• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

uTracer Tube Tester Build

Nice build, Brice, and creative use of the 'socket modules.' The ferrite beads are a must. I was seeing what I think was oscillation when testing high gain triodes (esp 12AX7) in the bread board set up, so I put a small bead in each lead that stopped it. I plan to wire the sockets with plenty of beads as Ronald recommends (including a loop for each set of pins), as well as using the pre-wired beads (identical to those you see on the bread board in the filament leads) for each set of uTracer outputs. Parts should be in this week.
 
Thank you. Agreed I have seen the same on my bread board also.
I used those which did the trick.
20180310_163356.jpg
 
Dave451 said:
The calibration procedure is fairly extensive and is in the last section of the construction manual. There is a test with 1% supplied 10K resistors to calibrate the gain of the anode and screen current amplifiers. The check is for linearity of Ia vs. Va and Vs and calibration of the anode and screen current amplifier gain by using known (previously calibrated) Va and Vs levels.
Click to expand...
In the past tube testers were very much indicators, with only a few being able to provide some semblance of calibrated result, and given the typical application is mainly about relative differences from a batch then result accuracy has never been an issue.

I'm just guessing that nowadays some will start using presented result absolute values as accurate levels to the number of digits displayed, without possibly realising that there is a tolerance subtly behind such a value. Valve testers have certainly come a long way in the last decade or so.
 
Aren't the use of ferrite beads a no-no for the heater - I just recall seeing that come up in discussion on heater supply design.
 
Yes I think you are right.
But I looked at other design and I saw beads on all pins, so what's the heck.
So far I haven't seen side effects to the pulsing algorithm used for the heater supply.
 
I was considering buying the kit and building one at some point. I envisioned a "grand system", built inside a TC162 Mighty Mite tube checker from Sencor, all controlled from a computer. You select a tube type in the sofrware, and the sofware automatically sets the heater voltage, etc via USB... Of course, I then realized I will never build such device, so I gave up on it. But using an old/broken tube tester is a valid idea: you just need to rewire it with uTracer...
Cheers, Paul.
 
Was looking at the documentation again, and Ronald says the beads on the heaters are for RFI suppression. I can see this, as the pulsed power supply for the filaments runs continuously during the test and I bet it's a heck of a radio noise generator. The pulse rate for the unit is 20 mHz, based on the frequency of the crystal installed and it has to be full of harmonics as well. There are already ferrite bead suppressors for each of the other outputs (mainly to suppress oscillation), wired directly to the circuit board, plus he recommends one between the power supply and the unit, probably to keep noise from the 18-21V switching supply out of the uTracer.
 
Prelius, some folks have indeed put the unit in an old tube tester (the USB or RS232 jack looks a little incongruous on the old checker's panel!). I, too, was seized with ambition at first for computer control, etc which I also abandoned in the interest of practicality (and limits of my meager skills). I bet someone has done it, though.
 
In my experience, long cables that joins several tubesockets might cause disturbances, visible as
"broken" or strange curves. If you experience this, try a single socket connected with short wires
straight to the board. Ferrites and/or resistors may dampen this.

This fenomen made me build small boxes with one socket each, only one such box is connected at a time.
 
Yes like I did.

If you see the compliance warning kicking in for no reason, and the trace shoot up or down to 0, that's because you have oscillation.

I am sure even old tube tester could oscillate with all those spaghetti wiring inside.
 
Well, I can confirm that the compliance function works as advertised. I was starting to test a 7591A today and negligently didn't recheck the socket wiring from when I had tested a 5881 before. This introduced a short and the unit kept kicking out and showing "compliance error." There certainly was. I fixed the wiring and all was well with no apparent damage to tube or uTracer. :confused:

Then, I was running curves on the 7591A and it kicked out again on the last trace, a -2V grid setting. I shouldn't have selected that one, because the current was headed north of 200 mA (as it should have) and it kicked out right at the compliance current set point. Ronald's design keeps saving me from myself, I guess!
Dave
 
I was also thinking of building one into a tube tester that allowed selection of functions by pin, but I worry about possible gremlins introduced with all that wiring. The one I specifically had in mind was an Eico 666 or 667. They have a bank of switches, one per-pin and you use those to set the functions. Rather handy, as long as you know the basing arrangement you can make any tube work as long as you have a socket for it.
 
You must log in or register to reply here.
Back
Top Bottom