"PentaBoost" - 12 volt Pentode Booster using Submini 5672 tube

[sweetwilly]

No worries.  As noted earlier in this thread, the tubes can be quite microphonic, so take that into account when planning the enclosure - you want something to dampen the stomp.  Most of the "mechanical" noise seems to transfer through the leads of the tube on mine, so not a great deal can be done there, but foam padding around and under the tube (you can glue a small piece onto the board under where the tube will lie) will make a big difference.

[stereovoid]

cool, i was holding my valve down with a plastic tie clip. used the holes of the vero board slightly enlarged to get it through. just to clarify, pin one of the lm317t goes in at h2 and pin one of the valve goes in at r1? not putting in a stomp as i'm looking at this being an 'always on' at the end of chain. could i incorparate an LED if it went from 12v pos on the wallwart to ground on the board? cheers.

[sweetwilly]

Yup, (although I had to look up the datasheet for the LM317 again to double check - you got me nervous!) pins 1 of the tube and LM317 go at R1 and H2 respectively.

If it's always on, any need for an LED at all?

[stereovoid]

cool thanks for that, yeah the LED idea was more for an artistic paint job idea once its complete, not essential but was wondering if that would be how to do it if i did put one in! got to get it working first though!

[mth5044]

just wire the led up from the powersource to ground. You could just put it with a resistor right across the power jack I guess.

[stereovoid]

cheers for that! if i get the circuit working i wanted to paint a lighthouse on the case...don't know why, just a bit of an art procect! was going to use an LED as the beacon! will be wiring up the jacks today, will let you know how i get on!

[stereovoid]

procect = project...can never find that j on the keyboard!

[sweetwilly]

In that  case you definitely NEED that LED!!!  Think about the sailors!  You can get flashing LEDs (they flash around 1 - 3 times per second) which could be a cool visual effect.  Mucho mojo!

http://www.elexp.com/opt_6bid.htm

[stereovoid]

now that is a super sweet idea! they do them at maplin too, and under a pound...could be well worth it! by the way sweet willy, i added you as a a friend on myspace (im club27). really like your bands songs! you guys should hos up to norwich sometime!

[sweetwilly]

Post pics when it's done - won't get the full flashing effect, but I think we can imagine it!

And cheers - is just my bedroom recordings that have been really well produced and mastered.  I play pretty much everything except the drums which I either program or steal, sh! 

[frequencycentral]

In that  case you definitely NEED that LED!!!  Think about the sailors!  You can get flashing LEDs (they flash around 1 - 3 times per second) which could be a cool visual effect.  Mucho mojo!

http://www.elexp.com/opt_6bid.htm

My concern would be that LEDs draw a lot of current when you turn them on, which can cause 'LED popping'. I'm not sure, but I think the flashing LED might cause ticking in the audio path. Maybe not, I guess the only way to find out is to try it. If the pedal ticks, you have a culprit!

[sweetwilly]

Learn something new every day around here!  Thanks Rick, I wasn't aware of that.

Just debugging my second Pentaboost now.  Is working OK until I close it.  There's a short somewhere me thinks.  This one's just a touch prettier!  Pics soon.

Voltages of the 5672

1 - 1.35
2 - 5.89
3 - 1.25
4 - -0.31
5 - 0.00

[frequencycentral]

Good news!

Did you see my Red Star Drive stripboard layout yet? Pots and tube on the board too.

[sweetwilly]

Yes, yes I did, just after I finished the board for this Pentaboost     (slight exaggeration!)

Don't think there are any 1n67a's amongst the diodes I have either.  Another for the list!

[stereovoid]

the LED doesn't matter at the mo...cant get the circuit working! i bet im doing something stupid wrong, like i said to fc, this is my first build. can someone maybe help me make sure i'm not wiring up wrong...

at the mo i have:
circuit out going to tip of output jack.
ground going to sleeve of out jack and across to sleeve of in jack.
sleeve of wallwart going to 12v in on circuit
tip of wallwart going to ring of input jack
circuit input going to tip of input jack

thats it, no switch, no LED. when i plug in it just makes white noise. as i turn the pot clockwise the white noise goes away to no sound at all. can't here any guitar sound. sure its something ive done wrong. any help would be most appreciated! steve.

[frequencycentral]

the LED doesn't matter at the mo...cant get the circuit working! i bet im doing something stupid wrong, like i said to fc, this is my first build. can someone maybe help me make sure i'm not wiring up wrong...

at the mo i have:
circuit out going to tip of output jack.
ground going to sleeve of out jack and across to sleeve of in jack.
sleeve of wallwart going to 12v in on circuit
tip of wallwart going to ring of input jack
circuit input going to tip of input jack

thats it, no switch, no LED. when i plug in it just makes white noise. as i turn the pot clockwise the white noise goes away to no sound at all. can't here any guitar sound. sure its something ive done wrong. any help would be most appreciated! steve.

Steve, you need to post voltages from all five pins of the 5672. Also, check all your resistor values and the polarity of the two electrolytic caps. Also, maybe post a close up photo of your build, boths sides of the board.

You didn't mention a ground connection from the board to the in/out jack ground - do you have that?

Rick

[stereovoid]

sorry, yep ground is going from board to out jack sleeve and this is also connected across to in jack sleeve. is the best way to post pics using photo bucket? i'll sign up and get some up.

[frequencycentral]

sorry, yep ground is going from board to out jack sleeve and this is also connected across to in jack sleeve. is the best way to post pics using photo bucket? i'll sign up and get some up.

Yup, Photobucket rocks!

[stereovoid]

i'll try get those readings up before work tomorrow. think ive done something bad though as the heatsink isn't warming up now! doh, i'll get it in the end!

[stereovoid]

my girlfriend has taken the camara to work today so will post pictures this evening. as for multimeter readings...getting no life to any of the valve pins. im pretty sure ive populated the board as of sweet willy's 'all on' vero layout, can't see any solder bridges or wrong values. one thing, is a 47nf cap equal to a 0.047uf cap? that is the only component that could be wrong if not. anyway, know you need the readings to try and help so might just start populating a new piece of vero. sorry i'm being a pain with this but thanks for the help!