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Hello all,

I built the champlifier kit and it worked... kinda. The amp sounded great on volumes 3-6, but going beyond 8 yielded an abrasive higher freq buzz while also raising the noise floor.

I wasn't too happy with this and attempted to fix the problem by replacing the long wire going from the volume pot to preamp tube pin 7 with some leftover Mogami guitar cable as a shielded wire. I did this also to the red power cable running from the volume to the fuse. I grounded the shield on the Mogami to the volume pot. However when I finished this my amp stopped working.

I put it on the bench again and then made two significant errors. While checking voltages, I failed to plug the speaker out. After approximately 30 seconds, there was a pop ( The fuse? ) that occurred which made me realize that the speaker out wasn't plugged in. I then continued, with the speaker plugged in, to check voltages. Upon probing a junction, the pop happened again, the 6v6 flashed, and smoke appeared from what appeared to be the 6v6 jack, or possibly coming from the output transformer. Now the amp won't turn on at all.

I doubt your output transformer was harmed, but it is possible. If the 6V6 flashed & smoked, it is more than likely done.

I recommend posting well-lit photos of all of your wiring to let us take a look.

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

Thank you for the reply, Morgan

Here are some photos

And some more photo

Note that the ground on the guitar cable was grounded to the vol pot but I desoldered the joint and just left it hanging while the amp is in limbo.

I'm not seeing anything major to worry about in the wiring.


This could very well be normal operation. Tweed champs tend to absolutely fall apart and sound pretty unmusical when you turn them up high. Where that transition happens depends on how hot your pickups are, the gain of the input tube, and tolerances of other components.



You don't need shielded cable on the AC power line, it doesn't provide any benefit. I would replace that with a decent gauge non-shileded wire to make sure the dual conductor wire is not causing any shorting issues. Also, I can't see your grounding scheme, so make sure the volume pot lug is also properly grounded.



The fuse looks like it is done to me. You can verify that by measuring continuity across the fuse. If it reads open, it has popped and you need to replace it.

I would not trust that 6V6 going forward. Do you have a known good one you can swap in?

This is what I recommend doing once you verify that you have a working fuse and power tube:
- check all ground connections to the chassis to make sure the grounds are all good.
- go back and inspect all of your solder connections looking for bad joints and possible shorts or incorrect connections.
- start over with the power-up steps in the instructions. Try it without any tubes, add the preamp tube and test, add the rectifier and test, etc, before installing a power tube.

_________________
MasterDelayer/Reverbrador/Ampaholic/TopJacker

Do not use shielded cable for the AC power lines. Who told you/where did you read you should do that?

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Hello Guys,
Here is an update on the situation:
Got new tubes, so went through the startup procedure as described in the manual. 5Y3 and 12AX7 look great. But when it came time for powering on with the 6v6, there was a stringent high pitched noise present even while the Vol. was at 3. I was prodding around with my meter and discovered that on the (-) end of one 8uF cap there was some voltage present with reference to ground. I will attend to this and update you all in a few days.

And in response to the shielding of the power wire, honestly I think what it was is that I read about how that wire is noisy in conjunction to reading about how the other wire can be shielded and I thought to just shield both.

The very thin core wire of shielded cable cannot hold up to large voltages. It's a must-do to change back to the large gauge cable supplied with the kit for this.

Hey guys
So last night I finally received a new set of tubes for this amp. I plugged them back in and voltages looked good but powering up with the output tube yields a extremely loud, unbearable, squealing sound out of the speaker. The sound begins about 10 sec from powerup when the tubes have warmed up. It quickly goes down in pitch upon powering off the amplifier.

Now I checked the grounds and voltages and they look good. However the voltages start higher than spec (430v-ish from the 5Y3) but they go down by the increments expected. And the low voltage point that should be 2v are 2v. I did see a potentially bad ground on one of the filter caps but I re-soldered and now it looks good.

There are a total of three things that I had done to the amp that are not in the BYOC instructions
1. The shielded heater wire. We went through this, I replaced the AC wire as instructed. Connections look good. I don't think that this is the culprit. (But it may!)
2. Installed two 100ohm resistors on the each lug of the pilot light that go to ground, creating a virtual tap. I got this from Mojotone's champ instructions and many say that it helps to reduce noise.
3. A 8 ohm/16 ohm speaker output selector switch. I will include a diagram of this. I had a dpdt lying around so i used that instead of a spdt.

I will add more pics. My next plan of attack is to check the bottom of the turret board to see if any of those wires disconnected or anything.
Thanks guys

From the other side of the chassis:

Please just build it stock and then try adding mods once you get it working correctly.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com