Shaun Merrigan's Information Pages


Tag: Electronics Repair


HP 3245A Capacitor Replacement

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on HP 3245A Capacitor Replacement

4th January

The HP3245A Universal Source (datasheet is copyright HP/Agilent) is a precision AC/DC voltage and current source that can provide a wide range of precise and repeatable voltages and currents up to +-100vdc and 100mA dc. It can also provide sine, square and arbitrary waveforms up to 1Mhz and 200vpp. Such an instrument is extremely useful in the lab for calibrating meters, driving current and voltage amplifiers and checking equipment. The particular units I have were built in 1992/1993 which means the electrolytic capacitors are approaching 30 years of age. I had decided to replace the RIFA line filter capacitors in (documented here) both my units and performed routine power rail voltage and ripple checking as part of that. For example:

+5.0840 4.4mv+15.194 30mV+18.625 29mV-18.691 28mV

The other power rails and HV Amp power supply also measured good, using an … Read More »


BK Precision 879B LCR Meter Repair

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on BK Precision 879B LCR Meter Repair

3rd January

The BK Precision 879B is a good quality, dual display 40,000 count LCR (inductance, capacitance, resistance) meter with 0.1% basic accuracy. It was first manufactured in 2010 and is still available (2021) for around $420 Cdn. I purchased mine several years ago and find it very convenient and easy to use.

BK Precision 879B

Things I like about the 879B:

Open/short calibration completes very quickly as opposed to the DE 5000Decent quality Kelvin clips and smd tweezers40,000 counts for extra accuracyVery good accuracy when compared to my HP4263ALong battery lifeEasy to use menu system and quick setup

A common problem with these units is the lack of robust input protection. What this means is that if you forget to discharge a sufficiently large capacitor and attempt to test it, you will damage the front end of the meter which will … Read More »


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 »