Category Archives: Uncategorized

HP 3457a SRAM Battery Replacement

Leave a reply

I recently picked up a HP 3457a 6.5/7.5 digit DMM! It is an old workhorse, fairly common in the 80s and 90s.

My 3457a seems to be working well, but I am a bit skeptical about the sram backup battery, which appears to be an original – it might be 30 years old.

Since I intend to send this out for calibration, it is worth replacing ahead of time. If this battery fails, I’ll have to spend more to get it calibrated/adjusted again anyway.

A bit of surgery with my Weller WX-1, with a 3.5mm jack inserted in tha back to make it float, allowed me to desolder the existing battery while the meter was running. It is very important to use an isolated soldering iron – otherwise you will short out the battery as you desolder it! I cut the battery off before de-soldering the pins.

I replaced it with a Panasonic BR-2/3AE5SPN, a primary long life 3V lithium cell, 2/3 A size, with PCB mount pins (with the right spacing!) already welded on.

The 3457a rebooted several times during the process which was extremely unnerving, but it seemed to work out ok.

Upgrading X8R Firmware / bind failure

Leave a reply

Watch out when upgrading the firmware on the frsky X8R receiver – if you update to a 2015 EU or LBT firmware, the internal XJT module of the taranis radio must be upgraded as well, or it will fail to bind.

Instead of upgrading my radio’s firmware, I rolled back the X8R to version 150115, which works. At some point in the future, I will upgrade all of my radios.

Also note, that when flashing firmware with frsky_update_Sport.exe, you must load the file and let the program start scanning before plugging in the X8R, or it will not find the receiver. It sounds like the receiver is only looks for a programmer very briefly on startup.

CyberPower UPS Battery Change

Leave a reply

My trusty CyberPower CP1000PFCLCD UPS was starting to only last for a few minutes, when it used to last for 20 – a pretty clear sign the battery is about to die. The battery is about 4.5 years old, which is about the rated service life.

Fortunately it is pretty easy to remove.

First flip the ups onto its back, unscrew and remove the panel with the arrow.
UPS Bottom

Then tilt the ups, and pull on the tab to get the battery out enough to see the power leads on top, they are just blade terminals.
tab

Pull the wires off the terminals and remove the battery. This step is a bit tricky because the wires are very stiff, not long enough to let the battery fully remove, and there is a molded plastic piece in the way. I had to very gently work the wires around to get them out enough to remove.
Bare wires

Inserting the new battery, a CyberPower RB1290 aka B.B. Battery HR9-12, is pretty easy with the same issues with the limited flex of the wires. It takes a bit of bending and force to get them realigned.

After that, snap / screw the base back plate in, plug it in and wait ~8 hours for the new battery to fully charge.

Testing the old battery on my charger shows it still has a good bit of capacity left for low drain applications, and perhaps regenerative discharge of other batteries – hopefully some more about that later.

Anderson Power Pole & PCB Mount

Leave a reply

Lately I have been doing more designs that involve high power, usually right around a kilowatt at 30A – 40A. Moving that much power takes a bit of effort in connector selection.

I have been using Anderson Power Pole connectors because they work up to the 45A-55A range with not too much heating and are somewhat cheap (as in only a dollar per housing and pin). They also have a PCB mounting contact that is handy.

The PCB mount contact comes in two versions, 45 amp (1335G1/1336G1/1337G1) and 25 amp (1317G2 / 1317G12 etc). Which is great, except the two pins are mounted 180deg relative to each other.

Welp >.< . Which makes it easy to look at the wrong picture in the catalog and design a board that is inverted. Remember, 45A are hood down, 25A is hood up. This actually makes sense, with the hood down, there is a little more room for airflow around the housing, which is part of the higher current rating, I assume.

New Domain, SSL

Leave a reply

I managed to get my hands on a shiny new .io domain, which makes me rather happy. The old domain should automatically redirect to the new one mostly transparently, and probably will for at least another year.

However, the main upgrade is actually a real, live, root trusted SSL cert, free from the Let’s Encrypt project. Thanks, by the way… All connections should now take place over a TLS 1.2 connection with AES-GCM crypto and ECDHE_RSA kex if your browser supports it.

Installation was rather painless, and is much easier if you generate the key on the same machine as is running the live website, as it spins up a server (or plugs into apache) to communicate with the certificate issuing server in order to validate that I actually control the DNS information for the domain.

Next steps are probably hosting my own DNS so I can turn on DNSSEC and all the related security enhancements like DANE. And maybe writing a few posts about some electronics.

LSI 9207-8i and P20 firmware

Leave a reply

This is a tale of woe on Centos 6.

Resetting drives. iuCRC errors. Bad blocks in ZFS. These are not things you want to see from your brand new 5000$ storage machine.

We just finished setting up the first storage server for my group at work. I ran badblocks on the drives as an acceptance test, and started noticing that the HBA, a LSI 9207-8i, would randomly freeze I/O complaining that the drives had timed out an operation, then eventually resend the command. Reducing the NCQ depth and increasing the command timeout did not help. The errors were intermittent but consistent on all drives. Badblocks passed, with no reallocated sectors so the disks platters should be fine.

Turns out, using mpt2sas driver version 16 and P20 firmware on the HBA does not work. I had to downgrade the firmware to P16, at which point things seemed to start working again. Downgrading required booting into the UEFI shell provided by the motherboard, and was actually not a bad experience. I like the idea of a recovery shell built in – no more digging around trying to find a live dos USB image that works.

This also demonstrates ZFS might be a good burn in tool… it detected silent data corruption the HBA likely caused.