Mbhp burner VDD testing problem

[MunterMania]

Hello I have assembled and am testing my first mbhp burner module. Everything went fine until testing the vdd pin voltages. The yellow light flashes on and off when I toggle vdd in the p18_18 software but there is no voltage change in the pins. I have noticed that the when testing the vdd pin on the ceramic capacitor line with the vss pin on the opposite side of the socket there is an exact change from 5 to 0 volts. Please can someone advise me what I am doing wrong. Many thanks.

[TK.]

Seems to be related to a bad solder joint? I guess that you can measure the right voltage at IC3, pin 12, right? Now follow the track with your multimeter to pin 11 and 32 of the PIC, and check where the voltage isn't available anymore.

Best Regards, Thorsten.

[MunterMania]

Hi I tested ic3 pin 12 and there is no voltage. I tested pin 13, also no voltage. i tested the vdd pin and ground and got just under 5v.I tested the nearest pin on the capacitor to vdd and got just under 5v. I swapped both SN74HC14N's and still got the same result. Does this mean there is something wrong with my soldering at pins 12-13? what should I do to progress?

 

Many thanks.

 

 

[TK.]

I've to doublecheck: you wrote that the Vdd LED can be switched on/off from the P18 software.

This LED gets it's logic status (on/off) from pin 12

But now you are writing that there is no voltage, neither at pin 12 nor at 13

So: what changed meanwhile?

Best Regards, Thorsten.

[MunterMania]

Hi Thorsten I feel I should mention that I am very new to electronics, I have only been doing this for 3 weeks, before that I knew not very much. I apologise that I got pin 13 & 11 mixed up. Yes there is a voltage at pin 13. I am also worried that the SN74HC14N's are damaged as I connected an incorrect voltage battery at first and blew the capacitor at vdd pin 32 which I have since replaced (I have tested every component as directed by online tutorials with the multimeter and that was the only component that showed an open-line reading.) Should the in/out pins of the SN74HC14N's as described at http://www.farnell.com/datasheets/1882348.pdf show some resistance when disconnected from the pcb and connected to multimeter leads as when testing a wire or fuse? at the moment I am getting open circuit between vcc and gnd and also between pin 13 and 12 on the SN74HC14N with the multimeter. Also some of my 1st time soldering was nervous and I didn't do a good job of the ground pins on the parallel cable and one of the ceramic capacitors on the vdd pin on ic3, I think I should re-solder them, could this be affecting anything?Many thanks.

[TK.]

Unfortunately you won't be able to detect a defect in the 74HC14 with an ohmmeter.

The 74HC14 is an inverter chip, if input 6A is at logic-0 level (around 0V), 6Y should be logic-1 (around 5V) and vice versa. If this isn't the case, lift 6Y (pin 12) - means, put this pin out of the socket - and measure again. If you still don't notice the inverting function, then the chip is defective and needs to be replaced.

Of course, overvoltage or wrong polarity could destroy this chip very quickly.

The MBHP_BURNER project is maybe not the best one for beginners. Actually today (10 years later) I would recommend to buy a cheap PICkit2 (clone) at Ebay instead. See also http://www.ucapps.de/mios_bootstrap_experts.html

So - if you are not able to get MBHP_BURNER running, consider to buy a PICkit2 at Ebay, it will be less troublesome.

Best Regards, Thorsten.