AC adapter voltage for Model 100 TRS-80

[Atari-Collector]

I picked up a "6 volt 700mA" AC adapter today at the surplus store with the plan to put a new connector on it for my Model-100, of course I put it on a volt meter before doing anything, and it's running about 7.5 volts by my cheap DMV (was to lazy to get my Micronta out)

 

I was wondering if anybody knows if the Model-100 needs a strict 6 volts or is it more flexible ? I suspect it's more flexible since there's interanal voltage regulation, but would like to hear some thoughts on the matter before going any further...

 

thanks

 

 

[mykrowyre]

It would probably work, I'm sure there is a 7805 in there to regulate the 6V down to 5V as you mentioned... but it may generate extra heat.

 

I think I used a 5V supply successfully, but I can't remember, it's been awhile since I had an M100

 

Also, check the polarity, I *think* the M100 wants center pin negative, not center pin positive as with most supplies.

[Atari-Collector]

Yes, it is a center negative, why they would do that is beyond me... I'm not super worried about being at 7.5 volts, since I bet the original power supplies for these were probably just unregulated AC adapters too. But I've never seen one, I'd moved on to the Atari by the time the model 100 came about.

 

I looked the schematics of the model 100 a while back, if I recall right, it's some kind of DC to DC setup doing the regulating, since it was designed to run on alkalines, Iit would have had to be able to compensate fore the discharge curve of a battery, I found one post on another site with somebody saying they were using a 9 volt adapter, sounds like they're asking for trouble to me..