Testing core_r4c voltages

[thejunkyardcatalyst]

Hi.

help.

I'm trying to isolate voltages on the core_r4c.

I got the core_r4c to work with a 9volt battery but wasn't successful with the Commodore 64 power supply. I concluded that it had to be the regulator or caps. The reason I say that is because they will pass a DC voltage but will change an AC voltage. So the 9v battery worked and I was able to load the PIC etc.

I want to use the power supply. So I have been trying to get the power supply to work with the core.

I figured I would try to replace each component starting from J1 to the bridge to the caps etc and trace the voltage.

Heres my problem I get voltages all over the place. I have the bridge and the 2200uF cap connected to J1, but thats it. The voltage should be isolated but I get voltages other places. Midi In, Midi Out, c3, pin 1 on the PIC, P1, P2, C8, etc.

What is the signal path? How can I isolate the voltage off of J1?

Make me sane again.

Thanks

Karl

[smashtv]

I got the core_r4c to work with a 9volt battery but wasn't successful with the Commodore 64 power supply. I concluded that it had to be the regulator or caps. The reason I say that is because they will pass a DC voltage but will change an AC voltage. So the 9v battery worked and I was able to load the PIC etc.

Changing an AC voltage is what these are supposed to do......Did you forget some info about how you reached this conclusion instead of suspecting the supply?  Are you sure the power supply functions correctly under a load?

I figured I would try to replace each component starting from J1 to the bridge to the caps etc and trace the voltage.

cool, but understand that some places here will have AC, some DC if fed from an AC source.  The operation of the power supply section of the core is well documented here in the forum, search is your friend....

Heres my problem I get voltages all over the place. I have the bridge and the 2200uF cap connected to J1, but thats it. The voltage should be isolated but I get voltages other places. Midi In, Midi Out, c3, pin 1 on the PIC, P1, P2, C8, etc.

Without a clear explanation of what you have done, there is no way we can chase this failure mode....Is the regulator in place?  are your electrolytic caps and bridge installed correctly?  Specific explanations breed specific help. 

What is the signal path? How can I isolate the voltage off of J1?

http://www.ucapps.de/mbhp/mbhp_core.pdf same as it ever was.....same as it ever was.....  ;)

Best

Smash

[thejunkyardcatalyst]

Thanks for the response.

>Changing an AC voltage is what these are supposed to do......

I know. Thats why I suspected that the bridge, caps and voltage regulator weren't working correctly. So I used a 9V battery. The flow would only go thru 2 of the diodes, skip the caps, go thru the regulator and drop to 5V. And thats what it did.

>Did you forget some info about how you reached this conclusion instead of suspecting the supply?  Are you sure the power supply functions correctly under a load?

Haven't tested it with a load yet...The voltages are correct though. I did test it with a multimeter. 

What has got me completely baffled is that starting with J1, I have the 2 pin headers connected to the power supply 9v and ground. I have the bridge connected. I have the 2200uF cap connected. I've disconnected c6, the BC337 transistor and the Voltage regulator. Looking at the circuit board I can't see anywhere for the current to flow other than from j1, and 2200uF cap. How the heck is current flowing passed those components whether it is AC or DC??????

j2 is connected to ground via the voltage regulator, BC337 is removed so current can't flow that way. c6 is removed so current shorts there, etc.  uhg.

Thanks again.

[thejunkyardcatalyst]

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

yeah it was the power supply. can we curse on this forum @#$^#$%#^$#.

i hooked up a different 9v ac wall wart and lownbehold 5v dc.

i'm still curious about the current flow though.

serious thanks for the time and help.

peace

[smashtv]

i'm still curious about the current flow though.

hehe your not the only one....Consider this chump stumped....  ???

By any chance.....did you have any MIDI cables plugged in (or any other core connections besides power in)?  I ask because its possible to backfeed power and ground from the MIDI OUT connection via R8.....

If no other connections I'll build up a set here exactly like yours and get the answer we seek.  :)

Best

Smash

[thejunkyardcatalyst]

UG! I'm getting -5V!!!!!

[thejunkyardcatalyst]

How the heck am I ending up with -5V for my test voltages? Everything seems to be connected correctly.

thanks

[smashtv]

How the heck am I ending up with -5V for my test voltages? Everything seems to be connected correctly.

thanks

If your using AC to power the core the only way to possibly get -5vdc readings is to swap your meter leads.

If DC in your ground/+5vdc are swapped, or you are connected to a -5vdc supply.

There is no possible wrong placement of parts in the core's power section that will generate a negative voltage from a positive DC supply voltage or an AC supply voltage.....You would have to substitute a 7905 (or other negative regulator) for the 7805 to make that even remotely possible.

Best

Smash