John's homebrew pages
This is a little interlude that came about, not entirely unexpectedly, as a result of a little accident.
I had always intended to fit "proper" DC connectors to the equipment I have been building, but couldn't find what I really wanted from the usual suppliers. Soon after I had rejoined the RSGB I read an article in RadCom discussing the use of Anderson Powerpoles, and I decided these would be ideal, once I could find a supplier. However, I didn't put much effort into it at first and as a result built three linear amplifiers with DC input into 4mm black and red sockets, with wiring harnesses that connected to the 12V SLABs via push-on blade receptacles.
A recipe for distaster, I knew, so was always very careful to (a) plug the 4mm plugs into the amplifier first, so there was no risk of a short, and (b) connect the battery end of the harness the right way round.
In fact, the risk was there with the FT-817 as well, since the external DC lead had also been wired up (by me) with push-on receptacles.
I had over a year of success, including operation at the top of some sometimes very cold hills, without any disasters. Of course you know what's coming next. In early December 2009 I was down in Wigan visiting family, and decided to give away a few points in the 2m Affiliated Societies contest, trying out the 2m linear and a decent Yagi, neither of which I had in December 2008. So I got up in time for the start of the contest, got the antenna up, set up the rig and linear, and on connecting the final push-on connector to the 24V worth of SLAB there was a very loud BANG and the horribly familiar smell of dead electronics. Yes, I had been over familiar with it (probably being indoors and hence more relaxed) and connected up the SLABs the wrong way round.
On taking the lid off the linear, I discovered that the fuse hadn't blown (it's a 5 Amp one), but the electrolytic capacitor across the 24V most certainly had - it had blown the end off and spewed its contents across the box - bits of aluminium and fluff everywhere. I went on for an hour anyway with my 4 Watts, but it could have been much more fun.
So - on getting back home I finally put in the order for the Anderson Powerpoles from the supplier I had eventually identified - Torberry Connectors who have an excellent web ordering service. The connectors arrived very quickly, though it being nearly Christmas there was a little delay before I started to install them. I had also come across a very useful web page of Anderson Powerpole ideas by KB1DIG and KB1GTR.
I decided to use my own colour code; red-black for 12V, orange-black for 24V, and yellow-black for 36V (these are what I currently use with linears). There are powerpoles attached to the individual SLABs (the blade connectors will be taped over in due course) and on each bit of kit; then each wiring harness (including the charger of course) also has the connectors. I have used the 30A contacts as standard.
Here are some of them - a single SLAB, the HF linear (24V) and harness (2 × 12V to 24V).
Now I have my supply of powerpole connectors, all the new projects will be fitted with them. Hooray - no more polarity disasters.