scorrpeio said: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~ said:could you give the information about the kit? at least give the circuit and the details about it.
scorrpeio said: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 said: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
mvs sarma said: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.
mvs sarma said: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
mvs sarma said: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.
congrats!!scorrpeio said:mvs sarma said: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!!!
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