ground the bus bar to the chassis....

Looks like this sucker will be ready when the ez81 comes in!

You are going to be bown away by this one Frank, I am just fitting mine into a scarlet red head with matching 2 X 10" cab.
Nigel

OK folks,

I'm done! All wiring is connected and ready to go....

Tomorrow I'm going to double check the layout, check all the connections for continuity and fire up the amp without the tubes.

Monday or tuesday I should be getting a rectifier in the mail and I can then fire it up loaded with glass...

-Frank