I have an older iPad Mini2 (Model A1489) running iPadOS 12.5.7. For the past year or so the YouTube app has been constantly asking me to update as follows:

YouTube is out of date (popup):

Update to continue

Click to Update

Cannot Update

Cancel

Continue using YouTube app

By cancelling, I have been able to continue running the YouTube app and ignore the update prompt. However, last week, I could not bypass the update prompt:

Update to continue

Click to update

Cannot update, download older version?

Cannot download older version

No option to cancel, so GOTO 1

The update prompt stated that iOS 14 or newer was needed to install the new YouTube app, but since my older Mini2 is fixed on 12.5.7, I could never do the update. The YouTube app was stuck in the update loop, so I could not use it.

This iPad is behind a … Read More »

The Hewlett Packard 70100A is the power meter module in the HP 70000 modular test system. This post will document a problem common to three 70100A units I have recently restored.

As part of the restoration process, I opened the modules to perform a visual inspection. What I found under the outer cover was this:

70100A PS CPU Board Solder Side Overview before repair

HP 70100A PS CPU Board Deteriorated Rubber Pads

HP 70100A PS CPU Board Deteriorated Rubber Pads

HP 70100A PS CPU Board Deteriorated Rubber Pads

HP 70100A PS CPU Board Deteriorated Rubber Pads

The rubber spacer pads between the circuit boards and the outer metal cover had deteriorated to the point of liquifying and running down board via gravity. All the pads in the three units I examined were afflicted to some degree. Several years ago, I documented a similar phenomenon … Read More »

I recently completed the construction of a PC controlled vacuum tester: The Roetest. This is a computer-controlled tube tester which works as follows:

Using the PC software, load the tube data from the extensive database

Verify the tube data and pinout on the screen; the tester configures the pin connections automatically

Run the tests for shorts and filament continuity

Run the required tests

Test the tube at full voltage and current (not a pulse test)

Save the result

Add the tube and test data to inventory

Roetest V10 Front Panel and case

Roetest V10 Main board and plug in boards

Roetest V10 Front Panel

Construction Details:

4600 Solder Joints

600+ Components

20 separate circuit boards

Mechanical work for socket boxes + drilling and tapping heatsink

150+ hours

Using the PC software, load the data for the TUT (Tube under Test). Pinout and base connection information is taken from an extensive database of over 22,000 tube types.

Roetest … Read More »

During a recent printing session, my Z3200 declared an “86:01 paper jam” error. Looking into the printer, I quickly realized that the carriage belt had gone slack. I replaced the OEM carriage belt a number of years ago with a very high-quality belt from LPS Computer, so I was quite sure the belt had not broken. A quick examination of the carriage belt path revealed that the belt tensioner had failed. More specifically, the shaft which holds the pulley had failed.

Belt Tensioner Pulley Failure

What to do? Obviously order a replacement part, but it would take several days to arrive, and my printer would be unavailable in the interim. So, I decided to repair the broken shaft. Past experience suggested that merely gluing the shaft back together would not work. I believe the shaft is ABS … Read More »

The Apple IIe personal computer was manufactured from January 1983 through November 1993. I purchased an Apple IIe several years ago and put it into storage at the time. I recently pulled it out from storage and began the process of refurbishing it. Part of that process was rebuilding the power supply, which I will describe here.

The power supply appeared to be original to the computer with a date code of 47th week, 1985.

Apple II PCB Removed from case. Original capacitors in place. Build Date 47th week, 1985.

Examining the circuit board showed that the electrolytic capacitors were superior quality United Chemi-con.

Original Capacitors in place, output side.

By contrast, the line filter capacitor was a RIFA film capacitor of a type known to fail. Cracks were clearly visible in the outer case of the … Read More »

I have previously written about the substantial number of different modules available for the Tektronix TM500 and TM5000 module plug-in systems. Since the equipment is now anywhere from 20 – 40 years old it needs to be refreshed and/or repaired before going back into service. This often means working on the modules while they are not installed in the power frame:

TM500 Extender Overview: Connects between module and power frame.

TM500 Extender Overview: Connects between module and power frame.

Dan Meeks Extender Closeup. This extender allows monitoring of all supply voltages and currents. It also has LED indicators for each voltage rail.

Extender Plugged into Power Frame

Extender Plugged into module. This allows working on the module outside of the power frame.

From the image above, the extender board projects beyond the edges of the plug-in. This means that the plug in … Read More »

Introduced in 1966, the Tektronix 106 Square Wave Generator is a signal generator which can produce fast rise (<1nS @50 ohm loads positive or negative going) or high amplitude (120 Volts, high impedance load) square waves from 10Hz to 1MHz. It is used for oscilloscope calibration, risetime testing and for triggering extremely fast rise (<100pS) tunnel diode pulsers. The 106 uses a combination of vacuum tube and discrete solid-state technology. This is the sort of equipment that was used for development and testing during the NASA Apollo Program through the 1960’s.

The cost of the Tektronix Type 106 was USD 590 in 1966 or about USD 4900 in 2021 dollars. I was fortunate enough to obtain one of these units in decent condition and I was able to restore it to better than factory specification. What … Read More »

The Tektronix TM5006 is a 6-Bay power frame which can host and power either TM5000 or TM500 plug-ins .

Tektronix themselves had about 130 different plug-ins available which comprised power supplies, signal generators, oscilloscopes, multimeters, test oscillators, calibrators, attenuators, filters, logic analyzers, frequency counters, audio analyzers and more. In addition, numerous third parties made plug-ins for the system. The total number of different plug-ins numbered at least 200. The system was introduced in 1972 and was available in some form through at least 1995. The system is remarkably interesting from a technology standpoint because it encompasses the move from discrete transistor circuitry in early equipment, evolving through microprocessor-controlled units in later equipment. The more modern TM5000 equipment also had network interface (GPIB) capability for control and data acquisition.

In terms of cost, a basic … Read More »

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