Ebay IC Tester Instructions Update: Several years ago I posted the instruction and datasheets that came with the ubiquitous, generic Ebay IC Tester. These can be found here.

This post updates the original datasheet with new information: The datasheet with the tester indicates that 5v is the upper limit for zener diode testing, but recently tomtektest discovered that the unit can test zener diodes up to about 50v reliably. I dug into my parts bins and confirmed his finding using a range of zener diodes up to 48v. This is welcome information as it gives the tester additional usefulness in testing a much larger range of zener diodes.

Thanks for reading.

Shaun Merrigan

This is the sixth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254.

Hickok 209A VTVM Restoration Part 6: Component replacement decisions

In this Part 6 of the series I will document the condition of the passive circuit components in the Hickok 209A VTVM, and justify why I decided to replace (or not replace) them.

Initial resistor and capacitor measurements Hickok 209A

Starting with the resistors, I measured 8 initially, and of those 5 were out of marked specification on the high side. One more was right at the high side specification and two were within specification. These were all 5% and 10% tolerance carbon composition resistors. Based on these data, I made the decision to replace all the 5% and 10% carbon composition resistors. I used 1% metal oxide resistors with … Read More »

I recently updated my iPad Air 2 to iOS 12.1 only to find that it would no longer charge via my computer’s USB 3.0 port. Specifically, I had been using, for many months, a decent quality aftermarket cable to connect/charge the iPad to my PC. There were no issues with charging or connectivity using the same configuration prior to the iOS 12.1 update.

A bit of digging suggested a two-part solution:

Power off and restart the iPadUse a genuine Apple cable

Well, powering off and restarting (using the same aftermarket cable) did not work; the iPad still would not charge. However either changing to a genuine Apple cable or a different aftermarket cable together with a power off and restart, did work. The iPad is now charging normally from the USB 3.0 port on my PC. … Read More »

Ebay IC Tester Instructions

The ubiquitous IC/Component tester found on Ebay usually comes without any instructions or documentation:

The unit I purchased came with a one page, 2-sided photocopy instruction sheet, so I thought I would share it here:

As far as I can tell, this unit will identify and test the following:

Common linear and logic IC’s
Some transistors; seems to be limited to bipolar
Zener Diodes

It does not appear to identify:

LED’s
JFET’s
Three terminal regulators

Thanks for reading,

Shaun M

Tektronix 7854 Waveform Keyboard Rebuild

From the Tek Wiki:

The Tektronix 7854 Waveform Processing Oscilloscope, introduced in 1980, is a 400 MHz combined analog / digital mainframe in the 7000 series that takes two vertical and two horizontal 7000-series plug-ins. In addition to a conventional analog (real time) scope, it contains an equivalent-time sampling 10-bit digitizer and a programmable waveform processor with GPIB interface. The waveform processor can be programmed using a detachable calculator-style keyboard, using postfix operators (“reverse Polish notation” like HP calculators) that operate on entire waveforms, not just individual numbers.

Tek 7854 Mainframe #2 after cleaning

Tek 7854 Mainframe after cleaning

It is to the repair of the detachable keyboard that this post is devoted.  I purchased a keyboard for a reasonable price only to find that some keys were intermittent, and some did not work at all.

Opening up the keyboard showed … Read More »

Ring Video Doorbell Cold Weather Charging

This is a follow-up to an earlier post I made concerning the cold weather performance of the original Ring Video Doorbell. I have had the opportunity to observe the behavior of both the original Ring (i.e., the non “Pro”) and the Pro versions through several cycles of very cold (down to -30C) weather over the past two years, and I can now draw some conclusions.

Background information:

I have both the original Ring and the Ring Pro
The original Ring is hardwired to my mechanical chime doorbell
The Ring Pro is hardwired to my mechanical chime doorbell
The voltage at each doorbell is in the 19-20 VAC range (Klein CL1000 portable DVM)

Conclusions:

The Ring Pro doorbell seems unaffected by external temperature.  It operates properly even through prolonged stretches (10 days or more) of -20C to -30C outdoor temperatures.

The original Ring doorbell … Read More »

Tektronix Scope-Mobile Cart Repair Part 2

This post continues my repair of the Tektronix Scope-Mobile Cart and  trunnion mounts. Here is Part 1, which details the problem and my proposed solution.

The original design used 5/16″ button head bolts which screwed into the bosses and attached the aluminum box frame member to the polymer trunnion mount:

Trunnion to member overview-1

Trunnion to member closeup-2

Trunnion to member closeup with original fastener-3

Trunnion to member closeup with original fastener and cover in position-4

It is obvious that overtightening these bolts put the bosses into tension which caused them to fail.  The gap between the member and the boss “spring loads” the system and puts additional tensile stress on the boss.  While an aluminum casting could easily handle these stresses, the polymer obviously could not.

What I did was to glue the fractured bosses into … Read More »

Fallout 4 Vacuum tubes and Nixie tubes

I have been working my way through Fallout 4 and during my explorations I noticed that the labs and military installations are loaded with vintage vacuum tube equipment.  I thought I recognized the front panel of at least one piece of gear:

Front Panel render from Fallout 4 (Bethesda Softworks):

Fallout 4 Front Panel

 Now compare this image with the front panel of the Racal RA-17:

Racal RA17 Front Panel

The resemblance of the Fallout 4 render to the real Racal RA17 is striking.  This Racal-like front panel appears in nearly every lab and/or military installation that I have explored.

Another rack of equipment very frequently seen in labs and military installations is this one:

Fallout 4 Equipment Rack (Bethesda Softworks

Fallout 4 equipment rack

This image clearly shows:

A nixie tube … Read More »

NEST Thermostat Network Isolation

With the proliferation of IoT (Internet of Things) objects such as smart thermostats, sensors of all kings, video cameras, video doorbells, light bulbs, media hubs and the like it comes as no surprise that security problems are cropping up.  These IoT devices are proving to be a door through which malicious software can gain direct access to your home network behind your router.  An excellent summary of the potential security problems with IoT devices can be found here InfoSec Resources Iot Security Summary.   The takeaway is that these devices are vulnerable, and attackers can use them to penetrate your home network.  Once an attacker gains access to the network behind your router, they have the “keys to the kingdom”.  What is the solution?  As usual with home network security, there are several solutions ranging from relatively … Read More »

Ring Video Doorbell Cold Weather Charging Problem and Solution

I installed a Ring Video Doorbell (RVD) last spring (2015) and overall, I am quite happy with the utility and performance of the unit. Like any new IoT (Internet of Things) device there will be issues, growing pains and problems to be solved.  This post concerns the cold weather performance of the Ring Video Doorbell.

There are several relevant background points:

The Ring Video Doorbell is installed hardwired
The Ring Video Doorbell charges from the wiring above about -19C (-2F)
The Ring Video Doorbell is installed in a single family residence with the camera facing the street
The Ring Video Doorbell wireless signal has to penetrate wire mesh stucco and several walls to get to my router

Initially, I had my RVD motion settings to maximum sensitivity (30 ft radius) and “Standard” Alert frequency.  This meant I was … Read More »