Germanium Transistor high Hfe

[tonyharker]

See this reply #3 from Jez Siddonds of Peak Electronic Design. http://www.diystompboxes.com/smfforum/index.php?topic=91115.msg902293;topicseen#3 The DCA55 does take account of leakage current in measuring transistor gain.

[Arcane Analog]

There are plenty of transistors with a true gain of well over 200.

The Atlas is a nice unit and it does calculate leakage but unlike the RG method it only captures the HFE and leakage at the moment it is hooked up - in other words it does not wait for the germanium to settle after being handled. That is where RGs tester is much more accurate in my opinion.

[LucifersTrip]

whether you use RG's method or the Peak Atlas, you should wait for settling before you take results...so the results will be similar whichever you use....unless, of course you don't wait long enough. The reason the RG test can be better is that you can hook it without waiting and actually watch it settle.

I did a bunch of testing when I first bought the Peak and the big failure is actually with vintage low gain silicon...Though the hfe's were close to accurate, it gave me wrong types...darlington, digital transistor, germanium, etc...

[LucifersTrip]

to answer the original poster's question:

one of my favorite builds is the Marshal Supa Fuzz with 3 high gains per DAM's info.  Here's the DAM info, first talking about voltages, then hfe:

========================
"Not the in a MKII. On vintage units it varies from around -7.6V - -8.9V.
Even seen em with 9.1V! I take measurements with Zinc Carbon batteries which are around 9.6 Volts when fresh. The original batteries used in the MKII's and its variants were PP4's (Eveready 226) which also read high at around the 9.6V level.
Hfe levels are usually higher also. For example my '67 Supa Fuzz measurements...

Q1 - 174
Q2 - 208
Q3 - 194
========================


I wound up using 3 x 2SB459 (leakage 150 -  200mA) with hfe 244, 193, 213

[Arcane Analog]

The point is that you cannot tell if it has settled with the Atlas even if you wait. With RG's method you watch it settle.

[LucifersTrip]

The point is that you cannot tell if it has settled with the Atlas even if you wait.

Really? So if I take a Peak measurement and it shows hfe 70 and leakage .30mA, then I wait 10 minutes and take a 2nd Peak measurement of hfe 70 and leakage .30mA, I don't know that it has settled?

[Arcane Analog]

You are right - how dare I question you Lucy. You know everything there is to know about fuzz pedals.  

[chromesphere]

Ive had plenty of germaniums with a gain of over 200.  GT402V and some AC176's to name 2.  Yes, I factored the leakage.  its not uncommon...

Skrunk, Those ac125's you mentioned...AC125's are placed in bins.  There is a roman numeral on the front of the bag next to the part number (ie ac125) that represents the approx range of hfe your going to get.  you must have gotten vII which is something like 125-200.

Don't know any circuits that are good for 200+ except what's been already mentioned.

Paul

[roseblood11]

one of my favorite builds is the Marshal Supa Fuzz with 3 high gains per DAM's info

Interesting! Could you please post a link to the exact schematic?

[LucifersTrip]

one of my favorite builds is the Marshal Supa Fuzz with 3 high gains per DAM's info

Interesting! Could you please post a link to the exact schematic?

I used this with no 100K on Q2 BC, used a switch to go from 10uF to a 5uF input cap, used external bias on Q2 C to go from 8 - 9V and tweaked the resistor on Q1 B to give me the hottest sound (> 10K)
http://img846.imageshack.us/img846/3797/supafuzzschem.png

[Electric Warrior]

This is the unit he was referring to:



It's pretty much identical with this schematic, except that it has 12k resistors instead of 10ks:



Note that the 100Ω resistor is wired out of circuit. This layout explains how it's done: