Author Topic: SSR03 (AD825, LM431, +-15V BOM)  (Read 149 times)

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Offline minionas

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SSR03 (AD825, LM431, +-15V BOM)
« on: March 12, 2020, 07:41:09 PM »
Got transformers and hooked it up to SSR03 (AD825, LM431, +-15V BOM). Final result +15.19V / -15.09V. If i would like to trim it down a bit, to 15V exactly, what needs to be done?

I measure 10-11mV of AC on outputs on cold, and 9mV on stable working unit. It is normal in my case?

Thanks in advance.



Offline peranders

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #1 on: March 12, 2020, 08:57:12 PM »
The AC voltage should be a few uV but this must be measured with special equipment. Check first the incoming voltage. It should be at least 4 volt more than the output voltage, in your case 19 volts. Measure at the input of the LM317/337.
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Offline minionas

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #2 on: March 12, 2020, 09:16:21 PM »
Lm317 has 24.5V at input and Lm337 has only 17.9V..

Offline peranders

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #3 on: March 12, 2020, 09:30:21 PM »
How high is your input AC voltage? How much do you load with? Current?
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Offline minionas

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #4 on: March 12, 2020, 09:33:58 PM »
AC input is ~21.4V.
Load is ~3-400ma per side.
« Last Edit: March 12, 2020, 09:37:54 PM by minionas »

Offline peranders

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #5 on: March 13, 2020, 06:29:46 AM »
I suggest that you reduce the R9 and R10 to 1 ohm. You could also place a wire jumper there. Both LED's should lit also. That is a sigh that you will get a proper regulation.
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Offline minionas

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #6 on: March 13, 2020, 07:14:58 AM »
I'll try that on the weekend.

Why do you think im getting 24+V on the positive side of the power supply while 17,9V on negative side after rectification..?
« Last Edit: March 13, 2020, 12:56:58 PM by minionas »

Offline minionas

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #7 on: March 14, 2020, 02:06:52 PM »
Ive installed R9 and R10 1 ohm resistors. Had some fun with one new resistor so had to open the schematic and look for problems why one LED does not emitt light on second power on while it did lit on first power on. And finally found one of new 1 ohms resistor faulty. Changed it again and now both LEDs are lit brightly.

Ignore my dumb measurement as i was not aware that pins of LM317 and 337 are alocated differently, therefore input is the same for both of them - ~25V.

Also ignore my dumb question/statement that i get different voltage after rectifier bridge, as it is the same for both sides as after inspecting schematics now i know where to measure :)



« Last Edit: March 14, 2020, 02:09:06 PM by minionas »

Offline peranders

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Re: SSR03 (AD825, LM431, +-15V BOM)
« Reply #8 on: March 31, 2020, 07:01:07 PM »
Sorry for the late response. Do you get a stable output voltage now?
/Per-Anders Sjöström, owner of this forum

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