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

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.

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

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.

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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, NOS NIB Sencore Continental II 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.

Here is a truly historical item — a LEEDS & NORTHRUP CO. Wheatstone bridge. It has Western Electric K.S.3011 designation.  I originally called the item a mirror galvanometer but it is more accurately termed a Wheatstone bridge.^[1]

The craftsmanship and build quality of this device is truly remarkable.  I cannot fathom how much money it would cost to build this same device today using identical components.  The unit consists of a large magnet, floating mirror, bulb, magnifier, panel scale, brass and silver switches with no measurable resistance, and a large number of precision resistors that were hand-wound and perfectly balanced using the finest balance bridge equipment available at that time. Truly the highest laboratory-grade accuracy that was possible — BEST of best.  Resistance accuracy should approach 0.1%.  For this reason, the unit makes a fabulous (true) precision resistance box for checking calibration.  This gives it a modern “use” instead of sitting on a shelf as a discussion piece.

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HP Officejet R-series

As a fan of vintage tube equipment, it should come as no surprise that I prefer older quality computer equipment.  In this article, I explain how to repair “Scanner System Failure” problems in a vintage HP Officejet R-series multifunction scanner-printer.  Model R40xi is shown in the photos, but all models (R40, R40xi, R60, R60xi, R80, R80xi) repair the same.  In fact, many similar HP multifunction units of this era are repaired in similar manner.

First, let me explain why I feel that these vintage HP units are worth repairing.  Why fix an “old parallel-port printer” when new models are so cheap?  Like most things in life, you really do get what you pay for, and if HP paid me to take their new models (with the assumption that I actually had to use them), I would not be interested.

During the Lew Platt years, HP was making top quality products.  This period of quality was from the early 1990s (Laserjet 4-series and beyond) through the Officejet R-series of 1999.   The hardware during this time was built-like-a-tank, and when compared to today, the ink supplies were reasonable (although they certainly seemed expensive at the time).

Let us look at the economics: Officejet R-series uses a #45 cartridge, holds 42-mL ink, retail cost $30.  This HP45 can be purchased for $5 on eBay. Modern HP cartridges hold as little as 5-mL ink and cost $15 — which is 4.2 times more expensive using retail price comparisons.  If you consider surplus #45 cartridge prices as your comparison, the cost to operate a new HP printer can be  42-times more expensive.  And if you are an environmentalist (or anyone who hates frivolous waste), ask yourself whether it is environmentally responsible for HP to manufacture an ink cartridge that only holds 5-mL or 10-mL? Certainly not, and those puny cartridges are only sold to pretend that the new cartridge price is cheap, when in fact it holds 4-to-8 times less ink.   That is an insult to your intelligence and an affront to the environment.

In another example, a modern HP toner cartridge (for a current model) costs $99 retail with approx 2,000 page yield.  Surplus HP toner cartridges for the old 4-series, 5-series, or 6-series can be purchased for approx $20-$30 on eBay, and have 3,000+ page yields.  Vintage Laserjets have been known to be run strong with 500,000 page cycles.  Any chance you will get even 50,000 page cycles with a modern unit? Good luck with that.  And how many Nag messages from the new drivers to “buy more ink” would you click on during that time?  Well — no nag messages with old HP units!

So when you analyze the situation, the answer is obvious why I fix these old HP units.  (1) High build quality of the hardware, (2) low cost of use (ie – cheap ink), (3) OS drivers that respect you as a person, without bloat or nag screens to harass extra ink purchases, (4) ink that does not “expire” because some Corporate Executive wanted to sell more ink to pay for his/her 7-or-8 figure CEO salary + stock options + benefits + perks + Golden Parachute retirement package.

Let us compare the “new” models.  By ‘new’ models, I consider any model released in the Carly Fiorina era and beyond to be ‘new’.  The only benefits that I can see in the new models are USB connection (which is easier for most users but otherwise adds no functionality) and much better color printing.  Since I have no problem with parallel ports and only print black-and-white, those issues are not important to me. Otherwise, it is my opinion that the quality of the new hardware is much lower than the older models, the cost of consumables (ink/toner) is outrageously expensive, the computer drivers are bloated and filled with nag messages that harass you to “buy more ink”, and some models “expire” the ink cartridges based upon a random date.   If you feel respected as a customer with that experience, more power to you.   Personally, I am not interested in participating.

With that explanation, let us move on to the repair.  As always, repairs are only suited for experienced electronic technicians with suitable training.  Also, it is useful to take a video of your repair project so that you can reexamine your work if you get stuck during reassembly.

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A common (and totally random) problem with GM vehicles that have the Passlock / Passlock II anti-theft system is that the vehicle will suddenly refuse to start.  The problem is a poorly designed GM Passlock anti-theft system that erroneously enters anti-theft mode and disables the fuel injectors. GM should be forced to recall this Passlock system — it is simply unacceptable to strand motorists because of an incompetent anti-theft system.

The vehicle in this example is a 2002 Chevy Malibu, but this Passlock system was employed in many GM models.  Thousands of motorists have been stranded and left helpless by these GM vehicles that refuse to start for no apparent reason.  The owner of this Malibu was stranded three times over the past two years, incurred 2 towing bills to a Chevy dealership, two “repair” bills from the incompetent Chevy dealer who obviously failed to solve the problem.  Now she was stranded for a 3rd time.  This time she called me.

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This article explains how I installed/updated Windows Vista® drivers for a D-Link® DWL-G122 Rev B USB network adapter. This article is informational-only and not intended as advice. Improper driver installation can cause your PC to crash, lockup, or fail to boot. Proceed at your own risk, and no ‘tech support’ is provided.

The article is only relevant to Revision B (known as B1) of this adapter (the DWL-G122 was available in 4 different revisions). The Rev B1 version was very popular because it had native Linux driver support, and also worked well with Windows XP. I have personally used the adapter under Linux (Suse® and Ubuntu®), XP, and Vista®. Unfortunately, D-Link has done a poor job of releasing new drivers for this adapter. To date, D-Link had only released one beta driver package for Vista 32 (Vista X86), and nothing for Vista 64. The Vista 32 beta driver is no longer available for download, either. Luckily, Rev B1 contains a Ralink® RT2500USB chipset, and Ralink has continuously updated the Windows drivers for this adapter. The latest driver package (as of this writing) is dated 11-11-2008, and contains drivers for Vista 32-bit, Vista 64-bit, XP 32/64.

Installing these drivers for D-Link DWL-G122 Rev B1 cannot be done conventionally, but the process is reasonably easy for any seasoned PC technician. To maintain a “clean” PC, I will extract the drivers in a Virtual Machine. This step is optional.

These are the steps that I performed to update the driver for Vista 32 (complete with screenshots):

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Discolored getter flashing (brown or black marks) does not mean that a tube was used. This fiction is believed by both uninformed buyers and seasoned tube jockeys. This myth seems credible because some new tubes have perfect shiny mirror getter flashing; therefore the assumption is that brown or black stains in the getter flashing must indicate a used tube. The myth says that the more brown/black discoloration, the “more used” the tube is. Wrong.

Excerpt from Electronics Magazine

The purpose of the tube getter and flashing is to remove gas inside the tube envelope during manufacture. This discoloration myth can be quickly debunked by reading the article in Electronics magazine, October 1950, entitled “Getter Materials For Electron Tubes”. The article explains that if the getter is vaporized very slowly during the manufacturing process, “the first barium atoms evaporated will absorb the gas present so that the remaining getter is deposited in a very high vacuum, exhibiting a shiny mirror.” If the getter was flashed very rapidly during manufacturing, then “the getter mirror will be discolored due to the dispersion of the barium.” The article then explains that the discoloration “does not mean that the getter is contaminated, but merely that the deposit is finely divided and therefore absorbs light.”

Several photos of NOS tubes below demonstrate this myth.  Likewise, I provide photos to demonstrate how the flashing looks when a tube is actually used. Let us proceed…

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Occasionally I plan to write about a few of my favorite items from my personal collection. Here is an NOS NIB NEW* genuine Tucker Corporation auto radio, built for the 1948 Tucker Torpedo car.

Tucker Corporation was the company founded by Preston Tucker to sell his revolutionary 1948 Tucker Sedan, known by most people as the Tucker Torpedo. This is the genuine Tucker factory radio for the Torpedo, NOS NIB NEW.

This radio was found from a very elderly man who had “put a down payment on the car” and someone told him that he “had to buy the radio right now” (even though the Tucker Torpedo had not been built yet!)

Obviously, the Tucker Torpedo was never built, so the old fellow was left with a new car radio that he could not use. So, it sat on a garage shelf for more than 50 years until I purchased it from him.

Here are some interesting facts about the radio….

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It is quite common to find tubes that have a “brand name” printed on them, but were actually manufactured by a different company. Yes, you can easily find “RCA” tubes made in a Sylvania factory, “GE” or “RCA” tubes manufactured in a Tung-Sol plant, etc.

So how do you know which company actually manufactured your tube? Most tubes have a Factory Code on them, an EIA code (Electronic Industries Association), and that code tells you the answer.

Here are the most common factory code numbers found on tubes:

• 111 = Amperex
• 158, 171 = DuMont
• 188 = GE / KEN-RAD (188-4, 188-5, 188-20, etc.) [info]
• 210 = CBS Hytron [info]
• 247 = National Union [info]
• 274 = RCA [info]
• 280 = Raytheon [info]
• 312 = Sylvania [info]
• 322 = Tung-Sol (USA)
• 323 = United Electronics
• 336 = Western Electric
• 337 = Westinghouse
• 722 = Sylvania-manufactured for OEM equipment makers (Allen Organ…)
• 1022 = Fisher branded Mullard/Telefunken/Amperex
• 1109 = Raytheon (Japan)
• U.S.A.3 (found on the glass envelope) = Tung-Sol
• Xf1,Xf2,Xf3,Xf4 = Mullard
• 7C,8I = Toshiba (Tokyo Shibaura Electric)

Examples:

(1) you have an “Admiral” tube with “188-5″ codes. GE made your tube.

(2) You have an RCA 5881 with “U.S.A.3″ code on the glass. Tung-Sol made your tube.

There are many other “clues” also. For example, many Sylvania 12AX7A tubes have the tube designation printed in white-gray letters, vertically stacking all three designations of “12AX7A ECC83 7025″  Only the Sylvania factory used this exact marking.

It just looks like an RCA...

Sylvania markings.

distinctive markings of the Sylvania 12AX7A

Example: Stacked printed designation “12AX7A ECC83 7025″.

Here is an example of unique Sylvania-manufactured designation for 12AX7A tubes, where the tube is printed as “12AX7A ECC83 7025″ vertically stacked. In this example, this tube is branded as an RCA, but was in fact manufactured by Sylvania. Compare to the Sylvania-labeled tube.



When I have more time, I will continue to add more clues here to help you determine who manufactured a tube when it does not have a factory code number.