Hi guys I have bought a number of the Lambda modules at fleamarkets usually for a dollar each or so. There are two sizes, a low power one designed to fit onto the 5-7 amp supplies and a high power one designed for the 24+ Amp supplies. The differences are mainly in the size of the SCR.
I have the datasheet including schematic for the Lambda OVP adjustable modules. If you want a scan or pdf, I could probably supply it for the files. Burt VE2BMQ>>> skipp025 wrote: > > > > [EMAIL PROTECTED] wrote: > > Unfortunately, I got a reply from Samlex saying the OVP is > > of a feedback type, not a crowbar, which explains Jeff's experience > > with the SEC-1212. > > Not so good... > > > A long time ago I happened to find a crowbar "bar" made by Lambda > > at the local TRW swap meet. I added it to a supply without built-in > > OVP to add said protection to the equipment. > > I have seen a number of small crow-bar pc daughter boards tacked > onto various "Power One" (a brand name) type power supplies. They > are easily copied or even lifted off the original supply for use > in other locations. > > > I wonder if similar devices are commonly available somewhere? > > They are but nothing comes to mind right away... You might check > with Kitsrus, Jameco, Electronics Rainbow, Marlin P. Jones and a > few other kit mfgr/retailers to see what they offer. If not I can > and would share some of my notes if you want to "roll your own". > > > That & a fuse on the output of an SEC-1223 & I think > > I'd feel comfy using it at one of my sites. > > Bob NO6B > > The key points are location, function & size. Where will the crowbar > be placed? What will the crowbar do to everything on the dc bus at > a fault condition? What happens after the fault condition goes > away and or remains? Does the crow-bar device/circuit have a > large enough capacity. > > Astron designed their crowbar circuit to short the supply output. > The shorted output protects the user equipment and tries to > force the AC Mains fuse to open through excessive transformer > primary current draw. > > The bad news is found when modest size power supply - ac mains > fuses are replaced with excessive large current values (the trusty > 25 or 30 amp 3ag fuse everyone seems to have a lot of...). Not > enough current draw through the faulted secondary side of the > supply to open the wrong size installed ac mains fuse. > > Somethings got to give... and it's often very hot when it does. > > cheers, > s. > >
