Dragon's Lair Fans - Arcade Lifestyle

General Chat => Technical Area => Topic started by: baritonomarchetto on April 23, 2011, 10:30:58 AM

Title: Punchout!! owners warning and a little question
Post by: baritonomarchetto on April 23, 2011, 10:30:58 AM

Hi dudes,

[WARNING MODE ON]
on KLOV forum i read about a problem on Punchout original switching PSUs (PP-1000A): there's a capacitor (C8, 47uF 35V) that when fails lets voltages higher than 5V going to the PCB. The failure damages the board!! For future reference, it's recommended to use a 100uF 35V in place of that 47uF
[WARNING MODE OFF]

Now the question: i recapped my PP-1000A and turned the pots (there are 2: VR1 and VR2): turning VR1 gave apparently no effects to the voltages, turning VR2 instead i could tune the 5V output... the problem is that i don't remember the starting position of VR1!! Reading the schematics VR1 is reported as "I adj", but i don't really know what it controls (which current) and how to turn it to the right position...

here is the schematic

(http://img855.imageshack.us/img855/6125/pp1000aschematics.png)

any help?

Title: Re: Punchout!! owners warning and a little question
Post by: italiandoh on April 23, 2011, 12:21:09 PM

The circuit around VR1 to me looks like a protection guard against overcurrent consumption. There's a photocoupler watching the +5 V output line, so I assume that IC1 will shut down the power supply if too much current is flowing in the +5 V output line. The current adjustment is probably the maximum current tolerated by that guard circuit. Anyway that's my guess after looking at that circuit for a minute, maybe someone else who is a power supply expert can confirm or correct me.
Bye,

Matteo