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Another Hughes & Kettner Attax 100 with no sound
Another Hughes & Kettner Attax 100 with no sound
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Old 21st September 2021, 01:14 AM   #1
kbhkiss is offline kbhkiss  Brazil
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Join Date: Sep 2021
Default Another Hughes & Kettner Attax 100 with no sound

Hello everyone

I'm currently trying to revive this amp but no success yet.
I have a Hughes & Kettner Attax 100 combo with no sound(kinda).

The power amp seems to be working fine. If I connect something to the FX Return, it plays nice.

All the switches LEDs are lightening fine, the spring reverb also works fine. (Oddly, this amp has the reverb after the FX return).

The 12ax7(ecc83) valve doesn't seem to warm, neither light up. But I have something close to 7/7.5v in the heater pins.

What makes me afraid is that I'm having HIGH voltages on the plate pins. Where it should be 270v according to the schematics, I'm measuring 440~480v.


If anyone have a clue, I'd really appreciate
I'll be uploading photos and the schematics here.

Thanks!
Attached Images
File Type: jpg attax100-example.jpg (393.3 KB, 45 views)
Attached Files
File Type: pdf hughes-kettner_attax_100_combo.pdf (761.7 KB, 8 views)
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Old 21st September 2021, 02:53 AM   #2
kbhkiss is offline kbhkiss  Brazil
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Join Date: Sep 2021
I measured the transformer outputs and got correct values
a little bit higher than expected but it's correct since the standard voltage in my country is 127v, and the transformer input is 115v.

output:
39v - 39v - 7.5v
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Old 21st September 2021, 04:12 AM   #3
PRR is offline PRR  United States
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Location: Maine USA
Another Hughes & Kettner Attax 100 with no sound
The tube is dead-cold. Re-re-check the socket joints, then try another tube.
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Old 21st September 2021, 08:01 PM   #4
kbhkiss is offline kbhkiss  Brazil
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Join Date: Sep 2021
[SOLVED]

Found the problem.
Just needed to solder again one point of the heater signal path that was not on contact anymore.

This amplifier have a terrible flat cable between boards which causes troubles through the time.
I also changed it for a new and more flexible cable ribbon, so it should give the amp a better life span now.

I feel like I wasted someone else's time, with this thread. Sorry

But I find this forum and its people awesome.

So thanks again for being such a helpful place!
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Old 4th October 2021, 06:46 PM   #5
Jsixis is offline Jsixis  United States
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Join Date: Feb 2011
Location: Columbus Ohio
did not waste my time, it is how I learn.
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I know nothing, so learning is really awesome.
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