Rangemaster Treble Boost Builders

[Harris]

I just finished up my first pedal build last night....Dallas Rangemaster Treble Boost.  It sounds/works great.  However, it only matches the volume of the bypassed guitar signal when the volume/boost pot is completely cranked.  Is this typical?  I have not played one before, so I don't know what to expect.

[Steben]

No, it is not normal. It should be louder than unity gain.
Do you have voltage readings? It could be out of the ideal biasing point giving tone, but bad volume.

[powerplayj]

Is this the only pedal in your chain or is it between other pedals?  Mine exhibits this behavior when placed in front of my BSIABII (when turned on). 

[MartyB]

Have/can you measure the hFe of the transistor.  It might be weak or leaky. 

[petemoore]

  I replaced a Rangemaster circuit with a Rangemaster circuit in my RM box.
  The one that came out sounded weak, and less than unity at full volume.
  This box now sounds great through the new amp, 5e3. It's Q came through Small Bear.
  Then of course there's the 'DarlingRangePig'...in yet anothe'rm box...


RM's are very particular about transistors / bias.
----------------------------------------------------
 

[Harris]

I did take some measurements last evening, but can't remember off the top of my head what they were...  So far, I've only used this pedal alone.  I did test the transistor on an old tube tester that  I have that has the capability of testing them.  It sounds great, just the volume is a bit low.  I take the measurements, recheck my circuit this evening and post the measurements when I get the chance.  Thanks!

[MartyB]

If the transistor is socketed, try switching the outer two leads the other way:  1-2-3 >  3-2-1

[1978]

I'm having the exact same problem as Harris.  I finished up the Rangemaster a few weeks ago (using the neg ground version at Tonepad) and it sounded great....until I stupidly snapped one of the transistor leads off (damnit!!).  After putting in a new one last night, and changing the Rb1 and Re resistors as recommended by small bear, I get the following voltages with a battery at 8.88 volts (the range maistro is negative ground)
E:  0.386
B:  0.372
C:  8.62

I'm thinking I need to change the two resistors again--right now I have 51k for Rb and 3k9 for Re .  Any suggestions for whether to raise or lower the values?  [From the Geofex article, I know I should start by raising Rb1, until it gets to 82k]

Harris - I don't mean to jump in on your original question.  There was an earlier post somewhere about a similar Rangemaster volume problem which could help--if I recall properly that person was able to fix it by resoldering the connections to ground.  It didn't help me but it might help you.
here it is:   http://www.diystompboxes.com/smfforum/index.php?topic=38170.0
Also, did you use the geofex layout, or a different one?  Even if you didn't use it, lots of "tuning" info:  http://www.geofex.com/Article_Folders/Rangemaster/atboost.pdf

[Steben]

The base is too low - collector too high.
Try placing a 100k trim pot (or even 250k) from base to ground instead of the 51k.
base should go towards 1.0V and collector to 7.0V or go by ear 
It should sound a little little bit mushy at full string attack.

[Harris]

No problem '78!

I only had a few minutes to work on mine last evening.  I used a 250K pot to rebias the base.  All the way up (250k), the lowest I could bring down the voltage on the collector was about -8.1 volts.  Tonight, if I can find the time, I'll mess around with the E resistor and see what readings I can get.

[Steben]

Yup if it doesn't work with a 250k pot you should tweak the emitter resistor.

[1978]

First I put a 100k trimpot for Rb and couldn't get it to work -- only the last 10-15% of the rotation resulted in any sound, and even at 100% there wasn't any effect happening.
Putting in a 10k trimpot for Re also didn't help.  I tried to systematically go through combinations of the two different trimpots to no avail.  It seems that no matter where things were set, the collecter and the base were also very close in value to each other.  Is this the sign of a leaky transistor?

The hFe, if I'm measuring correctly [which I'm surely not], is something like 680 (and I held it with pliers to put in).  680, evidently, is ridiculously high. 

So, I'm assuming my problem is a bad transistor--unless anyone has any other suggestions?  I'm so damn mad because it worked great the first time until I snapped off  the lead of that transistor.

Harris -- did you have any luck with yours?

Steben--thanks for your suggestions.  When you say "100k trim pot (or even 250k) from base to ground" do you mean a trimpot in place of the resistor, or do you mean changing the layout?

[Harris]

Harris -- did you have any luck with yours?

I'm not sure.....   When I bought the tranisistor for my pedal I bought a dozen on ebay.  After my first 3 tries to find one that would bias properly, I started using jumper leads to make the attempts go faster.  So, last evening I had 2 jumper leads for a pot for one resistor, 2 jumper leads for the other bias resistor, 3 jumper leads for the tranistors and 2 leads for the DMM. My pedal looked more like a spider than a rangemaster.  I did finally find one that biased (#10).  By the time I got all that done, the wife and kid were asleep and I couldn't give it a real test drive.  Will post my results this evening.

[1978]

HA! that's hilarious; I had the same mess of wires coming out the back.  I'm definitely getting a breadboard for Christmas.

[8mileshigh]

I took the easy route and got my transistor from Small Bear and saved myself the anguish of trying to bias a transistors but that's about to change after a recent transistor shopping frenzy.  Now, I've got over 200 germaniums from Germany, Bulgaria, England and the USA. 

My Rangemaster has a shitload of gain to it, makes my ears bleed.  Your ears will tell you when you have it right.

Chris

[petemoore]

E:  0.386
B:  0.372
C:  8.62
  Rangemaster passes signal without battery, iirc.
  Without the battery voltage as a reference for these numbers, I can see it has at least 8.62 volta to work with, so the battery's OK, what percentage the collector is of V+ can't be worked as shown.
  But the base must be about .6v difference to the emitter, or it's not biased properly. The collector should be ~ 7/9ths of supply voltage. That's nearer transistor/supply cutoff on one side of the signal swing..adjust the collector bias or...[   ]...
  GEO/RM Read.
  I've been working on mine for years, finally got a GE with Rangemaster bias that actually Duz Fuz into ~15w tube amp.
  Rumors say it's gotta be this certain ac30 or it won't work, I do believe having an amp thats already distorting [tubes making mild dist, RM turns that into Grind]...my guess is that's about the other half of the basis of RM legend.
  [sounded good through Zenith, RCA, Dyna tubes from 40's-50's. For the most part it sounded as labeled 'Treble Boost'.