Month: October 2018

Well it was only a matter of time until we had a major failure of the onboard hydraulic system on board the boat, and this weekend proved to be that point in time.

This is what remains of one of the main hoses to the propulsion motor, the fitting has been blown off the end of the hose! This occurred when I moved into reverse to stop the boat for oncoming traffic, and suddenly I lost all drive. The end result is a bilge filled with hydraulic oil, and zero power for manoeuvring.
The hose outer cover has been cut through by the fitting, like it had been sliced through with a knife, what remains of the inner liner & outer sheath is still in the fitting:

Here’s the end of the offending fitting, with the remains of the hose. I suspect this termination wasn’t done correctly in the first place – either the swage was done too tight, cutting into the hose, or the fitting was never pushed all the way onto the hose before swaging, resulting in reduced strength.

Now comes the effort of cleaning out the roughly 40L of oil now in the bilges, refilling the oil tank & getting new hoses made up.

Here we have another piece of tech from Sterling Power – this is their Advanced Alternator Regulator, the Pro Reg D. Since I’m rejigging the alternator setup onboard, I figured I’d do a little teardown.

Removing the top cover reveals the main PCB, which is slotted into the Aluminium heatsink extrusion. It’s a pretty well packed board, with both sides packed with tracks. There’s a small fan at the top of the unit, to keep the heatsink cool, but this has never worked for as long as this regulator has been in service.

Here would be the reason the fan has never operated – the thermistor which is supposed to monitor the temperature of the heatsink the MOSFETs are clamped to isn’t even in contact with it. Simply glopped with heatsink compound & stuck behind the SIL pad. This is a little sloppy to say the least, and should be in close thermal contact with the heatsink. I’ll have to adjust this mounting.

Removing the heatsink shows the main field control FETs, both a P-Channel IRF4905 74A for positive field control, and a N-Channel IRF1010E 84A for negative field control. These are selected by moving the blade fuse between 3 spade terminals. Incedentally, Automotive-type blade fuses are not quick enough to protect semiconductors in the event of a serious fault, the likely result being an intact fuse & totally blown MOSFET. Nevermind.

The unit is controlled by a Microchip PIC16F874, in a large package. There’s a couple of trimmers onboard for tweaking the calibration of the regulator, along with a dual DIP switch & a 12/24v link. Display is taken care of by a large row of indicator LEDs on a mezzanine board, there’s also a 4-pin Molex connector for a remote status display.

The LED board is mounted to the main PCB with long pin headers, with no other support. Given the naturally vibrational nature of boats & their engines, having solder joints flapping about in the breeze isn’t a great plan, and fatigue is likely to set in here before long.

Speaking of vibration, since the cable loom emerging from the aluminium case of the regulator is totally unprotected, the sharp edge of the extrusion has already begun chewing through the insulation! This has occurred after about 50 hours running time since the unit was installed. I’ll add a sleeve over the loom where it pops out of the corner to protect things better. Having the earthed aluminium casing munch it’s way through the insulation & short the entire loom out would not be a great result.

While I’ve got the board out of the casing, I’ve applied a heavy coat of PCB conformal coating to the back to help keep the moisture out, once everything is back together the top of the PCB will get the same treatment after masking off the parts that wouldn’t take kindly to a blasting with conformal coating.