Nautilus not powering on

[Badd427]

DMCll with auto tune switch,5 knobs,no hi-low switch and four 9v batteries,Plugged in 15” coil and turned on and nothing I have good batteries I checked voltage it’s around 18v was working perfectly fine a few seconds before switching coils now it’s dead even with the coil I had just removed from it ,any help would be appreciated

[coinfarmer]

Do you have a multi-meter?

A good place to start is to look for easy to find faults, see if the power continues past the switch and shows voltage on the board.

[Badd427]

I gets to two different transformers and stops

[coinfarmer]

OK so there is power getting to the board. (Those things most likely aren't transformers because transformers don't pass DC.)

Measure the unattached coil plug with a multimeter to identify the loop(s), then see if you get a similar measurements on the corresponding wires connecting to the board with the coil plugged in. I don't know that the measurement will be the same as measuring the bare coil plug, rather checking for a mechanical issue with the plug.

If that doesn't work it would be useful to dig up a schematic for it. I assume the 15" coil is compatible with the machine, if not perhaps there is some component damage to the output devices.

[Badd427]

Apparently the 15” coil isn’t not compatible I’ve been told by multiple sources and would explain why is was working normally until I hooked up the 15” coil and powered on,it never made a single sound and hasn’t since I’m pretty sure the 15” coil is bad because the detector I had used it on goes silent with the 15” but works perfectly fine with 10” that’s how I ended up in this situation I swapped coils on the two detectors to check the 15” coil and just happed to power on the one I put the 15” on first then put 10” back on in and realized I had a problem,,the 10” works just fine on my other detector but the 15” was silent on it

[coinfarmer]

I suppose the 15" could have damaged the output circuitry either from too low of resistance or short due to a pinout incompatibility.

I'm not sure if it would be anything visible, worth a look though. Then maybe lookup and measure the transistor(s) with a multi-meter that has a diode function.
It wouldn't hurt to probe some of the resistors and caps to look for shorts, sometimes you may have to lift one leg of the device to test if you're unsure of the reading.

If the original transistor(s) is not available, there should be something similar that would work, possible requiring mild changes of associated component values.

[Carl-NC]

Apparently the 15” coil isn’t not compatible I’ve been told by multiple sources and would explain why is was working normally until I hooked up the 15” coil and powered on

Maybe, but I'm a little skeptical. Even if you dead-short either coil it should not burn up anything.

Do you have an oscope? That would help a lot. In your other thread I suggested you measure the charge pump output (across C6) with the 10" coil plugged in. Did you do that? If it is 0V then the TX is not working.

[Badd427]

Detector circuitry isn’t my wheelhouse,I’m very knowledgeable on cnc machine tool boards but detector boards are totally different,I was a machine repair tech and had to diagnose problems in boards,thank you for the information and I’ve traced everything and tested everything and can’t find the source of the problem

[Carl-NC]

Sorry, I think you're stuck then.

[Badd427]

I do not own an oscilloscope,I had access to one in the repair shot at work but I’m now retired and the company shut down after 49yrs so I don’t have access to one but I’ve thought of buying one but I’m not too sure how well a cheapo will work and I can’t justify the price of a fluke,thank you all for the help

[Altra]

Without an oscilliscope you can open up the coil connector on the 15in coil. Look for shorted or broken wires. Those coils have a preamp inside that run directly off the 12v regulator. I am a little confused about the situation. You have two detectors, one 10in coil and a 15in coil. One of the detectors works only with the 10" coil and the second detector not at all. A short in coil could have damaged the LM78L12 voltage regulator in the dead detector. Coils rarely go bad internally, most of the time it is a cable problem at the connector end or where it enters the coil housing

Looking at the schematic, the newer units used a negative voltage generator and a npn transistor as a 10v regulator. The older units had the LM78l12 regulator. either way, a short could damage the regulator

[Badd427]

Thank you looks like I have some homework to do,thank you again

[Badd427]

I checked the soldier joints on the coil connection and they are nice and clean,the wire going into the coil housing isn’t damaged or kinked,might be a problem in the coil itself,it’s been well used over the years relic hunting

[Badd427]

If anyone is familiar and comfortable enough with the nautilus circuitry and is willing to troubleshoot and repair it,I will gladly ship it and pay for parts and repairs

[Qiaozhi]

If anyone is familiar and comfortable enough with the nautilus circuitry and is willing to troubleshoot and repair it,I will gladly ship it and pay for parts and repairs

You haven't said where you live. Which country?