Ambassador output issue

[lexluthier]

I built this a few months ago, the clean side works fine, but the distortion side has very little output. I thought maybe I cooked a pot, so I replaced them but no joy. I've double checked the components and can't find any anomalies. I'm using a One Spot with 1700 ma to power it. Can it be a transistor or chip?

 

[lexluthier]

FWIW, I built 2 Black Eye kits and they worked great.

 

[vigilante398]

Are these known-good tubes? The clean channel only uses one tube but the dirt channel uses both, so if one tube were weak then it would affect the dirt channel and not the clean channel.

Can you verify the value of the 56k resistor (just above the tube header pins on the right side)? If I'm reading the bands correctly I think the value may be off, and where that is in the circuit would certainly result in a very low output if the value is too low.

Nothing else is really jumping out, it's a clean build. Verify the tubes, verify component values (particularly that 56k), and check for cold solder joints is all I can really give you.

 

[lexluthier]

Hmm, I think that might be the problem. Maybe Tayda sent me the wrong value resistor in the package, it happened before. I metered across the resistor and it reads 56 ohms instead of 56K. I tested the tubes with my old Sencore tube tester and they were healthy. Now I just need to scrounge up the right resistor. Thanks for the help!

 

[vigilante398]

Hmm, I think that might be the problem. Maybe Tayda sent me the wrong value resistor in the package, it happened before. I metered across the resistor and it reads 56 ohms instead of 56K. I tested the tubes with my old Sencore tube tester and they were healthy. Now I just need to scrounge up the right resistor. Thanks for the help!

If you don't have 56k on hand you can substitute something in the same order of magnitude (47k or 68k) in its place, should work to give you an idea of whether or not that's the fix.

 

[lexluthier]

I found a 56k, I'll try it this afternoon, thanks

 

[lexluthier]

SUCCESS!! Works great now, thanks! Are there any tweaks that can be done to the tone circuit? Seems to be a little raspy on the treble, even turned all the way down. Otherwise I like it!

 

[vigilante398]

SUCCESS!! Works great now, thanks! Are there any tweaks that can be done to the tone circuit? Seems to be a little raspy on the treble, even turned all the way down. Otherwise I like it!

It's definitely a bright one, that's typical of Matchless designs. There are a couple things that can be done to beef it up, I'll pull the schematic up when I get home from work and give you a couple things you can try out.

 

[lexluthier]

Thanks!

 

[vigilante398]

Mmkay, to darken the dirt channel I would recommend the following:

• Increase C12 from 1u to 22u
• Increase C13 from 100n to 22u
• Increase C9 from 56p to 240p

Might not be perfect, but hopefully a good starting place.

 

[lexluthier]

I will give it a try, thanks!