Motorola germanium transistors

[tjdracz]

Hi! I've recently found a seller in Europe offering some AC128/188 for sale. He hasn't got them listed on the website so can't see any pictures but says they are made by Motorola.
Now, I've never seen any ones branded like that before. Some googling shows some listings in Asia with transistors branded with something looking like Motorola logo and correct part numbers but they're in bit strange case, looks like TO-5.
Now has anyone encountered anything like that? My guts say fake but would like  second opinion. Rest of the stuff looks legit and got some sweet deals on the likes of 2N2369A, 2N2219A but these germaniums sound bit weird

[vigilante397]

My main question would be if he has legit germanium transistors, why aren't they listed on his website? This doesn't always mean they're fake, but I'm always skeptical of under-the- metaphorical-table deals.

[LucifersTrip]

just for reference..


http://www.jacquesstompboxes.com/ac128.htm


http://tinyurl.com/mqmokxa

[zombiwoof]

I've seen these from sellers in Indonesia and China on Ebay.  Here's a pic:

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/FbUAAOxy4fVTAYm2/$_57.JPG

Motorola usually had a proprietary numbering system, you had to have a handbook to find out what they really were, but it's possible they did make these, who knows?.\

Al

[duck_arse]

http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/FbUAAOxy4fVTAYm2/$_57.JPG

^ that's an interesting pic. if that is meant to be a motorola "M", it is possibly the worst looking one I've ever seen. and the AC128 doesn't come in a TO39 case, and that shown is not a TO18, as the ebay claims.

make up your own mind.

[R.G.]

We need to review germanium transistors again.

(1) A physical transistor is any device that fits within the minimums and maximums listed on the datasheet. In that sense a transistor type is not a physical transistor, it is a datasheet.
(2) Datasheets do not specify all of or necessarily ANY of the properties that make the transistors valuable for pedal use, perhaps especially in the case of the Fuzz Face. A lot of what we want there are side effects of the manufacturing limitations at the time the devices were made.
(3) There is a wide allowable variation inside the datasheet specifications, and on top of that wide variations in the same device under different circumstances.

Some pertinent questions and answers:
Q: I have this device that just came out of the transistor ovens. It's marked "AC128" or "NKT275" or whatever. It can't be a real one, can it?
A: If it meets the datasheet mins and maxes, it's as real as a vintage one. Yes, it CAN be a real, no fooling whatever one.

Q: I have this device that is marked [insert favorite type number here]. Will it make a good Fuzz Face?
A: There is no way to tell from that data. The type number is merely an indication. The material, gain, and leakage are the best indicators we have found so far in replicating [insert pedal circuit being cloned here] circuits. The number printed on the case is as useful as what color the case is spray painted - or not. It's as useful as the hair color of a prospective spouse in predicting whether the person will be compatible with you. And as changeable.  

Q: Butbutbutbut the [insert vintage effect circuit name here] only used the [insert transistor number here] for the real ones. Doesn't that mean that I need that part number?
A: No. The number printed on the outside is no guarantee of what's inside. Worse yet, the wide variation in the characteristics in really real, no fooling AND vintage ones was even worse than new made parts, so MANY OF THE ORIGINAL VINTAGE PEDALS MADE WITH UNSELECTED TRANSISTORS DO NOT SOUND LIKE WE VALUE THE CIRCUIT FOR.  Jimi Hendrix is anecdotally supposed to have been notified when a new shipment of Fuzz Faces got to Manny's and went down to interview them, searching for the one that sounded good out of the pile that came in.

Can these be real Motorola AC 128s? Maybe. Motorola no longer exists. That might be a "Manitoba" M. AC128 is an abstraction, a datasheet. If they meet the numbers, it's a one of those. And the marking on a can is easy to do. Just look at the market for fakes.

What matters is the actual gain, leakage, frequency response, etc, etc. of the part inside. Gotta measure them to find that out.

[karbomusic]

Not sure if this helps but I ordered 4 of those a few weeks back (from another seller on Amazon) and I've used one in a hybrid PNP Fuzz Face thus far:



I expected them to be a crapshoot but I have no complaints at all with this first build. I'm definitely not a Ge connoisseur but I had my choice between those and a handful of grab bag NOS versions I had lying around and I ended up using the Motorola. I should iterate that I'm not as familiar with the sonic differences as the rest of you likely are.

[duck_arse]

karbo - have you done gain/leakage/Vbe on those transistors? can we see numbers?

[midwayfair]

We need to review germanium transistors again.

(1) A physical transistor is any device that fits within the minimums and maximums listed on the datasheet. In that sense a transistor type is not a physical transistor, it is a datasheet.
(2) Datasheets do not specify all of or necessarily ANY of the properties that make the transistors valuable for pedal use, perhaps especially in the case of the Fuzz Face. A lot of what we want there are side effects of the manufacturing limitations at the time the devices were made.
(3) There is a wide allowable variation inside the datasheet specifications, and on top of that wide variations in the same device under different circumstances.

Some pertinent questions and answers:
Q: I have this device that just came out of the transistor ovens. It's marked "AC128" or "NKT275" or whatever. It can't be a real one, can it?
A: If it meets the datasheet mins and maxes, it's as real as a vintage one. Yes, it CAN be a real, no fooling whatever one.

Q: I have this device that is marked [insert favorite type number here]. Will it make a good Fuzz Face?
A: There is no way to tell from that data. The type number is merely an indication. The material, gain, and leakage are the best indicators we have found so far in replicating [insert pedal circuit being cloned here] circuits. The number printed on the case is as useful as what color the case is spray painted - or not. It's as useful as the hair color of a prospective spouse in predicting whether the person will be compatible with you. And as changeable.  

Q: Butbutbutbut the [insert vintage effect circuit name here] only used the [insert transistor number here] for the real ones. Doesn't that mean that I need that part number?
A: No. The number printed on the outside is no guarantee of what's inside. Worse yet, the wide variation in the characteristics in really real, no fooling AND vintage ones was even worse than new made parts, so MANY OF THE ORIGINAL VINTAGE PEDALS MADE WITH UNSELECTED TRANSISTORS DO NOT SOUND LIKE WE VALUE THE CIRCUIT FOR.  Jimi Hendrix is anecdotally supposed to have been notified when a new shipment of Fuzz Faces got to Manny's and went down to interview them, searching for the one that sounded good out of the pile that came in.

Can these be real Motorola AC 128s? Maybe. Motorola no longer exists. That might be a "Manitoba" M. AC128 is an abstraction, a datasheet. If they meet the numbers, it's a one of those. And the marking on a can is easy to do. Just look at the market for fakes.

What matters is the actual gain, leakage, frequency response, etc, etc. of the part inside. Gotta measure them to find that out.

There must be a dozen posts RG has made on here with this same info, but this is one of the best worded ones.

[karbomusic]

I have not, well sort of but didn't really know how to do it correctly because I don't trust the hfe reading on the meter that has that functionality. I had tried the hfe/gain tute on the small bear site but was obviously doing something wrong. Translation = anyone who can help me properly and accurately measure so I know the result is right, I will be happy to.   I have 4 of these and wouldn't mind knowing myself even though my ears are elated with the one I built. I have plenty of parts and gear so I'm sure I have the necessary stuff to do so.

[duck_arse]

as we all always say "there's a page over at geofex ....." go there, look for technology of the fuzz face. there is a circuit included for ge testings.

[karbomusic]

I almost have that site memorized by now.  I just figured I was missing something last time I tried and didn't want to fry a transistor but I'm in no hurry so no worries; next time I cycle back around to fuzz face land I'll try again.

[zombiwoof]

I have not, well sort of but didn't really know how to do it correctly because I don't trust the hfe reading on the meter that has that functionality. I had tried the hfe/gain tute on the small bear site but was obviously doing something wrong. Translation = anyone who can help me properly and accurately measure so I know the result is right, I will be happy to.   I have 4 of these and wouldn't mind knowing myself even though my ears are elated with the one I built. I have plenty of parts and gear so I'm sure I have the necessary stuff to do so.

I found that Smallbear's method for checking transistor gain and leakage was much easier to understand and implement than the one at GEO (even thought it was based on Keen's method).  I had no problem doing it with this method, the main thing to remember is to let the germanium trannies settle for a while until the reading stabilizes.  You just need to follow the directions exactly as he explains them.

Al

[karbomusic]

I did Keen's test last night but I don't know if I got it right so I used 2 3906's as a control. Does the below look anything near correct? I have a feeling I'm doing the wrong math here. Left to right is:

(V1) 1st reading
(V2) Reading w/switch engaged
(Hfe) The difference of those * 100
(Leak) V1/2471 which is the actual value of the resistor.

The left most column designates the transistor under test. MotoX are the ones we are discussing, SBearX are some random unmatched from Small Bear and of course the 3906 are the control. I apologize but I'm very green in this area of measurement and could very well be misinterpreting his explanation:

[duck_arse]

I've read those instructions a million times, I can only ever follow what I'm doing when I've got things in sockets connected to meters. but it looks like yr readings are right, with your leakage numbers showing in mA. looks like a mkIII tonebender in the first 3 moto's.

[karbomusic]

I've read those instructions a million times, I can only ever follow what I'm doing when I've got things in sockets connected to meters. but it looks like yr readings are right, with your leakage numbers showing in mA. looks like a mkIII tonebender in the first 3 moto's.

Thanks, that's reassuring. I went ahead and made a vero version of the test rig last night while I had it up and running so at least now it's plug and play next time I test.

[Guurf2]

Not sure if this helps but I ordered 4 of those a few weeks back (from another seller on Amazon) and I've used one in a hybrid PNP Fuzz Face thus far:



I expected them to be a crapshoot but I have no complaints at all with this first build. I'm definitely not a Ge connoisseur but I had my choice between those and a handful of grab bag NOS versions I had lying around and I ended up using the Motorola. I should iterate that I'm not as familiar with the sonic differences as the rest of you likely are.

Hi, only seen this post now.
did you try to make a FF using only two of these Ge's without the Si's?
if not can you please make one on a breadboard and tell us if it has a good Fuzz sound / attach a short recording here?
i know it's a lot to ask but i think it might help a lot of people here.

Thanks!

Guy.

[diy-tubes]

I've got this type in stock too. hFE from minimum (diode junction at my Peak Atlas) to very high hFE (over 200). I always select them to make 70-200+

hard to say what it is, but testers define them correctly as ge transistors, must be ok for Fuzz Face. I'm interested in sound clips too.

[PRR]

> hard to say what it is

Says it is "AC125", a old standard part.

https://www.radiomuseum.org/tubes/tube_ac125.html

Good for 32V, 200mA, hFE about 125, promoted as an audio transistor.

Odd to see the Motorola brand; this was a Valvo part widely made in Europe but less common in the US.

And that is not the usual AC125 case, but a US-type case.

[karbomusic]

Wow, I had no idea this had recently been replied to. Yes, it turned out fine, I think this was my first fuzz? I'll dig it up and post a sample if the desire still exists but well, it sort of sounds like a fuzz. I ended up making many fuzzes after this one that were all Ge using various Ge transistors I'd gathered over the course of a year but this on is still as above and still working.