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HP 3562A ROM Repair

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on HP 3562A ROM Repair

26th December

Early in 2018, I purchased an HP 3562A Dynamic Signal Analyzer for an excellent price on Ebay. The display looked great and it was physically in good condition. However, the unit failed the power on self test as follows:

HP 3562A Error Message on boot

This error code indicates a ROM IC failure.

HP3562A Diagnostic LED’s indicate Hex code 4 4 (0100 0100)

This code indicates a failure of ROM Chip U105:

HP 3562A Rev B ROM board. The problem ROM chip is the fifth chip down in first column (U105)

HP 3562A ROM Board Rev B

This ROM board is an older version using 32kx8 chips in two groups (Low Byte & High Byte) of 18 chips each. I had access to a second 3562A, and swapping ROM boards confirmed that the ROM board was the problem. Now I needed to:

Locate a suitable set … Read More »


AC Line Voltage 34 Hour Log

Posted by Shaun Merrigan in Electronics, Time and Frequency. Comments Off on AC Line Voltage 34 Hour Log

26th December

AC Line Voltage 34 Hour Log


Site Updated to HTTPS

Posted by Shaun Merrigan in Site Updates. Comments Off on Site Updated to HTTPS

22nd December

I have completed updating this site to use HTTPS. Enjoy!

Update: Having a few hiccups after updating to HTTPS. The public facing site became unreachable after a day or so, while the backend was working fine. GreenGeeks support suggested that my Cloudflare configuration was the culprit and recommended a couple of changes to the configuration.

It looks like this was the case, because the site is now reachable again after making the suggested tweaks to Cloudflare. Another issue arose with some pages not loading/working I had to manually edit the code to point to the correct https source which fixed that problem .

Also this prompted me to get rid of a fragment of Adobe Flash code that was still running on the site (a good thing) but served no useful purpose.

As EDI said: “It … Read More »


HP 8903B Audio Analyzer PCB Pad Replacement

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on HP 8903B Audio Analyzer PCB Pad Replacement

18th August

HP 8903B Audio Analyzer PCB Pad Replacement

Visual inspection of my recently acquired HP 8903B Audio Analyzer revealed that the polymer pads on the bottom side of the main PCB were seriously deteriorated:

 

 

 

Besides making an unsightly mess, this residue may form corrosive products which, over time, could damage the PCB.  Also, the pads no longer perform their bottom cover to PCB isolation function.  So all the old pads and residue had to be removed and new pads installed.  Lintless wipes, isopropyl alcohol, and nitrile gloves were the chosen tools.

 

 

 

The residue cleaned up completely, and new pads were installed. I won’t need to be concerned with this failure mode again.

 

Thanks for reading.

 

Shaun Merrigan

 


Tektronix 7854 Waveform Keyboard Rebuild

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Tech. Comments Off on Tektronix 7854 Waveform Keyboard Rebuild

15th August

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

 

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 that it was filled with debris:

The … Read More »


The uTracer Tube Tester and Curve Tracer

Posted by Shaun Merrigan in Electronics, Vacuum Tubes. Comments Off on The uTracer Tube Tester and Curve Tracer

14th August

The uTracer Tube Tester and Curve Tracer

I have completed building my uTracer (micro Tracer) computer based vacuum tube tester and curve tracer.  This unit, designed by Ronald Dekker described on his website:

The uTracer is much more than a simple tube tester; it is also a curve-tracer. It measures both the anode as well as the screen currents for a range of specified bias conditions, and arranges the measurements in meaningful sets of curves. From these curves parameters like the transconductance or the output resistance can then be extracted and plotted as a function of bias. Alternatively the uTracer can be used as a tester which extracts important parameters like Ia, Rp, gm and um in your favorite bias point in a matter of seconds. http://dos4ever.com/uTracer3/uTracer3_pag0.html

Ronald Dekker makes this tester available as a kit, with detailed assembly and testing instructions.  One of … Read More »


Tektronix DSA602A Digitizing Signal Analyzer

Posted by Shaun Merrigan in Electronics, Oscilloscopes. Comments Off on Tektronix DSA602A Digitizing Signal Analyzer

14th August

Tektronix DSA602A Digitizing Signal Analyzer Part 1

I recently had the opportunity to purchase one of these units, and I am thoroughly enjoying the process of  checking its operation and getting to know how to use it.  This unit is a laboratory grade, very accurate digitizing oscilloscope from about 1990.  From the Tek Wiki entry:

Inputs
3 amplifier bays, up to 12 channels (using 11A34 plug-ins)

Resolution
8 bits; averaging of N acquisitions increases by log2(N) up to 14 bits

Display resolution
50 pixels/Div

Sample rate
DSA601, max 1 GS/s; DSA602, max 2 GS/s (one channel, left plugin)

Record length
512 to 32768 samples

Sweep rate
50 ps/Div  to 100 s/Div

ENOB
7.2 bit up to 10 MHz, 6.3 bit @ 250 MHz, 5.7 bit @ 500 MHz, 4.5 bit @ 1 GHz

Screen
magnetic deflection color computer monitor, 10″ diagonal (130 mm × 168 mm), 552×704 pixels, 22×11 infrared touch-screen grid

Power
90-132 V or 180-250 V, 48-72 Hz, 465 W (DSA601A) / 585 W (DSA602A)

Features

Automated signal measurements (rise, fall, period, frequency, width, delay, phase, duty … Read More »


Tektronix Scope-Mobile Cart Repair Part 3

Posted by Shaun Merrigan in Electronics, Oscilloscopes. Comments Off on Tektronix Scope-Mobile Cart Repair Part 3

7th May

Tektronix Scope-Mobile Cart Repair Part 3

 

Part 1

Part 2 

This is the conclusion to my repair of a Tektronix 202-2 Scope-Mobile Cart.  Recall that the problem was three fractured trunnion mount bosses which rendered the cart useless (and unsafe) under load.  My proposed solution was to place the bosses into compression by putting a 6mm countersunk bolt through the trunnion mount concentric with the existing hole in the boss.  By using appropriate sized washers between the top of the boss and the frame member I ensure that the boss is placed into compression and the frame member is securely clamped.  This avoids the tensile loading which fractured the bosses initially.

 

The holes in the trunnion mount were countersunk to fit the flat head socket bolts:

 

 

 

 

The cart was reassembled with the repaired trunnion mounts:

Felt lining was added to the plug in storage compartment:

 

Finally, the cart … Read More »


Ring Video Doorbell Cold Weather Charging

Posted by Shaun Merrigan in Ring Doorbell, Tech. Comments Off on Ring Video Doorbell Cold Weather Charging

24th February

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 556 Dual Beam Oscilloscope Testing: Vertical Bandwidth

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Tektronix 556. Comments Off on Tektronix 556 Dual Beam Oscilloscope Testing: Vertical Bandwidth

27th January

Tektronix 556 Dual Beam Oscilloscope Testing: Vertical Bandwidth

I have been doing some basic testing of my Tektronix 556 Dual Beam Oscilloscope, and I have documented some parts of this process.  I have also captured images of the traces, which I will share here.

Test Setup: Tektronix 556, 1A2 plug-in, Timebase A, Tektronix SG 503 Generator, and Tektronix TG 501 Time Mark Generator

I found the -3db vertical bandwidth of the 1a2/556 to be 65 Mhz, which is to be expected for the 50 Mhz rated 1A2.

 

TM 500 Module with Plug ins

50 kHz Reference Signal 6v peak to peak

5 MHz Sine Wave 6v peak to peak

20 MHz Sine Wave 6v peak to peak

40 MHz Sine Wave 4.8v peak to peak

50 MHz Sine Wave 4.3v peak to peak

65 MHz Sine Wave 4.2v peak to peak

I will continue this testing by investigating the absolute maximum trigger … Read More »