User Port voltage at recommended maximum
#1
Question 
Firstly, I've really enjoyed populating the board over the last few months. Been interesting (mainly on the parts ordering side), but I'm pretty close to populating with ICs...

During the voltage tests I've found the User Port voltage measurement is at the max recommended level on Page 89 at 5.25v. Other voltages are within range, it's just this one. Is this okay, or should I be looking somewhere specific for a fault/component issue?

Thanks,
Phil.
Reply
#2
The USER PORT voltage comes directly from the 5V output from the power supply. So, if you see 5.25V there then it will also appear on all of the logic ICs too. 5.25V is about the maximum you want to see. I am surprised it is this high though. What power supply are you using? Typically, the Commodore "brick" power supply outputs >5V when it is about to die! When they die the voltage can go over 20V, killing all of the chips.
Reply
#3
(04-06-2023, 10:24 AM)admin Wrote: The USER PORT voltage comes directly from the 5V output from the power supply.  So, if you see 5.25V there then it will also appear on all of the logic ICs too.  5.25V is about the maximum you want to see.  I am surprised it is this high though.  What power supply are you using?  Typically, the Commodore "brick" power supply outputs >5V when it is about to die!  When they die the voltage can go over 20V, killing all of the chips.

Thanks for the info, it's a Commodore White brick PN: 251053-12 and I've just checked and it's measuring 5.25v at the plug. The PSU came supplied with a C64C I recently purchased (incorrectly as a donor.. long story.. didn't realise it had a short board in it)

Any recommendations on an alternative PSU?

Thanks,
Phil.
Reply
#4
It could be that the voltage is floating higher than normal without a load, but personally, I would toss it.. that is a tell-tale sign it is going to die!

Any type of power supply (meant for the C64) should work fine. I really can't recommend one over another... you just want something with 5V at least 1.5A of current so it can handle extra devices like cartridge, REU, modem, EPROM burner, etc.
Reply




Users browsing this thread: 1 Guest(s)