Shaun Merrigan's Information Pages



Cubic CDR-3250 Display Replacement

Posted by Shaun Merrigan in Electronics, Radio. Comments Off on Cubic CDR-3250 Display Replacement

9th January

The Cubic 3250 VLF-HF receiver is a 10kHz – 30 MHz DSP based radio receiver with 51 IF bandwidths and 7 receive modes. It falls into the category of professional/military grade equipment and the build quality certainly reflects this. According to Fred Osterman’s book, “Shortwave Receivers Past and Present, 3rd Ed.”, it was manufactured from the mid 1990s until at least 1998 (possibly later). I have found that the audio recovery and readability of this receiver is outstanding.

These receivers have a VFD (vacuum fluorescent display) as part of the front panel/human interface. The VFD in one of my units must have had many, many hours on it because it was quite fuzzy and dim, to the point of being blurry:

Aged, dim, blurry VFD

The old display on the CDR 3250 showed considerable burn in when viewed using … Read More »


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 »


RIFA Safety Capacitor Replacement in HP Gear

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on RIFA Safety Capacitor Replacement in HP Gear

3rd January

In a previous post, I had documented the condition of several RIFA Y Safety capacitors, showing clearly the cracked condition of the outer case. This condition is a precursor to the well documented failure of this style of RIFA capacitor. Reportedly, these problems have been solved since Kemet squired RIFA in 2007. Of course the equipment which contains these potentially failing capacitors is typically older than 2007.

For example, I recently replaced six (two from each instrument) of these capacitors from the following equipment:

HP 3245A (1992)HP3245A (1992)HP 3458A (1989)

HP 3245A (1992) Original RIFA Safety Capacitors. The line filter is on the bottom right.

HP 3458A (1989) Original RIFA Safety Capacitors. The line filter cutout is on the bottom right.

Each and every RIFA Safety Capacitor I removed from this equipment showed cracks in the case.

Cracked RIFA … Read More »


Hickok 209A VTVM Restoration Part 7

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on Hickok 209A VTVM Restoration Part 7

3rd January

I have completed the electrical restoration of one Hickok 209A VTVM. This included:

Replacing all the paper and electrolytic capacitorsReplacing all the carbon composition resistors (most were out of tolerance)Installing a polarized AC plug, line fuse and proper safety capacitorReplacing the meter movement (original was mechanically damaged)Rebuilding and restoring the battery holderBalancing the bridge tube resistorsGiving the unit a full check on all modes and ranges

With all of the above complete I can declare the unit ready to use. The cabinet still needs to be cleaned and refinished, but that will have to wait until warmer weather arrives and I can work outside.

The results of my testing were very interesting. I used my lab equipment (see below) to check the 209A on all of its ranges and modes (with the exception of the decibel range). … Read More »