MBHP Core not working correctly

Testing/Troubleshooting
1

Yo

I finished building my Core today and I just came to testing it and i’m getting very strange results!  I tested with Pin 1 being positive (+ve) and negative (-ve) and recorded the following results:

Pin 1 - +ve

IC1:MCLR(1) - IC1:Vss(12) = 9V

IC1:Vdd(11) - IC1:Vss(12) = 9V

IC1:Vdd(32) - IC1:Vss(31) = 9V

IC2(8) - IC2:(5) = 9V

Pin 1 - -ve

IC1:MCLR(1) - IC1:Vss(12) = 1.5-1.6V

IC1:Vdd(11) - IC1:Vss(12) = 1.5-1.6V

IC1:Vdd(32) - IC1:Vss(31) = 1.5-1.6V

IC2(8) - IC2:(5) = 1.5-1.6V

Now, I did use a couple of different parts which could explain the strange results.  

These are the different components i used (same values but different types.. don’t know if it makes a difference)

C4 - 100nF Resin-Dipped Ceramic Capacitor

C6 - 330nF Resin-Dipped Ceramic Capacitor

X1 - W005 bridge rectifier*

The spec of the W005 bridge rectifier is :

Part - W005,

PIV- 50V

Ifav. - 1.5A

Max RMS- 35V

Max cap- 5000µF

Max Vf per diode- 1.1V/1A

I was going to use 4 1N4001’s but i was unsure of how to solder them.  I posted an idea of how to connect them, but no-one could tell me if it was right! See-

http://www.midibox.org/cgi-bin/yabb/YaBB.cgi?board=parts_q;action=display;num=1058810967

Also the 7805 got extremely hot quickly.

I’ve checked my soldering, and checked the positions of the parts (and polarity) and that’s all fine.

Any suggestions!?  

2

Do you have a short somewhere ?

3

I’m not sure.

I don’t know how to test for that  :-/

One more part i forgot to mention was my crystal - it is a 10 mhz, but doesnt look like my 20 mhz one its about a quarter of the size. Damn Farnell and their too much choice! (my crystal is Farnell order code: 485-081)

My crystal looks like the one on the left <–

Well I could say I’m dissapointed that my core doesn’t work, but as it’s the second time i’ve built it, i’m just glad the voltage is running through it!!  ::slight_smile:

4

9V is quite a bit… you shoud check the voltage regulator, is it a 7805 ?

Make sure your crystal is a parallel cut, mine is a series and my core doesn’t work because of that.

5

Thanks for the advice nat.

Yes its definately a 7805 “L7805ACV” to be precise :slight_smile:

Not sure if my crystal is serial or parrallel cut (just pouring throught the datasheet now).  But would this have any effect on the voltage?

I think the voltage difference must be due the the bridge rectifier, so i’ll see if i can find the proper one in farnell somewhere, which could take a few hours.. :cry:

Thanks for your suggestions tho nat..

6

I also doubt that the crystal could have an impact on the voltage, my crystal is the wrong cut but my voltage is at 5v..

Good luck!

7

Ok so i dropped the voltage from 9 volts in my first experiment, to 7.5 volts.  These are my results:

+ve

IC1:MCLR(1) - IC1:Vss(12) = 7V

IC1:Vdd(11) - IC1:Vss(12) = 7V

IC1:Vdd(32) - IC1:Vss(31) = 7V

IC2(8) - IC2:(5) = 7V

-ve

IC1:MCLR(1) - IC1:Vss(12) = 2.5-3V

IC1:Vdd(11) - IC1:Vss(12) = 2.5-3V

IC1:Vdd(32) - IC1:Vss(31) = 2.5-3V

IC2(8) - IC2:(5) = 2.5-3V

:-/

At 6v i get 6v for +ve, 2.5-3v again for -ve.

I’m starting to think this is something to do with my 7805.  

My power supply is capable of 1.2A i think so i’m guessing thats whats being sent into the circuit, which would explain the heat being generated by the 7805 so i dont know if thats got anything to do with it.  ???

I’m stumped..

8

did you try with a less powerful supply ?

9

I haven’t got another one  ::slight_smile:

:EDIT: Hmm. .i tried my soundcard supply (9v) and that yielded the same results but thats rated at 1amp as well.

The thing that confuses me is the fact that mains polarity is meant to be unimportant, yet i get 2 different sets of results depeding on if i use + or -.  hmmm  ???

10

you don’t have a wireless phone or something like that ?

11

Everything I have is either wrong voltage or more than 1amp!  >:(

Right well theres nothing more that i can do tonight.. i’m gonna sleep and hopefully it’ll have fixed itself by morning!  ;D

12

Good luck :slight_smile:

13

HI

NOTHING WRONG WITH THE W005 I’VE GOT ONE ON MY CORE WORKING FINE  ;)

THE PROBLEM IS THE C4 CAP IT SHOULD BE AN ELECTROLIC

SEE SMASH’S SITE FOR PIC

http://avi.dezines.com/mbhp/mbhp_core.htm

TRY THAT FIRST IF STILL GOT PROBLEMS GET A NEW

7805

14

Ok i’ll try that :slight_smile:

Thanks!

15

well, the current the PSU can drawn is not important! i mean that it just has to be able to draw enough current for the core, but it can be higher (you can 40000000A if you want!).

mayb very stupid but : are you sure you use the good connector for your supply (on J1 and not j2??)? because is when you use 9V you get 9V where you are supposed to get 5V, and 7.5V when you poser it with 7.5… it seems that the 7805 is bypass!!! no short with the in and the out of the 7805? (maybe hard because there’s the ground in middle)…

the best solution is to plug a transfomer directly to the core (on J1)

16

THE PROBLEM IS THE C4 CAP IT SHOULD BE AN ELECTROLIC

Ok, but arent Electolytic Cap’s polarised? I dont want polarised do i? Worth a try though isn’t it :wink:

well, the current the PSU can drawn is not important! i mean that it just has to be able to draw enough current for the core, but it can be higher (you can 40000000A if you want!).

Ahh I understand!

are you sure you use the good connector for your supply (on J1 and not j2??)?

Oh shoot! i just checked and i was using J2!!!  HAHAHA! I thought that was J1 (the one next to the 7805)… well that would explain my problems. ::).  I’m such a retard. heh

Right i’m off to go solder it properly!

Thanks for your help everyone!  :-*

17

Yes that works  ;D

Yet another time when i should have read the instructions slowly  :-/

THANK YOU ALL!

18

great!!!

we all make stupid error! and I do this very very often!!!

(I spent 3hours last night on one of these ;))

19

Hey Pulsewidth-

I believe that xstal is a series cut, I had one similar to that before that didn’t work.

20

Same problem here, I have series and it doesn’t work.

Sephult, with the wrong crystal, did it output anything ?