Component Testing Is Breaking My Brain

[Ginsly]

I've come a long way in mere weeks because of this incredible community, but I'm at another crossroads... I REALLY need some help here.

Keeping in mind that much of component testing is getting "close enough" when it comes to building, I'm still having some real trouble finding a good baseline for testing components. I have a couple mid-grade multimeters (one with transistor slots), and a couple cheapo TC1s. Not top-tier, but since I can't really buy a Fluke and DCA75 at the moment, they'll have to do.

@Brett & @owlexifry suggested making an RG Keen tester on breadboard, which I did. Used a TC1 to come up with resistor combos that pretty much hit 2.2m and 2.472k on the nose. The 2nd TC1 came up with the same number, within 1 ohm. Even ran the "self test" calibration on them a few times, although I'm not really sure that does much...

Then I tested the resistor combos with both multimeters (fresh batteries) - one said 2.443k and one said 2.455k. Tried two different sets of leads on each, one with probes, one with clips. I didn't expect them to be that different than the TC1s.

So... who do I trust? Since both pairs of testers came up with similar results (TC1s were an exact match, MMs were very close to each other), it must come down to whatever wild card the MM test leads introduce or the basic mechanics (voltage/current) of how each kind of tester operates. In a situation like an RG Keen tester which seems to need exact resistor values, I'm not sure which tester to trust.

I went with the TC1s numbers and set up the Keen tester, including a battery reading very close to 9v. I'll need to test some Ge soon, but first I tried some Si to see how they fared. Here are the results of a basic, TO-92 2N2222A:

Keen Tester w/ MM#1 reading DC v on the 2.472k resistor: 202 hfe (2.02v)
Keen Tester w/ MM#2 reading DC v on the 2.472k resistor: 204 hfe (204v)
Transistor Testing Slots in MM#1: 191 hfe
TC1/TC2 - 285 hfe

I was little surprised at how long the Keen testers took to land on the final reading - they started high and and took several minutes to tick down about .15 -.2 volts, and keep in mind this is Si.

The Keen testers and MM#1's hfe slot tester are all very close. The TC1s read way higher, and this is something I observed across several different transistors. I'm not saying one is right and one is wrong, but again - who do I trust? Which would be the reading that best reflects the hfe in say, a fuzz pedal circuit? This will be much, much more important when I test Ge.

Obviously the hfe slots won't work well for Ge, and it sounds like the TC1 isn't great with those either. I'll have to trust one of the MMs in a Keen tester, but again, I need to get those resistor values bang-on and keep the voltage close to 9v. Even with a trimpot I'd need to set it to 2.472k with the help of a MM, and their resistance reading were quite different than both TC1s. Getting a DCA55/75 would seem to solve the problem, but some say that their 5mA testing current isn't optimal... plus, it doesn't test resistors or capacitors - I'd still need to trust a TC1 or MM for that! Ack!

I totally get "close enough for rock n roll", "use your ears" and all that, but... can someone please help simplify/clarify where I should go from here? I'm in the weeds with all these discrepancies!

PS:

- a battery at exactly 9v doesn't stay there long, so powering a Keen tester seems tricky. Is it ok to be a little higher/lower than 9v? I have a rechargeable 9v lithium battery that I'd love to use, but is closer to 9.3v fully charged.

- I accidentally popped a few PNPs into the Keen tester when it was set up for NPN and vice versa. I realized my mistake, reset and restested them - they seem ok, is there any concern that they might still be damaged? I added the 220r resistor to +9v after doing that a few times... Missed that advice from @Brett the first time around! Yeesh...

 

[Brett]

So... who do I trust?

I'm not sure which multimeter you're using, but trust your multimeter. In my own experience, the inexpensive multi-component transistor testing units are usually great for ballpark values, but aren't super accurate.

See this link if you need more evidence that these testers aren't highly accurate:

TC1 multi-function tester tested

Daniu's TC1 differs from the numerous low-cost microcontroller controlled component testers by its Li-ion battery, the possibility of testing zener diodes up to 30 V and the recognition of infrared codes. You can even measure battery voltages. We tested the specifications and found a few very...

chinese-electronics-products-tested.blogspot.com

When testing across multiple devices, you're likely also testing at different currents, another factor that can explain the discrepancy you're seeing in gain. Personally, I'd trust the RG Keen method (for BJTs) and the Run Off Groove method (for JFETs) over the results from the inexpensive TC1s. These methods have been used for a while, are cheap, and pretty well accepted for our purposes.

The TC1 and other similar devices also don't factor leakage into their gain values. Leakage shouldn't be a major issue on the Si you're testing, but for germaniums, this can (and likely will) make a significant difference.

 

[Ginsly]

See this link if you need more evidence that these testers aren't highly accurate:

The thing is, the TC1's resistance measurements were found to be satisfactory by them and they didn't verify the data found in transistor tests other than pinout and type. The problems measuring battery voltage aren't great, but I wouldn't really use it for that. That review wasn't as bad as I thought it would be! They also didn't start with resistors that were proven to be on-the-nose, and you'd need that.

When testing across multiple devices, you're likely also testing at different currents, another factor that can explain the discrepancy you're seeing in gain.

Yep, but how do I determine which one is going to give me data that is most relevant to pedal circuitry? When a TC1 says a basic SI transistor is 300 hfe and an RGK test (with resistors that MAY be the exact specification, running from a battery close to 9v) says that it's 200 hfe, that's a pretty big discrepancy. This seems to be true across the board for transistors I tested, and if that's true for all TC1s (and similar) then many builders using them may be choosing transistors based on a testing setup that is likely not giving them relevant info.

Say I needed an Si that was very close to 200 hfe based on a build doc. Results from both the TC1 and RGK/MM may both be valid within their testing parameters, but it's still tough to know which data set is "right" for me - RGK says 200, the TC1 says close to 300. I'm sure adding in Ge leakage complicates this further, so I'm really trying to get this right before I head there.

I'm curious to see what a DCA55/75 would come up with compared to a TC1 and the RGK tester I set up. It may be an incredible tool, but if its testing parameters are also suboptimal for testing components that will go in pedals, that seems like a problem. So many people swear by them, I have to assume the numbers they spit out are determined in conditions acceptable/favorable to builders. @jwin615 didn't you do something like that recently? What was your takeaway?

Personally, I'd trust the RG Keen method

This is where I'm leaning, but I still want to make sure it's set up optimally resistor-wise and battery-wise. It sounds like the 2.2m and 2.472k need to be really close to that, and there is even discrepancy between the multimeters I have - not sure which to trust. I wish I had a testing module or something! There is a "self calibration" that you can do on one of the MMs (a Kaiweets), but with no reference values I don't see how it's doing anything at all.

I went with the TC1 to measure resistors in part because I just plug components right in to the zif sockets, not the wired test leads - I figure that eliminates the possibility of the test lead cable affecting the outcome..? Not sure how important that is, and based on what you're saying I might just go back to the multimeters to find the necessary 2.2m and 2.472k resistors... Ugh

 

[PedalBuilder]

Say I needed an Si that was very close to 200 hfe based on a build doc. Results from both the TC1 and RGK/MM may both be valid within their testing parameters, but it's still tough to know which data set is "right" for me - RGK says 200, the TC1 says close to 300. I'm sure adding in Ge leakage complicates this further, so I'm really trying to get this right before I head there.

I don't know a single pedal that requires a transistor with an exact specification, e.g. exactly 80 hFE and leakage of 20µA when the collector current is 5ma. A transistor's hFE is not a static value, and it will vary with the collector current (and not always in a predictable fashion):*

When you test the transistor on different equipment with different collector currents, the different results are not the result of one piece of equipment being wrong or untrustworthy. Rather, you're getting two data points from somewhere along the curve of hFE plotted against collector current. Neither one is "right" or "wrong," they are both measurements of current gain at a specific collector current/temperature/etc.

So when a build doc says that a circuit works well with a transistor with an hFE of 200, that statement really means something like "I built the circuit and it sounded good. When I built it, I used a transistor with an hFE that my test equipment measured as 200." That test equipment might be a TC1 or a DCA55 or something more exotic, so take that number as a ballpark figure for your purposes. You usually don't know what the person used as test equipment and depending on what they used, the resulting figures may be pretty far off from your equipment. And that's ok!
Instead of reading the build doc to mean that the transistor needs to have exactly that hFE or the pedal will sound terrible, what you should take away is that a transistor with an hFE of 200 on whatever equipment you are using is a good starting point. Depending on how similar the parameters of your equipment are to the parameters of their equipment, and how similar your preferences are to theirs, you may or may not find that a transistor that you measured as hFE = 200 sounds fantastic. As cliche as it sounds, you really do need test and experiment and use your ears.

The reason that a TC1 or DCA55 or RG Keen tester is good for testing transistors for pedals is (1) other people who build pedals use them and their measurements offer a good starting point; and (2) that they all use roughly similar parameters, e.g. a collector current in the neighborhood of 3-10ma. Each of them has their pros and cons, but none of them is "the right one." Rather than getting hung up on whether you used the "right" transistor, try the transistor, see how it sounds, and check your voltages to see whether they're in the ballpark.

For example take a Tone Bender Mk. II. A build doc might say that you need to use hFEs of 60/70/100, but that doesn't mean that you need to use values that are anywhere close to that range. I've built great sounding Tone Bender Mk. II's with hFE's as divergent as 45/60/55 and 239/300/188, and with a few minor adjustments here and there, they all sound like Tone Bender Mk. II's. David Main, who knows a thing or two about building pedals (and a thing or two about marketing them) has posted measurements from original Tone Benders that are just afield from the values that you see listed in build docs as though they were the official values.

All this to say that you shouldn't force yourself down a rabbit hole in search of The One and Only True HFE. There are some parts of this hobby that require perfect precision, but transistor hFE testing is not one of them. Feel free to try a range of transistors and pick the ones that you think sound good, regardless of what someone else wrote down on a build doc.

*Also note that not every example of a particular model number transistor will have the same curve and may well have a curve that looks completely different.

 

[Brett]

Feel free to try a range of transistors and pick the ones that you think sound good, regardless of what someone else wrote down on a build doc.

@PedalBuilder explained it much more eloquently, but @Ginsly, are you starting to notice a common word being used? Ballpark. That's all you're looking for. If there are critical parameters, they will be listed as such.

Let your ears give you the precision you so desperately seek. Find a transistor in the ballpark of what the circuit calls for. Install it. If it sounds good, then roll with it. If it does not, try something else.

 

[Ginsly]

@PedalBuilder That is very, very helpful and furthers my understanding of gain measurements in pedals. I really appreciate you and @Brett taking the time to help. It's not rocket science, but... it's still science, kinda! ha... Still, it all seems more ballpark than I figured. Still, if someone was say, selling Ge components and advertising a specific gain and leakage, they'd need to have a dependable figure that most people would be able to match with whatever tester they have - right? Otherwise, how do they know what they got?

Having such a big discrepancy between the TC1 and the Keen/multimeter setup had me wondering which one is the "right ballpark" for my purposes. If they were closer I probably wouldn't have questioned it at all. To even set up a "close enough" Keen tester to begin with, I'd need to really pin down a couple resistor values which also proved difficult... I guess I still have a couple questions:

- I may be wrong, but it sounds like hfe readings at a certain collector current level are what people are looking for. What collector current would that normally be, and how do I test that while a transistor is in a Keen setup? Or are there too many variables to determine that for most pedal circuits?

- how important is it to have exactly 9v going into a Keen tester with resistors that are exactly 2.2m and 2.472k? Since 9v batteries drain with use, and I have three different resistor readings from three devices, I'm wondering how much these variables might affect results. I take your point about "ballpark" to heart, but I really do want to make the most dependable Keen tester possible.

- it sounds like I may want to save for a tried and true "good" multimeter before I go for a Peak. I have a Crenova 890z and a Kaiweets ht118a - both ~$40 Amazon buys. No idea how accurate they are because I don't have a Rolls Royce mm to test em against. What is an affordable Fluke that has what most people in my position would need? Resistance, continuity, voltage, current... I assume nothing comes close to a Fluke when it comes to accuracy, but I'm all ears for any suggestions. I really appreciate it.

 

[owlexifry]

- I may be wrong, but it sounds like hfe readings at a certain collector current level are what people are looking for. What collector current would that normally be, and how do I test that while a transistor is in a Keen setup? Or are there too many variables to determine that for most pedal circuits?

- how important is it to have exactly 9v going into a Keen tester with resistors that are exactly 2.2m and 2.472k? Since 9v batteries drain with use, and I have three different resistor readings from three devices, I'm wondering how much these variables might affect results. I take your point about "ballpark" to heart, but I really do want to make the most dependable Keen tester possible.

- it sounds like I may want to save for a tried and true "good" multimeter before I go for a Peak. I have a Crenova 890z and a Kaiweets ht118a - both ~$40 Amazon buys. No idea how accurate they are because I don't have a Rolls Royce mm to test em against. What is an affordable Fluke that has what most people in my position would need? Resistance, continuity, voltage, current... I assume nothing comes close to a Fluke when it comes to accuracy, but I'm all ears for any suggestions. I really appreciate it.

you don't need a super awesome multimeter to measure bjt + jfet with the methods described above (rg keen; runoffgroove). close enough will be good enough.

getting close to 2.472K isn't that difficult with a 2K and 470R resistor in series. i didn't get exactly the right number, but it doesn't matter and i'm not gonna lose sleep over it.

i will reiterate @Brett 's point:

Let your ears give you the precision you so desperately seek. Find a transistor in the ballpark of what the circuit calls for. Install it. If it sounds good, then roll with it. If it does not, try something else.

obsess less and just try things - put a transistor(s) in the circuit and listen to it.

 

[PedalBuilder]

If someone was say, selling Ge components and advertising a specific gain and leakage, they'd need to have a dependable figure that most people would be able to match with whatever tester they have - right? Otherwise, how do they know what they got?

Are you buying single transistors that have been measured individually or are you buying transistors whose data sheet specifies an hFE range? If it's the former, you can ask the seller. If it's the latter, then check the data sheet. If you're going off of the data sheet, then I'd take whatever you find with a big grain of salt, as the test parameters might be very different than the ones used by a DCA55/Keen/TC1. If you're looking for a transistor for a specific project, ask people here and you'll get helpful suggestions. Quite a few of us also have large stashes of germanium and would be happy to sell you a pre-measured set if you'd rather go that route.

- I may be wrong, but it sounds like hfe readings at a certain collector current level are what people are looking for. What collector current would that normally be, and how do I test that while a transistor is in a Keen setup? Or are there too many variables to determine that for most pedal circuits?

It's whatever the collector current used by the device is, probably somewhere in the neighborhood of 2-10ma. I think you're still overthinking this. People aren't recommending an in-circuit hFE; they're recommending whatever hFE their transistor tester spat out.

- how important is it to have exactly 9v going into a Keen tester with resistors that are exactly 2.2m and 2.472k? Since 9v batteries drain with use, and I have three different resistor readings from three devices, I'm wondering how much these variables might affect results. I take your point about "ballpark" to heart, but I really do want to make the most dependable Keen tester possible.

The further away you get from the RG Keen values, the further away you will be from other people's measurements using an RG Keen testing rig. Unless you're using significantly different values, you should be fine. I'd encourage you to play around with the formulas for gain and leakage to see how significant each factor is. Hold all values constant except for one of them and see what happens. If you input 2.25 MΩ into the formula, how far off is the hFE when you input 2.2MΩ? How far off if you input 8v instead of 9?

- it sounds like I may want to save for a tried and true "good" multimeter before I go for a Peak. I have a Crenova 890z and a Kaiweets ht118a - both ~$40 Amazon buys. No idea how accurate they are because I don't have a Rolls Royce mm to test em against. What is an affordable Fluke that has what most people in my position would need? Resistance, continuity, voltage, current... I assume nothing comes close to a Fluke when it comes to accuracy, but I'm all ears for any suggestions. I really appreciate it.

You don't need a Fluke for testing resistors and voltage in a pedal. I doubt that there would be even a 0.5% difference in the measurements. Unless you're using high voltages or have some other esoteric requirement, the multimeters that you have are perfectly fine.

obsess less and just try things - put a transistor(s) in the circuit and listen to it.

This.

 

[Ginsly]

@PedalBuilder Incredible. There it is. You just saved me a lot of money and unnecessary troubleshooting for a problem that doesn't really exist, essentially. I've found that the builders here are very diligent and detail oriented, and I guess I didn't realize where that line needed to be drawn. This is an important lesson to learn while I'm figuring all of this stuff out. I truly appreciate the clarification, and that you didn't judge me for being a pedantic dum-dum! Ha... As always, PPCB forum comes through. Unreal.

 

[Feral Feline]

"one said 2.443k and one said 2.455k"
and
202 hfe (2.02v) vs 204 hfe (204v)...

Close enough. Don't overthink things too much (like I do).


The only time I'm really getting nitty-gritty with multiple measurements of the same component is when I want it to match another component for
OCTAVE effects
PHASERs
anything similar to the above two where getting a close match gets you a better sounding effect.

 

[Ginsly]

The one thing that concerned me during the testing process was accidentally putting an NPN transistor in a Keen tester set up for PNP and PNP in an NPN setup. They tested normally once I realized my lunkheaded mistake, so is it safe to say they're ok? The Keen tester is battery powered, and the "wrong" transistors weren't in there long. Just curious if they're bound to fail and should be set aside or something...

 

[RetiredUnit1]

I've come a long way in mere weeks because of this incredible community, but I'm at another crossroads... I REALLY need some help here.

Keeping in mind that much of component testing is getting "close enough" when it comes to building, I'm still having some real trouble finding a good baseline for testing components. I have a couple mid-grade multimeters (one with transistor slots), and a couple cheapo TC1s. Not top-tier, but since I can't really buy a Fluke and DCA75 at the moment, they'll have to do.

@Brett & @owlexifry suggested making an RG Keen tester on breadboard, which I did. Used a TC1 to come up with resistor combos that pretty much hit 2.2m and 2.472k on the nose. The 2nd TC1 came up with the same number, within 1 ohm. Even ran the "self test" calibration on them a few times, although I'm not really sure that does much...

Then I tested the resistor combos with both multimeters (fresh batteries) - one said 2.443k and one said 2.455k. Tried two different sets of leads on each, one with probes, one with clips. I didn't expect them to be that different than the TC1s.

So... who do I trust? Since both pairs of testers came up with similar results (TC1s were an exact match, MMs were very close to each other), it must come down to whatever wild card the MM test leads introduce or the basic mechanics (voltage/current) of how each kind of tester operates. In a situation like an RG Keen tester which seems to need exact resistor values, I'm not sure which tester to trust.

I went with the TC1s numbers and set up the Keen tester, including a battery reading very close to 9v. I'll need to test some Ge soon, but first I tried some Si to see how they fared. Here are the results of a basic, TO-92 2N2222A:

Keen Tester w/ MM#1 reading DC v on the 2.472k resistor: 202 hfe (2.02v)
Keen Tester w/ MM#2 reading DC v on the 2.472k resistor: 204 hfe (204v)
Transistor Testing Slots in MM#1: 191 hfe
TC1/TC2 - 285 hfe

I was little surprised at how long the Keen testers took to land on the final reading - they started high and and took several minutes to tick down about .15 -.2 volts, and keep in mind this is Si.

The Keen testers and MM#1's hfe slot tester are all very close. The TC1s read way higher, and this is something I observed across several different transistors. I'm not saying one is right and one is wrong, but again - who do I trust? Which would be the reading that best reflects the hfe in say, a fuzz pedal circuit? This will be much, much more important when I test Ge.

Obviously the hfe slots won't work well for Ge, and it sounds like the TC1 isn't great with those either. I'll have to trust one of the MMs in a Keen tester, but again, I need to get those resistor values bang-on and keep the voltage close to 9v. Even with a trimpot I'd need to set it to 2.472k with the help of a MM, and their resistance reading were quite different than both TC1s. Getting a DCA55/75 would seem to solve the problem, but some say that their 5mA testing current isn't optimal... plus, it doesn't test resistors or capacitors - I'd still need to trust a TC1 or MM for that! Ack!

I totally get "close enough for rock n roll", "use your ears" and all that, but... can someone please help simplify/clarify where I should go from here? I'm in the weeds with all these discrepancies!

PS:

- a battery at exactly 9v doesn't stay there long, so powering a Keen tester seems tricky. Is it ok to be a little higher/lower than 9v? I have a rechargeable 9v lithium battery that I'd love to use, but is closer to 9.3v fully charged.

- I accidentally popped a few PNPs into the Keen tester when it was set up for NPN and vice versa. I realized my mistake, reset and restested them - they seem ok, is there any concern that they might still be damaged? I added the 220r resistor to +9v after doing that a few times... Missed that advice from @Brett the first time around! Yeesh...

Wow, about 15 years ago I got 'burnt' by the first gen "9v" lithium, which were more like 8v. Had to toss them. Good to see they got that fixed.

You can find REALLY good deals on used flukes on eBay. Dirty, beat to hell, but work perfect. And if they don't you just go to Contact seller/return item/not as described - even if they don't take returns, if it's not as described they have to refund.

fluke multimeter for sale | eBay

Get the best deals for fluke multimeter at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

 

[Ginsly]

Wow, about 15 years ago I got 'burnt' by the first gen "9v" lithium, which were more like 8v. Had to toss them. Good to see they got that fixed.

It's very funny you mention that... they kind of haven't fixed it! Ha... Most of them still hover around 8.5, but some of them still work quite well for use in pedals. This one has decent mAh and I've had good luck with them: https://www.amazon.com/9V-Battery-Rechargeable-Batteries-Devices9V/dp/B09N1RWWD7

There ARE, however, some that have a higher voltage rating (9v plus), but are incredibly noisy in pedals or other musical equipment. I use them in tuners and they work fine, but I'd never trust them anywhere else.

 

[owlexifry]

The one thing that concerned me during the testing process was accidentally putting an NPN transistor in a Keen tester set up for PNP and PNP in an NPN setup. They tested normally once I realized my lunkheaded mistake, so is it safe to say they're ok? The Keen tester is battery powered, and the "wrong" transistors weren't in there long. Just curious if they're bound to fail and should be set aside or something...

datasheets will tell you.

this is for a 2N3904


exceeding max thresholds may not always damage a device, but it's not ideal.

if it works, it works.

if it's going to bother you knowing these were 'socketed the wrong way' and could potentially be compromised, save them and set them aside as backups for that rainy day when you've got only x3 2N3904 in your stash and you need x4 for that big muff build

 

[RetiredUnit1]

It's very funny you mention that... they kind of haven't fixed it! Ha... Most of them still hover around 8.5, but some of them still work quite well for use in pedals. This one has decent mAh and I've had good luck with them: https://www.amazon.com/9V-Battery-Rechargeable-Batteries-Devices9V/dp/B09N1RWWD7

There ARE, however, some that have a higher voltage rating (9v plus), but are incredibly noisy in pedals or other musical equipment. I use them in tuners and they work fine, but I'd never trust them anywhere else.

Ah, okay. That makes sense. I switched to NIMH to get a real 9v. They last a long time especially in a low drain device like an active pickup in an acoustic. And no possibility of self combustion....
edited:
I just read the link you posted "it is strictly prohibited to short circuit" and shows a pic of two mated together. {{{BOOM}}} {{{FLAME THROWERS}}}

 

[Ginsly]

I switched to NIMH to get a real 9v.

Not sure I was aware those existed… gotta link? I’d love to check them out!

Edit: I checked em out and have indeed seen some of those before - I think I opted for lithium because they were way higher mAh than NiMH. Didn't realize they got up to 9v (and over, I assume?).

 

[Feral Feline]

Ginsly, there are some circuits that intentionally reverse the transistors —
- "peyote mode" in a modded Jordan Boss Tone, ie a switch that flips between normal and reversed;
- several of Devi Ever's circuits.


What's really damaging is over-voltage, like feeding something 18v when it's only rated for 9v.

 

[Ginsly]

Ginsly, there are some circuits that intentionally reverse the transistors —
- "peyote mode" in a modded Jordan Boss Tone, ie a switch that flips between normal and reversed;
- several of Devi Ever's circuits.


What's really damaging is over-voltage, like feeding something 18v when it's only rated for 9v.

That’s great to hear, and oddly enough I DID indeed think of your comment about the peyote mode flip when I accidentally did it during testing! That’s wild.

 

[Ginsly]

One thing I've noticed when testing transistors for ballpark figures is that Darlingtons like MPSA13s seem tough to measure! The TC1 comes up with astronomical figures that seem high even for this type of mega high-gain transistor (37k??), and the Keen method comes up with something like 5-800 hfe, which is obviously far lower. The gain range of those seems so vast that it'd be nice to get a better ballpark than 500hfe-37k hfe! Ha...

 

[Ginsly]

Can I ask how one might reduce the voltage coming from a 9v battery leading to a Keen tester? I'm using a rechargeable lithium 9v and it's usually at around 9.3v... Trying for as close to 9v as possible. I've seen it mentioned to insert a 10k pot (where exactly?), but I've also seen warnings that it could burn out the wiper... Would love some tips!

@PedalBuilder I swear I've taken your advice to chill out about this stuff to heart! Ha... Still, this Keen tester is the best chance I have to get ballpark figures, and feeding it more than 9v may skew the results too much.