RE: Sega G-80 PSU - Audio Amp

The problem with linears is that you're limit to the Pd of the BJT in the circuit. That BJT leads to a lot of wasted heat in the system.
Having said that; I like them too... for less than 1A of draw.
 
I'm going to not be discouraged and continue the project... so so we are clear; I'm replacing the linear regulator w/ a switcher on both the 5v and 12V rails.
The Transformer and diode bidges will remain. My intent it to have the board somewhat drop in place of the existing board.
I say somewhat; because the power-MOSFETs will need to be bolted to the existing heat sink on both switchers. I'll proably keep the linears for the negative rails.
 
I imagine one will have to drill and tap the existing heatsink with some new mounting holes for the mosfets.
 
When I have it done; I'll post the schematics and the boards online for review.
 
However, my original question hasn't been answered - does anyone know what the audio amp specs are?
Or am I going to have to spice the circuit to get a ballpark?
John

From: andy@andysarcade.net
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Sega G-80 PSU - Audio Amp
Date: Fri, 4 Mar 2011 19:55:12 +0000

just adding my 'me too' here...
 
I much prefer repairing linears.. its what games were designed with, and often do include things like POR circuits, isolated audio power supplies, custom sound amps, battery backup voltages. All of which neatly fit and work in the cabinets that we restore everything else on, why slack off here? just cos power supplies aren't glamourous, doesn't mean they should be neglected, but i _know_ most people do neglect them because of the percieved toughness of testing and repairing on your bench.
 
In essence, i think the reluctance for anyone to rebuild/test an old linear is that the input voltages to linear supplies vary on so many games, you can't make a 'universal' linear PSU test rig. I actually have 3 or 4 transformer rigs taken from scrapped cabients that i use to fix several common models of linear supplies that i come across, and have built a switchable dummy load for load testing of each one. It does take a lot of time and affort to built transformer rigs up so that you can test linears on a bench properly. But when you do, they're dead easy and cheap to fix!
 
Phooey to switchers i say.
 
:-)
 

--
Andrew Welburn
http://www.andys-arcade.com
----- Original Message ----- 
From: SVerlander@aol.com 
To: vectorlist@vectorlist.org 
Sent: Friday, March 04, 2011 6:54 AM
Subject: Re: VECTOR: Sega G-80 PSU - Audio Amp 
I never under stood why people think a switcher is better than a linear power supply. 
I guess I just like to keep a classic original and not hack up the wiring harness. I have 3 star trek games and have never had a problem from the power supply's. I have seen a few that had problems with the inline pins having bad contacts and burning up but just replace the pins and plugs and their good as new.
It can and has been done so good luck.
 
In a message dated 3/4/2011 1:29:25 A.M. Eastern Standard Time, zittware@hotmail.com writes:
  		 	   		  
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