Desperately Seeking Schematic / Info on SMM for a Tesoro Silver Sabre II Hybrid Board

[Corsairisen]

All,

First post here, please pardon any errors in protocol / attachments...

I have a Tesoro Silver Sabre II metal detector that gives no indication of receiving power when turned on. Unfortunately, I am having a devil of a time identifying the SMM that I believe to be causing the issues. Part of the reason for this is the board is apparently a hybrid used for a short period of time as an intermediate between models and thus am having difficulties locating a schematic that matches the board, and the layout is such that it is very difficult to track the circuits. The other issue is that none of the surface mounted modules are marked.

Below are pictures of the board with arrows going to the component that I believe to be the problem since it gets super-hot when voltage is applied. The hope is to replace this SMM but have no way to tell if it is a capacitor or a resistor (or other) since it is a faulty part and none of the surface mounted components are marked.

It is possible it the fault extends to the LF353, but am having trouble finding an exact replacement and hope to try to replace the unknown SMM before delving any farther into replacing things.



Any insight would be hugely appreciated!!


Thank you, Corsairisen

[Carl-NC]

Below is a Silver Sabre plus schematic, should be close. You are right, Tesoro made these for a year or two before they switched to regular SMT. The hybrid module was made by a company in England, it is a ceramic plate with most (all?) resistors printed with thin film ink (the black blotches). All the other passive components are probably capacitors.

The component you point to looks like a cap, and caps don't usually get hot, almost no matter what. Measure its resistance, see what you get. In-circuit measurement is fine as a start. It might also be R4 which should be 150kΩ, and that's pretty high to do in thin film. Also, there is a similar component on the other side of the LF353 that might be R18. In any case, I can't see R4 heating up either. Another option is to remove it and see if the hot spot goes away.

[kt315]

thinking this circuit is closer.

[Corsairisen]

Carl-NC / KT315

Thank you for the assistance. I have been struggling with this detector for weeks and was lucky to finally find Geotechforums, and good people within to provide help! The 150k resistor looks to be inline, but also see a .22 uF capacitor very close in some previously viewed schematics that didn’t really match the layout of this detector (but hoped would help ID), but because of the way the boards are arranged also have a really difficult time tracing. The component that gets hot looks to possibly be fractured since there are wires visible under high magnification and can feel slight ridges on surface. Anyway, I will check out the supplied schematics, give the above suggestions a go, and report back.

Anyway, thank you, again! Schematics and suggestions should go a long way in helping resolve and / or preventing further issues from missteps while trying to cure..

[Sean_Goddard]

That is a capacitor, probably a Kemet 220nF or 22nF (Kemet are renowned for going short circuit). You say it's getting hot, are you SURE it's not the LF353, those can pop. Measure the resistance, if it's getting hot, it will be short circuit.

All the resistors are the black lines you see under the coating

I have repaired many of these machines. I have only have ONE hybrid go wrong in nearly 100 machines fixed. The other problem is unstable threshold. Change the mode switch. They get dirt in them and become conductive (M Ohms).

I once bought a box of 100 switches for these and not ONE of them worked as the grease used was conductive. Farnell sent me a new box. I got to keep the old box which were OK for other projects.

[kt315]

this is second sch given FatBob.
Carl's sch referenced to another SS+, i put the board pic too.

[Corsairisen]

Sean_Goddard,

Thank you for the input on the capacitor. Helps me out a great deal.

As far as I can tell, it is the capacitor that is getting hot, but the space is cramped enough that can’t be positive by putting little my finger on it since detecting the exact location of pain can sometimes be difficult. I will break out the probe for the digital thermometer to make sure before trying any desoldering. Much more accurate and a less painful means of testing, You could be right, though and may be the LF353. Thus far, I have been somewhat been building up for repair post accurate diagnosis and ID of parts needed…which is getting pretty close to complete (I hope).

BTW, timely you should mention the switches going bad from grit grinding into the switch. I have a Tesoro Eldorado, as well, that is doing exactly this! Though, even with the problems emerging after ca. 30 years of use, Tesoro have been some of the best detectors i have owned.

Thanks, again, to everyone who was gracious enough to offer help on this! I am a much better tinkerer than electrician, so the help goes a long way!

[kt315]

That is a capacitor, probably a Kemet 220nF or 22nF

every SMD capacitor is marked by color. yes the color is pale, but that is. so there is not another cap with the color. rare value.
thinking 100- pF. you can not check the value desoldering another.same cap and measure it. so then the schematic. he must do his Home Work. i show an example. not so hard. just tester and image editor.

[Carl-NC]

Even if the cap is shorted it's not going to get hot. Remove it from the PCB, see if the heat is still there. I suspect the LF353 got zapped.

[kt315]

zombie topic again?