Surf PI Burnout help!

[Metalmatt]

4.98v
The battery is putting out 11.48v

[Qiaozhi]

4.98v
The battery is putting out 11.48v

The 78L05 must be ok then.

[Metalmatt]

So your thinking the ICL555? or the ICL76605? Is there a way to test?

[Koala]

what about the voltage on pin 5 of the 7660 ?

[Carl-NC]

The output of the 7660 should be ~ -5V (pin 5).
The output of the 555 (pin 3) should be a 600Hz pulse train. Do you have an oscope? If you hear a threshold hum in the speaker then likely the 555 is working. I would then look at the coil FET, it would have seen the entire reverse battery voltage.

[Koala]

How's was the minus volts ?

[Metalmatt]

Hi Koala and Carl
Im not getting any reading on pin 5. (Neg to pin 3 positive to pin 5?)
I dont have a scope and i have checked the fet and thats seems kaput.
On the 555 6.38.

Thanks guys for all your help

[Koala]

Sounds strange. But finding incorrect voltage is progress in the correct direction.


take it you have a diode function on your multi meter and the FET is measuring a dead short. If so it should be cut out.


After a quick check for bulging or leaking and shorts of the three large capacitors I would lift the 7660 out of its socket, bend pin 5 out slightly so it will miss the socket when you reinsert the IC the test for minus volts again

[Metalmatt]

Ive replaced the 1N diode and the 78L05. Ive taken the FET out and thats def Kaput. Ill chase this up again tommorow hopefully ill have a new FET on the doormat.
Thanks for your help guys

[dbanner]

Test the circuit without the fet and 7660 installed, those parts are not to be risked damaging willy nilly. Make sure the circuit exhibits proper behavior (ie no magic smoke and the B+ and +5volt are present. Once the circuit seems fine, then you can install the 7660 first and check that the negative rail is up and running. Lastly, install the mosfet into the circuit.

[Metalmatt]

Hi All.
I got to thank all the folk that have helped me out on my dilemma, purchased 3 components which were advised and now all is well.
To which component had fried...Def the fet, but replaced TLC555 IRF9640 and 1N4001.

Thanks to everyone for their time and advice. Ive included a few pics of the finished project.

Carl-NC
Xtrem
Waltr
Quozhi
6666
Koala
dbanner
and most of all Marty

[WM6]

Quozhi

Not easy those Chinese script, I need always to check it again.

Otherwise great outcome. Congratulation and happy searching.

[Koala]

looks Good

happy hunting.

[waltr]

Great it is now fixed. Build looks very nice.

[kt315]

Not easy those Chinese script, I need always to check it again.

Otherwise great outcome. Congratulation and happy searching.

yup. mandarine is hard. i have to use his manradine in the logo... but not able to find (((
OOPS! this 'george'. 乔治