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Model 620 Electrolytic bypass - Printable Version

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Model 620 Electrolytic bypass - David B - 01-27-2008

Newbie question. Restoring a model 620; part 52, 16 MFD electrolytic is being bypassed with new 16uf cap, I see where the components attach to the positive side of the cap but is there anywhere in particular where I should connect the negative side of the new cap, is the chase frame OK or should I use a specific ground point. Please advise, your help is greatly appreciated.

God Bless,

Dave

- rghines1 - 01-27-2008

Hi David, Chassis frame is fine. Richard

Philco 620 - David B - 01-27-2008

Richard, thank you my freind, I appreciate it, kudos to you. Icon_biggrin

God bless,

Dave

- planigan - 02-11-2008

David B, hi. You used the word "by-pass" and I got the feeling you may be placing the new cap across the old one. You can't do that as the old cap will still be in the curcuit. You have to remove all components attached to pos on old cap to a new attachment point (small terminal strip) with pos of new cap and other end of cap to chassis. PL

Filter caps do NOT go to ground - AI2V - 02-11-2008

The filter caps do NOT go to ground. They go from B+ to the top of the large (usually overheated looking) rectifier B- resistors (#70 on schematic). Download your schematic and parts locator from NostalgiaAir.com

Sometimes it helps the radio by connecting an extra 10uuf from B+ to ground, but first the raw filter caps, the ones connected directly to the cathode of the 80, must be replaced.

As mentioned in the other post, you MUST disconnect at least one side of each of the old filter caps. Most restorers do the one-lead disconnect so that the original cap can be left in place for appearances. Leaving both sides connected leads to disaster- and lots of hum.

- planigan - 02-11-2008

Dave AI2V is correct, the negs go to B- not chassis ground. Usually the clue is that the cap can is isolated from the chassis either by a non-metallic mounting wafer (twist on cans) or a cardboad or paper insulating tube around the can (clamp type). Manufacturers would not go through the added expense of isolating the cap only to wire it back to chassis. PL