Repair a White's 2900/D Trooper?

[Darter]

I received this detector as a gift in the mid to late 80's. Would love to have it working again to let my kids try their hands at it, but I don't know much about electronics. It's a very clean, lightly used unit, so even though it might not have much value compared to a newer analog detector, I hate throwing something away that might be easy for someone (else) to fix.

What I know so far:

• Battery light comes on momentarily when turning on and off
• Hear static momentarily when inserting headphone plug
• No sound from speaker or headphones with any sweeping at any setting
• The tuning knob/pot is very, very hard to turn and can't turn fully in both directions
• it looks nice

Thoughts?

[Valhad]

Not a lot to go on there, but a couple obvious questions come to mind:

1) did it work when you put it away?
2) if not, can you remember anything about when it stopped working?
3) was it stored with batteries in it? Did they explode/leak?

Other than that, I'd say start with the obvious - the knob should turn pretty easily. If it doesn't, then probably you should start with loosening it up. A bad connection in there could easily prevent the detector from detecting properly. Sometimes you can just turn a knob like that back and forth a lot until it loosens up, which is basically using the corrosion inside against itself to scrub the pot clean. A gentler, and better, method would be to go to a Radio Shack and ask if they still carry potentiometer spray. They did when I worked there, but that's been 10+ years now, so who can say... You just spray it in, an then turn the knob back and forth, letting it help break up the corrosion.

Good luck!

[Darter]

Thanks, valhad. Sounds like I may have some cleaning to do. I don't know when it last worked. It was always stored at my parent's home, either in a closet or the basement, in it's original vinyl bag. No idea if my nephew ever tried it out or got it working recently, not sure when it last worked. It wouldn't be out of the question for it to not have been in use for at least 15 years.

The 9v battery was in there when I opened it up last weekend, but amazingly no leaks or other corrosion were found. The battery lead contacts look quite good.

[Valhad]

Well, that's a spot of luck with the battery, at least!

I did find this, in case you don't have the manual:
http://media.whiteselectronics.com/m...n%20Manual.pdf

It sounds like the process of turning it on and calibrating it is a few steps long, and should result in some audible tones at points if everything is working right.

Let us know if getting the dials to turn freely helps!

Valhad

[Darter]

Got the cleaning spray, but I don't think I'm making much progress. After a few shots and lots of turning, I believe the knob is turning on the pot stem, rather than turning the pot. I backed off on the set screw to try to remove the knob to see if I could turn the stem by hand, but the knob is only rising by about 4mm. Should I keep forcing it up, or is there something else that needs to be loosened first?

On with the pics. Not that there's much to see...

The victim




Opening 'er up




Bottom of the pcb




The culprit




Should this just pop off?

[Darter]

A few more observations:

• with a fresh battery, the batt light stays on dimly as the manual says it should, so apparently we have power
• there's a faint click in the headphones when turning the power on
• with the pcb exposed, I can see parts movement inside the openings of the undersides of the pots on the other 3 knobs when turned.
• no movement on the tuning pot when turning the knob with the setscrew in place

So my guess is at this point that the tuning pot is still completely frozen. If I can safely get the knob off and turn the stem of the pot and force it free, I'm hoping to maybe hear something. Right now it seems to be frozen in the min sensitivity setting, which hopefully explains why the detector isn't picking up anything. However, I would guess that even in that setting, it would pick up an object swept immediately beneath, no?