Re: Broken Royal Paper Shredder

Thanks budm and stj for the correction. The fuseable resistor (gray one under S5) meters at 306 ohms (banding: orange/black/brown/gold (300 ohms 5%), so that seems okay. Thanks.

Re: Broken Royal Paper Shredder

Quick question re: transistor substitution:
This weekend, I was trying to find replacement transistor 9013, but having difficulty. Looking for an alternative, I came across PN2222A. Both 9013 and PN2222A are BJT TO-92, with V-CBO=40V and 75V, respectively, I-C=500mA and 1000mA, and P-D=625mW (same for both).

The datasheet for the 9013 transistor is here:


The datasheet for the PN2222A transistor is here:
[url]https://cdn.badcaps-static.com/pdfs/739a1f1d45a43e65d12b1314ac8f0249.pdf[/url]
...

Re: Broken Royal Paper Shredder

Thank you all for the wonderful and helpful discussions. I have been following the comments (in the midst of trying to get paperwork done), and trying to understand it, as it is above my knowledge base. However, this is providing a wonderful learning opportunity, as I have been reading, re-reading, looking things up on the internet, trying to gain a better understanding, with much of this starting to make better sense.

What budm stated in post #10, that "I also do not expect the BASE current flowing through the 18V zener (18V drops...

Re: Broken Royal Paper Shredder

Thanks for all the responses.

I will definitely proceed with replacing the Zener with a higher voltage/wattage such as 25V/1W, and uprate the 300 ohm resistor wattage (current resistor look like only 0.25W). Not knowing much about the Operational Amplifier LM324 IC, I will read about it, and consider replacing it too as stj suggests.

It makes sense that if the function of ZD1 and R21 is to switch on a dummy load so that the L7812 input does not receive excessive DC voltage (with the consideration that excessive DC voltage...

I was given a broken paper shredder which I was reluctant to discard since it seems so wasteful, and so I am trying to repair it.

It has a sliding Panel Switch for rev/off/auto (see image P2-Shredder-Extrnl). The shredder's symptoms are as follows: (1) The rev works; (2) Auto does NOT work as the shredder will not come on when paper is placed into the paper slot; (3) The Panel "Ready" Light also does NOT illuminate at any time.

I opened the case, and the shredder consists of: (1) Motor/Shredder Blades, (2) Mechanical Safety Switch, (3) Transformer, (4) Panel...

Re: New Members - please post your introductions here

After reading some of this "New Member" thread, I sure feel old! I started working with mainframe computers and punch cards, before personal computers came out. Then, when the old DEC PDP-11 Unix minicomputer machines came out, I worked with those...great machines! Later, I worked on development of 8-bit Zilog Z80 systems and applications for CP/M OS using Z80 assembler, while dabbling a bit with 6502 assembler. I helped in development of bank select memory and writing drivers to interface Z80 systems with early hard...