#garfield Logs

Jun 08 2023

07:58 AM rue_mohr: the zeners would prevent it from going crazy cause its an intigrator
08:09 AM rue_mohr: fan is attached to the output, its speed is proportionate to the drop across the transistros
08:09 AM rue_mohr: its just capped to 12V
12:09 PM WormFood: rue_mohr, this is the conclusion I've come to, about that schematic: C (opamp) is wrong. It's pin 4 and 8 can not be connected. Yeah, I thought some current regulator at first too, but that simply makes no sense. D is the voltage regulator, and B is for overvoltage "protection"
05:09 PM aandrew: that is an orcad SDT386 schematic, I'd recognize that anywhere
05:10 PM aandrew: C can't be right, although I think it's the V+ pin that's wrong, not the output
05:11 PM aandrew: I think V+ is tied to the top wire which looks like the positive rail
05:11 PM aandrew: the output is pulled up to that same net by 220k
05:12 PM aandrew: unless they're doing soemthing REALLY weird with the power supply for all for of those op amps
05:13 PM aandrew: oh wait, maybe rue called it... notice that there is nothing tied to pin 11, the negative supply pin
05:14 PM aandrew: did you see this? https://bryceautomation.com/index.php/2017/10/28/alinco-power-supply-repair/
05:20 PM aandrew: that is a very odd schematic
05:21 PM aandrew: I can only guess that op-amp A isn't shown but that's where pin 11 is connected
05:22 PM aandrew: How do you figure C is in integrator? + and - are both connected to the same signal through individual 1k resistors
05:22 PM aandrew: I see the .01u in the feedback and the diode+zener in parallel, but what exactly is it integrating?
05:23 PM aandrew: oh wait, I see now, I think
05:23 PM aandrew: the negative side of that top left 1u/50V cap is the common
05:24 PM aandrew: - to common through 1k, out to - through the .01u cap, and 1/3.2 divider on the +
05:24 PM aandrew: these "hanging" power supply schemes always throw me
05:25 PM aandrew: that is one crazy circuit
08:13 PM WormFood: aandrew, I did see that other page. That .01uf cap is for RF. Alinco is a radio manufacturer, so this PSU was intended to be used with radios. If you'll notice, they put 0.01uf caps all over the place. That's why.
08:15 PM WormFood: If you look at the schematics to a "floating ground" radio (that is a radio that can be used in a positive or negative grounded vehicle), you'll see that the chassis is connected to ground via 0.01uf caps. Sometimes I'd short out all that shit, and make it a negative ground chassis. The 0.01f caps pass RF, so at RF frequencies, the chassis is connected to ground. Does that make sense? RF is some weird shit.
08:20 PM WormFood: Also notice how the output of the 2 transformer outputs are connected together. It appears that all the regulation stuff sits on top of the power rail.
08:21 PM rue_mohr: yea it does
08:21 PM rue_mohr: on mine, I'm trying to place it all on the output rail
11:01 PM polprog_: im going sailing for a week, so i will be away
11:02 PM polprog_: hard to get IRC access at sea
11:03 PM polprog_: hopefully I can start vacation afterwards. there is a cool robotics project coming up that I wanna take part in
11:03 PM polprog_: keep your fingers crossed :)
11:53 PM rue_mohr: I hope you have fun