hFE - low gain, high gain - can someone help answer some simple questions

[LucifersTrip]

A couple beginner questions. I read here so many times about low & high gain transistors...

1) Is there a standard hFE range that is considered low, medium & high?

I am troubleshooting a Jen Fuzz with no sound.
http://fuzzcentral.ssguitar.com/schematics/jenfuzzschem.gif

I didn't have BC238B so I used the NTE cross reference. It crosses to NTE123AP
I chose a 2N1149 (I still cannot find a datasheet) from my stock because it also  crosses to NTE123AP
The schematic for the Jen Fuzz says "all transistors are high-gain low noise"
After getting no sound from my Jen Fuzz, I checked the hFE on a bunch of 2N1149's and they're all in the 5-15 range...insanely low!
which leads me to:

2) Why would my 2N1149 cross to the same transistor as a  high-gain trasistor like the BC238B? NTE mistake? ...or does the cross not take the gain into consideration?

Numerous times I have read on this forum about checking the hFE and that if you are not sure of the ebc configuration, the one with the
higher hFE reading will be almost always correct.

If I check the hFE using the correct configuration
http://www.demonsdisks.com/pics/2n1149a.jpg
...as I wrote, I get very low readings in the 5-15 range

If I check with C & E flipped
http://www.demonsdisks.com/pics/2n1149b.jpg
...I get readings from 50 all the way up to 400

The first config is correct since that's the only way it works in my Fuzz Face

which leads me to:

3) What type of transistor do I have?...did I do something wrong?


thanx

[linny1982]

nte mistake... yep. they take seconds parts and label them as there own. plenty of threads on here about nte parts just do a search. as for your transistors have a look at this http://semiconductormuseum.com/MuseumStore/MuseumStore_2N1149_Index.htm . no data sheet but maybe some explanation as to why its not working

[LucifersTrip]

nte mistake... yep. they take seconds parts and label them as there own. plenty of threads on here about nte parts just do a search. as for your transistors have a look at this http://semiconductormuseum.com/MuseumStore/MuseumStore_2N1149_Index.htm . no data sheet but maybe some explanation as to why its not working

An NTE error...I guess with a half million components in their DB, they're gonna be wrong a good percent of the times...

I've checked semiconductormuseum.com with no luck. My pics above ARE from semiconductormuseum.com !

how bout questions 1 & 3?

thanx for the info

[R.G.]

1) Is there a standard hFE range that is considered low, medium & high?

No.
This is one of those things which exist only in context. Gains of 5-25 are clearly low by even yesterday's (i.e. 50 years ago) standards. But a gain of 100 used to be normal, and above 200 high. But modern semiconductor processing produces gains of 400-500 regularly, without much stress. Today a gain of 400 is highish but not unusual, and gains of 500-1000 for a single/not darlington bipolar is high.

I am troubleshooting a Jen Fuzz with no sound. http://fuzzcentral.ssguitar.com/schematics/jenfuzzschem.gif

Read and follow "Debugging: What to do when it doesn't work".

I didn't have BC238B so I used the NTE cross reference. It crosses to NTE123AP
I chose a 2N1149 (I still cannot find a datasheet) from my stock because it also  crosses to NTE123AP

Aproximately 50 kagillion NPN transistors cross to NTE123AP. That just means what is common knowledge here: almost any small signal NPN transistor can be subbed for any other and work, kind of.

2) Why would my 2N1149 cross to the same transistor as a  high-gain trasistor like the BC238B? NTE mistake? ...or does the cross not take the gain into consideration?

Aproximately 50 kagillion NPN transistors cross to NTE123AP. That just means what is common knowledge here: almost any small signal NPN transistor can be subbed for any other and work, kind of.

Numerous times I have read on this forum about checking the hFE and that if you are not sure of the ebc configuration, the one with the
higher hFE reading will be almost always correct.

This is because bipolars have a gain in the reverse direction. This gain is smaller than the forward direction because the base-collector junction is built differently from the base-emitter junction. A bipolar in forward direction has high gain and high collector-emitter breakdown voltage. A bipolar used in the reverse direction, collector and emitter swapped, has low gain and very low breakdown voltage, usually 5-9V.

3) What type of transistor do I have?...did I do something wrong?

The 2N1149 is a very old "grown junction" transistor. It is likely that it has a gain of 50 or under, and also likely that it has a fair amount of leakage. In a modern multimeter tester, leakage appears as gain, as the meter assumes the transistor has zero leakage. Your meter probably can't pick out what the device really does.

The bottom line is: get some good transistors. Use Keen's Second Law: when in doubt, use a 2N5088. The 5088 is a modern, low noise, high gain (400-800) preamp transistor will will work in most signal amplifier circuits that effects will use. Mouser electronics has the 5088 for $0.30 each, or $5.20 per HUNDRED. I buy them in hundreds.

Also read and follow the Debugging thread. It will help a lot.

You might also sell the 2N1149's to collectors. They're worth more as objects of sculpture than transistor to solder in.

[LucifersTrip]

1) Is there a standard hFE range that is considered low, medium & high?
No.
This is one of those things which exist only in context. Gains of 5-25 are clearly low by even yesterday's (i.e. 50 years ago) standards. But a gain of 100 used to be normal, and above 200 high. But modern semiconductor processing produces gains of 400-500 regularly, without much stress. Today a gain of 400 is highish but not unusual, and gains of 500-1000 for a single/not darlington bipolar is high.

Thanx much for the info. That does clear it up. I should've known the standard was different 50 years ago

I am troubleshooting a Jen Fuzz with no sound. http://fuzzcentral.ssguitar.com/schematics/jenfuzzschem.gif
Read and follow "Debugging: What to do when it doesn't work".

Yes, I read that and did post a thread a short time ago, but I did not post voltage readings yet. I wanted to sort out the
2N1149's first

I didn't have BC238B so I used the NTE cross reference. It crosses to NTE123AP
I chose a 2N1149 (I still cannot find a datasheet) from my stock because it also  crosses to NTE123AP
Aproximately 50 kagillion NPN transistors cross to NTE123AP. That just means what is common knowledge here: almost any small signal NPN transistor can be subbed for any other and work, kind of.

2) Why would my 2N1149 cross to the same transistor as a  high-gain trasistor like the BC238B? NTE mistake? ...or does the cross not take the gain into consideration?
Aproximately 50 kagillion NPN transistors cross to NTE123AP. That just means what is common knowledge here: almost any small signal NPN transistor can be subbed for any other and work, kind of.

Good to know. I had a feeling since I subbed a load of random NPN's into the fuzz face and alsmot all worked.

Numerous times I have read on this forum about checking the hFE and that if you are not sure of the ebc configuration, the one with the
higher hFE reading will be almost always correct.
This is because bipolars have a gain in the reverse direction. This gain is smaller than the forward direction because the base-collector junction is built differently from the base-emitter junction. A bipolar in forward direction has high gain and high collector-emitter breakdown voltage. A bipolar used in the reverse direction, collector and emitter swapped, has low gain and very low breakdown voltage, usually 5-9V.

3) What type of transistor do I have?...did I do something wrong?
The 2N1149 is a very old "grown junction" transistor. It is likely that it has a gain of 50 or under, and also likely that it has a fair amount of leakage. In a modern multimeter tester, leakage appears as gain, as the meter assumes the transistor has zero leakage. Your meter probably can't pick out what the device really does.

Excellent info. That does explain my readings. thank you

The bottom line is: get some good transistors. Use Keen's Second Law: when in doubt, use a 2N5088. The 5088 is a modern, low noise, high gain (400-800) preamp transistor will will work in most signal amplifier circuits that effects will use. Mouser electronics has the 5088 for $0.30 each, or $5.20 per HUNDRED. I buy them in hundreds.

I actually did buy a bunch of the 5088's. My mistake was thinking it'd be more fun to use the vintage 1149's since they
crossed to the same NTE123AP. I bought the 5088's from futurlec for $0.09 each
http://www.futurlec.com/cgi-bin/search/qty_price.cgi?part_no=2N5088
It looks like the price went up at Mouser. $0.37 ea or $24 per hundred
http://www.mouser.com/ProductDetail/Central-Semiconductor/2N5088/?qs=sGAEpiMZZMutXGli8Ay4kAHmCxIxFTXSrmiWn4mwkv0%3d
I bought many of my other modern transistors from tayda since they're only $0.02 - $0.05 each !
http://www.taydaelectronics.com/servlet/the-Transistors-cln-2N-Series/Categories

Also read and follow the Debugging thread. It will help a lot.

I definitely have...

You might also sell the 2N1149's to collectors. They're worth more as objects of sculpture than transistor to solder in.

Amazingly, they worked the best out of 10 or so transistors I tried in my modded fuzz face (put in backwards as Q1 combined with 2N2222 as Q2).

Thanx again for all the info...very helpful