Would anyone have experience or link to circuit information?

Receiver is dead.

Powered by 4-9Vs. 2 circuits.

One 9V circuit with 2-P-9Vs.
One + & -/9V circuit.

Lcd is not "on"

Voltage check shows <3vdc to lcd control chip (low).
Batteries all checked good.
Internal battery check= good.

Accidentally left power switch on overnight. Locator was working the next AM.

Display was dim though.

Sorry for the long story!!!!!!!!!!!!

Battery voltage was only 8.5 each so I put in a new set and it worked perfectly.

After a few checks/days it is back to low voltage to the lcd and dead.
New batteries don't bring it back. Still low voltage to lcd.

I'm confident it's a simple ps problem, but haven't been able to find a likely suspect.

Heat, cold, and shock have no effect.

Any information out there?

 

If you post good PCB photos (both sides!) the experienced repairers here might be able to offer some simple tests and/or solutions.

 

Thanks for taking the time to respond.

I will stumble thru the circuit eventually.

The layout is such, with 5 boards plugged into a main board, that it would be almost impossible to trouble shoot remotely.

By the time I get it drawn out, I should be able to solve it.

Was just hoping on a long shot that someone had inside info.

After 4hrs in. I have a drawn the 5 volt regulator circuit using 1-pnp pass, driven by 2-npn darl. connected.
Base of darl. is referenced around .6 volts from a voltage divider.

Top of divider is the +5V output. Bottom of divider is -2.5V from a LM336 (2.5V shunt reg.) between -9V and ground.

I'm pretty proud of getting this far as earlier I didn't even know what voltages to expect.

All parts and board are plastic coated.

Have the advantage now of circuit working. I can record levels thru the circuit.

If only I can get it to fail again, I should have a shot.

Why it takes 20+ components for a 5V reg. I'll never know. Don't see any current limiting.
And referencing to -9V? There are other ways to get the +5 to swing around the .6V BE junction.

I suspect the shunt reg. as the culprit. It checks low with diode test. Out of circuit. Yet reinstalling it's ok. Subbing 4 signal diode string didn't seem to work. But that was before I understood the circuit.

 

Here's what I'm up against..................

 

This may help someone else with dead Microtech 810 locator.

Supply to LCD <2.6V when dead.
Supply to LCD >5V when working.
LM336 suspect on middle board.

 

Congrats on getting it working.

That's about the worst "regulator" I've ever seen in a commercial device.

A cheap 7805 would have been a heck of a lot simpler, more reliable, and regulated better.