micro controller Kit problem

[scorrpeio]

transistors c557b

Hi...

I am using prolific 89V51RD2 kit.
By mistake I gave the 12v to the controller...which made overload to the variable power supply.

Since then even if I give the 12V from the power supply...the kit takes only 6 to 7v.

I took out all the ics on the kit but there is no change in the situation.

Have anybody faced the same problem??

Please tell me if you can have the solution to this.

 

[~E3016~]

c557b pin

Hi...

I am using prolific 89V51RD2 kit.
By mistake I gave the 12v to the controller...which made overload to the variable power supply.

Since then even if I give the 12V from the power supply...the kit takes only 6 to 7v.

I took out all the ics on the kit but there is no change in the situation.

Have anybody faced the same problem??

Please tell me if you can have the solution to this.

could you give the information about the kit? at least give the circuit and the details about it.

 

[scorrpeio]

could you give the information about the kit? at least give the circuit and the details about it.

Thank you for the reply....I am sending the circuit diagram as an attachment with this post...

Please check it out

 

[mvs sarma]

where actually you gave 12V as input? . the variable supply could well tolerate 12V as input. what is the expected input and what is the regulator used at U7 ( perhaps LM317as per the pin details). 12V input is nothing for it.

as per the user manual, what was the output expected at CON11.
Perhaps if needed you can try to set it back by adjusting the pot2 over there

in case you have connected 12V at Vcc pin of pot1, nothing much damage happens to the LCD display. by readjusting the pot1 to get around 0.75V at the pin3 of LCD, the display should work.
I know that many a time the Rs232 chip (U1 in your case ) fails and we used replace it
in many equipments. please try out.
hope this info, helps you
Sarma

 

[scorrpeio]

Actually, I gave 12V at the CON12, where expected vtg is 5V. This CON12 is directly connected to the VCC of controller.

At the same time I gave 12V to the MAX 232 external patch(the 232 section of the kit not working)

So, the supply got overloaded as suddenly the vtg on it reduced from 12 to 5V & remained 5v even if tried to increase it.

 

[mvs sarma]

Actually, I gave 12V at the CON12, where expected vtg is 5V. This CON12 is directly connected to the VCC of controller.

At the same time I gave 12V to the MAX 232 external patch(the 232 section of the kit not working)

So, the supply got overloaded as suddenly the vtg on it reduced from 12 to 5V & remained 5v even if tried to increase it.

this connector once it gets 12V , it would supply across all Vcc points. while you are writing reply i added a sentence in my post . I repeat it here for you.

I know that many a time the Rs232 chip (U1 in your case ) fails and we used replace it

this is most probable. i only hope that the main chip would not have failed due to 12V at Vcc.

try to check and replace U1.
Sarma

 

[scorrpeio]

where actually you gave 12V as input? . the variable supply could well tolerate 12V as input. what is the expected input and what is the regulator used at U7 ( perhaps LM317as per the pin details). 12V input is nothing for it.

as per the user manual, what was the output expected at CON11.
Perhaps if needed you can try to set it back by adjusting the pot2 over there

in case you have connected 12V at Vcc pin of pot1, nothing much damage happens to the LCD display. by readjusting the pot1 to get around 0.75V at the pin3 of LCD, the display should work.
I know that many a time the Rs232 chip (U1 in your case ) fails and we used replace it
in many equipments. please try out.
hope this info, helps you
Sarma

Sir, I think the problem is with transistor Q1( C557B - PNP transistor ). I dont have much experience but when I check the vtg at the this transistor I get this....

emitter - 0 wrt GND
collector - 5V wrt GND
base - 5V wrt GND .....but when vtg is checked at base, the multimeter start whistling.

So, I thought it is the problem in Kit with transistor

 

[mvs sarma]

it is simple to check
check J4 inputs. and see whether the gate is functioning as expected.
if base and emitter are at 5V, the buzzer is off.
try connecting ga 10k resistor to ground from base the buzzer should come up
if not , take a DMM in diode range and check for shorts between base emitter or base collector junction.
To my understanding a transistor would not fail for 12V instead of 5V

BTW what are these J4 gates, are they SMD version single gate chips?

(the 232 section of the kit not working)

this is direct indication and i suggest that you replace the U1 chip
perhaps a MAX232.

 

[scorrpeio]

it is simple to check
check J4 inputs. and see whether the gate is functioning as expected.
if base and emitter are at 5V, the buzzer is off.
try connecting ga 10k resistor to ground from base the buzzer should come up
if not , take a DMM in diode range and check for shorts between base emitter or base collector junction.
To my understanding a transistor would not fail for 12V instead of 5V

BTW what are these J4 gates, are they SMD version single gate chips?

(the 232 section of the kit not working)

this is direct indication and i suggest that you replace the U1 chip
perhaps a MAX232.

Sir, J4 is not a gate. It is jumper connection with pins 1 & 2 short.

I made ground base of PNP using resistor of 10K. The buzzer played with very low sound & power supply started loading.
Please tell What should be the next step of testing???

 

[mvs sarma]

try to remove the jumper and connect the R2 to ground
i feel that the resistor that we used is higher. so we try using the designed value
.if it is still low, you can replace the buzzer not the transistor. i feel Q1 is doing its job.
BTW, why not replace MX232 and try for main finction of inter-connectivity instead of worryinmg for a small issue like Buzzer.
Sarma

 

[scorrpeio]

try to remove the jumper and connect the R2 to ground
i feel that the resistor that we used is higher. so we try using the designed value
.if it is still low, you can replace the buzzer not the transistor. i feel Q1 is doing its job.
BTW, why not replace MX232 and try for main finction of inter-connectivity instead of worryinmg for a small issue like Buzzer.
Sarma

Sir, The RS232 section which is on board has some problem so max232 IC is already removed from the board.
In fact all the ics are removed from the board......under this condition when we power the board using the regulated variable power supply...it takes the power 12V for a minute & then automatically the power supply gets overloaded....
I think there is problem with capacitor, as transistor is working fine. Or what do you say???

 

[mvs sarma]

yes
you imagination is correct
the electrolytic caps around the Rs232 and other places if working voltage is below or around 12V would be culprit
but this can be seem by finger touch-- i mean thermal sense
. and replace doubtful one.
Transistors , i don't suspect.

 

[scorrpeio]

yes
you imagination is correct
the electrolytic caps around the Rs232 and other places if working voltage is below or around 12V would be culprit
but this can be seem by finger touch-- i mean thermal sense
. and replace doubtful one.
Transistors , i don't suspect.

The power supply overloading issue resolved.......perpetrator was tentaculum decoupling capacitor
Any ways thank you for the help!!!

 

[mvs sarma]

yes
you imagination is correct
the electrolytic caps around the Rs232 and other places if working voltage is below or around 12V would be culprit
but this can be seem by finger touch-- i mean thermal sense
. and replace doubtful one.
Transistors , i don't suspect.

The power supply overloading issue resolved.......perpetrator was tentaculum decoupling capacitor
Any ways thank you for the help!!!

congrats!!