trying to repair a Tesoro Vaquero.

[ejudasf]

Hello all.

Found a used and abused Vaquero on the marketplace for $80.00. I didn't notice it was missing the GB knob in the pic, so I talked him down to $40.00. He handed me a bag of replacement knobs and the GB pot with both nuts and washers.

At first turn on, without the GB in place, it just put out a solid beep. Re-installed the GB pot and after fiddling with it, on-off-on-off, it started to work in DISC mode. Switched to ALL-METAL, and it works. The GB feels a little janky with 'detents'. It's supposed to be smooth. I have ordered a new one from Mouser. I measured the resistance across the range, and it seemed to be good.

Here's the weird part. It won't detect a high conductive target in min DISC mode. It will beep on a nickel with the DISC at max. So the phase is way off. I don't see a way to adjust anything, as there aren't any tiny pots inside. I found a spot where one could go, but it doesn't look like it has been removed.

The sensitivity and DISC level pots have a built in switch. I have ordered a pair of those as well.

I see a total of 5 caps that can easily be replaced. I could do that.

I almost forgot. It came with an 8x11 DD coil. The DC resistance for pins 1&3 measure 4.9 ohms. GOOD. Pins 2&4 measure 100 ohms. Not sure if that is okay.

I was hoping to see a gutshot of another Vaquero, and also a DC resistance reading of another 8x11 DD coil.

Any suggestions, questions, and comments are welcome to get this machine back to tip top.

I know 1 person, who lives about an hour away, that owns a Vaquero. I think I will have to call him up to try his coil on my machine, after the cap replacement.

Thanks for any help.

[Carl-NC]

I get 4Ω and 60Ω. Are you sure you have the right GB pot value? Is it ground balanced?

[Qiaozhi]

This might be the Tesoro Vaquero schematic.
The GB pot is shown as 50k.

[ejudasf]

Thanks guys, for asking questions so quick.

The GB pot is the original pot. 50k and 3.75 turns. I have a new one coming in.

The ground balancing does work. It's not as drastic as my Bandito at extreme NEG. At extreme POS, they seem to be about the same.

I was kinda thinking that the coil might be 'out of whack', since it's measuring 100 ohms on pins 2&4. My first Tejon coil measured 5.1 and 65 ohms. This was back in the 90's. I kept notes on stuff like that.

I'll look over the schematic and hope that I can find my buddy to borrow his coil for a quick test. I really am leaning towards the coil being bad.

Thanks again guys.

[Aleks85]

Hi amigo, the link contains all the information I have about Tesoro sensors.

https://drive.google.com/drive/folders/1ASPL3g5LF8XwkOgdEB-RpY51ftprIp0N

[ejudasf]

Hi amigo, the link contains all the information I have about Tesoro sensors.
https://drive.google.com/drive/folde...-RpY51ftprIp0N

Thanks Aleks85 for sharing that info with me. Your notes look like mine, except I still have mine in a notebook.

I must come to the realization that the coil I have is the culprit for the failure.

What's 40 ohms between friends? Just enough to cause havoc.

Tomorrow I should get all the parts I ordered from Mouser. It will have new pots and electrolytic caps.

The schematic that Qiaozhi shared, helped for verification of the caps. I think it might be a different version though. It does not match up 100%. I will try to mark the differences between my machine and the schematic.

I shall report back next week.

ed

[Carl-NC]

Most detectors are not especially sensitive to RX coil resistance. In the case of the Vaquero, a 100Ω shift will cause about a 0.16° phase error which is probably unnoticeable. However, it could be symptomatic of something else. I almost always recommend trying another coil when a detector is acting up, it's the weakest element in the circuit.

[kt315]

this is all i have.

[ejudasf]

Thanks for the images kt315. I see that there is an added cap on mine, touching the 8 o'clock position of the circle.

I did receive my parts in, so I will replace them and the GB pot. Everything else looks good.

BRB

ed

[ejudasf]

Small fun update.

Electrolytic caps and GB pot have been replaced.

I did order a couple of 100k w/switch pots as well. Mouser sent 10k. Oh well. I don't have to change those since the OEM ones do measure correct.

Since the coil does measure 100 ohms on the Rx side, pins 2&4 of the connector, I tried to fool the machine by placing a 180 ohm resistor across the pins. The Disc 'acts' a little more true. It detects a quarter. But the threshold is non existent.

I'll just wait to test with a friend's coil and/or till I get a chance to buy a replacement coil.

Thanks for ya'lls input on this matter.

[ejudasf]

UPDATE

I was able to acquire a used 8x9 stock coil.

At first, I thought something was wrong. When in All Metal, I couldn't get a threshold tone, unless I pressed the PinPoint button. I was feeling like, maybe that's the way it is supposed to be. I had to read the manual. then I started to feel like I bought a dud machine.

I re-opened it up, and noticed the soldered tabs were touching the All Metal tabs. A slight bend, and re-tested for threshold, Voila! Fixed!

The machine works excellent. $40.00 for the machine and faulty coil, and $87.00 for the stock coil. Not bad for a soon to be classic hott Vaquero.

Thanks for reading!!!

[ejudasf]

Carl-NC YOU WERE RIGHT!

The dc resistance reading of my Vaquero coil, 5 ohm and 100 ohm, does work correctly.

I found a fault in the Disc switch pot, and after correcting it, I was happy with my stock coil. I started to wonder about the DD coil and what you said about the 100 ohm reading. I put a connector back on it, and it does operate correctly. WOW! just WOW!

So, Thanks for your help and the help from the Geotech1 forum members.

ed

[Carl-NC]

[ejudasf]

New fear unlocked.

My Vaquero is working fine. WAS.

I packed it for a trip to Virginia over a weekend. AirBnB was in an 'old' part of town. I pulled out my machine, and it just screamed a threshold, with no control. The all metal mode made a slight change in pitch.

I didn't have a screw driver to save my life.

Finally got a screw driver from a neighbor. Opened it up. No broken wires. Still no control over the threshold.

No detecting for me. Sheesh!

Came back home. Waited a week. Opened it up to really look at it. Can't find the fault. Checked it with my thermal camera, and still can't find a fault. Pulled off the pots and replaced with a temp pot, to test for function, and still no change. Cleaned the original pots. Placed everything back to regular.

Decided to give up, and when placing it back together, I touched the 3.## oscillator, and the screaming threshold went quiet. I removed my finger, and the screaming threshold came back. In the quiet state, it does not detect metal. Then as I was placing the main ckt board in place, with it on and the screaming threshold, I touched another component, and then it went quiet, normal. The threshold knob works, the machine works. Powered off and then on, and the failure comes back.

Seems that a particular component may have failed. But in fact, a few months previous, the caps were changed and the flux used was an alcohol based, no clean, that caused a film of some sort to cause a high resistance short across 2 components. I cleaned the area with alcohol and a natural fiber brush, and the machine seems to be back to normal. Whew!

As long as it works, I'm happy. Sad that I couldn't detect that yard though.

Laterz

ed

[Carl-NC]

Usually solder residue isn't a big deal, but some metal detector circuits have an ultra-high impedance retune circuit that is especially sensitive to leakage. This is probably where your problem was, because if it leaks it will quickly rail out and send the audio either to dead quiet or full blast.