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

Started by frequencycentral, September 04, 2008, 03:22:05 PM

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sweetwilly

#100
October 17, 2008, 04:25:33 AM Last Edit: October 17, 2008, 04:30:24 AM by sweetwilly
 :icon_redface: :icon_redface: :icon_redface:

I think I may have made a slight error.  I can only apologise!  Pretty sure the jumper from Pin 4 to Row M should be to the right of C1 and R1. 

Really, really sorry if this turns out to be the only problem!

Jimmy-H

#101
October 17, 2008, 04:28:58 AM Last Edit: October 17, 2008, 04:32:27 AM by Jimmy-H
Quote from: stereovoid on October 17, 2008, 03:59:45 AM
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?

How about the voltage of your powersupply.
If there is no life, then no life on the rest.
The cap should be O.K.

Succes with your build! ;D

sweetwilly

#102
October 17, 2008, 04:38:02 AM
Stereovoid - have you got the 12v in at J1 on the board?  Should be feeding 12v to Pin 3 of the LM317.  Maybe check the heatsink isn't shorting against anything also.

Pretty sure about that jumper to Pin 4 being wrong, but can't see how that would stop all power from getting to the tube.  Or am I missing something forhead slappingly obvious?

stereovoid

#103
October 17, 2008, 04:43:38 AM
jimmy, tried a diff power supply, same thing. but think my multimeter might be bugging cause its old and tatty! sweet willy, will try moving the jumper. think what it really comes down to is i'm trying to 'paint by numbers' rather than understand how things work. hopefully with the help of people like yourselves and fc and can better my understanding. asking my girl if she'll get me an electronics book for that pagan festival day at the end of december...any recommendations? seriously, thank you guys, this is a great forum to be part of. steve

stereovoid

#104
October 17, 2008, 04:48:53 AM
yep, in at j1. put my voltage regulator on the otherside of the board as i have a diff heatsink to you, but its still oriantated the same way round as yours, pin one, when looking at the written side of the chip, to h2...its like internet chess...bishop to f4!!  :icon_lol:

sweetwilly

#105
October 17, 2008, 05:02:28 AM
I'm in much of the same boat.  Full time work + wife + band + recording + building = not a lot of time for theory.  Got a breadboard now so going to be spending some time figuring out why these things are so.

I've built a 2nd one now (the Pentabeast is being shipped to a mate in Australia).  Kept the prettier one for myself -



I got 1 dud tube, but found it makes an attractive pointer for the knob!

stereovoid

#106
October 17, 2008, 05:05:45 AM
yaahoo! with the jumper moved, life we have!! lots of interferance though, but its not in a box at the mo and i've been pulling things out and bending components so could well have a dodge solder or something now! one thing that seems strange...as i turn volume counterclock the signal goes up and viseversa signal goes down, so my pot is working backwards! no biggy though!

sweetwilly

#107
October 17, 2008, 05:12:25 AM
me again!!!   :icon_redface: but then, I've left it that way on everything I do.  and besides, reverse wired pots sound SO much better! :icon_wink:

again, sorry about that!  it sucks when you're sure you've done everything exactly as instructed only to find out the instructions were wrong.  glad it's getting sorted now though. 

The power supply you get is probably the most important component of all with this.  I bought a supposedly clean, regulated PS for over £13 and it hissed and sputtered like a cornered snake.  The one I got for £8.99 from Maplin is dead silent (thanks to Rick for the tip!).

stereovoid

#108
October 17, 2008, 05:12:39 AM
that build looks sweet man, could you maybe show its insides?

stereovoid

#109
October 17, 2008, 05:17:00 AM
might pop up to the old maplin now, with the smile of success ;D on my face! i have two more of these valves so might try another one of these and a redstardrive! thank you all. will still put up pics and take some readings!

sweetwilly

#110
October 17, 2008, 05:18:44 AM
Gladly, just ran out of memory on my phone last night and couldn't be bothered emptying it!

This was from when I was planning the layout.  Was trying for a tiny build so was using a salvaged mini pot from a dead Boss pedal, but ended up getting a slightly larger one to allow for foam padding and such.



It's a great booster when you get it running - just can't say that enough!

That box is only £3.49 at Maplin also.  Even has room for a 9v battery (this thing sounds good on either 9 or 12!)

stereovoid

#111
October 17, 2008, 05:30:13 AM
looks sweet man! i'll post pics of mine later tonight! think the multimeter is defo dead! still nothing! had the black to common ground. put pos on each pin of the tube and no readings! looks like its time to make some investments! so what is a bread board? you can lay out parts and make sure its working before soldering?

sweetwilly

#112
October 17, 2008, 05:39:29 AM
yup



You can pick somethig like this up for less than a fiver.

stereovoid

#113
October 17, 2008, 05:49:33 AM
ah cool! will have a look in town! the feeling of getting something working is grand! think the two probs were the jumper and also a dodge solder on the wallwart. just wired it to a 9v battery and no interference, just lovely sound! new power supply it is! right, part 2...what is the smallest enclosure i can get this in! haha!

sweetwilly

#114
October 17, 2008, 06:01:30 AM
With a bit of planning it would fit the MXR size box at Maplin.  That's the one I used.  It's 111x60x27 inside.  Also depends on what offboard components you've got.  Enclosed jacks tend to be a bit smaller than open ones, etc...  Lead dress (how you lay the wires in the box) is also pretty tricky, so having a bigger box 1st time might be a better idea.  When your skills improve you can always rehouse it.

frequencycentral

#115
October 21, 2008, 07:13:34 PM
Jasper Oosthoek over at AX84 has come up with an interesting variation on the PentaBoost/Red Star Drive. He's used a low current bipolar PNP silicon transistor as a constant current source instead of an anode resistor. Technically, it's not in the signal path, from what I understand, using the transistor mean more voltage is available to the plate instead of being used up by the anode resistor. A very significant amount more gain is the result. I just breadboarded some of his ideas tonight. I've put a trimpot in the schematic, though on the breadboard I measured the ohmage of the voltage divider created by the trimpot and the 1M resistor, and was able to replace the trimpot with a 68K resistor, so the trimpot is there to take account of transistor variances. Here's the PentaBoost MkII schematic, I'll be updating the Red Star Drive shortly - the mod with that one is similar but slightly different.

http://www.frequencycentral.co.uk/

Questo è il fiore del partigiano morto per la libertà!

sweetwilly

#117
October 22, 2008, 10:18:06 AM
I'm really looking forward to trying out the new version - only wish I'd left room on my layout for mods!  Might have to make a up an add-on board for this. 

Bring on the Red Star MkII!

~arph

#118
October 22, 2008, 10:38:58 AM
A so also more gain when 9V is used ?  ;D
I'll try this when I get back home..

~arph

#119
October 22, 2008, 12:16:12 PM
 ;D

Well, what can I say, that really makes a lot of difference! actually usable now at 9v.
Thanks, I had seen the same kind of arrangement too with a j201 somewhere (I believe on tim escobedo's site)
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