Tube matching jig recommendations?

[Bill Ferris]

FWIW, while I purchased a Amplitrex AT-1000 around 10 yrs. back, and love it, prior in the early 2000s, I bought the originally released Maximatcher common popular output tube test set matcher, and later ordered several less commonly used output tube type test adaptors like 7591, 6BQ5 (EL84) tubes, at that time, to make it more useful for my friends output tube testing needs, as its original 4 tube type capability suited my own tube amp tube type testing requirements.

With the purchase of the Amplitrex, I rarely pull out the Maximatcher anymore, but its still very useful for initial grading multi-hr. HV & burn in stress test of any of common output tube types brought to me by friends, be it singles, pairs, or quads, claimed to be matched, or randomly individually purchased, and then for more complete examination of the output tubes, or any small signal types, I fire up the AT-1000, and check the tubes parameters more completely, and my friends can read off the display & log any information about each tested tube, or reject any questionable tested tube(s), if they wish, the 1000`s headphone jack is quite helpful for microphonic & initial internal noise determination during the fingernail tap test.

 

[Jfaustus]

FWIW, while I purchased a Amplitrex AT-1000 around 10 yrs. back, and love it, prior in the early 2000s, I bought the originally released Maximatcher common popular output tube test set matcher, and later ordered several less commonly used output tube type test adaptors like 7591, 6BQ5 (EL84) tubes, at that time, to make it more useful for my friends output tube testing needs, as its original 4 tube type capability suited my own tube amp tube type testing requirements.

With the purchase of the Amplitrex, I rarely pull out the Maximatcher anymore, but its still very useful for initial grading multi-hr. HV & burn in stress test of any of common output tube types brought to me by friends, be it singles, pairs, or quads, claimed to be matched, or randomly individually purchased, and then for more complete examination of the output tubes, or any small signal types, I fire up the AT-1000, and check the tubes parameters more completely, and my friends can read off the display & log any information about each tested tube, or reject any questionable tested tube(s), if they wish, the 1000`s headphone jack is quite helpful for microphonic & initial internal noise determination during the fingernail tap test.

Super interesting Bill. Does the Maximatcher handle compactrons/sweep tubes?

 

[Bill Ferris]

Super interesting Bill. Does the Maximatcher handle compactrons/sweep tubes?

Not that I`m aware of, unless the manufacturer offers adaptors.

The tester/matcher was originally conceived for very common/popular guitar tube amplifier`s tubes like 6L6,EL34, 6550, 6V6 family of output tubes,
My first adaptor for the Maximatcher was for 7591 tubes that started to be manufactured/sold sometime in the ~late nineties, I believe, and then I bought the 6BQ5 adaptor at the same time.

Some sweep tubes require a plate cap wire attached to the top of the tube, which the Maximatcher does not provide, but the much more versatile and expensive Amplitrex offers, as well as having much more tube types testing capability without the need for any optionally purchased socket adaptors, though the Amplitrex is designed for testing specifically audio type tubes, as explained on their website.

 

[gadget73]

you could DIY adapters, need an octal plug and the Duodecar sockets, cross-wire it so that it comes out to a 6V6 type pinout. Bring out a plate lead on a cap if needed. One of those things thats technically not hard, just very tedious.

the other part is figuring out sane values to run it at for matching, no idea what sort of options you get there.

 

[Bill Ferris]

you could DIY adapters, need an octal plug and the Duodecar sockets, cross-wire it so that it comes out to a 6V6 type pinout. Bring out a plate lead on a cap if needed. One of those things thats technically not hard, just very tedious.

the other part is figuring out sane values to run it at for matching, no idea what sort of options you get there.

Yeah, I know I could have created my own tube type adaptors via my RCA tube book, but with the use of only one hand would have made the construction tasks difficult and time consuming, so I elected to go the manufacture`s reasonably priced adaptor availability turn key route w/ the included a printed cheat sheet for setting & readings that were different to the Maximatcher`s front panel silkscreen settings for the tester`s common tube tube type default settings/readings, that they offered, also was similar convenience driven mindset with Amplitrex`s socket savers that I decided to be included & installed for the commonly used testing sockets when I ordered the AT-1000.

Like I said earlier in this thread, once I received the Ampltrex AT-1000, the Maximatcher`s prior frequent use became pretty curtailed for regular general purpose testing, but still perfect for sustained HV energized burn in of multiple (up to 4) output tubes of the same type, so the Maximatcher still has occasional desired use/value.

 

[gadget73]

Understood, just presenting an option in case there is no adapter for the specific tubes needed for this amplifier.

 

[Jfaustus]

So I just talked to a tech who used to work for NYAL, and later for George Kaye, and had serviced Futtermans for quite some time. He walked me through exactly how to go through tubes to find ones that work.

So there’s an upper bank and lower bank. The three tubes in a bank are in parallel and then the two banks are in series.

He recommended starting with just two tubes, one in each bank. The ‘balance’ pot adjusts the grid of the lower bank. Get the two tubes in balance, don’t touch the pot, add two more. If they skew the balance one or both are off. Get the second two in order, then go for the final. Same procedure.

I’m out of town for the weekend but will do that when I’m back with the tubes I have. Fingers crossed I can get at least one channel.

EDITED because I typed too fast and inverted series and parallel.

 

[Jfaustus]

So I just talked to a tech who used to work for NYAL, and later for George Kaye, and had serviced Futtermans for quite some time. He walked me through exactly how to go through tubes to find ones that work.

So there’s an upper bank and lower bank. The three tubes in a bank are in parallel and then the two banks are in series.

He recommended starting with just two tubes, one in each bank. The ‘balance’ pot adjusts the grid of the lower bank. Get the two tubes in balance, don’t touch the pot, add two more. If they skew the balance one or both are off. Get the second two in order, then go for the final. Same procedure.

I’m out of town for the weekend but will do that when I’m back with the tubes I have. Fingers crossed I can get at least one channel.

EDITED because I typed too fast and inverted series and parallel.

I’m going to post this last one on the main restoration thread and then probably leave this one alone. THANKS ALL!!!!

 

[Lavane]

Low value cathode resistors would be fine, but i'd probably keep to 1 ohm here since the whole goal of all this is to have suitably low output impedance to drive a speaker. Sticking a resistor in series with the tube flies right in the face of that.


my comment about the Amplitrex was intended to mean that it tests what it tests, not just any tube you might want. Confirm its capable of doing what you need before buying one. I do not know enough about them to say if its possible to get them to test other types. Socket adapter part is fairly easy, but I haven't got a clue about their setup in terms of voltage or current values.

I put 1 ohm resistors on the cathodes in a guitar amp that had a quad of
6P3S-E's. To bias that amp a watt meter had to be connected to the mains voltage and adjust the bias for 120W-150W draw. Having the resistors allowed me to know for sure where I was setting the bias. I didn't want to adjust the bias too hot. I just left the resistors connected to the cathodes for future bias adjustment.

 

[gadget73]

Its possible to do it by mains current draw but certainly more difficult. Unless you have very deeply analyzed the amp its hard to relate a mains draw to individual tube current levels.