White's PI3000 Rebuild

[Tony]

I picked this up the other day for a decent price and it works just fine. It's not the last word in pulse delay sensitivity but I plan to use it in fast salt water (just behind where the 2 footers break). I believe the pulse delay is in the high twenties and I'm okay with that. I have stripped it down and removed just about everything. I'm guessing it only has seen one or two outings and is pristine. The O-rings were still greasy from the silicone lube and all cables are like new (have been treated with 303 Protectant already). This particular unit was from the far south of my state here in Western Australia so it was never subjected to hot temperatures as the area is cool and cloudy just about all the time. The coil is near flawless and importantly the coil cable is shiny and very pliable....no signs of any age related problems. I will probably swap headphones depending on how my other spare waterproof headphones sound. The PCB is out and although it didn't need it, I cleaned the whole board down with a specialist PCB cleaning spray. The voltage converter (charge pump) chip has been removed from the board (that's the bare spot on the board at the lower left) and will be replaced with a higher rated one to 12v (thanks to Geotech on that advice). I will replace the 6 electrolytic capacitors with new ones as well. A new snap connector power lead will also be soldered on.

I ran a magnifying glass over the whole board and nothing appears out of the ordinary as far as dis-coloured components is concerned.

Unfortunately I don't have the skills to actually mod this detector (faster delay) but I'm not too worried about that considering how I will be using it. All cable gland and O-rings will be replaced as well but don't appear to need it. I will also Plast-Dip the lower half of the coil for added insurance. These 950 Zero-Buoyancy coils are well regarded and are almost impossible to find in this condition....they are nice and heavy and require no effort to keep down.

If anyone else has any other ideas then feel free to comment.

[phrunt]

What about a spray of something like this PCB protective coating on the PCB?  Jaycar also sell a variant of it.

Clearcote LQR Circuit Board Lacquer | Chemtools® Australia

The initial PCB on my Spa pool lasted about 5 years before corrosion kicked in and killed it, when I fitted the replacement, I sprayed it in something similar, I've now had the Spa over 20 years and even moved countries with it.  PCB still going strong.

Yours is obviously going to be in a more protected environment but can't hurt, most of them can be soldered through too making repairs easy enough.  Probably overkill on a sealed unit but helps with vibration and shock, maybe useful.

Check it out under a magnifying glass/microscope or your phone on zoom, you may have some dry, cracked or damaged solder joints by now on a detector that age.  Easy to fix on that big spaced out PCB.

The tracks look all good from what I can see, but they're huge regardless check for any rotting on them 🙂 I had to repair this PCB recently, this is zoomed in under a microscope, but the tiny track had dissolved, I just bridged it with some Kynar wire.  Had this PCB had a coat of that protective spray this likely wouldn't have happened.  Anyway, if you're using flux doing your cap replacements make sure you clean it off VERY well, it gets corrosive over time and will eat away the PCB, possibly the cause of this.

[Tony]

Thanks Simon....some good ideas there. I'll take another look at the copper traces to see if anything needs attention.

[phrunt]

15 minutes ago, Tony said:

Thanks Simon....some good ideas there. I'll take another look at the copper traces to see if anything needs attention.

Those old PCB's are like old cars, mechanics love old cars for a reason. 🙂

 

[Tony]

New electrolytic capacitors and a few other parts are on the way. All new strain relief glands and main housing / control switch O-rings as well. Everything is being replaced with exactly the same specification parts except the voltage charge pump IC which can now handle a 12v battery input.

Also managed to grab some of the last remaining White's lower rods and hardware from Australia. Lower half of the coil is now fully sealed and protected with yellow Plasti-Dip.

I will have to test the original White's headphones against my spare GG Amphibians and Garrett blue headphones.