Need help with first pedal

[fuzz guy]

Hi everyone, just joined up after starting my first pedal build, a Rangemaster kit with a PNP Russian transistor. My only electronics experience has been rewiring some of my guitars and building a tap tempo switch, so I'm a bit of a newby.

I've got it done, but I'm getting lots of radio interference, more so when I touch the guitar strings. Is this a grounding issue? If so what steps do I follow to find the fault?

Also, the boost is pretty weak and thin sounding. On lower settings it actually sounds like it's cutting the signal and even all the way up it's not boosting it much. It certainly does add some treble.

Could these two issues be linked? I've never used a Rangemaster style pedal before, am I expecting too much? Thanks

[garcho]

provide more info and you'll get more help

Post the schematic, if you don't have the rights to repost it, just redraw it and post your drawing. For something like the Rangemaster, I wouldn't worry about intellectual property, or respecting-the-designer type issues. Redraw it and you'll get to know the circuit better too. If it's from a company that has that stuff online, provide a link. Sure, Rangemaster is famous but who can know if the one you built is the one they know? There are many "versions" of legendary pedals.

Can you record something and post it? your germanium transistor might not be biased correctly or might not be the right specs for the circuit, who did you buy the kit from?

Post a picture of your wiring and that might solve the possible ground issue

Like i said, a lot of pedals are called Rangemaster and might/most likely not have the same exact components, layout, etc. that's why important to know the details: the schematic, pictures of your layout, pictures of the board, pictures of the interior wiring, etc. the more pictures and info, the better.

If you don't have a multimeter or a breadboard or a bunch of odd resistors, capacitors, hook up wire etc., this might be the time to buy that stuff. Then, when you run into a problem you can't solve and come here, you can test for leakage, give voltage readings, try something before soldering it, etc.

If you want to build pedals with mojo components like germanium transistors, then you have to either know how to finesse them (lots of info online, here, just search) or you have to buy them from a trusted seller who knows how to do that and sets up each kit accordingly. This would be Small Bear for instance. That's one of the most trusted, and most well known. There certainly are others, but my personal experience is with Small Bear, that's why i've only included their link. You'll find it's absolutely worth the price to buy from reputable people, ask around, there are a few. The aggravation alone is worth 20 dollars to avoid. Also, after trying a few from sellers that don't guarantee specs, you'll waste money completely on something that is useless. The only thing worth doing with most germanium transistors is to make jewelry out of them. Considering how much a true boutique pedal goes for, dropping $50 on a Cadillac fuzz pedal is still a very good deal, especially considering how satisfying it is to build yourself your own.

anyway, sounds like you're about to head down a long road of building cool stuff, congrats!

[fuzz guy]

Thanks for the reply. I got the kit from Fuzz Dog in the UK. Here's the link, https://shop.pedalparts.co.uk/Range_Master_Germanium_Treble_Boost/p847124_7396874.aspx

On that page there's a link to a PDF of the build instructions, including a schematic. I'm not sure if it's okay to post it myself here.

I do have a multimeter and I checked the hfe of the transistor which was about 56 I think. I installed it with sockets so I could always pull it out and check again. The kit came with a second Russian can too.

The instructions said to bias the transistor between 6.8-7.1v and I set it right on 7v.

I can take a photo of my wiring and post that too if it will help. I'm not sure if it's a ground issue or not. Unfortunately at this stage I know how to solder and follow instructions but not really how all this stuff works.

[Chuck D. Bones]

The RFI problem is most likely grounding.  Make sure all of the grounds are connected: board, battery, power connector, input connector, output connector, box.  If you box is painted on the inside, scrape away some of the paint on the inside next to the in & out connectors so that they make good electrical contact with the box.  You can also try putting a small capacitor (470pF) in parallel with R1 to see if that helps get rid of RF.  You did the right thing socketing the transistor because Germanium transistors don't like heat and soldering can damage them.  It is normal for the signal level to go all the way to zero when you turn the Boost pot counterclockwise.  This circuit is as much as bass cut as it is a treble boost, so the thin sound is to be expected.  You can also try adjusting the bias trimmer by ear and see if that helps.  Turning it clockwise will increase the gain and maybe fatten the sound up a little, at the expense of some headroom.  FYI, testing HFE with a multimeter is not accurate if the transistor is leaky, as many Ge devices are.

Have fun!

- Chuck

[Govmnt_Lacky]

I see you are getting lots of good help but, I gotta ask you one question....


WHO'S THE MASTER?

[PRR]

> I'm getting lots of radio interference
> more so when I touch the guitar strings.

Radio may mean you don't have a closed metal box. Is it still out in the open on the bench?

However more radio when you touch the strings sure does suggest a bad ground.

[fuzz guy]

WHO'S THE MASTER?

SHO NUFF!!

I'm certainly not the master of the range right now though.

Thanks for the suggestions, I'll open it up and start checking grounds today and play around with the bias.

[fuzz guy]

The RFI problem is most likely grounding. If you box is painted on the inside, scrape away some of the paint on the inside next to the in & out connectors so that they make good electrical contact with the box. 

- Chuck

That was it. I checked if things were grounding to the enclosure with the meter and it seemed fine, but there was a fair bit of overspray on the inside. Sanded that back and it's all good. The circuit sounds much better now too. I will still play around with the bias and adjust it for the sound I want.

Thanks for the help. I'm definitely planning on doing more kits. Hopefully someday I'll be able to offer help too.

[garcho]

^ nice and tidy, bravo

[Chuck D. Bones]

Sweet!  Glad we could help.  Beware those cheap Chinese batteries, they will puke all over the inside of your box without warning.  Personally, I use only external 9V power.  When I do use batteries, it's either Eneloop rechargeables or Energizer alkalines.  Never had one of them leak.

- Chuck