beginner voltage question

[1wahfreak]

I'm having a problem troubleshooting a rangemaster. I know my trannies are good but I only get ~ +2.5 volts at the collector. If I try to bias the resistors they fall out of the range described at GEO. So I'm question my measuremnts. I built the neg. ground version. So if a positive ground circuit calls for -7v at the collector, and I'm actually measuring a neg ground circuit, do the signs simply switch or should I be getting a "complimetary" measurment 9.5v minus 7v = +2.5v which would be perfectly good circuit.

thanks

[1wahfreak]

bump...

[Ge_Whiz]

You should be getting +7V at the collector for a negative ground circuit. Have you checked the circuit thoroughly, especially the other resistors? What transistor are you using?

That said, if you are using germanium it's still not unlikely that the collector resistor value may need to be outside the suggested range.

[1wahfreak]

Thanks for answering...maybe I should have asked this in the beginners forum.
I'm using either OC44's, OC42's and OC76's and I get basically the same thing on all of them (regardless of gain).
Using a 110 hfe OC44, to keep the 7v at the collector I pegged a 100k ohm pot (68K resistor) to 92K and that leaves me to reduce a 10k pot (3.9K resistor) to 922 ohms.
With the collector at 7v the base reads 8.4v and the emitter is 8.6v

Using a 70 hfe OC44 I used the same value pots. Keeping the collector at 7v, base=8.61v and e=8.77v
Battery is 9.39v

The boost pot is also running backwards (full boost in the zero position). I swapped #1 and 2 lugs around leaving the 3rd lug to ground but it is still operating backwards.

I used the layout from GGG (on PCB) and everything is exactly as suggested. The only thing I noticed reading through RG's explaination, is at one point he referes to a 4.7k instead of a 470k but all the schematics I've seen says 470k so I'm asuming it's a typo. Any thoughts or suggestions...??

[modmod]

i got the same problems also here :
1.oc44 gain 88 , leakage 58ua
2.trim pot set to rb1 68k, re 3k9
3.input cap 6n8
4.voltage , C=2.31v B=7.86v E=8v
5.negative ground

i'm wondering should i plug my guitar into the circuit while testing the voltage ? does it affect the voltage ? it sounds ok but i dont hear any crackle noise while turning the boost (10k) pot ? how can i adjust it so that C=7v ? so many question.....thanks guys :roll:

[petemoore]

I'm confused....
 But, Rangemaster, as PNP [this means PNP Transistor] and Pos Gnd.  scheme works...
 [Neg. Gnd. you'll need a npn transistor, I haven't been reading how good Neg Gnd Rangemasters actually work tho.]

[modmod]

pete,i was trying this

same as the one at GGG,any hints