Repairing Garrett ACE 250

[Ruben2000]

Hello friends!
I have a Garret Ace 250 that takes a long time to turn on and once it turns on it doesn't detect anything. I've been comparing it with a schematic I found in the KT315 shared files but there are some differences. Because I also took the patience to draw it.
Here I share the schematic, but I want to know if there are any flaws in the schematic because I want to ask some questions to those who have experience in repairing this detector.
Please note that I drew this schematic as the detector is (that is, with the fault), which is why I need your help to repair it.

[Ruben2000]

Here I also share a photo of the plate and also the number of components according to the diagram I drew.

[Ruben2000]

I would like to know first if the GATE of VT6 is connected to +4V or is it only connected to pin 47 of U1?
Because according to my board, pin 47 of U1 and the GATE of VT6 are connected to +4V.

[ivconic]

Click to enlarge:

[ivconic]

Here is the Sprit Layout file I made some time ago.
I haven't finished that work, so don't trust that pcb design 100%.
Because it is a multi-layer pcb and it is possible that I made mistakes.
If you don't see all 4 layers; activate them (bottom left) in the Sprint layout software.

[Ruben2000]

Excellent Ivconic!
Thank you very much for sharing your files!
I will compare with mine to find the fault, I will do it tomorrow.

[profesor]

Hello friends!
I have a Garret Ace 250 that takes a long time to turn on and once it turns on it doesn't detect anything. I've been comparing it with a schematic I found in the KT315 shared files but there are some differences. Because I also took the patience to draw it.
Here I share the schematic, but I want to know if there are any flaws in the schematic because I want to ask some questions to those who have experience in repairing this detector.
Please note that I drew this schematic as the detector is (that is, with the fault), which is why I need your help to repair it.

A while ago I had a faulty garret ATpro. The detector would not turn on. When I held down the on button I saw that the tx sinus signal was very distorted. I suspected the LM 386. And I changed it. The detector was fixed.

[Ruben2000]

Hello friends!
The diagram that I published and comparing it with the one that Ivconic shared with me is drawn correctly. Thank you Ivconic, you were a great help to me! As for your PCB, several tracks need to be drawn, just follow my diagram.
Here I publish my scheme, it only has some tweaks.

[Ruben2000]

Friends, I have been checking the power supply and have taken voltage measurements at the points shown in the image.
Red readings are taken without the sensor and blue readings connected with the sensor.
I would like to know if the output voltage of U3 should be around 8V, if so it could be that the IC is bad or there is something that causes the voltage to drop too much.

[Ruben2000]

A while ago I had a faulty garret ATpro. The detector would not turn on. When I held down the on button I saw that the tx sinus signal was very distorted. I suspected the LM 386. And I changed it. The detector was fixed.

Hello friend, I have measured the enTX frequency with a mini oscilloscope, that is the only thing I have at the moment to be able to visualize the waveform. Here the image. Point measured in KT9.

[ivconic]

Friends, I have been checking the power supply and have taken voltage measurements at the points shown in the image.
Red readings are taken without the sensor and blue readings connected with the sensor.
I would like to know if the output voltage of U3 should be around 8V, if so it could be that the IC is bad or there is something that causes the voltage to drop too much.

Glad to help.

Looks like: "...or there is something that causes the voltage to drop too much..."

[ivconic]

I don't know if this will be of any help to you, I just browsed through my disk and have found this from another forum:

[ivconic]

If U3 were to burn out; then there would be no voltage on U13, at least that's what I assume.
It seems that the voltage "+EA" (8V) is under some load and therefore has a voltage drop.
Another possibility is that the U13 is a bad circuit. Because U13 should divide the voltage of U3 in half.
It's really hard to pinpoint the problem. Because everything is interconnected.
Perhaps the best method is to somehow separate the power supply part from the rest of the detector and check
what voltages it will give when there is no load.
...
Couple of questions:
Are you getting any printout on the LCD?
Can you use an oscilloscope to check if there is any receive signal on U8, pin 6?
With the coil connected, wave above the coil with some metal and watch what happens at pin 6 of U8.
The picture from your post #10 shows the TX working.
Although it is surprising that it even works with such a low voltage.
However, the LM386 can work with low voltages.
So U2 should be beyond doubt that the problem is at it.
When you feel the chips with your finger; are any of them heated?
(maybe you shouldn't keep the detector under power for too long, to aviod further damages)
...
In which software do you draw the schematic? I like the aesthetics.

[Ruben2000]

I don't know if this will be of any help to you, I just browsed through my disk and have found this from another forum:

Thank you very much Ivconic for your help!

[Ruben2000]

...
Couple of questions:
Are you getting any printout on the LCD?

As for whether it turns on the screen, it does turn on, but when I connect the sensor, the screen does not display well because the voltage drops a little, as I showed you the voltage measurements without the sensor and with the sensor.
Here I send you an image of what the screen looks like without the sensor and with the sensor on.

Can you use an oscilloscope to check if there is any receive signal on U8, pin 6?
With the coil connected, wave above the coil with some metal and watch what happens at pin 6 of U8.

I have done what you told me but I don't notice any changes because the signal is unstable and the frequency varies a lot. I also put the oscilloscope on PIN 3 of U8, there the signal is a little stable and the frequency can be read. Anyway, I'll show you the two images.

When you feel the chips with your finger; are any of them heated?
(maybe you shouldn't keep the detector under power for too long, to aviod further damages)
...

I have not found any hot or warm IC

In which software do you draw the schematic? I like the aesthetics.

I only drew it in PAINT that the same PC comes with, I only used a KT315 scheme and I only had to modify it according to my hand-drawn scheme; It was easier for me that way. I was drawing it in EasyEDA but it took me a long time and I'm just learning how to use it.