[Jukebox-list] Selenium Rectifier

[Steve Wahl]

A bridge is simply four diodes.  

I don't have my F-120 manual available at the moment, but I found both
center tapped and four diode bridged power supply schematics on
the web:

http://ourworld.compuserve.com/homepages/g_knott/elect207.htm

http://www.wam.umd.edu/~toh/ElectroSim/FullWave.html

A bridge is four diodes in one package, with external connections at
the four "corners" where they meet, reffering to the first schematic.

If the G schematic has both diodes tied together like that second
schematic,  it looks to me like you could use half the bridge (the two
AC connections going to the transformer, and the + (?) DC output) in a
center tapped circuit.

I know using one half the transformer would also work, but I'm not
sure if you'd go over the power rating, since you're taking 100% of
the power from one side, rather than 50% from each side.  Somebody
else would probably be more qualified to comment on that.

I'd guess all three methods (replacing with two diodes, using half a
bridge, or using one half the transformer with the full bridge) would
be subject to the differences between selenium and silicon: voltage
would be slightly higher, and shorting mode of failure being more
common (requiring appropriate fusing).  

--> Steve Wahl

On Tue, May 01, 2007 at 11:29:42AM -0400, Jim Poe wrote:
> When I was working on my AMI G-200, I was going to replace the diodes in 
> the power supply with a bridge.  Got it wired up, & realized I had 60 
> volts instead of the required 30.  The transformer has center tap that 
> is 30V.  Not being that knowledgeable, I went back to 2 diodes as the 
> original design.  Is there a way to get the bridge to work in that 
> situation, where the transformer has a center tap & each side is 30V? 
> Could I only use 1 side of the transformer?
> 
> Thanks
> Jim
> 
> Jay Hennigan wrote:
> 
> >Replace CR501 in the TSU7 with a silicon bridge.  I use the MP154 for 
> >just about all selenium bridge replacements.  It's way overkill as it is 
> >capable of 15 amps at 400 volts, but easy to mount to the chassis.
> >
> >http://www.rectron.com/data_sheets/mp1505-1510.pdf
> >
> >Mouser has them for under 3 bucks.
> >
> >http://www.mouser.com/catalog/629/358.pdf
> >
> >Make sure that the line fuse is correct and not overfused.  If the new 
> >rectifier should fail shorted you want the fuse to blow rather than have 
> >the power transformer damaged.  Some people also place an extra fuse at 
> >the transformer secondary, but I generally don't find this necessary.
> 
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-- 
Steve Wahl    steve at pro-ns.net

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