Heathkit TT-1 plate current meter, rebuilt restored calibrated, pristien

Shipping in the Continental USA and cards fees included in this price.

Your tubes and equipment are an investment. Your tube tester should be one too. How can you know the condition a tube you purchased, if you can't rely on your tester readings, it's accuracy?

Offered is a fully rebuilt electrically, mechanically and cosmetically restored, and calibrated gm/mutual conductance tube tester, with custom digital plate current meter. Plate current is something only professional tubes sellers are able to measure, but now you can match your own tubes just as they do. Verify what you bought. The digital current meter will read up to 199.9ma and has its own power supply so there is no parasitic influence on the tube.

Great care has been taken to recondition this tester to a highly reliable state. The parts we use for rebuilding the electronics are top notch premium grade, the best. We measure all new resistors and capacitors, tubes for true value before we install them.

All switches are carefully cleaned (as a note NEVER use de-oxit or similar on any tube tester, you will ruin it's accuracy permanently and shorts will appear on all tubes tested). We then triple calibrate to manufacturers documentation and test against assorted references for verification and tweaking.

Electrically, the tester will last for decades with no further need for part replacement or calibration. Copies of the operation manual and supplement tube data thru 1978 are included, and our "Cliffs notes" on testing..

The plastic meter face is resurfaced to remove all scratches and signs of age, and roll chart windows is now glass not yellowed plastic. Even the meter itself is removed and completely checked out. The case has almost no signs of wear and tear and case hardware is in bright condition, even the screws have been polished. This is now in remarkable condition for a late 1960' tester analyzer. In fact, you can proudly put this right in your living room, it looks that good.

You can test a hugh variety of audio tubes including direct heated triodes such as 2A3, 300B, 10, 45, and many others. Test Pentodes like 6L6, el types, KT types, 7591/7868, etc. Test dual element tubes such as the families of Ecc/12axx types, 6dj8, etc WITHOUT RESETTING THE SWITCHES!. Please see the photos of the Mullard and Mazda 12ax7 and 6550 tubes tested for gm and plate current...note the different gm for the Mazda vs. the Mullard for the same plate current .

No need to fear damage to frame grid tubes with the TT1 (many testers will short out frame grids tubes such as 6dj8 types during the testing where there was no short before).

It will test nuvistors, novar, 10 pin miniature and compactrons. The TT-1 can test at a relative high plate voltage of 225vdc with precision bias and a proper applied signal voltage to derive an active gm reading. Russian tubes are not on the following list of tubes that is included with the tester, but setting for many Russian tubes can be created and we already have many on file. Standard American and European tubes on the tube set up can be seen here: http://www.pestingers.net/pdfs/heathkit-test/t1a-supplemental-78.pdf

This will not test high power triode transmitter type tubes.

Shorts and leakage tests are among the best, and a grid current test for power tubes will show low as 2 microamps leakage. Life Test to estimate remaining useful service, independent plate buss, cathode buss, and grid buss each selectable, and full disconnect from the tube. The TT1 has one of the largest sag resistant transformers of any tester.

The TT1 is one of the best testers ever made. With the digital current meter, It is right up there with the best Triplett, AVO, RCA, high-end Hickok 539c series, and Western Electric testers. The results are very close to a Triplett 3444 on most tubes without math conversion.

We offer continued support after a sale. We have been in business since 1973. We rebuild, restore, tweak and 'hotrod' tube gear and one specialty is tube testers. We break our necks to do it right, even if the time we put in exceeds what we charge. We have been on eBay ( as budngreg ) for over 20 years, 1500 feedbacks and over 200 repeat customers, and full 5 star rated on all categories.

Plate current measurement….why?

Why is the plate current so important now when it wasn’t when this tester was made? Simple, the audio gear that was available then was far from being ‘audiophile’ and ‘audio’
was not that important then as an industry. It was not until the late 1960’s that the problem of plate currents being unbalance in a push pulls amplifier became important for most manufacturers to consider. The ‘thought’ was if you, the amp owner, can’t hear it, then we manufacturers can ignore it (because it costs big money to fix). Then came transistors as the main form of audio reproduction.

Transconductance or gm measures the grid’s ability to control
the A.C. signal function of a tube. Any change in the grid A.C. voltage creates a change in the plate current output. An emission tester can’t measurethat because it tests the tube as a DIODE. A tube could measure 100% good on an emission tester and fail on a Transconductance tester. If the grid can’t control the plate, the signal can’t be controlled. The Transconductance roll chart number is an average or bogie number for a new tube on a like kind tester (it is NOT a magic number, but is an average number from thousands of tubes tested). The important point for audio is that gm is the A.C. dynamic signal condition of the tube.
This is only half the picture. Plate current is the second characteristic of the tube
“audiophiles” must consider for modern amplifiers to function properly and to
hear the amps real potential. The plate current is the static D.C. condition of the tube ( no signal applied). If the D.C. currents are unbalanced for a given set of tubes, the
transformer’s core will saturate and simultaneously low frequency response
suffers, highs are muddy. The current imbalance turns you output transformer into a magnet because it cannot discharge those D.C. currents to zero, even as the signal crosses over the zero A.C. line. Further, it takes as little as 1 milliamps difference between two medium power tubes to double distortion figures (this may still be under 1% but you get the idea).

For pre-amp tubes a 10% plate current difference is acceptable in most stereo applications, beyond that, there will be a loudness difference (phono should be as close as possible especially for moving coil types as well as driver/phase splitters). Generally the gm is more important for small signal tubes and should be as close as possible.

Match your used power tube plate currents as close as possible, and consider the gm secondary. It is a good idea to recheck new power tubes after 50 hours or so to see if they still hold the same D.C. value relative to each other, meaning the same
milliamp difference. If the balance is still good, they have “burned-in”.
Recheck them after 300 hours or so is a good idea. Always replace the tubes in the same socket they were removed from. New power tubes should be tested when you buy them to establish a reference point for your used tubes to be compared to. Never use a power tube with less than 1 mega ohm leakage ( which 90% of Hickok tester will never catch).

So now you have the ability to match your tubes statically and dynamically for the best performance. Your numbers should be considered specific to your tester or one which
has the same characteristics for plate, grid, signal, as per the plate curve characteristics. .

C. G. Industries

305.849.2665

[email protected]