How to upgrade the memory of your HP 35665A Dynamic Signal Analyzer - Page 1
Forum section: electronics / testgear

author: Sören_Marodören
author_rank: Contributor
timestamp: November 06, 2020, 09:39:31 pm
content: In October 2019 I bought a HP 35665A Dynamic Signal Analyzer on Ebay.It was in nice condition but with only option 1D2 (Swept Sine Measurements) installed. See Installed_Options_Before_Upgrade.JPG below.After checking the “HP / Agilent 35665A Options Upgrade” athttps://www.glkinst.com/test-equipment/I was able get the remaining SW upgrades (1D0 - Computed Order Tracking, 1D1 - RealTime Octave Measurements, 1D3 - Curve Fit/Synthesis, 1D4 - Arbitrary Source and 1C2 - HP Instrument BASIC).But there are two options, 1C1 and ANA, that can’t be installed via SW upgrade. The 1C1 option upgrade the 2 MByte standard memory by additional 2 MByte, resulting in 4 MByte, and the ANA option add another 4 MByte, resulting in the maximum 8 MByte memory. My instrument only had the 2 MByte standard memory.When I opened the instrument and looked at the memory board (35665-66585) I could see that both the STANDARD RAM area and the OPTIONAL RAM area were populated with 16 circuits of M5M44256BL-10 (256k x 4bits, 100 nS). The memory mounted on the board is in total 16 x 256k x 4 bits that are arranged so they result in 2 MByte.To be able to upgrade to option 1C1 the memory board has to be replaced by a 4 MByte board (35665-66586) or for the option ANA it has to be replaced by an 8 MByte board (35665-66587). After Googling for pictures on these boards, it looked like it was the same PCB but with different memory circuits mounted on them. On the 4 and 8 MByte boards they used 8 or 16 memory circuits of M5M44400AL instead. On these boards the 1M RAM jumper (R101) was also removed.So instead of trying to find a memory board on Ebay I purchased 16 circuits of the M5M44400AL-7 from a dealer in China. (This component is no longer available from the well known component distributers. So I had to look at other places.) It can be a bit risky to buy components there. But I was lucky and got functioning components after a week.After a tedious work of desoldering 16 x 26 = 416 pins and then solder the same amount of pins on the new components, I also removed the 1M RAM – jumper. The board no looks as shown in: 8MByte_of_memory.JPG. The startup showed that I now have: Main Ram 8.388.608 Bytes. See picture: Boot_up_after_Upgrade.JPG.And finally I now have all possible options installed as shown in Installed_Options_After_Upgrade.JPGI hope this information can be useful if someone else want to upgrade an HP 35665A. Hopefully there are plenty more of the M5M44400AL-7 memories available. If not I suppose it can be possible to make a small 8 MByte RAM board that can be soldered to the pads and glued / tied to the board. (Can be a fun project to design…)

author: mightyohm
author_rank: Regular Contributor
timestamp: October 01, 2022, 08:11:41 am
content: I followed your instructions and was able to upgrade my analyzer to 8MB (option ANA).I also unlocked all options.I used 16 x M5M44400AL-8 (80ns) and the new RAM seems to be working fine.Thanks for writing this up, it made the whole process relatively painless (aside from sourcing the obscure RAM and desoldering over 300 pins..)