burner question

[carsten_the_dane]

I dont know what is wrong with the topic "burner question continued", personally i cannot view it. So here goes again.

I have some problems with the formulation in the documentation. Could anyone please explain these sentences to me:

"switch on Vpp - the red LED should go on. Measure the voltage at the MCLR# pin, it should be the same like adjusted before"

- Should MCLR# read 12,5 - because mine only reads about 1,4.

"Click on the "Data In" button - Data In should get the same value like selected with one of the above sData buttons."

Anyway. All readings are good, except maybe that VPP reading at mclr# which seems kinda low.

P18 says: division durch null, and does not reconize the pic. I dont have printers or scanners installed, and my cable is new.

[EDIT]: Sorry i just saw that you put my question into the other thread. I dont mean to flood the forum with my problems. it just seemed appropriate to make a new thread, since my problems had changed a lot since my original thread.

[carsten_the_dane]

I can turn the LEDs of, but it has no effect on my measurings. VDD stays on 5v and VPP goes from 1.5 to 1.88

[TK.]

I've merged it with the old topic, because it is not necessary to open new ones, this only leads to a bad oversight in the forum.

I'm currently in hurry, maybe I can think about possible problems tomorrow evening.

Or maybe somebody else can help?

Best Regards, Thorsten.

[carsten_the_dane]

Should MCLR# really be 12,5 - As far as i can see resistor R2 drops the voltage to almost nothing just before mclr#.

I have attached a schematics where i have marked the places i supposed to measure. Im pretty sure about this, but its just to be completely sure that its right. I have to affirm everything in order to troubleshoot.

[TK.]

This resistor is very important, because without T1 would connect it with ground -> short circuit (T1 would be destroyed).

Since the impedance of the MCLR# input is much higher than 1k, most voltage will drop over MCLR#->ground and not over the 1k resistor when T1 is open

When T1 is closed, nearly the full voltage will drop over the 1k resistor, and MCLR# should be ca. 0.7V

Best Regards, Thorsten.

Which voltage do you measure without T1?

[carsten_the_dane]

Ok. i will measure T1 tomorrow afternoon. My batteries are dead now, so i have to buy a new pair.

Dont forget my new problem is that turn of VDD and VPP makes no difference to the voltage.

see you tomorrow

/carsten

[carsten_the_dane]

Bought a new pair of batteries and readjusted the trimpot.

Not plugged in to computer:

J2: 12,5

MCLR#: 2.04

T1 b: 1.94

T1 C: 2.04

Plugged in:

J2: 12,5

VPP ON:

mclr#: 1.75

t1 c: 1.75

t1 b: 1.66

VPP OFF:

mclr#: 2.04

t1c: 2.04

t1 b: 1.94

VDD ON/OFF: both 5 volts.

Also, i have noticed that the red LED will turn on,a second or so after i turn it off, particularly for maybe the first minut it is plugged in. Could it be "plug n play" looking for something in the LPT1 port?

[EDIT]: I answered this myself, and found a little app called "unplug n pray" which disables universal plug and play. And although the LED problem disappeared, i cant say if plugnplay was causing the problem. Anyway, it made no difference to the voltage... unfortunately.

If i use linux (which i dont right now), would i be able to just feed the "channels" with a negative value?

From what i´ve been reading, i can understand that bc337 works like an on/off dingsbums - do you think that it is broken. Based on what i descriped in the beginning of this thread, that i had turned around on the bc337 and lm317 which caused the lm337 to burn.

[TK.]

The voltages don't look correct.

General proposal: buy 3 Transistors, 5 x 74HC14, 1 LM317 (some are indented as replacement)

1) Unmount the transistor and the 74HC14s

2) Disconnect the batteries at J1

3) Mount a new 74HC00 into the socket of IC3

4 ) connect the batteries

5) Check if the Vdd and Vpp LED can be toggled from P18

6) Check if the voltage at the cathode of D2 toggles between 5V/0V together with the red Vpp LED

7) Solder T1

8) check if MCLR# toggles between ca. 0.5V and ca. 12.5V together with the red Vpp LED

If one of these test fails - don't continue! But try to get it passing first (check soldering, check right orientation of ICs, diodes, transistor), otherwise you will fry some components again

Best Regards, Thorsten.

[carsten_the_dane]

great. thanks - i will do that asap

[carsten_the_dane]

Im back  ;D

What part of this system amplifies the voltage from the LPT.

I measure 3.3 volts directly from the LPT. and 1.38 at the cathode of D2.

the vdd and the vpp can be toggled from p18.

I was only able to find 74HCT14N - is this a problem, the dealer told me they had kinda taken over after 74hc14, which he told me wouldnt come back in his store again.

[TK.]

HC works with CMOS levels on the inputs, and HCT with TTL levels, so HC is normaly the better choice

It's strange that your dealer doesn't purchase them anymore, because HC is normaly the prefered choice - maybe it's just sold out, and he wants to get rid of the other chips before buying new ones...

However, not sure if this is the problem, because 3.3V is still within the TTL range (>2.4V for high level)

But I (and most of us) are using HC chips - so, it's a difference which could matter for any reason.

Best Regards, Thorsten.

[carsten_the_dane]

Ok, i have found a danish netshop who sells 74hc14. I should have them tomorrow. I do have a question though: As i understand the 74hc14 works as a trigger that affects the transistor. What i dont understand is how (according to your steps above) the circuit can go from 0 to 5 volts, without the batteries being connected. Without the batteries connected shouldnt it just switch between 0 and something low (like 1.38v).

Thanks, Carsten

PS: if you know where there is some documentation on the web about the mbhp_burner, could you please post a link. I have been reading about Brenner5 and picprog, but it doesnt give me much insight into whats going on in the circuit. Also i have used wikipedia as a refernce to the different components.

[TK.]

Hrmpf, this was an error in my step-by-step instructions - the battery must be connected to J1, otherwise the 7505 won't be supplied, and the logic chips would get their voltage indirectly from the LPT port, which cannot work properly.

So, I've changed my list above, could you please check this again?

If you know where there is some documentation on the web about the mbhp_burner, could you please post a link.

I haven't written such a detailed documentation where the purpose of each single component is described, I know that this could be useful, but I don't find the time for such stuff. I also don't know, where you could find more hints about such digital designs...

Best Regards, Thorsten.

[carsten_the_dane]

I just read the sticky about "keeping your noob status" - Guess i have done

everything written in that document  :-X  :-\

Anyway. I just want to say that i really appreciate your help, and i can perfectly

understand if your starting to get a little annoyed.

Now, the LEDs toogle allright, and i also get a difference in voltage which is

4,15/0. I guess thats better than nothing, but why im lagging a little under 1 volt,

i dont know.

(This was both with the new HCT and my "old" HC, since i havent bought the new ones

yet). I guess the problem was with the transistor, which i have changed now. I know

it was a little early...

So i guess todays question would be: have you experienced the "toggling" working

like this 4/0, and what could cause the circuit to not output 5v?

[TK.]

What is the output voltage of the 7805?

Best Regards, Thorsten.

[carsten_the_dane]

78L05: 5v

5v through the circuit down to IC3 #5

IC3 #5: 5v

IC3 #10: 4,85v

D2 Anode: 4,85v

D2 Cathode: 4,15v

[edit]: Did the regular tests this morning. And suddenly everything seems to work great. Lights toogle on and off, MCLR toggles between 12,5 and 0. clck and data between 5 and zero.... And vdd toggles between 5 and zero on pin 14 at IC3 and IC4.... ONLY, IT IS INVERTED. its zero when vdd is on, and 5 when its off ????

[Edit2]: Just tested on another machine which has a higher voltage from the lpt (about 4,something) - Here vdd just doesnt turn of, but keeps feeding 5v. Again, everything else works (though here "check data in" returned 0 and not 1)

So my only problem now is VDD.

/Carsten

[carsten_the_dane]

WOHOO - i have burned the PICs  ;D :D 8)

No doubt there was a problem with mclr, earlier on, but changing t1 changed that. The problem with vdd was just me. As you can see in my earlier post, where i posted an image of where i was measuring, i thought i was supposed to measure vdd at IC3 and IC4.

And now i have finally burned the pics and i am on to create more problems with the core  ;D

Just wanna say again that you have been a great help, and i really appreciate it.

/Carsten

[TK.]

...finally! :)

Best Regards, Thorsten.

[carsten_the_dane]

One final remark that you might find interesting. I burned them using the 74HCT14, if it comes up in the future.

/carsten