‘Blog’ Category

PR: new hiring of Chief Technical Consultant

April 1, 2011.  TubeSound, a worldwide vendor of audiophile tubes & test equipment and service center, is pleased to announce the appointment of Snickers T. Dogg to the position of Chief Technical Consultant.

“Snickers will be a valuable addition to our team by growing our service center in a valued-added result-driven manner.  He is a strong strategic fit with our core competencies.”

Snickers brings a goal-oriented approach to servicing.  “The endgame is simple — get it done.”  As pioneer of the Spray-and-Pray service technique, he has been proactive in driving down the cost of repairs.  “I once stepped on a can of WD-40, and the rest was history.”  This user-friendly servicing technique has empowered millions of technicians worldwide.

Never satisfied with the status quo, Snickers has leveraged the synergies of spray & service to expand the effectiveness of his Spray-and-Pray methodology.  “If the spray don’t work, you can whack it with the can.”  His outside-of-the-can thinking will allow unparalleled speed-to-repair.  This is a win-win scenario.

“The one thing that impressed us the most was Snicker’s 24/7 customer-service mindset.  His proactive networking creates a strong foundation of trust.”

Snickers also brings to the table a rare ability to find bad transformers without need for any test equipment or powering-on the equipment.  “I must have a nose for it” quips Snickers.

Competition to land Snickers was fierce.  In turning down a position as a jukebox technical consultant with a Pittsburgh-based music distributing company, Snickers explained “I can’t be associated with nothin’ lame.”

Snickers also plays a mean game of “Bullshit Bingo” and feels that he will have many opportunities to play here at TubeSound.  In fact, he is barking “Bingo” right now.

Tube Matching with a Tube Tester

Copyrighted by Bob Putnak, all rights reserved.

“Sometimes output tubes must be selected which will provide a satisfactory balance adjustment.  A tube tester usually will indicate whether a pair of tubes have reasonably similar characteristics.” – Robert Middleton, 101 Ways to Use Your Audio Test Equipment, Howard Sams Inc.[1]

“Tube matching” is a controversial and complex topic, and there is no consensus regarding “what is best.”  In fact, some people even feel the whole topic is a waste of time, arguing that matched tubes “kill the mojo” of what makes a tube amp sound special.

People ask me about tube matching using a tube tester.  In most cases, they just want to do a reasonable job at matching tubes for themselves, and they have reasonable expectations.  Others are not satisfied unless some guru tells them they need to spend big bucks buying “matching” gizmos that will magically take care of it.

I will try to provide an simple overview of the tube matching topic vis-a-vis a tube tester.  Since the topic has no absolute answer, no conclusion can be offered…only opinions.  It is important to remember that this discussion has nothing to do with the importance of a tube tester as a diagnostic tool.  As a diagnostic tool, tube testers excel.  The question is whether they also do a good job at tube matching.


when E283CC tubes are actually a 12AX7

This is one of many examples where tube testing requires experience to properly evaluate any tube.  In this situation, using a tube tester would yield a completely wrong answer.

12AX7A tubes - incorrectly factory marked as E283CC

12AX7A tubes - incorrectly factory marked as E283CC

These tubes were factory marked as E283CC, but are actually 12AX7A tubes.  Hence, if you tested them in your tube tester using E283CC settings, you would have concluded that the tubes were shorted and defective, and you would have discarded valuable NOS 12AX7A audio tubes.

The fact that these were not E283CC was readily apparent to anyone with experience.  E283CC is a “special quality version 12AX7 for audiophile” with three distinguishing characteristics: (1) different pinout than 12AX7, (2) only a 6.3v heater, (3) a shield between triode sections that terminates at pin 7.

A shield between triode sections would be easily visible, and these tubes do not have a shield.  Hence, they are not E283CC.

Since E283CC is a “special quality version of 12AX7”, that was a logical place to start.  Experience shows that they look like Amperex 12AX7A tubes, and testing them as 12AX7A verified that premise.  In fact, each tube is well balanced between its triode sections, and they are quality audiophile 12AX7A examples.  (Tube #1: Triode #1 = 36, Triode #2 = 36.   Tube #2: Triode #1 = 31, Triode #2 = 30.  Test scores from my professionally calibrated B&K 707 mutual conductance tube tester, and also without shorts or leakage.  For 12AX7, scores of 22+ good, with scores in 33 range considered typical new).

Lessons: (1) experience matters, (2) tube tester results MUST be interpreted based upon experience, and not blindly accepted as gospel, (3) you should have the experience to recognize when a tube does not look correct as marked, because blindly inserting a wrong tube into your equipment may cause serious damage and/or fireworks.

HP Laserjet 4L – 4P refurb and repair

by Bob Putnak, ©2010.

Of all the subjects that I have discussed, I receive the most inquiries about my HP Officejet “scanner system failure” repair article.  That article also fondly mentions the old-school Laserjet’s, and I had several inquiries about repairing them.  These old dinosaurs are still useful to any small business that prints traditional business text documents or for printing schoolwork.   So here is an article about how I have repaired and refurbished these Laserjet 4L and 4P printers in the past (not so much anymore!)  Do not attempt if you are not qualified to perform such repairs or do not want to risk further damage or inability to reassemble your printer.  The basic concept is similar with other models not shown here, although disassembly will be somewhat different.

HP Laserjet 4L

HP Laserjet 4L

These printers were built like a tank and page-feed problems are the most common complaint.  A general overhaul will take care of most of these issues.  In summary: the printer is torn down, thoroughly cleaned with compressed air (including the 4 optical sensors on the mainboard), rubber rollers are treated with rubber rejuvenator, the sticky-stuff is cleaned off of the relay coil, the relay coil arm is wrapped once with thin black electrical tape.  If you have a dead printer, you will also inspect the power supply fuses, although a blown fuse is usually the symptom of a real power supply defect.


my tube tester collection

Today was my annual warehouse spring cleaning day, so it was a good opportunity to take a “family photo” of my tube tester collection.    My collection changes all the time, sometimes daily.    I did include all of the models that I use everyday for tube sales and bench servicing, and also models that I “rotate in” regularly to keep familiar with them.  Many of these are a permanent part of my collection, others will be repaired/calibrated and sold to customers who want a quality tester that works great.


TubeSound tester collection as of April 2010

Columns are numbered left to right and models listed from top to bottom:

  • Column 1: B&K 707. Jackson 648 early tweed case version, Precision 620, Simpson 555, EMC 206, Sencore Continental MU140, Jackson 648R, Simpson 330, B&K 700
  • Column 2: Hickok 532, Precise 111 Mutual Conductance, Knight 600B, Hickok 800, Sencore TC28 Hybrider, B&K 550, B&K 747, Hickok 800, Simpson 1000, Hickok 533
  • Column 3: US military I-177-B, US military I-177, Hickok 6000A, Precision 10-40, Knight 600C, Triplett 3423, Jackson 648S, B&K 707, Jackson 648A, B&K 707
  • Column 4: US military I-177-B, US military I-177-B, US military TV-7D/U, B&K 700, B&K 700, B&K 500, B&K 700, Precision 640, Heathkit TC1, US military I-177-B, Jackson 637
  • Column 5: Mercury 1000, Eico 625, Heathkit IT-21, Sylvania 620, B&K 550, B&K 700, B&K 700, Jackson 648-S, mint Western Electric KS-15560-L2, Heathkit IT-17, Supreme 550
  • Column 6: Eico 666, Precision 612, Eico 667, Precision 10-12, Eico 666, Precision 10-12, Jackson 598, Philco 9100
  • Column 7: B&K 747B, Sencore TC28 Hybrider, Sylvania 220, Accurate Instruments 151, Jackson 648, Jackson 648-S, Hickok 533A
  • Column 8: Hickok 6000A, US military TV-10D/U, US military TV-7A/U, Hickok 6000, B&K 707, NRI Professional 70, Jackson 561, Sencore MU150
  • Column 9: B&K 707, Hickok 533, Hickok 533, Hickok 539A, Hickok 752

One nice thing about having a large personal collection is that it makes easier troubleshooting of strange wiring problems in a customer’s tester that they have sent for repair. Being able to quickly examine another unit is often much faster than tracing the circuit. It is also nice to have another unit to compare, especially if I suspect that a component may have been replaced many years ago with a non-factory part.

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