Burns Buzzaround build...

[PorkyPrimeCut]

The guitarist from Wolf People

[mijmog]

I'm really looking forward to this, take your time Mark!

[Fiddy]

Right, I've been through all sorts of ups & downs with this pedal.

Once built & still not working I took it to Ben's place & we troubleshooted the fucker for a few hours with zero results.
So, something could really only be wrong with the original soldering of the tagboard. Bummer!!

Fast forward a few more weeks. Work got in the way & when I finally got round to working on it my soldering iron died (less than 3 week old).
So, after more work & a long wait for a refund I've got this bad boy to help me...



It seems way too advanced for amateur me (an LCD temperature gauge? Really?) and if it doesn't get the job done I might as well give up.

Fingers crossed, folks. I have a Wolf Person patiently waiting.

Do yourself a favor, throw that sponge in the garbage and get one of these bad boys. They're cheap, do a much better job at keeping the tips clean and one should last you a lifetime. No heat loss in case that matters to you.

[andy_tchp]

+1.

I resisted getting one of those tip cleaners for years, thinking the damp sponge was 'just as good'.

I was wrong . Curly brass FTW.

[PorkyPrimeCut]

Interesting suggestion. I'll look into it.

I'm back from Leipzig now so will pick up where I left off later today, so long as work don't call.

[PorkyPrimeCut]

I've got completely sidetracked with this pedal build but really want to get it done.

I've made 2 attempts at wiring it up, based on this diagram...



...each time it's not worked.

The diagram was done by Ben (theworkoffire) who's a very competent electrician so I trust it's correct. It was a rehash of the original Burns wiring that didn't work out first time around. Something's not right & I'm starting to think it's the circuit board.
He mentioned a way of checking the board without having to wire up the 3 pots. I'd love to do that now but can't remember how it was done. I also don't particularly want to bother him with this again. It was enough of a headache for the both of us, first time around.

So, can someone help me out with this? What's the easiest way of checking the board actually works?

[lasermonkey]

There's an error on that tagboard layout. The Balance pot lug 3 should go to the -9v rail, when on the layout it goes to the positive ground, which is the same as lug 1 of the Balance pot. If you move Balance 3 three tags to the right (the right-hand side of the 24K resistor) it should be good to go, assuming you've got everything else correct to the layout.
Hope this helps!

Edit: The Balance control is actually more like a bias control for the last transistor, rather than a volume control. With the error on the layout, there's no bias voltage whatsoever on the collector, and it's pulled down to ground via that 15K resistor. When you connect Balance 3 to the RHS of that 24K resistor, you'll put the bias voltage onto the collector, and it should work.

P.S.
You may well find that on certain settings, the Balance control won't be able to reduce the volume enough, and you'll have waaaaaay more than unity gain. It's useful to add a passive volume control at the end. Use a 100K-470K log pot wired as follows:
Timbre 2 -> Volume 3
Volume 2 -> Output
Volume 1 -> Ground

I've made a few Buzzarounds now, and it's one of my favourite fuzzes. When you get the perfect set of transistors, it sounds incredible!

[PorkyPrimeCut]

I really appreciate your input, thanks!

I posted on DIYStompboxes as well & got the same observations back (wrongly wired Balance pot) so I'm doubly sure this is a relatively easy fix. I may well tackle this later today.

[PorkyPrimeCut]

Firstly, MODS, CAN YOU MERGE THIS THREAD WITH THIS ONE? Thanks!

So, after a load of head scratching & a little help from lasermonkey I got this thing to work. Fortunately it was a simple mistake on the wiring diagram & not a duff component on the tagboard. Typically though, some of the transistors I originally bought for the build aren't all that...

The NKT213s, as rare as they may be, are very underwhelming. Very sputtery but no fizz or rich, crackly decay that I expected. I think the problem lies in the fact that none of them are leaky enough, or in the high HFE range that Q3 is supposed to have. I'll probably sell them on (they were £11 a pop!!)

Next up were some hand picked 2N404As, given to me by a guy who used to post on this forum (not sure if folk remember him but he basically found a load of of obsolete transistors & was selling them in small batches. These just killed the signal so I'll have to test them again. I could've sworn they worked though.

Lastly, I bought a set of Tonebender MkIII transistors, AC125s from Australia. Q1 & Q2 are in the high 50/low 60 HFE range & Q3 is right up at around 130 & very leaky. They work a treat & will probably stay put, even though they're the cheapest of the lot.

The biasing trim pot I added in place of the 24k resistor doesn't do much, if anything. I was hoping for more of an almost "all or nothing" sweep. Is this normal?

[lasermonkey]

Getting a perfect set of NKT213s is going to involve either a lot of luck, a lot of money or both. The first Buzzaround I built featured three perfect '213s that I got for an absolute steal, and I sold it! Not one of my brighter moments. Idiot.
As you've discovered, it's not so much the tra
nsistor variant, but the characteristics which are important. With the Buzzaround and Mk III/IV Tonebenders, the trannies for Q1 and Q2 form a Darlington Pair, so anything with little to no leakage and an hfe of between 50-70 will do. Getting the right characteristics for Q3 (hfe of around 130 and leakage over 400uA) is much harder. The last one I made had a pair of 2G361s (I think) and an AC125 that was leaky and had an hfe of around 150. It was good, but not perfect, like the first one. The three knob Tonebenders, whilst similar, seem to be more tolerant of the Q3 gain.

The Buzzaround's biasing for Q3 is a combination of the 24K resistor, the Balance pot and the 15K resistor. On the three knob Tonebenders, if a biasing trimpot for Q3 is added, it's usually in place of the 18K resistor. The equivalent of this on the Buzzaround is the Balance pot (5K) plus the 15K resistor. If you wanted more range you could swap the 5K pot for a 10K and then lower the 15K resistor to a 10K. You're not going to get the same kind of control over the bias as you would on a Mk II Tonebender though.

I'm glad you got it working!

[PorkyPrimeCut]

That's good, clear info, thanks!

....Getting the right characteristics for Q3 (hfe of around 130 and leakage over 400uA) is much harder....

I wish I'd noted down the leakage of the AC125 now. It's written on a piece of paper in the little baggie it came in but I'm out of town.
I know it's a lot leakier than Q1 & Q2 as I made a quick comparison but the numbers escape me now. I'll find when I'm back in London.

Thanks again for all the help.

[ludobag1]

Trust your hear not the reading ,it is only a starting point
I made a mkiii last month and after carefully test the transistors and wrote hfe and leak of m'y différents trainés
I have test it in the circuit and play it with différents combinaison of hfe ,also try different diode
And the best to m'y taste is an oc 44in q1 ac 128 in q2 an ac125 in q3 hfe 53/60 /87
the last more Leakey
I have ôther with more hfe but it is This ones who sound the more i l'ike