Superlead 69 non working controls

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Superlead 69 non working controls

Post by Xplorer » Thu May 15, 2014 8:10 pm

Hello !

i'd like to ask you something, my metro superlead 69 actualy always had the basse and treble controls not working, and i didn't even really realise for a long time. it's when i made my 45/100 that i noticed it more.

i tested the resistance over the lugs 1 and 2 or 2 and 3 of the pots, and it works . i tested the continuity with their connections on the board, and it has continuity. i'm not sure what to check now, and i'd love to (re) discover my first amp ever made !
any advice ?

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Re: Superlead 69 non working controls

Post by JimiJames » Thu May 15, 2014 8:53 pm

Are they of the right value ?
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Re: Superlead 69 non working controls

Post by Xplorer » Thu May 15, 2014 9:45 pm

aaah, it's a pleasure to receive a metroamp notification after the last weeks down :)

yes, both are of the right value.

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Re: Superlead 69 non working controls

Post by ValveStorm » Fri May 16, 2014 6:20 pm

Do any of the tone controls exhibit a scratchy sound when you turn them?
Is the tone stack connection to ground solid?
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Re: Superlead 69 non working controls

Post by Xplorer » Fri May 16, 2014 9:24 pm

hi !
no, they aren't scratchy, they're fully silent. no effect.
i'll check the tone stack connection.
But the mediums are working perfectly.

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Re: Superlead 69 non working controls

Post by ValveStorm » Sat May 17, 2014 9:08 am

The schematic below should be a fair representation of the connections you should have.
If the mid control (at the bottom) is working, you can work your way up from there.
Check connection(s) between mid and bass pots.
Check that bass pot wiper is not open.
Check connection(s) between bass pot wiper and bass cap.
Check that bass cap is not damaged (test or replace).
Check connection(s) between bass cap and 33k.
Etc. (work your way up the stack)
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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 9:51 am

thanks a lot, i'll check soon.
i could measure the pots resistance variation, so i guess it says they're not broken.

what do you mean by wiper opened please ?

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Re: Superlead 69 non working controls

Post by ValveStorm » Sat May 17, 2014 2:52 pm

Open wiper would mean the middle lug on the pot is not making contact internally. If you can put an ohmeter across the two connections to the bass pot and see the value change when you turn the pot then it is OK.
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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 2:56 pm

yes indeed, when i use the meter between lugs 1 and 2 ( 2 being the wiper ) , or 2 and 3, the value changes, so i guess they're ok.

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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 6:50 pm

oooooh ! i noticed something , i didn't check everything yet but the middle pot is a 250k instead of a 25k in your schem. and the treble is a 25k instead of a 250k !
so i swapped them when i built it.
i'm not sure it could explain everything though.

bass pot is still 1M. but why not, only 25k takes the signal off the ground, instead of 250k , so it's hardly noticeable ( it's like 1/10 of the effect wanted ) . and the middle pot gives perhaps too much effect : 250k off the ground, instead of only 25k.
But the bass pot .... mmmh ..... it's the right value, so i don't see why it doesn't work.

will do some further tests.
and if i don't find anything more, i'll swap the pots anyway, and it'll perhaps work, who knows ..

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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 7:14 pm

damned ! i built this amp like a complete newbie !!! indeed i was lol, it was my first build.

Now i see that the 500 pf of the treble pot is actualy a 100pf ...
i'll replace it with an src silver mica.
it seems that there are other mistakes ..

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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 7:39 pm

ok now i've put a 472 pf SRC instead of this 100 pf.

also another SRC 497 pf in place of the 510 pf modern black silver mica

damned ! i can't believe it !!! the 47pf was ..... a 500 pf !!!

i guess i didn't know about the caps and measuring caps back then, and i just put the black caps just like metro guide said, but i'm very surprised.

it sounded good though !! :)

i'm putting a little red square lemco 53 pf there.

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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 7:48 pm

there's also a 500pf accross the lugs 1 and 2 of the bright volume.
i suppose it's normaly 100 pf ?

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Re: Superlead 69 non working controls

Post by Xplorer » Sat May 17, 2014 9:03 pm

done !
it's working now :)

but it's amazing, compared to the 45/100, the effect of the basse, mediums and trebles is not much noticeable ....

changing the medium and treble pots to some high values may be a good mod. previously, when the mediums had a 250k pot, i could clearly notice a big effect on the tone. not much anymore.
So if i put a 250k for the mediums and a 500k or 1M for the trebles, i suppose it'll have a big effect.

i removed the 500pf accross the bright volume, lugs 1 and 2, maybe i should put it back ?

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Re: Superlead 69 non working controls

Post by Strat78 » Sat May 17, 2014 11:08 pm

Try a 1000pf up to 5600pf on the bright channel pot and see what you think. With the value that high you do have a sudden jump in volume at 2 or 3 but the gain is great and you can tighten up the low E string by backing the volume back to around 6 or 7. :D Just leave the bass pot unhooked and use the normal channel volume pot to bring in some extra fullness, it's pretty cool.

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