Developing the DIY "Champ" for first time builders

[RJ Guitars]

That is the Rev for the Eagle 100. It is fundamentally the same but the Eagle premium has a different power and output transformer. I'll be working on the Premium schematic and layout over the next few days... sorry I am late in getting this out.

Let me know or post it up here if it isn't obvious what to do on your transformer wiring. Also be aware that you don't need that terminal block and the 100 Ohm center ground resistors with the Edcor power tranny. It has a center tap that can go straight to ground. The Edcor also has a 5V heater tap that you want to tie off and make sure you don't short or ground those leads.

Hope to see your posts as you create this amps. Feel free to post on this thread or create your own. And no matter how simple or silly the question, you can count on everyone being helpful and kind in answering your questions... well almost everyone anyway.

rj

[jrc]

I could use an exact description on how the PT (6k49vg) is connected for the basic build. I'm not sure on the proper wiring for the primary (2 black, 1 gray). On the secondary it looks to me like red/yellow to ground, green (heaters) to pins 2&5, 7&4 (no resistors per rj's prior post?). Red(s) to the rectifier. I'm as noob as they come so please keep the laughter down to a minimum. Thanks

John

[RJ Guitars]

I could use an exact description on how the PT (6k49vg) is connected for the basic build. I'm not sure on the proper wiring for the primary (2 black, 1 gray). On the secondary it looks to me like red/yellow to ground, green (heaters) to pins 2&5, 7&4 (no resistors per rj's prior post?). Red(s) to the rectifier. I'm as noob as they come so please keep the laughter down to a minimum. Thanks

John

John,

You have most of it I think, but with the Allied transformers, you do need the two 100 ohm resistors to make the artificial center tap on the heater wiring.

That gray wire is a shielding wire so it would go to ground and the two black are your 120 volts AC. I see on my drawing that I've used a gray colored wire for one of the 120 mains. A mistake in choosing the colors on my part. I haven't got the original drawing with me to fix that immediately so don't let that picture confuse you between the 120 leads and the shield wire. You don't want any voltage on that gray shield wire.

Keep posting if you have questions. I am out of the country for another week but you have some good help available here on the forum.

https://tubeamparchive.com/download/file.php?id=16055

rj

[jrc]

Ok I've got her all wired up, powered up slowly w/variac after many checks, all seems just fine except when I plug in my guitar no mojo. Amp sounds as if nothing is plugged into the input (guitar and cable good). When I crank volume on amp it sounds like what I would expect an amp that has nothing in the input to sound like ie a little bit of hum and that "opened up" sound, nothing out of the ordinary.
The only thing I see different from the layout pic is the parallel cap (c7) is installed according to schematic (not shown on layout).

John

[RJ Guitars]

John,

I'll start with a guess that it's either your input jack or output jack... maybe even my fault if you built it exactly as I've drawn it and it doesn't work.

Now that the first guess is over with...

1- Does the power tranny get hot? Hopefully it will blow a fuse before the smoke comes out but this can be painful if you don't catch it quickly.

2 - Do you have heater power to the tubes? If they are lighting up and the power tranny is cool, life is good.

3 - Start measuring some voltages and see what you have. I don't think the 5F1 schematic has voltages listed on it but the 5E1 does and it is essentially the same as what we built. Print out a copy of that 5E1 and write your voltages down as you go along.

4 - As you measure those voltages listen for a pop in the speaker as you move your probes around... I suppose that is not an official test but if that happens you know your output section is good.

Report back with those voltage measurements and let us know what you have.

In the meantime hopefully some of the good eyes here and my old ones can take a look at your photos and see if anything jumps out.

rj

[Firestorm]

I think the input jack is wired backwards (the layout drawing is a little misleading). Swap the purple wire and the green wires to the opposite lugs and it should work.

[RJ Guitars]

I am inclined to go with Firestorm on this - If you are not familiar with those jacks (or get bad advice) they have a tendency to give you the silent treatment... experience speaking. In my drawing it's hard to tell which contact is the chassis ground and which is the center conductor. If you get them reversed your input is grounded out all the time.

You can see this part on this web link below although it's still not clear where to hookup your wires. I'll work on some high res photos after I return from my current travel and also rework that part of the drawing.

http://www.tubesandmore.com/scripts/fox ... m=W-SC-12A

The plan is for the signal or center conductor on the input to be grounded out until a cord is plugged intp the amp. On the input this keeps the amp quiet. On the output we do the same thing but in this case it offers some very inexpensive protection for your output transformer if you forget to plug a speaker cable in.

See if the web picture and the explanation help this make sense.

Once I get one of those in my hands again I'll rework the drawing so that the logic and the picture mesh together smoothly.

thanks,

rj

[jrc]

Yes! Thank you Firestorm and RJ. I must have looked at that input connection 20 times and didn't notice my error. Amp sounds good, real nice around the 2 o'clock position. Thanks again RJ for putting this together.

John

[M Fowler]

rj, the zip code was off by one digit on my package which arrived yesterday after a long journey

Nice cab, chassis, faceplate, and iron buddy. I owe you big time!

Mark

[Zippy]

I'm as noob as they come so please keep the laughter down to a minimum.

Yes! Thank you Firestorm and RJ. I must have looked at that input connection 20 times and didn't notice my error. Amp sounds good, real nice around the 2 o'clock position.

Nothing but respect for you, John. Nice job!

[RJ Guitars]

rj, the zip code was off by one digit on my package which arrived yesterday after a long journey

Nice cab, chassis, faceplate, and iron buddy. I owe you big time!

Mark

Glad it made it... I had a note from UPS saying something about an address correction but wasn't sure what it all meant.... now I guess we know.

I have never seen a transformer that looks better than an Edcor. The paint is first rate, the wire is top notch, no varnish spilled on it and nothing but good sonic reports so far. I just sent a complete set of Pacific, Heyboer, and Edcor trannies for an Express build over in England. Will be very cool to have the head to head comparison.

Let us know how this next build goes for you!

rj

[RJ Guitars]

Yes! Thank you Firestorm and RJ. I must have looked at that input connection 20 times and didn't notice my error. Amp sounds good, real nice around the 2 o'clock position. Thanks again RJ for putting this together.

John

John,

Congrats, I am pleased for you. These are highly useful amps and a great way to break into the addiction, I mean habit... I mean hobby. Thanks for sharing the build progress. There are some good guys here for sure!

Firestorm, thanks for lending your help on this project. I am greatly appreciative of your added input and assistance!

rj

[RJ Guitars]

Hey guys,

Take a look and see if the schematic will give us what we think we need. It's the same general idea except for the addition of the tone stack. I also have not made any adjustments to resistor or capacitor values in consideration of the EL-34 (or other) output sections. One thing that has occurred to me that is relevant to all these builds is that the feedback resistor may need some adjustment from the original Champ values because all the output sections we are using have an 8 ohm tap. Maybe someone else said this earlier in the project, but either way it's worth a look.

I've also created the layout and there should be no surprises here but again let me know if I've gone too far astray anywhere. I changed the grounding scheme to be more conventional. As you can see there is tons of extra space so this is really a chassis waiting for amp mods to happen. I redrew the input and output jacks so that I think they more closely represent the Switchcrafts that we are using.

The transformers are on order and the chassis drawings are turned in to the machine shop. For this effort I decided not to attempt to hand drill all the chassis again. Hopefully this all comes together about the time I return to the US.

Let me know if you see something we need to look at before we build a few of these. I did all this work on my mini sized laptop and it's a bit hard to see everything so I appreciate a few good eyes toward seeing the not so obvious if you have time.

rj

Post edited routinely as the schematic and layout are refined...

[surfsup]

RJ, pin nine on the 12ax7 is a heater pin, I believe, and you have it going to a ground lug. You also have both heaters going to 4/5 on the 12ax7 and one should go to 9, the other to both 4and5 (again I think).

You have three ground lugs off the turret board bolts in the corner, are those grounded to the chassis in each of the three locations? Will that cause concern for ground loop(s)?

For the eyelet/turret just to the right of the v1a plate resistor, is that kinda close? What's the spacing on that or what spacing should be used? I would love to know this answer as I am laying out the Xits X10 as well.

The end of the lead from the bass pot's right pin has no vertical segment to connect it to the board, fyi.

V1a pin 8 shows a C5 cap on the Ck, and there's no cap on the layout (that I can tell)...

The blue lead from pin 5 on the EL34 (again I think) on the layout should connect to the turret/eyelet at the center of the board between the resistor and 02uF cap, not the end of the resistor and that resistor should have a ground lead off it?

I hope these suggestions are not a waste of your time!

BTW, nice to see the schemo with the two secondary PT options! I wish I knew this yesterday when I ordered those switches....I would've ordered another one!

[Firestorm]

RJ --

You've got R12 and R13 swapped from their 5F1 values. That said, what you're essentially building here is the AA764 circuit in which the screen dropping resistor (R13) is 1K and the preamp supply dropping resistor (R12) is 10K. With the tone stack in place, you lose so much signal, Fender was likely trying to boost voltages on the V1 plates.

I think I would add a separate screen resistor of 470R to 1K in deference to the EL34 since its suppressor grid will have to be connected to the cathode's (small) positive voltage.

With feedback connected to the top of R7 (47R) the stock feedback resistor value is 2K7 (also the values used in the Princeton). Maybe that should have been the value in the Basic version, too, but now you can compare and contrast different values to see what sounds best.

You should indicate on the schematic the tie between output tube pins 1 and 9 as you have done on the layout.

You might want to build in a provision to lift the tone stack ground in order to get the raw tweed sound, too.