Aberration Questions

[joelorigo]

I bought the Aberration Fuzz in the sale this Weekend and have a couple questions.

1. I assume the board is designed to fit in a Tayda 3 knob 125B, yeah?

2. I have some BC109 transistors, can that be substituted for the BC107B listed in the BOM?

3. For the MP38A, I found these on eBay that one person on this forum had a good experience with:

6pcs Germanium Transistor NPN MP38A ~ 2SD195, 2SD33, OC75 Tone Bender USSR | eBay

Similar to the 2SD195, 2SD33, OC75, 107NU70. Power dissipation 0.15W. Maximum temperature 85°C. Forward current transfer ratio (hFE) 45-100. Collector capacitance 50pF.

www.ebay.com

Where else could I try to find them? Are there any substitutes to try?

The BOM says hFE ~80, leakage 0.195mA. What device measures the leakage? I have seen the TC1 as a good tester but it doesn't do leakage, right?

 

[Cybercow]

Right. The TC1 does do leakage. I use a Peak Atlas DCA75 for testing JFETs, BJTs and other active transistor/diode device. If you have a Windows based PC, the software that comes with the DCA75 for displaying the curve traces of such devices. However, the DCA75 is over 150 zorkmids in price. The DCA55 is less expensive, but less robust in device parameter readings. [EDIT: Learned that the TC-1 DOES do leakage.]

For other reliable Ge BJTs, there are these MN20B (МП20Б) on eBay too. Stateside, 100% seller with combined shipping - unfortunately, no returns. All are pre-tested, measured and recorded.

MP20B МП20Б (AC125 eq.) NOS PNP Hfe: 80-89 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

MP20B МП20Б (AC125 eq.) NOS PNP Hfe: 90-99 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

MP20B МП20Б (AC125) NOS PNP Hfe: 100-109 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

MP20B МП20Б (AC125) NOS PNP Hfe: 110-119 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

MP20B МП20Б (AC125) NOS PNP Hfe: 120-129 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

MP20B МП20Б (AC125) NOS PNP Hfe: 130-137 Germanium Lo-Leakage Transistor USSR | eBay

It is similar to the AC125, AC126 and AC128 (when used within 150mW dissipation, 30V max). MP20B / МП20 Б Germanium Transistor USSR. Note that the pinout is (viewed from the underside with the center pin at the bottom) Collector, Base, Emitter from left to right; note that the Base lead is...

www.ebay.com

 

[joelorigo]

Thanks for sharing those. The first one has a similar hfe and the leakage is "≤ 125µA" (which I guess is .125mA?). In terms of leakage is .125mA and .195mA close? How would a lower leakage effect the operation?


EDIT: The MP38A is NPN, the above links are PNP, so I cant use them, right?

 

[Feral Feline]

... EDIT: The MP38A is NPN, the above links are PNP, so I cant use them, right?

Right.

Sort of.
A couple ways you could, but the amount of effort and knowledge required...:
1) convert the entire build to positive ground
2) Use an NPN and the PNP to make a Sziklai pair

Personally, I'd stick with just NPN, 'cause if I converted the build to positive ground I'd be pestering ChuckDBones and others to check/correct my conversion. I might go for the Sziklai pair, 'cause that's more straightforward and I just love those pairings, they're Szik!

 

[Cybercow]

Thanks for sharing those. The first one has a similar hfe and the leakage is "≤ 125µA" (which I guess is .125mA?). In terms of leakage is .125mA and .195mA close? How would a lower leakage effect the operation?


EDIT: The MP38A is NPN, the above links are PNP, so I cant use them, right?

Oh snap! Right. I didn't pay attention to the NPN/PNP difference. The MN20B BJTs will not directly work in place of the MN38A.

And for Gemanium BJTs, most any leakage value under ~300mA is usually fine. The lower, the quieter and more stable. Higher leakages tend to exacerbate the noise & temperature drifting commonly exhibited by Germanium BJTs. Biasing is always the trick.

 

[joelorigo]

Right.

Sort of.
A couple ways you could, but the amount of effort and knowledge required...:
1) convert the entire build to positive ground
2) Use an NPN and the PNP to make a Sziklai pair

Personally, I'd stick with just NPN, 'cause if I converted the build to positive ground I'd be pestering ChuckDBones and others to check/correct my conversion. I might go for the Sziklai pair, 'cause that's more straightforward and I just love those pairings, they're Szik!

I’m going to stick with NPN.

 

[joelorigo]

And for Gemanium BJTs, most any leakage value under ~300mA is usually fine. The lower, the quieter and more stable. Higher leakages tend to exacerbate the noise & temperature drifting commonly exhibited by Germanium BJTs. Biasing is always the trick.

I see, thanks!

 

[szukalski]

FWIW the TC-1 does measure leakage.

 

[Cybercow]

FWIW the TC-1 does measure leakage.

I discovered that fact just last knight. I made the incorrect assumption that the TC-1 was just another one of those super cheap Chinese test units.

 

[joelorigo]

Oh wow, cool, I've al. Here is a screen shot from a video about the TC1, is leakage the "Ic =6.2mA" reading?

 

[Fama]

I discovered that fact just last knight. I made the incorrect assumption that the TC-1 was just another one of those super cheap Chinese test units.

But it is a super cheap Chinese test unit! That's why I have one!

Well, for the super cheap part, I don't care where it's manufactured.

 

[szukalski]

I discovered that fact just last knight. I made the incorrect assumption that the TC-1 was just another one of those super cheap Chinese test units.

It’s actually an open source project. The doc is somewhere to read how it works. The cheap units are just chinese implementations of the code.

 

[Cybercow]

It’s actually an open source project. The doc is somewhere to read how it works. The cheap units are just chinese implementations of the code.

This why I really like this forum. The people are great and even us old cows can learn new stuff.

So, are you saying the code, being open sourced, is continually being updated? Is the TC-1 a firmware-upgradable unit?

(I just ordered one yesterday. I figure 20 bux and some reading could teach me more about it too. I already have a couple different cheap Chinese GM-328 units, a Peak Atlas DCA75 & LCR45. I find learning these different units intriguing and educational enough to help keep m'whistle wet.)

 

[Cybercow]

Oh wow, cool, I've al. Here is a screen shot from a video about the TC1, is leakage the "Ic =6.2mA" reading?

TBH, I'm not sure if that is the "Leakage". From a search I found: "How much leakage is too much? 100µA is common, 200 happens pretty often. More than 300µA means the device is suspicious, and more than 500µA I would say is bad."
So, if that "Ic =6.2mA" reading is the leakage, that value is goona set it outside a stable working range with regard to leakage. 6.2mA is 6200µA.

 

[szukalski]

GitHub - Mikrocontroller-net/transistortester

Contribute to Mikrocontroller-net/transistortester development by creating an account on GitHub.

github.com

I think that’s the original but I haven’t delved into the alternative “improvements”.

 

[joelorigo]

TBH, I'm not sure if that is the "Leakage". From a search I found: "How much leakage is too much? 100µA is common, 200 happens pretty often. More than 300µA means the device is suspicious, and more than 500µA I would say is bad."
So, if that "Ic =6.2mA" reading is the leakage, that value is goona set it outside a stable working range with regard to leakage. 6.2mA is 6200µA.

Yeah, that makes sense. So what/how does the TC1 measure leakage? @szukalski ?

 

[szukalski]

Yeah, that makes sense. So what/how does the TC1 measure leakage? @szukalski ?

What is Iceo. How is described in depth in the link I provided.

 

[Cybercow]

Yeah, that makes sense. So what/how does the TC1 measure leakage? @szukalski ?

I do not know. When my TC-1 arrives this coming week, I'll dig into it and see how it performs compared my DCA75 and my GM328. The GM328 does NOT show leakage, but the DCA75 does. I'll post back.

 

[joelorigo]

I do not know. When my TC-1 arrives this coming week, I'll dig into it and see how it performs compared my DCA75 and my GM328. The GM328 does NOT show leakage, but the DCA75 does. I'll post back.

Well, what do you think?

 

[joelorigo]

Getting back to looking at this since I have been assembling the PCB. Just to be clear, it doesn't have to be an MP38A in this project, a Ge NPN with similar hfe and leakage should work, right?