Seeburg MRA5-L6 Cap Question

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rvalkenburg
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Seeburg MRA5-L6 Cap Question

by rvalkenburg » Fri Oct 03, 2014 4:58 am

I am not sure if anyone is familiar with the Cap kits from Victory Glass but...

I purchased a cap kit for my Seeburg MRA5-L6 Amp from Victory Glass and have installed all but 4 caps on the Amp.

The Can Condenser C3, I have questions about as everything else was a one to one replacement, C3 has 4 new capacitors in the kit.
2 - 22uf 450v capacitors (black) C-3b & c
1 - 47uf 450v capacitor (black) C-3d
1 - 10uf 450v capacitor (blue) C-3a

How should these be installed to replace the original C3?
Does one cap connect to each one of the 4 leads coming into the original C3 and then to ground? If so, since they are different capacitors in the kit what is the distinguishing factor as to what cap goes where?
Is only one cap from the kit used to replace C3?

I have sent Victory Glass an email prior to me posting here... looking for any help to finish this amp.
Thank you for your help.
Ron Valkenburg

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MattTech
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Re: Seeburg MRA5-L6 Cap Question

by MattTech » Fri Oct 03, 2014 6:47 am

Usually, the schematic shows which value is wired to what area.
And usually, the terminal symbols of the original denote the values marked on the can body.
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Rob-NYC
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Re: Seeburg MRA5-L6 Cap Question

by Rob-NYC » Fri Oct 03, 2014 9:49 am

Ron, this is difficult to describe w/out giving connected component values.

All multi-section electrolytic caps have a legend stamped-printed on their can. You will see a dome (half circle) a square, a triangle and possibly a terminal with no symbol right next to the values they represent. On the can bottom those same shapes will appear right next to the actual terminals.

So, if you see on the can that a triangle represents the 20uF section of that cap, when replacing it you look for that terminal symbol at the terminals and remove the existing connections to it and connect them to the new cap. While doing this work, you should also check the values of any resistors that connect between the sections.

The common terminals (negative side) from each cap should be kept as close to the original connection point as practical, but the most important point is that they have a solid electrical connection to chassis ground.

Rob
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MattTech
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Re: Seeburg MRA5-L6 Cap Question

by MattTech » Sat Oct 04, 2014 1:27 am

Rob-NYC wrote:The common terminals (negative side) from each cap should be kept as close to the original connection point as practical, but the most important point is that they have a solid electrical connection to chassis ground.

Rob


That would be "common ground" - not particularly chassis ground, since in some cases the negative is isolated by a fiber wafer for biasing or voltage-doubling considerations.
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Ron Rich
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Re: Seeburg MRA5-L6 Cap Question

by Ron Rich » Sat Oct 04, 2014 1:48 am

Hi Matt,
On the MRA-5's, they ran a common, buss bar, ground, to the chassis. I have never had any problems hooking to the buss bar-- Ron Rich

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MattTech
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Re: Seeburg MRA5-L6 Cap Question

by MattTech » Sat Oct 04, 2014 3:03 am

Ron Rich wrote:Hi Matt,
On the MRA-5's, they ran a common, buss bar, ground, to the chassis. I have never had any problems hooking to the buss bar-- Ron Rich


So noted, Ron.
But my statement was directed in the broad general sense, concerning electronics.
Thus the "in some cases" mention.
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Rob-NYC
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Re: Seeburg MRA5-L6 Cap Question

by Rob-NYC » Sat Oct 04, 2014 4:12 am

So noted, Ron.
But my statement was directed in the broad general sense, concerning electronics.
Thus the "in some cases"


Matt, the only slightly exotic stuff was in the Tormat era selection receivers. These had hi-ground and some floating neut's. the amps were all pretty textbook AB-1 w/cathode bias in the mono amps and fixed bias in the stereo 6973 based designs. There was the issue of AGC for gain leveling, but it is classic single-ended reactance tube feedback loop.

If you want to peruse a few schematics, Vern Tisdale's site has them: http://www.verntisdale.com/Seeburgschem.htm

Rob
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