Problem with White´s XLT

[Waka]

Hello forum

I have a problem with my XLT, when I turn on, mark on the screen 18 volts and when it happens to operation mode is very unstable, very noisy.

I changed U14 (LM 2574) and remains the same.

Any solution?

Thanks ........

[homefire]

I think it is just the way you have it set!

[ivconic]

Hello forum

I have a problem with my XLT, when I turn on, mark on the screen 18 volts and when it happens to operation mode is very unstable, very noisy.

I changed U14 (LM 2574) and remains the same.

Any solution?

Thanks ........

What 18v??? Shouldn't be the 12V?

[Waka]

18.7v to be exact.
I do not understand why, but that's what makes the test battery.

regards

[ivconic]

18.7v to be exact.
I do not understand why, but that's what makes the test battery.

regards

Strange!?
Older Spectrum is using one 4.8-6v battery and usually indicate "4.8v -6v" on LCD.
XLT is newer design, supplied by one 12v battery pack and (logically) should display "10-12v" on LCD.
There are few possibilities;
first, circuitry that measure battery voltage is corrupted (but than the rest should work fine),
second, somehow dc/dc is getting wild and rising up battery voltage more over defined level,
I don't know if this is possible, but in case it is - than 18v should destroy some components in it.
Did you measured battery with ordinary voltmeter?
We don't have schematic of XLT (we have only Spectrum schematic here), otherwise it would be easier to analyze and troubleshoot the problem.

[ivconic]

BTW, what about LT1054? Have you replaced it?

[ivconic]

Also check: C31, C32, C33, Q7 and Q10.

[ivconic]

Aha! One more thing!
I heard rumors that dc/dc (separate one) that supplies LCD backlight can go wild after longer use and kill the rest of electronics.
Not sure if this was related to Spectrum or XLT?
But in that case you should cut backlight dc/dc as soon as possible and disengage it's circuitry from the rest of electronics... if it is not to late...
(Don't panic, because is the same to you now, first check whether this rumor makes some sense or not)

[Waka]

Ivconic thank you very much for your help.

I changed C31, C32, C33 were wrong.
Q7 and Q10 are OK.
LT1054 I'm hoping to change it.

Anyone know what the mission of R3?

[kt315]

IMO, you need to find and check:
- two resistors on op amp's input
- op amp itself
- all circuit - from batt to chip's leg
i did draw by red color all way you need to go...

[Taktyk]

scheme

HI,


Here a better part of the schema presented by KT315...

Good Luck!

Taktyk

[Waka]

Thanks to all

today I will try. It will comment the results.

Anyone can tell me what function does the POT R3?

[Taktyk]

HI,

He is used to set the standard signal parameters => phase and amplitude => for preamp.

Best Regards

Taktyk

[kt315]

Anyone know what the mission of R3?

RX preamp's gain preset

[Waka]

Hello again.

I tell you that everything works perfectly. Apparently the capacitors were bad. Now the machine is very stable. I have also tapped to replace the battery with a Li-Ion 6500 mA seems that is never exhausted.


Thanks to all for the help

regards