Boob tube V1.5 & charge pump

[dexxyy]

Raking through my unboxed circuit drawer last night I came across the tagboard version of this, I`d built it ages ago even tho` I didn't have a tube (DUH). Anyhoo stuck a tube in it and it works great so I thought I`d draw up a vero version. I`ve also adapted Mark`s charge pump layout to make it a little more compact and added a 12v regulator for the heater. Original layout here. This is NOT verified but triple checked and it looks ok to me.

[IvIark]

Nice job matey, I'm sure more people will want to use vero than tagboard for this as a lot of people building aren't interested in mojo, so should get used by a few I reckon

[alltrax74]

I'm very interested in building this one, I will probably use the tagboard layout along with this power supply veroboard as I will power it with a regular 9V supply.
Here comes a question : will the 78L12 handle the current needed for the heaters or should I use a 7812 that can theorically handle up to 1A ?
And pin 9 is not connected I guess ?
Thanks

[rocket88]

looks fantastic. thanks man

[Freppo]

Great job!
I was thinking of doing that myself, but you beat me to it :)
I'm gonna have a go at building this one soon.

Thanks
/ Freppo

[Luke51411]

Are the capacitor values of significance in the charge pump? I don't have 10u rated for 50 volts but I do have 22u 50v caps

[IvIark]

22u should work ok.  You usually see 10u caps for that position but I've seen different values used.  In fact in the Klon it's only a 1u

[Luke51411]

Thanks, I thought I saw it with different values somewhere. I'll probably just wait until I get 10u50v caps in anyway. What would the cap value have an effect on? Or does it just need to be big enough to hold a certain amount of charge?

[IvIark]

C2 is the cap in question, and from an application guide I have it says:

The amount of charge transferred from C1 to C2 depends
upon the amount lost from C2 to the load, and this charge
must be made up by C1 from the basic power supply. The
switches themselves also have series resistance, leading to
further theoretical complications, but the net result is a
typical overall output impedance of around 55Ω (100Ω Max),
provided that the capacitors are sufficiently large. For the
natural oscillation frequency of the built-in oscillator
(approximately 10kHz) values of 10μF are adequate.

10u is always the value shown in the datasheets, but as we use the boost function a higher value capacitor may be preferable anyway.  But then again it certainly works in the Klon with 1u, so it obviously isn't that critical.

[Mark SL]

Does pin 5 connect to anything?  Also do we need the 12 volt regulator if we are only using the 33v wire to power the tube board?  

[Mark SL]

12V to pin 5, DUH! I did this but got a very minimal amount of gain out of the circuit.  Im using an ecc83. I'll check the voltages.

[alltrax74]

I built the charge pump, I'm getting 16V at pin 5 instead of 12, all the other voltages are good...
I'll check back my circuit

[dexxyy]

You shouldn't be getting 16v from a12v regulator, if the rest of the voltages are good I'd check the regulator first.

[alltrax74]

Right, it was a faulty regulator
I replaced it and now I get 12V on pin 5 (and 37.5V on the max output with 9.65V from the power supply)
Here is the main board so far

[alltrax74]

Just tested it, this thing is fucking awesome !
Extremely dynamic, loud, touch responsive. From clean boost to light crunch. I can imagine how well it must stack with other pedals.
Should get boxed within a few days !

[Luke51411]

Very cool! I intend on throwing one together soon.

[Heath]

I can't seem to get any decent output from the charge pump.  With the 7660 from a good regulated power supply I was getting about 7v where I should have been getting 12, and about 12 v where I should have been getting 33v or so.

Swapped it for a MAX1044 and it's better.  I'm getting about 11v at the 12v spot and around 22v at the 33v spot.

At this voltage with the 12au7 it's a clean boost at best.  I swapped for a 12at7 and I get a very tiny amount of overdrive.  I don't have any 12ax7 tubes around.  That might give it a bit more gain.

Before I dismantle it, can anyone tell me how to tweak the voltage a bit on the charge pump to boost it a bit more?

[alltrax74]

You must have a poblem with the regulator, which should give you the same output tension whatever IC you use.
I have a 7660S on mine an I get exactly 12,0v at pin 5

[Heath]

Yeah, but my other voltages, not touching the regulator, are very low as well.  They were ridiculously low with the 7660 and still way below what it should be with the max1044.  I'm thinking I must have something going on with the chargepump board itself.  

It's weird.  tried this with both a fresh battery and 9v regulated from the wall.

9v battery:
9.2v alone
7.7v where the + lead connects to the board... wtf?
9.4v out of max1044 (should be 17-ish)
7.7v out of the 78l12 regulator
9.4v at 17v lead
13.1v at 25v lead
16.8v at 33v lead

after that testing my "fresh" battery reads 8.4v, so it seems this thing eats batteries.


9v regulated from wall:
9.27v alone
9.16v where the + lead connects to the board
13.4v out of max1044 (should be 17-ish)
11.4v out of the 78l12 regulator
13.4v at 17v lead
19.3v at 25v lead
25.4v at 33v lead

better, but still not right.  Grrr.

[Heath]

with a 7660s chip:

9.27v alone
9.27v where the + lead connects to the board
12.5v out of max1044 (should be 17-ish)
10.5v out of the 78l12 regulator
12.5v at 17v lead
17.3v at 25v lead
22v at 33v lead

7660s chip became very warm within seconds.