|Identifying 82120a components|
Message #1 Posted by Vieira, Luiz C. (Brazil) on 22 Jan 2003, 12:23 p.m.
I'm taking the 82120A wave and I'm repairing the rectifier/regulator board of mine, serial # 2309S80xxx. Battery leakage corroded part of some components terminals and, in some cases, the terminals are broken and I'll have to replace some of them. The problem is that the existing diodes had their ID's removed and I'm in trouble to identify them. One of our contributors offered himself to identify these components for me, and I believe this information is useful to all of us here. So, as I do not mention names in here prior to their authorization, if this friend agrees with, I'm expecting any information from someone at the Forum and I'll post any contribution sent to my e-mail about this particular subject, O.K.?
Dave, if there is any trouble regarding to copyright material, please, let us know. I'll expect e-mails only, in this case.
The general circuitry description for the 82120A is:
> from the AC input, four diodes connected as a bridge rectifier; the diodes connected to [+] pole are different of those connected to [-] pole. Is there any reason for that? Fast rectifiers will do the job? Which ones to use there?
> The first component after the [+] is an electrolytic capacitor, 100uF/25V, no trouble to identify
> Right after the capacitor there is a SOT-package regulator, 1826-0275 (output voltage?). The way it is connected lead to this conclusion: one terminal in the [+] pole, the mid terminal in the [-] pole, and the third terminal to the load through the following two components:
> A 10nF capacitor, parallel to load (opposite terminal to [-] pole)
> A series diode (anode to regulator, cathode to load), no identification too; is it a fast rectifier?
The other components are:
> Connected to the cathode of the last diode, a 365 ohms, 1% resistor (at least it seems to be), series with load; the opposed terminal goes to the [+] of the batteries
> parallel with the batteries a zener diode; working voltage? test current? max. dissipation power?
I'm sorry asking so many questions, but I prefer knowing these components' characteristics instead of risking and loosing the pack, the (external, test purposes only) NiCad batteries OR the calculator itself.
Thank you very much.