Matsumin Valve Caster Debug

captntasty · January 23, 2008, 01:11:06 PM

I would sure appreciate a little help on this one. I was inspired by this post: http://www.diystompboxes.com/smfforum/index.php?topic=63479.0
I also had a few 12au7's around serving no purpose whatsoever. It's wired up correctly according to schematic and layout and has the following measurements:

V=9.84v

Pin 1 = 8.07v
Pin 2 = 4.92v
Pin 3 = 0.00v
Pin 4 = 9.84v
Pin 5 = 9.84v
Pin 6 = 8.95v
Pin 7 = 6.66v (could that be the problem?

)
Pin 8 = 0.00v
Pin 9 = 9.84v ( I included this even though it is not used)

The filament isn't glowing and there is sound on pin 2, the input but nowhere else including the output, pin 6. I'm stumped, I thought this would be a no-brainer that even I could not screw up.
Any help is much appreciated....
Patrick

gnognofasciani · January 23, 2008, 01:19:57 PM

Pin5 should be 0v (GND) and the voltage at pins 1 and 6 should be about 5v (increase the value of plate resistors until yo ureach this value)

snoof · January 23, 2008, 03:50:47 PM

schem says grnd pin 4, and pin 9 is no connection. I've seen pin 5 grounded instead of pin 4 b4 as well... So lift the 9v from pin 9 and your heaters should work. plates (pin 1 and 6) should have output sig.

gnognofasciani · January 23, 2008, 04:43:33 PM

Yes, I forgot to say that pin 4 and 5 can be swapped

captntasty · January 23, 2008, 05:24:23 PM

Six eyes are better than two...

>

I left off the ground on pin four... filaments light and it is a go - Sounds good, but......................
The tone control has no effect. I wired it every which way and zip - still sounds good as an extra stage for my amp.

I post the new readings for reference:

V=9.76v

Pin 1 = 6.99v
Pin 2 = -.035v
Pin 3 = 0.00v
Pin 4 = 0.00v
Pin 5 = 9.76v
Pin 6 = 0.00v
Pin 7 = -.188v
Pin 8 = 0.00v
Pin 9 = 4.96v ( I included this even though it is not used)

Different readings than what has been suggested but it works well, nice bit of overdrive boost. It would be nice to get the tone control working - it's so simple I just don't get it, maybe I need four more eyes

Krinor · January 23, 2008, 05:35:10 PM

Well here's two more eyes at least.

The tone control in the layout is backwards.

I wired mine like this:

- Cable from Volume lug 3 to Tone lug 1.
- 1uF capacitor with negative leg onto Tone lug 1 and then a cable from positive leg of capacitor to pin 6 on the tube socket.
- 10nF capacitor from Tone lug 2 to Volume lug 1 and on to ground.

That should work for you as well.

dano12 · January 23, 2008, 05:39:31 PM

Quote from: Krinor on January 23, 2008, 05:35:10 PM

The tone control in the layout is backwards.

No, it's right. Everybody else in the world is backwards.

captntasty · January 23, 2008, 05:42:13 PM

Even if it were backward, it would still work, right? Mine does nothing either way....

Krinor · January 23, 2008, 05:43:36 PM

Quote from: dano12 on January 23, 2008, 05:39:31 PM
Quote from: Krinor on January 23, 2008, 05:35:10 PM

The tone control in the layout is backwards.

No, it's right. Everybody else in the world is backwards.

Oh come on Dano

Okay so it is right, but I left mine left.

Krinor · January 23, 2008, 05:46:05 PM

Quote from: captntasty on January 23, 2008, 05:42:13 PM
Even if it were backward, it would still work, right? Mine does nothing either way....

Yes it works both ways. You might even theoretically find that it could work yet another way, but you'd have to ask Dano about it.

captntasty · January 23, 2008, 10:48:59 PM

Yes, it does work... but it doesn't work with a .001uf cap - doh! Works with a .01uf but I find I like it run straight out so I left it off.
Pretty cool - me likey!

gnognofasciani · January 24, 2008, 02:38:17 AM

Are you sure that you're counting the pins number in the right way?

(pin1 is the one on the left looking the tube from the bottom)
Anyway 0v on pin 6 isn't a "good" thing $:-\$

captntasty · January 24, 2008, 11:50:56 AM

Yeah, I'm reading the pin #'s correctly... It actually is not really producing any overdrive/distortion any longer... it's a bit more of a clean boost, but not much.

I'll have to go back in for exploratory surgery later today.
Thanks....

Zben3129 · January 24, 2008, 12:37:56 PM

Quote from: gnognofasciani on January 24, 2008, 02:38:17 AM
Are you sure that you're counting the pins number in the right way? (pin1 is the one on the left looking the tube from the bottom)
Anyway 0v on pin 6 isn't a "good" thing $:-\$

Gap at the top, pins toward your face, pin numbers go clockwise starting on right side of gap.

Zach

Caferacernoc · January 24, 2008, 03:59:04 PM

"Yeah, I'm reading the pin #'s correctly... It actually is not really producing any overdrive/distortion any longer... it's a bit more of a clean boost, but not much. I'll have to go back in for exploratory surgery later today.
Thanks...."

No voltage at pin #6 seems to indicate that the second triode half is not adding gain. No wonder there is no real distortion.

captntasty · January 24, 2008, 09:55:50 PM

Something was screwy because I got back into it tonight and pin 6 reads 6.59 after putting a 220k in to bring the voltage down from where it originally was.

Quotepins 1 and 6 should be about 5v (increase the value of plate resistors until yo ureach this value)

Should I keep increasing the resistors - what are the detriments of running pins 1 and 6 up around 7v? Shorter tube life?

Krinor · January 25, 2008, 04:17:59 AM

I think it's time for a photo of the interior of your build here. That might save you some time.

gnognofasciani · January 25, 2008, 05:24:40 AM

Quote from: captntasty on January 24, 2008, 09:55:50 PM
Should I keep increasing the resistors - what are the detriments of running pins 1 and 6 up around 7v? Shorter tube life?

Don't Worry, It's just a matter of polarization: if it'll sound good you won't have to change it

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Matsumin Valve Caster Debug