uTracer (Micro Curve Tracer)

[MakerDP]

Here's a place to start looking...

https://www.mouser.com/Search/Refine?N=19978893

[dorrisant]

Martin and others thanks for all the information you guys are providing. I bought a kit last year and waiting for cold winter and quiet times to get started on mine.

The only parts I need are those ferrite beads where did you get yours? I guess I need to know what size wire I will be using first.

Mark

If you are looking for the through-hole type that look like diodes, PM me and I'll send you however many you need.

[martin manning]

The only parts I need are those ferrite beads where did you get yours?

Mouser 710-74270015 10mm long 4mm OD. I used 22 AWG wire with thin insulation for the sockets. The usual 22AWG 600V PVC insulated wire won't fit through these ferrites.

[M Fowler]

Thanks guys. Tony I'll get ahold of you. Thanks

[markusw]

Wow, 18 months since I've updated this thread. My uTracer has been down for some while due to a computer upgrade, which required a new memory partition (MacBook running Bootcamp), a new copy of Windows 10, and a new FTDI USB-TTL cable (the old one was obsoleted by the new Windows 10).

I'm planning to build a uTracer and like your apporach to use a FTDI USB-TTL cable.
Which cable did you end up with that worked with Win 10?
BTW, thanks a lot for sharing all your observations! It is always a pleasure to read your postings!

Best regards,
Markus

[dorrisant]

Martin, how many of the ferrite cores should you need for one tracer?

Mark, what I have on hand is not what is referred to in the context. I will order a bunch and send you some.

[martin manning]

I'm planning to build a uTracer and like your apporach to use a FTDI USB-TTL cable. Which cable did you end up with that worked with Win 10?

TTL-234R-5V-AJ. I like the TRS plug.
Edit: TTL-234X-5V-AJ

[martin manning]

Martin, how many of the ferrite cores should you need for one tracer?

Depends upon how many sockets you have. I put one at each pin on each of three sockets, 7, 8, and 9-pin, so 24 total.

[markusw]

I'm planning to build a uTracer and like your apporach to use a FTDI USB-TTL cable. Which cable did you end up with that worked with Win 10?

TTL-234R-5V-AJ. I like the TRS plug.

Thanks a lot! I like the TRS plug too!
Best regards,
Markus

[markusw]

I'm planning to build a uTracer and like your apporach to use a FTDI USB-TTL cable. Which cable did you end up with that worked with Win 10?

TTL-234R-5V-AJ. I like the TRS plug.

I can't find a TTL-234R-5V-AJ cable, only TTL-232R-5V-AJ.
Do you have a link?
Thanks again!
Best regards,
Markus

[martin manning]

My apologies, TTL-234X-5V-AJ is the one I am using now, and it is available from Digi-Key: https://www.digikey.com/product-detail/ ... ND/6823720

The 232R is the first one I used (originally with Windows 8). It worked with my Windows 10 upgrade, but as far as I can tell it is not supported for new Windows 10 installations.

[markusw]

My apologies, TTL-234X-5V-AJ is the one I am using now, and it is available from Digi-Key: https://www.digikey.com/product-detail/ ... ND/6823720

The 232R is the first one I used (with Windows . It worked with my Windows 10 upgrade, but as far as I can tell it is not supported for new Windows 10 installations.

Thanks a lot, Martin!

Best regards,
Markus

[martin manning]

Ronald’s “Grid Loupe” is up and working. This add-on circuit solves the problem of getting to true 0V Vg, and enables tracing curves with up to +5V on the grid. In addition, the screen current measuring circuit can be used to measure grid current for triodes.

Basically, the Loupe creates a regulated 12VDC supply, isolated via a DC-DC converter (the black box on the board), which is then stacked on top of the 20V main power supply (to which the cathode is referenced). The loupe then has 32V to work with, -20 to +12 with respect to the cathode. To set the grid bias, the existing grid circuit control voltage is tapped and fed into a pair of op amps that convert it’s 0-5V into -10V to +5V, with some current sinking capability. Two more op amps and a transistor create a current equal to the grid current, as determined by a 10 ohm current sensing resistor, and that can in turn be fed into the screen current measuring circuit.

The plot shows 12AX7 anode curves for Vg = -4 to +1.5V, and the me.asured grid current, which does not increase significantly until the grid voltage goes above 0V. There is an offset of about 300 uA in the indicated grid current that does not look correct, though. I'll have to look into that.

It looks like it will be possible to mount this little board inside the enclosure, and add a 3-way switch on the panel to select the normal grid bias circuit, the low-Vg loupe, or the same with Ig measured by the screen circuit.

[martin manning]

A new 3-way switch has now been added to the panel to select normal, low/positive Vg, and same with Ig measured using the screen circuit. The availability of positive grid voltage opens the way for tracing more transistor types, too. The low-Vg board is mounted with two layers of foam tape for now; a technique I’ve been using for pedal circuit boards. It's getting very crowded in the box!

[M Fowler]

You the man Martin, very nice thanks for keeping us up to date.

Mark