Crossing 90's IC caps

[King Forrest]

TLDR Modern replacement for Illinois Capacitor RLR (M) 39µF 10 vdc

Hey there! I am trying to recap the autolamp sensor for my '94 SHO. Specifically the two on the sunload amp circuit. They are Illinois Capacitor RLR 39µF 10V. I believe the part number would've been 396RLR010M, but they discontinued these in the nineties. They were replaced by RLS, then RKR, then Cornell Dubilier SK. Problem is I can't find any 39µF in that series, nor any specs on the original, other than 10V, +-20 and S85^c.

 

[Harald Kapp]

You can use any 39 µF capacitor rated 10 V or higher (not lower). +10/-20 % is standard, no need to worry here. 85 ° is also quite standard, for longer lifetime you may want to use 105 ° types, however. These will last longer than 85 ° types under the same conditions as the stress is much less compared to the nominal limit.
The size of modern capacitors will usually be smaller than the original ones, also no need to worry. If you can'z find the correct pin spacing, the leads can always be bent to match existing PCB holes.

 

[King Forrest]

What about ripple currents 'n stuff, how important is that? I'm trying to take a DC current from a photoresistor and send it to a NOR gate if that makes any difference.

 

[Harald Kapp]

Ripple current is of no importance at all in this application.
Ripple current is to be considered in power supply circuits where high ripple currents are present.
If you are concerned, though, get low-esr type capacitors. These withstand ripple currents better as they don't heat up that much (P = i² × R_esr).

I'm trying to take a DC current from a photoresistor and send it to a NOR gate

DC will not pass a capacitor. Show us a circuit diagram to help us understand what you want to do.

 

[King Forrest]

DC doesn't pass a cap? wut? I don't have a schematic for this device, but i got some photos and can point out what goes on.

Ok, turns out I can't upload the photos and the website isn't kind enough to tell me why. But here's what I got:
+ goes through a fixed resister, into the photocell, through one leg of an adjustable pot (the other leg on -) through another resistor, into both caps, + on one, - on the other, a couple more resistors and then the NOR gates.

 

[Harald Kapp]

DC doesn't pass a cap? wut?

Trust me.
From your description I take it that the DC doesn't "go through" the capacitor but bypasses the capacitor which, together with the resistors, makes an RC low pass filter.

Ok, turns out I can't upload the photos and the website isn't kind enough to tell me why.

Resize to less than 300 kB.

 

[King Forrest]

Nope, didn't work. Anyway, here's some links. I've spent hours studying the circuit, albeit with my limited knoledge. I've traced everything I believe is relevant but please correct me if i've got something wrong
Ginger FerroChrome on Twitter: "https://t.co/BFJbviuHHe" / Twitter
Ginger FerroChrome on Twitter: "https://t.co/V69oSwx3jv" / Twitter

 

[bertus]

Hello,

The links do not work.
Resize the pictures to about 300 kB and post them here.

Bertus

 

[King Forrest]

 

[King Forrest]

Ok, my understanding of DC certainly isn't up to snuff. Really there is no such thing as - or + currant, it's just flowing from one end to the other. Is there a good resource to help me break this circuit down?

 

[Harald Kapp]

I don't know of a specific resource. What I'd do is first place the symbols for the components on a sheet of paper in a configuration that roughly matches the placement on the pcb (This will no be perfect, but a good first approximation). Leave enough room between the components. Then follow the traces between the components on the pcb and draw the equivalent connections on the paper. USe a photo of the pcb and mark the traces you ave done do avoid unnecessary effort.
When finished, rearrange the drawing to a neat schematic.

You can use a schematic tool instead of paper, provided you accept the steep learning curve associated with this kind of tools. See e.g. this discussion.