First Champ Build with Pics

[tyru007]

After going through the wiring schematics a few times and the checking voltages (with and without tubes). I said "what the H#%!", plugged in my guitar and speaker hit the power button. OK, nothing blew up and filaments glowing.

Turned the standby switch to PLAY. Hit some strings....
....nothing.......Hmmmm.....

Turn the Volume up on the amp and guitar and hit some strings...
...nothing........Hmmmm...

.....Plugged the "Correct Patch Cord" from my guitar to the amp and hit some strings.....

......lots of great guitar sound .... turned on the NFB switch.....

SQUEEEEEEEEEEEEEEEL...... Plugged my soldering iron back in.

[Jag]

Sounds like your NFB is wired positive instead of negative. Reverse the secondaries on the OT and the squeal should stop.

[Jag]

BTW, did you cut that chassis youreself or is it a kit? Nice job.

[tyru007]

OT was wired backwards

Hoffman 16x8x2 aluminum box that I cut.

Here's a couple more pics:

[tyru007]

I seem to have an issue in the tone stack. Mid and Treble seem to work OK but BASS pot has no audible effect on the sound. I checked the pot with an ohm meter and it seems to be OK. The stack is wired as follows:

[ATTACH]3679[/ATTACH]

I am connected to a new 8 ohm G12H speaker that is not mounted in a cab yet. The speaker is connected to a 8 ohm 5000K tap on the OT.

[STRUNGOUT]

Hi,

I have the same problem with a "5W champ" that I have just built.

The bass pot doesn't seem to do anything?

[tubeswell]

Tone stack is wired up wrong

see the three knob fender/marshall/vox e.g. on this page

http://amps.zugster.net/articles/tone-stacks#Three

[tyru007]

As suggested by another member

Moved the wire from pin 1 on the MID to pin 2 on the mid.

Works fine now

[tyru007]

Champ AA764 Blackface Clone Build

Voltages:

Pin 12AX7
1 215
2 -
3 1.74
4 3.5
5 3.5
6 214
7 -
8 1.81
9 3.5

Pin 6V6
1 -
2 3.5
3 372
4 366
5 -
6 -
7 3.5
8 26.2


B+: 377
B+1: 371
B+2: 335

EH 6V6 and a JJ 12AX7

Using a Strat SSH playing into a WGS Reaper G12H30. Sounds good and very clean up to volume 7 on the single coils. Breaks up earlier with the stock humbucker. Very good and clean sounding amp. Takes my clone TS-808 OD well at even low volume levels.

Very sensitive but is forcing me to not be sloppy as a beginner player.

Absolutly no hum using both the choke and extra filtering cap stage. Probably overkill, but what the heck?

[tyru007]

Here's the turret board layout



and her's the board populated



From left to right on the populated board pic:

12" x 3" Garlite Turret Board
(4) UF4007 diodes (full wave rectifier)
220K 3W MO grounding resistor
100R 3W MO power supply resistor
Atom 40uF 500V filter cap
1.5K 3W MO resistor
Atom TVA 20 500V filter cap
15K 3W MO filter resistor
Atom TVA 20 500V filter cap
5W 470R resistor and 5W 100R wirewound POT (cathode resistor)
25 uf/50V Atom cap
2.7K 1W CF resistor (NFB)
47R 1W CF resistor
1.5K 1W CF resistor (12AX7 cathode)
25uf/50V Atom cap (to switch)
.022uf 715 Orange Drop cap
100K 3W MO Plate resistors
250pf Silver Mica Cap
.047uf 715 Orange Cap
.10uf 715 Orange Cap

turrets for two (68K) input resistors (i'm starting with a 33K right off the tube)

1.5K 1W CF cathode resistor
25uf/50V Atom cap

wire is 20 gauge solid

Power and filiment wire is 18 gauge solid

[Steve Conner]

Nice

The transformers look incredibly big and meaty for a Champ, though, and I see two power tube sockets. Is it some kind of Ninja Champ?

[tyru007]

Nice

The transformers look incredibly big and meaty for a Champ, though, and I see two power tube sockets. Is it some kind of Ninja Champ?

I have 2 octals that can be connected in parallel. I have also configured that octals so that I can insert at 6L6 or EL34 if I want. Therfore, I went with a 15 watt PT and OT.

I wish I had used the second octal for the 6v6 and the second 9 pin for the 12AX7. I could have used the first octal as either a second power tube or a tube recitifier, although I do like the simplicity of a dioode recitifer. The second 9 pin I could have then used as a second gain stage or even added a reverb. I can still do this but means more rewiring

Actually 5 watts is plenty power for what I use it for. I can't realy crank it up now unless I'm home alone. Hence, I've been giving my wife some $$ to go christmas shopping alot. She thinks I'm being generous.

If I built this amp again I would go with a smaller PT, OT and choke.

[tyru007]

Thought I would add the final schematic to this thread. Great small practice amp that you can crank up or add pedals to. Almost no hum.

[tyru007]

I have modified the above schematic:

forgot to show the 220K resistor to ground after the second gain stage of the preamp.

I added .01uf/1KV ceramic caps around each of the diodes.

Change the 2.7K NFB resistor to a 22K if you use the ohm speaker connections. I eliminated the NFB from my circuit.

I reversed the "play" led in the oppositer direction of the "power" led to balance out the 6.3VAC power. Not sure this matters.

I connected the second Octal and changed the power tube resistor to a 220R with the 100R wirewound pot so I can run two parallel 6V6s or a 6L6 or a EL34 without changing anything.

Final Amp:

[Gunny]

Nice work. I built a similar one and also included a choke. For good form, you might want to solder a jumper from the unused tab on the bias pot to its wiper. Otherwise, if the wiper loses contact (with age or ??) your output stage will be silent - unless the cathode just hums from the elevated heater volts.