New Fender Champ 600 - some repair findings

[Crawfish]

Some of you may have some experience with this little amp already, but this was my first go-round so I thought I'd share.

I had seen and read about them on ebay and thought it might make a good practice amp. Didn't really want to spend the money for a new one, and bought mine off ebay relatively cheap - advertised as "powers up, no output." I'm thinking the absolute worst thing could be a blown OT - and in an amp less than a year old? Probably not likely. So I took the plunge and won it.

So...got the amp, bring it up on my variac in case it smokes or draws excessive current. The preamp tube lights up as does the pilot, the 6V6 does not. Amp is drawing hardly any current at all. Take out the 6V6 ("Made in China Oct 2006"), it has a rattle when shaken. Nice. Try a different 6V6. It lights up, but nothing happens.

Took some voltage measurements, and found R11, the 1K 2W resistor after the first filter cap is open. Not burned looking, but open. R26, the 470 ohm 2 W screen resistor, is somewhat torched looking, as are the two 100 ohm resistors (1/4 watt!) from the filaments to ground - I think just from heat off R26 since they're very close by. There are also some light brown marks around (bada bing) pins 3 & 4 of the 6V6 socket.

I was thinking the cathode bypass cap or the screen bypass cap had shorted. Wound up taking them out to test on my Heath tester. They were ok, but since I had them out I just replaced them and the filter caps with better-quality electrolytics. Replaced R11, R26 and the two 100 ohm resistors (with 1/2 watters). It seems the 6V6 went south, drew a lot of current, and took out R11.

Fired it up and all is well. I could have probably gotten away with just replacing R11, but I have a little more peace of mind now.

Observations: the tubes are junk. If you have one of these amps, replace the tubes with something better. After what I found I wouldn't trust them. I've had bad experiences with Chinese tubes before so I'm not totally surprised.

This is the first PC-board Fender I've worked on, and it's a pain in the neck. I can't imagine something more complex like a Bassman. That must be a nightmare. I also have an issue with the use of 1/4 watt resistors throughout this thing - probably another accident waiting to happen.

I also changed out the preamp tube for an old Admiral-labeled one I had and found the tone much improved. One little 'mod' I did was swapping out the coupling cap for an Orange Drop. It now seems to be a little more defined and detailed tone-wise.

The speaker is also junky...I'll be replacing that as well. There is no way an 8" can go in it, unfortunately. You're stuck with the 6".

Having said that, for a few bucks in parts to 'upgrade' a little, some better tubes, it's a fun little amp, just enough volume for practicing.

-Kevin

[stokes]

The 1/4 watt resistors were a problem in a couple of Bassman reissues I repaired,they used 1/4 watt plate load resistors,one amp had a crackling problem (resistors were about to fry) the other actually fried the plate resistors.I think Fender may have stopped using them,not sure though.Its not uncommon for a screen resistor to go south when a power tube shorts.Sounds like Fender took the "cheap" road in making these amps,1/4 watters are almost sure to fry eventually in any place in a tube amp,the heat gets to them eventually.PCB's are a nightmare in any amp,in my experience.But thats the tradeoff for "affordable" amps.

[Konny]

Are you gonna doing some mods on the Champ in the future or will you keep it as it is?

[Crawfish]

I think I'm already headed toward modding it. I have a Weber speaker on order. Will see how it sounds with that, anything would be better than the stock speaker which gives up, has flabby bass and sounds buzzy when it's cranked to '12'.

The amp has a sort-of BF Fender tone circuit in it, even though there is no tone control per se. I'm thinking about bypassing that and putting in an .02 cap like a 5F1 has...should make it more like a real tweed.

-Kevin

[Konny]

Yeah, saw the schematic yesterday, it has the tonestack but fixed resistors instead of pots.

Some people like lifting the mid-r from ground, that gives you much more signal but the treble-pot still works. If I were you, I´d just install a switch so you can dial in which sound you need.

Do you gonna remove the negative feedback?
I heard lots of people doing and liking this mod.

[Jaybird]

I just picked up a Champion 600 today. I switched the tubes and put in a nice little AlNico speaker I had laying around. The difference in sound is truely amazing. It is now a cool little harp amp. Does anyone know where I could find the schematics for this amp?

[Chuck_Farlee]

I just picked up a Champion 600 today. I switched the tubes and put in a nice little AlNico speaker I had laying around. The difference in sound is truely amazing. It is now a cool little harp amp. Does anyone know where I could find the schematics for this amp?

If you email Fender's customer service, they will send you the schematic and layout of the PCB.

chuck

[Jaybird]

Thanks for the tip Chuck, I will do that.

[tboy]

Champion 600 schematic

Here it is.

[Jaybird]

Thanks tboy. Happy New Year !!

[Jaybird]

I did some more mods on my 600 and have been plased with the results.
I found some directions for removing the fixed tone stack, which really , in my opinion, opened up the amp and improved the tone. I am using an 12AT7 preamp tube to reign in the gain, and was able to install an 8" speaker.


I found that by placing the new speaker offset to the right and as low on the baffle as possible, an 8" peaker will fit.
I removed all components after the tube plate and before the connector to the volume control. In place a .022 cap. So parts(all marked with a dot).....R18,19,20,21,22,and C1, C8, C9. Defiantly do this next step! Solder a .01 or .02 400v coupling cap from the connection of pin 1 on the tube to the connection that connects the middle pin on the connector or the junction of R21 and R20. Also, in the original champ circuit there is no series current limiter resistor(10k ohm, R25) before the 2nd half of the 12ax7. I soldered a jumper in it's place(marked with a line).

[christinejm]

Fender Champ 600 RI trouble

Hi,
I have a Fender Champ 600 RI 2 years old, with a Weber Signature 8” speaker.
Yesterday as I was playing, a loud crackling sound came from the amp, like a ½ way plugged ¼” jack input. It was crackling and very loud. I was playing at 10 volume, with a fuzz box.
I immediately unplugged the amp. Now only a slight crackling amplified sound comes out of the champ when volume is cranked. The GT6V6R groove tube lights a violet color at the plug side, the bottom side, inside the tube looks slightly blackened but appears ok. When I turn off the amp, a slight but audible sucking "whirring" or whining sound, is heard briefly.
Do you know what may be going on here? and if an upgrade kit like Mercury Magnetics will get her up and running again, even better ?
Thanks,
Christine

[Jaybird]

Christine, I would try swapping tubes and see if the crackling sounds go. Try first the 12AX7 and then the 6V6. Often a bad tube can cause the problem you describe, and only after it has heated up a bit.

[jrfrond]

I've sold a lot of Champion 600 mod kits. It's no secret by now that the first run of these cool little amps had piss-poor Chinese tubes in them, and THAT was part of the mod kit upgrade. The 6V6 would short, and bye-bye cathode resistor, and perhaps even the screen and heater balance resistors. This was common, and it was the reason I had so many dead amps around to perfect the mod kit, since Fender was just swapping them out for customers.

I won't go into any mod details and such, but Fender now equips these amps with Russian tubes, and I can't remember the last time one came into our shop. You got an early one.

[moosie]

I won't go into any mod details and such, but Fender now equips these amps with Russian tubes, and I can't remember the last time one came into our shop. You got an early one.

I just bought a new Champ 600 that was shipped directly from Fender. The 12ax7 was Sovtek, but the 6V6 was Chinese crap. The 6V6 lasted 13 days before blowing and taking out the plate resistor.