Help! Tesoro tejon threshold issue

[Badd427]

Hello all,I have a Tesoro tejon (grey) that only has threshold when it decides to have a threshold and when it dose it’s only for a few seconds and very faint on max and drifts in and out periodically,it operates normally in disc mode ,I have very mild soil in my area so it’s not a mineralization issue like some people have had with the tejon in bad soil,I removed front panel and can wiggle the boards and threshold will come in and out faintly with threshold knob maxed out and twice I was able to position the boards so that it has a loud normal threshold and it did quite down when knob was turned towards min from max so I assume the pot is functioning,I have used tweezers to wiggle each and every wire and can’t locate a wire that might be causing the problem,all soldier joints are clean ,it ground balances perfectly fine and pinpoints with trigger pulled but is silent until it’s over a target while pinpointing,I’m scratching my head because I know it should have a threshold and I know it’s a wavering sound not steady like most detectors are but it’s basically silent in all metal with discriminate knob clicked to off but will sound off with trigger pulled back while over metal,I have tried a different coil also from a normal working vequero ,any direction as to what to check next will be greatly appreciated, thank you in advance

 

[vito]

Hello @Badd427 .
The threshold pot is a 100k.
The outer contacts lead to +5V and -5V.
So 10V can be measured with a DC Voltmeter and the detector switched on.
You also may measure from one outer contact to the middel. The voltage has to alter if the pot is turned.
The oposite can be measured over the other outer and middle contact.
The voltage has to slide if the pot is turned. No dropouts or sporadic uprises.
Have you tried to push in the axis of the pot gently?
I think the pot has gone haywire.
Reporting back would be nice.

 

[Badd427]

Hello @Badd427 .
The threshold pot is a 100k.
The outer contacts lead to +5V and -5V.
So 10V can be measured with a DC Voltmeter and the detector switched on.
You also may measure from one outer contact to the middel. The voltage has to alter if the pot is turned.
The oposite can be measured over the other outer and middle contact.
The voltage has to slide if the pot is turned. No dropouts or sporadic uprises.
Have you tried to push in the axis of the pot gently?
I think the pot has gone haywire.
Reporting back would be nice.

Hello,I checked the pot and I get 0v-9.8v from min to max and vice versa when I check both outer tabs both to the middle tab ,thank you ,James

 

[Badd427]

Hello @Badd427 .
The threshold pot is a 100k.
The outer contacts lead to +5V and -5V.
So 10V can be measured with a DC Voltmeter and the detector switched on.
You also may measure from one outer contact to the middel. The voltage has to alter if the pot is turned.
The oposite can be measured over the other outer and middle contact.
The voltage has to slide if the pot is turned. No dropouts or sporadic uprises.
Have you tried to push in the axis of the pot gently?
I think the pot has gone haywire.
Reporting back would be nice.

I reread you message and I Checked between the two outer tabs and it reads 9.7 on min and max and will drop into the 4v range in between min and max sometimes but not everytime I rotate it up and down thanks again,James

 

[autopilot42]

I reread you message and I Checked between the two outer tabs and it reads 9.7 on min and max and will

I reread you message and I Checked between the two outer tabs and it reads 9.7 on min and max and will drop into the 4v range in between min and max sometimes but not everytime I rotate it up and down thanks again,James

drop into the 4v range in between min and max sometimes but not everytime I rotate it up and down thanks again,James

I reread you message and I Checked between the two outer tabs and it reads 9.7 on min and max and will drop into the 4v range in between min and max sometimes but not everytime I rotate it up and down thanks again,James

Try some tech spray it will clean the pot and maybe help. Good stuff. It is a tuner cleaner but might help. Just a small squirt than actuate

 

[Badd427]

Try some tech spray it will clean the pot and maybe help. Good stuff. It is a tuner cleaner but might help. Just a small squirt than actuate

I’ve cleaned all the pots with no improvement ,I also replaced the threshold pot with a new b100k pot (no improvement) that I had leftover from a pot replacement I made on a different detector,I had bought a 5 pack so I have 4 extras,thank you so very much,James

 

[Rick(ND)]

I dont know if my help will do any good or not, but to me it sounds like a bad connection which more than likely a bad solder connection. I used to see this a lot on my TV repair I used to do. I have had a couple of Bounty hunter come in and that was the problem and easy to repair on them, used to turn them on and wiggle the circuit board with the nylon probe I had and when the acted up I knew the area that was the bad connection. being you were moving the board a little and got the threshold makes me think a bad connection which most cases is a bad solder connection. From experience it is hard to see from looking at them and had to resolder all the solder connection if I couldn't see it. I never had a Tesoro apart myself, but know lot of the uMax had the circuit mound components and may be hard to solder them without making some bad connections between circuits, so hope you can use a wooden probe to work on pushing on different spots to see if it makes a difference then you may know where it is. I remember many TV and radios that I had to solder all that I could to get them, but if moving the board as you say and the threshold came back I would be looking for a bad contact which more than likely a bad solder contact, give it a try and let us know if it helps. It hasn't been dropped or something as that can crack a circuit board, so look over it well to see a crack.
One more thing is you do know there are different pot even if the K ohm are the same and if you change it make sure it is the correct one, but if not they wont work as the suppose to. If changing it and may no difference it is probably not the problem.
I hope some of this may help as it is just some of the things I learned in TV repair, now the new flat screen digitals are throw aways as you can not repair them as everything is micro.

Good Luck

 

[vito]

@Badd427
May be the CD 4053 is faulty. But that's not for sure, and I don't know how to check it, except replace.