eTracer Build and Review

Tracing valves: an obsession

Since my early days of valves and DIY audio, I developed an obsession around testing and tracing valves. This led me to design and build my analogue curve tracer which I used for many years successfully until I build my uTracer, which was a great innovation in curve tracing. I do have many valve testers (some which I made myself) so why building another one?

Well, Chris Chang from Essues Technologies developed a fantastic new digital curve tracer for valves, the eTracer.  There are a few things which will grab anyone’s attention on this curve tracer. Firstly, the power supplies can accommodate a large range of valves which the uTracer can’t. HT can go as high as 750V @ 300mA and the grid supply down to -170V! This is exactly what you need to test your transmitting valves or even a 300B.  Secondly, the tracing speed is surprisingly fast. This is a nice feature, specially when you want to trace pentodes at various screen voltages to develop a Spice model  for example. 

Build process

The tracer can be purchased from Essues and thanks to my feedback now Chris offers pricing broken down between the Hardware and Software. This helps to minimise the costs associated with the hardware shipping and import duties. I purchased the full kit for assembly and I believe you can buy ready units at a premium price of course. The PCB is very well made and is fully assembled, tested and calibrated. The SMPS supply can also be purchased from Essues. There are some additional parts which you need to procure yourself:

1. Low noise FAN – optional. 
2. 4mm stackable plugs
3. HT PTFE cable
4. Additional ferrite beads (I added more)

I had some challenges with my shipping as there were a couple of parts missing. Chris sent me everything at no extra cost. I think it would be good to have a detailed BOM of what is supplied and what you need to buy yourself. Also some extra header pins would be nice in case you have an issue when crimping/soldering them. 

The build process is simple, you only need to take special care to the polarity of the supply as it’s not well marked on the PCB and you can make a real mess if you get it wrong.  There’re not many pictures in the build guide and the description is high level and doesn’t focus on the practical aspects of building the kit. I guess if you are an experienced builder you won’t have an issue. However, if you are not, you may struggle a bit to get through it so beware.

Chris has done a great job with the chassis. Sockets are provided and these are low cost Chinese ones. Some work fine, but others are really poor. This has been my struggling experience with the local socket over the years. I replaced the Octal, Loctal and B9a Noval with NOS ceramic Russian ones.  The loctal doesn’t fit on the existing hole so you need to mount it on top:

The socket wiring is very tedious job. You have up to 10 pins and 10 sockets. Chris provides you with ferrite beads, but if you want to allocate one bead on each socket connection (like I did) you have to add several more. I had some NOS Russian ferrite rings at hand which I used them:

Here is a side view of the tester. You can see the SMPS supply on the right and the marks I added to make sure I remembered well the polarity of the cables into the PCB connector. Also I had to use a different pin in the GND connection of the 6-pin header as I was short of the original ones. I used a circular one which did the trick:

The result is a fantastic finished product. Below is my initial test of a 4P1L once I hacked the top plate to place the NOS socket:

The clever design of the chassis allows you to swap in the future the socket plate and cater for different sockets. This is a nice feature. I’d love to add the transmitting tube sockets (e.g. 813/GM-70) as well as a varied set for Compactron (B12C – 12 pin) and others.

The Software

The software is very easy to use and intuitive. I managed to find some bugs which helped Chris to refine the beta releases. There is a major release planned which will incorporate features missing. There are some drawbacks in my opinion which some of them are being addressed by Chris in the new version:

1. Heater voltage compensation on the 0.1Ω sensing resistor. This is needed for larger heater currents
2. Curve graphics are basic, you can’t zoom/re-size without loosing your current plot. 
3. Display of measurement (e.g. current at specific voltage)  with the mouse dragged over the curves.
4. Variety of tracing types (like the uTracer does) for Screen drive, transfer curves, etc.
5. If you don’t set properly the axis type with pentodes you will get the wrong measurements. The eTracer doesn’t enforce or check your setting for pentode mode.

The speed is very good, here is a video with an example of the 4P1L pentode curve tracing:

A quick test on the 10Y/VT-25:

 

Also Chris has developed a conversion tool to use the output files from eTracer to match the input requirements of Derk Reefman’s ExtractModel tool to create pentode Spice models. I haven’t tried this yet, is on my list

Conclusion

The eTracer is an amazing piece of technology. I’d highly recommend you get one if you work with valves often. As every new product, there is further enhancements which will come over time as it can be developed and refined via Software. The hardware is solid and provides an ample voltage range. 

I still have lots of tests to do with this little unit, but didn’t want to miss the opportunity to write up an initial review. I look forward to the new Software release.

Happy New Year!