(https://i.postimg.cc/gn7CRf4d/deluxe-electric-mistress-v5-schematic.gif) (https://postimg.cc/gn7CRf4d)
Between pin 8 and 9 of the Lm324 there's weird symbol- a 15uf NP cap, since we believe in SMD Versions I'm thinking of using just a polarized one(unless someone gonna prove me other).
Where should the positive placed?
Early versions were using two caps like this:
(https://i.postimg.cc/WdBt9Ypc/deluxe-electric-mistress-v2-schematic.gif) (https://postimg.cc/WdBt9Ypc)
The newer XO seems to ditch it:
(https://i.postimg.cc/MX9HkpZD/e70u4z2ekyaxmkcbaso7.jpg) (https://postimg.cc/MX9HkpZD)
Pin 9 of the LM324 is basically a virtual ground*, and the output will switch from close to one rail to close to the other.
So that's why they used a non-polarised cap (or the equivalent arrangement of a pair of polarised caps) - because either orientation of a polarised cap is going to be wrong half the time!
HTH
* It's not exactly at the midpoint voltage since 2.4K+820R is not 3.9K, but that doesn't matter here.
Quote from: AMK on March 17, 2025, 04:34:43 PMThe newer XO seems to ditch it:
(https://i.postimg.cc/MX9HkpZD/e70u4z2ekyaxmkcbaso7.jpg) (https://postimg.cc/MX9HkpZD)
Are you sure?
(https://i.postimg.cc/SYjJBpb5/image.png) (https://postimg.cc/SYjJBpb5)
When you see caps marked NP it generally means non-polar electrolytic capacitor. They have no polarity marking. These are different to the more common polarized electrolytic capacitors, which have a polarity marking.
Unless you know better you shouldn't replace an NP cap on a circuit with common electrolytic, or visa-versa for that matter.
Using two back-to-back connected polarized electrolytic caps in place of an NP cap is a valid change - as is done on the two examples.
What's on the PCB's is a different matter but the idea still applies. Check the polarity markings and the value.
Used NP in the AE Tremolo. 1uF, 3 places, probably matched them. They didn't replace polarized electrolics.
(https://i.postimg.cc/FfjQzQ1x/ggg-eat-sc-improved-2.png) (https://postimg.cc/FfjQzQ1x)
Quote from: GGBB on March 17, 2025, 05:02:57 PMAre you sure?
(https://i.postimg.cc/SYjJBpb5/image.png) (https://postimg.cc/SYjJBpb5)
Good spot, Gord! That does look a lot like it!
Quote from: ElectricDruid on March 17, 2025, 04:57:47 PMPin 9 of the LM324 is basically a virtual ground*, and the output will switch from close to one rail to close to the other.
So that's why they used a non-polarised cap (or the equivalent arrangement of a pair of polarised caps) - because either orientation of a polarised cap is going to be wrong half the time!
HTH
* It's not exactly at the midpoint voltage since 2.4K+820R is not 3.9K, but that doesn't matter here.
Ohhh I see
Quote from: GGBB on March 17, 2025, 05:02:57 PMQuote from: AMK on March 17, 2025, 04:34:43 PMThe newer XO seems to ditch it:
(https://i.postimg.cc/MX9HkpZD/e70u4z2ekyaxmkcbaso7.jpg) (https://postimg.cc/MX9HkpZD)
Are you sure?
(https://i.postimg.cc/SYjJBpb5/image.png) (https://postimg.cc/SYjJBpb5)
Nice catch! pin 8 and 9 seems like they're connected together, that got me confused...
Quote from: AMK on March 18, 2025, 08:50:49 AMpin 8 and 9 seems like they're connected together,
Good for a buffer (voltage follower), like IC4d..
which method is more recommended- two polarized 33uf back-to-back or 15uf np?
do you have any 15uF non-polarised on hand? can you source them [do you want to have to?] easy and cheap?
do you have 33uF [or 22uF or 47uF] polarised on hand? space to fit them?
same either way electrically, so comes down to what you've got/can get/will fit.
Quote from: AMK on March 18, 2025, 09:28:17 AMwhich method is more recommended- two polarized 33uf back-to-back or 15uf np?
+1 what Duck said. Same difference. Whichever is easiest, cheapest, fits best.