Hello,
i used the tl866cs and see problems, here i give my experience and the turnarround...
All is not not contact good pins...
I try to prog a 16F877 old PIC, and it does not work, an other not use the same but on a beeprog (1000€), all is ok.
I find the schematic of the tl and find problems.
First I see can the pulse clock send by the tl866cs,on RB6/7 to the pic are not all the same,
in 16 clock block the first and the last are very shorter than the others, with data.
If the time is correct the up time is slow. But it is software and nothing to do.
Now for enter to prog, you must apply a 13V+-0.5V on MCLR, the Vpp supply is 12.9, but with R at 5%?,
the Vpp value can change from tl866 to other.
Just after it is the limiter, and you lost supply, 0.3 by a diode, 0.1 by the Q9 and by R3 of 3 ohms.
If the voltage is 0.6V the current limiting and overcurrent go on.
But with this lost, you are under 12.5V, at MCLR on, a dip surge can be see. You can no enter in the prog mode.
To have a good supply, the soluce is to connect the feedback resistor R8 33K to D8 anode (Q9), cut on C14.
Now the supply conpensate the voltage lost of the detector of the limiter, the security is active because Q9 is outside of the feedback. I try also to put a 2,2uF/50V in // on C20.
But nothing for the prog of the PIC 16F877!.
The next is the better...
The pic 18F87J50 in your tl866 control all and must be supply at 3.3V open the tl866, see the 3.3v chip suply regulator..
But during read, prog.. you see the supply up at approx 3.6, its normal because when Q8 is off but it is not good for the life of the chip. Why up the supply?.
If you read the pic datasheet, you see that on RB6 and 7, the input use schmit trigger and the "one" is at 0.8*Vcc,4V min with 5V supply Vcc.
The 18F87J50 is supply with 3.3V, cannot give 4V, but it is more possible with 3.6V...
Now you must see shematic: the supply Vcc, with a voltmeter put the power(USB), and with a voltmeter you see Vcc on the pin.Now, select a pic, 16F877 for example, select no check device ID and do a read. The Vcc change and up (may be zero at first time when you connect). I see 5,3V.
But it is high, and the signal of 18F87J50 is too low...
Bingo it was the problem!!.
At first I solder 2 pull up on RB6 and RB7, and bingo I can read, erase and prog the PIC16F877!!.
But solder on a chip to program it is bad!!.
The soluce is to reduce the Vcc supply.
The power UP because Q5 tunr on, and put a 6K8, the soluce is to adjust the value, I put in serie a pot of 4,7K (in resistor).
Now at 0, Vcc= 5.3V (not work the same before),but at 4,7V at max (4K7) and for the middle 4,9V it is ok.
And now no problemo the prog is ok, and not a contacts problems...
I solve my problem for the PIC 16F877, for the others you can use this story to try to find why, and not to think that it is the contact...
In fact the design is not so good, but for the price....