It was a big search for these switches. Fortunatly, these switches can hold 3A at 28 volt dc. And indeed switch 125 mA at 125V ac. They have an Insulation resistance of 1000MOhm at 500V, an a dielectric Strength of 600V for 1 min.
So they are sutable for this purpose, it's just important not to switch during a test..
Hi A+,
You did a great service job to all your tubetesters ......! They just look fine. I think you have the same passion for such equipment, as I have for amplifiers and AR speakers
Best regards
Kim
Hi molekuul,
Thank you for your info. I shall have a closer look at the "uTracer" site....by use of an old powersupply from a pc, I don't have to worry about that part!... And you have solved the switch problem for us with the Omron A7PH-203-1 contact-switches.
We might need advices to the assembling of the uTracer ....hobe it's ok to ask questions here?
Best regards
Kim
You really need the 19V laptop PSU, not a 12V ATX PSU - you can pick them up on eBay for under USD 10 delivered (in the UK at least). The heater supply is derived by using PWM on the supply voltage - with a 12V PSU, you won't be able to drive any heater higher than just below 12V. Laptop PSUs are much smaller than ATX supplies, and very cheap.Hi molekuul,
Thank you for your info. I shall have a closer look at the "uTracer" site....by use of an old powersupply from a pc, I don't have to worry about that part!... And you have solved the switch problem for us with the Omron A7PH-203-1 contact-switches.
We might need advices to the assembling of the uTracer ....hobe it's ok to ask questions here?
I quite like the idea of the thumbwheel switches, but also quite like the idea of plain old 4mm plugs & sockets - haven't decided yet...
So far I've spent just the 195 euros cost of the kit (worth every penny) as the sockets etc. are from my workshop. I suspect by the time its boxed and with a decent top panel I'll be looking at close to 300 euros...
My uTester is proving very useful for tube matching - its not tricky to build, but you do have to be careful and follow the instructions carefully...
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Yep - they look good. You are right, so long as you don't switch the heaters when on.
Very expensive, though!
Not to pour cold water on all the tube-tester-collecting out there...I own a half dozen myself...but if I had a dollar for every tube that someone sold as measuring excellent or better that didn't have either a short or was so weak it may as well not be used at all, I'd have enough money to buy several more testers...the problem IMO is that many many testers are in need of a thorough going over and re-calibration themselves as to be virtually worthless as far as gauging the real condition of a particular tube.
Nothing...and I mean nothing, substitutes sticking a tube in a circuit designed for that tube and seeing how it performs under actual operating and load conditions...especially when you have a known good tube to compare it against....
Don't get me wrong...I love equipment too, it's just that I've seen a lot of supposedly fail tubes measured in someone's unmaintained and uncalibrated tester do just fine when placed in circuit....
And nothing beats slapping a tube in a phono stage or guitar amp to determine if its noisy or microphonic either....
Nothing...and I mean nothing, substitutes sticking a tube in a circuit designed for that tube and seeing how it performs under actual operating and load conditions...especially when you have a known good tube to compare it against....
Don't get me wrong...I love equipment too, it's just that I've seen a lot of supposedly fail tubes measured in someone's unmaintained and uncalibrated tester do just fine when placed in circuit....
And nothing beats slapping a tube in a phono stage or guitar amp to determine if its noisy or microphonic either....
In addition to the cal issue, I seriously doubt that more than a hand full of people selling tubes are using a variac to adjust the voltage to the tube tester. Running on high line (current line voltage is above what they were designed for), the heater voltage is too high, causing false readings.
The uTracer compensates for all that - has an ADC that reads the supply voltage so it gets its maths right on PWM etc... the screen & anode voltages are generated from on-board SMPS supplies, so are unaffected too.
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Oh... It seems that you've discovered hot water, indeed ! And when you have an Ampeg SVT, an Ashdown BTA-400 to service, with 6 to 8 6550 or KT88, your substitution trick can turn to a fireworks for a brand new set of these costy tubes. So you need a tube tester, and a good one, well-calibrated, even if it is a simple emission tester as my NRI-70 below, that I bought for cheap :
An externally hosted image should be here but it was not working when we last tested it.
But yes, an uncalibrated Hickok 539B or C is nothing more than a nice toy... And most of them need a serious calibration job ! It would be more easy to calibrate and check if the Hickoks complied to the tube datasheet - like my Metrix 310CTR - instead of relying on an always questionable proprietary tube chart...
A+!
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