Indispensable DIY Tool

UPIf you build pedals, you REALLY want this $41 tool.

UPDATE: A Facebook friend of mine found the same tool on eBay for $25.49.

Jon Cusack — the pedal builder, not the actor — recently turned me on to one of the best DIY tools I’ve ever owned: The Multi-Function Tester TC1.

Jon’s Michigan shop manufactures  the pedals I design. He and I were trying to pinpoint the optimal gain for the germanium transistors in two of the new pedals I’m about to release.

I’d been using a multimeter to test gain, which is measured in terms of hFE. An old germanium transistor might have hFE of 50 or less, while a hot silicon Darlington transistor such as an MPSA13 might check in at hFE = 5,000. As you can imagine, it’s a crucial measurement for any stompbox that employs transistors.

But like many before me, I encountered two big problems. First, most multimeters don’t have an hFE function. (To make such measurements, the device needs a trio of sockets so you can plug in the transistor’s three legs.) It’s not a matter of cost. In fact, most high-end multimeters, such as the Fluke models  whose prices start at well over $100, omit the function. (To be fair, we’re talking about antique transistor technology, which is pretty much extinct in most modern electronics.) You’re likelier to find an hFE tool on cheaper, more obscure models. So I’d been using bunch of cheap-ass Chinese multimeters just to measure hFE.

But there’s another problem: Those multimeter hFE testers are notorious for their inaccuracy. They’re especially prone to overstating the actual gain. They’re not quite useless, but they’re close.

Jon recommended the TC1 ($41.50), which apparently is only available via eBay in the US. And it’s more useful than I could have imagined.

First off, it gives accurate hFE readings within a hundredth of an hFE unit. It works with silicon and germanium BJTs, FETS, JFETS, and MOSFETS. And dig this: It doesn’t matter which way you orient the pins — it knows which leg is which, so no more  jumping online to verify the pinout of a particular part.

Check out the photo: The LCD image tells me that the pin in socket 3 is the collector. Had I inserted it the transistor the other way around, the collector would be marked with a 1. Better still, it also works with resistors, capacitors, and diodes. You don’t even have to switch metering functions, as on a  multimeter. Just pop in the part, secure it with the clamp, and TC1 does the rest.

Trust me — if you work with transistors, resistors, caps, and diodes, you want this tool. Now I seldom use my crappy multimeter unless I need its continuity (“beeper”) tool.

Thanks for the excellent tip, Jon! 🙂

3 comments to Indispensable DIY Tool

  • Great, thanks for pointing that out Joe. I shall have to get one, there are a number of listings on for it at around £30. I do have a couple of earlier models which have a monochrome display and no case. I also use a more expensive PEAK DCA55 semiconductor component analyzer.

    The reason that the multimeter testers often seem inaccurate is because they do not distinguish leakage current. The majority of Germanium transistors leak like sieves and this leakage current is incorporated into the gain measurement. These large leakage currents cause all sorts biasing problems in effects circuits. The PEAK tester, and presumably the TC1, use more sophisticated measurement techniques coupled with a micro-controller to separate leakage current from gain current and display gain and leakage values separately – at least the PEAK does. Apparently the TC1 can ‘display IR waveforms’ as well? Some sort of IR diode and TV remote test I guess. Included USB rechargeable battery too!

  • Bear

    I need more time to parse the functions. It looks like the cap tester doesn’t get as far into pF range as I would like. My multimeter is already decent at hFE, so the cap tester is a bigger thing to me. Gonna look at the other functions.

    Another cool, cheap piece of test equipment on my radar: Supposed to be a good, cheap digital oscilloscope. Runs on 9v or a very well regulated 9v supply (be careful about polarity), and can handle moderate voltage tube amps with a 10x probe, which a few people have reported receiving included in the package.

  • I received my TC1 today. I like it for the ZIF socket which makes it easy to connect any transistor with reasonable lead length, the colour display, the ability to test capacitors and the rechargeable battery. And it puts all the info it has measured on screen at the same time, with the Peak you need repeated button presses to cycle through the info.
    But it only identifies leakage current as Iceo. My Peak DCA55 makes it really obvious by labeling it in English ‘Leakage Current’ and it will identify Germanium devices as Germanium.
    When testing the same AC128 transistor, with the TC1 I get an Hfe of 95 and an Iceo of 0.19mA, with the Peak I get an Hfe of 102 and a Leakage Current of 0.17mA. These leakage currents seem normal for most Germanium transistors I have measured, but they are enormous compared to most Silicon transistors. These often have leakage that is so low it cannot be measured by the tester. Each tester is applying its tests under slightly different conditions (base current, collector voltage and so on) so I suppose the values for the AC128 are fairly close. You do have to be very careful when testing and selecting Germanium transistors because they are so temperature sensitive. If I hold that AC128 between my fingers for 2 seconds the Hfe reads 105 and the Iceo is 0.37mA measured with the TC1.
    I still haven’t worked out what the IR diode on the TC1 front panel does. Perhaps it emits a data stream of the measurements for remote collection and logging. Some test instruments do have an IR data logging output.

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