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Pic kit 2 clone vdd short when troubleshooting

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I have recently built a pic kit 2 clone and have a genuine pic kit 2 as a backup device.The circuit I used is on this website https://www.obddiag.net/prog/pickit2.pdf. After construction I found the device was recognised, by the pic kit 2 software and could communicate with the device via usb.The problems started testing the unit within the pic kit 2 software version 2.61. When testing vdd it detected a short on the vdd line and could not conduct the vpp test due to the previous vdd fault detected. As all the transistors are mosfets and majority are controlled by the pic18f2550,is the microcontroller faulty or is it a problem with the mosfets ? Getting supply to op amp and microcontroller green led lights up and amber led when supplying power to target.Only shows fault when troubleshooting in pic kit 2 software.Any ideas as I had high hopes of this actually working,unless it is something obvious I have overlooked.
 
Would suggest many problems relate build errors such as wrong part in the wrong location, wrong orientation of diodes and transistors and damaged /shorting pcb tracks; are you sure you have eliminated all of them ?

If yours is a simple diy board, suggest you run the back edge of a scalpel or similar thin blade between the tracks and component pads as that often removes any solder whiskers etc.

When getting the Vdd error, have to measured output Pin 2, do you see a voltage ? also what about across C8 , the main 5v feed when active.

What happens when you have 2.61 running (no pic chip connected to the pk2) and in 2.61 you check the VDD pk2 box on and set the voltage to 5v.
Does the Target , orange led come on and do you get +5v on the output pin 2.
If it does that ok, if you then reduce the voltage in 2.61 does output pin2 follow correctly.
 
Need to establish what else is happening with vdd at the moment .The orange led comes on when vdd is selected from pic kit2 .Will check to see what voltage is measured and see if it varies in line with the software .The voltage across c8 needs to be checked as well.
 
On further investigation voltage across c8 is constant at 3.67v . No load on output.vdd supply to op amp and microcontroller is 4.97v .Pic kit software 2.61 vdd on and set to 2.5v .amber light on .vdd measured at 3.61v does not go lower than this until voltage set to 3.5v vdd then rises to 3.7v .
Set voltage 3.6v. Vdd 3.8v
Set voltage 3.7v Vdd 3.89v
Set voltage 3.8v Vdd 4.02v
Set voltage 3.9v Vdd 4.08v

No change in vdd after set level rises until 4.9v then Amber light goes out and red led flashes . Voltage still on vdd of 3.71v and does not lower until set voltage drops to 3.5 then vdd drops to 3.24v.

Have my suspicions about microcontroller to be truthful. Mistakenly put 5v on pin 21 instead of pin 20 vdd pin.However even after this managed to reprogram hex file into chip. Also device is still recognised by pic kit 2 software and communicates via usb with computer.
 
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Turns out p channel mosfets bs250's were all in the wrong way around. Will replace and ensure correct polarity this time.
 
Still trying to get pic kit2 clone to operate as expected.vdd raises and lowers in pic kit 2 software as expected.Orange light on throughout and turns off when vdd check box used in pic kit 2 software. When troubleshooting in software ,unit passes vdd test but when vpp is tested software shows vdd short don't figure but vpp has 11.5v on it whilst vpp test is taking place.Usb voltage is slightly low and unit has been calibrated. The circuit used can be found using the following link https://www.obddiag.net/prog/pickit2.pdf. Would appreciate any help in resolving this issue. Many thanks.
 
In one of your earlier posts I gave 2 proven circuits, basically the same, but less the variable voltage ic.
If all else fails would suggest you build one of them, and then try adding the variable voltage ic later, though for 99% of the work its easy enough to run at fixed 3v3 or 5v rather than varying it.

You have those 2 diagrams plus the actual Pk2 circuit diagram in the Pk2 user guide, so its just a case of comparing them and checking the substitute components are valid.

A quick look shows that on your diagram, RB5 , the program switch is not pulled up ..?
 
Hi colin,,
please use smd version NDS356 instead of BS250for p mosfet. likewise i used si2302 in place of 2n7000 or bs170 for n mosfet. stick it and n solder side and hand wind
i had triangular pads for bs250 where i could place smd just by turning it. woks well and i am using it
the said devices have very low On resistance and work well.
all the best
 
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This gets more confusing by the minute. I appreciate the fact that other versions of this pic kit programmer, have been posted.I would like to get this one the one I have built working !! The unit has been calibrated in the pic kit software. Passes the vdd test in troubleshooting also the Pgc and Pgd high and low tests also the 30 kHz toggle tests .The vpp test fails quoting vdd short.Yet the voltage on the vpp pin stays at 12.5v throughout and the vdd drops to 650 millivolts.This is all without any load / device being connected.

When a chip is connected device cannot be read and vdd short error returns.Please can someone look at this circuit, as if there is a short I'm buggered if I can find it and why, would there still be 12.5 volts on the vpp pin and not hardly any on the vdd pin.I don't get where using different versions of the mosfets,will help my problem either.After all they will still be in the same part of the circuit and doing the same job.
 
Hi Colin,
Do you ever get a sensible voltage (About 5 volts) on the Vdd pin on the connector that goes to the pic that is to be programmed ? If so under what condition does this occur ?
What are the voltages (With respect to ground) on the gate, source and drain of Q6 and Q7 both when Vdd is correct and when it is low ? What are the settings in the software in these two cases. Post #10 is the first time you have given any indication of what tests you were running in the software. This is why I have not attempted to answer as there was no real information to try to deduce what may be happening.

Les.
 
This gets more confusing by the minute. I appreciate the fact that other versions of this pic kit programmer, have been posted.............
Perhaps the statement is confusing.
So far I am concerned, i had suggested better substitutes to BS170(2n7000) and BS250 and NOT another version. In fact i had similar issues with BS170 and Bbs250. i had to switch over to better ones.
 
Les I was hoping that the p channel mosfets, in the wrong orientation would have solved my problem.This is not the case, I will check the voltages as suggested and come back with the results. Thank you for your continued help.This does look a good circuit and at least partly works as indicated in previous posts .Falling at the last hurdle with the vpp voltage.
 
Apologies mvs Sarma.The statement about other versions of this circuit, was not referring to you more member wp100.
oh,
i did never mean seeking apologies, Collin. It is OK
I being an ardent kit builder, know what are feelings of failure after a careful assembly. i am trying to make same to be able to observe the differences and troubles.
but i need to change the board to single side.to be able to home brew the pcb.
I have through hole pickit2 (complete microchip cct, perhaps i can use same by judiciously jumpering other element and pin swapping the mosfets

PS:
please see your post 5
can you replace the MCP601 to mcp6001 dip or mcp6271.
MCP601 is rail to rail output only while other chips are in/out rail to rail and this makes the difference.
 
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Update on the pic kit 2 clone saga.when troubleshooting in pic kit 2 software v2.61, vdd test passes and vpp test fails on first attempt, quoting vdd short then proceeds to pass ,on a second vpp test attempt .What gives why would it say there's a short one minute and clear the next ?Have not tried as yet to read a device,as the last try when vdd powered from clone said no device found quoting again vdd error.
 
My crystal ball is not working. It is not showing the voltages on the pins of Q6 and Q7 when the test passes and when it fails.

Les.
 
Vdd varies with pic software until 4.6v does not get any higher than this .q6 and q7 voltages are as follows :

Vdd voltage. Q6. Source voltage. 2.22 volts ( vdd 2.5 )
2.75 volts. ( vdd 3.0 )
3.3 volts. ( vdd 3.5 )
3.83 volts ( vdd 4.0 )
4.35 volts. ( vdd 4.5 )
Gate voltage matches source voltages throughout

Q7 Gate voltage. 18.2 millivolts constant through all tests
Drain voltage 2.4 volts ( vdd 2.5 )
2.93 volts ( vdd 3.0 )
3.5 volts ( vdd 3.5 )
4.02 volts ( vdd 4.0 )
4.55 volts ( vdd 4.5 )

When vpp is tested fails and you get 11.69 volts on both source and drain of q6 with 1.81 volts on the drain of q7. When you retest vpp 2.14 volts on drain of q7 and orange led showing vdd powered from pic not lit.
 
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Hi Colin,
I think Q6 is faulty. The voltage on the gate should be about +5 volts (RB4 output) when Vdd is turned off. It should close to zero volts when Vdd is turned on. Q6 should just behave as a switch to turn on Vdd to the output pin. The level of Vdd is set by the duty cycle of the PWM signal IC2. There should be no way that any connection on Q6 should go above 5 volts. It looks like you have a short to the Vpp voltage (Possibly intermittent.)

Les.
 
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