Radioshack Discovery 3 questions

[gerson]

I would spray contact cleaner on the controls and work them a bit, see if that solves the problem.

Hi Carl... thanks for the reply... I'll try... it would be better to remove it to clean the area. What do you think?

[Carl-NC]

In the past I've used contact cleaner with the controls mounted to the PCB. I don't think it will harm the PCB, but others may have a different opinion.

[gerson]

In the past I've used contact cleaner with the controls mounted to the PCB. I don't think it will harm the PCB, but others may have a different opinion.

Ok, Carl. I'm going to do this procedure you suggested. Thank you for your kind attention. I'll come back here to report the results.

[gerson]

Hi Carl. I did the cleaning procedure, but it didn't work. Looking more closely, I noticed that the 4-position rotary switch was stuck, and it turned to the last auto-notch position with great difficulty, very heavy. I believe this indicates that the switch is indeed faulty. I'll have to replace it, but even so, I believe there's another problem in the circuit, causing the object detection part to not work. Near this switch, there must be a component causing this malfunction. The switch is a 4-position, 15-pin switch that I found here on Shopee.Brasil. If you have any suggestions where I might find this problem, at some stage of the circuit, I hope you can guide me. Thank you

[gerson]

[gerson]

This is the 4-position, 15-pin rotary selector switch (power/mode) for off-disc notch and auto notch on the dicovery3

[Carl-NC]

If you have any suggestions where I might find this problem, at some stage of the circuit, I hope you can guide me. Thank you

Sorry, I know nothing about the circuit and I don't think I have a schematic.

[gerson]

Sorry, I know nothing about the circuit and I don't think I have a schematic.

ok. carl. As soon as the new component arrives...selector switch...I'll replace it and see if it works...thanks...

[gerson]

Hello everyone. I replaced the 4-position selector switch, but the Discovery didn't work. It turns on, shows an arrow on the analog display, then goes out, and nothing else. The coil isn't oscillating. I found the technical manual with the wiring diagram for patent 4677384 for the Discovery 3, which I own. Since I'm not an electronics technician, I don't have the necessary knowledge to find the fault. I hope someone here on the forum can guide me to which part of the circuit the fault might be and which component should be replaced. I appreciate your help if possible. I hope this schematic information is helpful to others who want to repair this detector model. Thanks again.

[dbanner]

I believe that patent(4677384) is for the big bud. The Discovery 3 seems to have a microprocessor chip on the PCB. However, the front end electronics should be similar if not identical, including the Tx oscillator.

Basic troubleshooting as follows:

First, assuming you're satisfied that all the switches are working properly and are not at fault, then:

1 Visually inspect the PCB carefully(with magnifying glass). Look for damaged or burnt components. Do some basic diode and transistor checks. Check the PCB for dry solder joints, basically running some fresh solder throughout, especially where things are looking suspect.

2 If the coil isn't oscillating(assuming you know how to check this), then suspect a bad search coil or a faulty connector or cable.

3 Check the power supply on the PCB, make sure the correct voltages are present throughout.

4 Check to see if the micro or any other chip is getting hot to the touch.

5 Suspect that one or more of the chips may be faulty.

[dbanner]

Looks like the micro is a dip40 zilog,Z86C9012PSC perhaps. There should be an xtal somewhere close by the chip. I'm not sure, but the micro could also be producing the Tx pulses, these are things you could check with a scope. If the micro is bad then it's a total loss.