Thrift store find

[Tom Bavis]

Originally posted by faustian bargin
understood.

listened to it a few minutes here at the end of the day...lots of hum, but it still works.

So you'll need to replace the electrolytic can with a few separate caps. And the selenium rectifier with a silicon one, I hope...

[dhaen]

Originally posted by Tom Bavis

So you'll need to replace the electrolytic can with a few separate caps. And the selenium rectifier with a silicon one, I hope...

When replacing a selinium rectifier with a silicon one, the series resistor value needs to be adjusted. Unless it smells, leave the selinium rec in place as a solder point, with just one end disconnected.
If you need to repace the main smoothing "can", you can hollow-out the old one, and fit individual replacement caps inside.

The hum from these AC/DC sets is typically higher than we'd expect now days, so don't expect too much.

Please heed Tom's earlier warning about the live speaker connections.

Cheers,

[jackinnj]

Originally posted by dhaen


If you need to repace the main smoothing "can", you can hollow-out the old one, and fit individual replacement caps inside.

Mallory has a line of high voltage electrolytic caps which are "mini" in size -- these would fit within a hollowed out container. Wonder why I never thought of that?

Jack

[dhaen]

Hi Jack,

modern caps are so much smaller that often there's room for regular types.

cheers,

[faustian bargin]

thanks for the great suggestions

yes, adding a headphone out is no longer a consideration, until i'm ready to figure out the isolation transformer.

so...the smoothing cap: in the schematic, is it the 3-lead one? labeled C38A, B, & C, at 40, 60, and 80 microF's respectively. can i use 3 separate caps, or do i need to use a triple lead to replace it?

also, the specs say the resistors are typically 10% tolerance carbon, and the caps are typically 20%...should i attempt to use components that more closely match the designed values? there are actually some resistors that are called out at 20% - why was that? were they less critical and therefore cheaper?

[jackinnj]

Originally posted by dhaen
Hi Jack,

modern caps are so much smaller that often there's room for regular types.

cheers,

I use a pair of 180uF / 450 V Mallory's (the chubby guys in the back( in the refashioned Fairchild 255 power supply -- it fits within the chasis, not on top:

[faustian bargin]

i found a neat 'tips' page for beginners like me. it's a commercial site so no flames, but the info is good. they sell capacitors, schematics, etc....they will even assemble a 'capacitor kit' for a particular make/model of radio. (no i'm not associated with them, i just thought it was an interesting service.)

Just Radios - capacitor tips

one tip/warning i didn't realize: if your radio hums, it's best not to let it play until you've replaced the filter caps, as that can be hard on the tubes.

also i learned the 'multisection' filter caps were originally used to save space and cost.

[faustian bargin]

ok, so i have on order some capacitors to re-cap the radio. good job, me.

now, i'm wondering if someone can clue me in on replacing the rectifier/resistor combo. i don't know how to go about determining which silicon rectifier replacement i need. there aren't any values written by the 'SE1' symbol, so I assume it should be easy for the experienced eye to tell just by looking at the surrounding schematic. I can sortof sense what I'm supposed to be looking for (i.e. wattage rating), but I'm not sure what else I'm missing.


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dear moderator - if you feel i have totally hijacked this thread please do not hesitate to make a new one...i originally felt i was contributing to the 'thrift store' theme, but now it seems i'm running my own project here.

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/andrew - is not a hijacker, but he plays one on TV.