Difference between revisions of "User:Deriss"

Revision as of 10:07, 4 April 2017

Bought a 464 or 6128 from eBay ? Broken or not working right ? Read on..

Firstly, make sure you have a 5v regulated power supply and that your monitor / tv are working ok. (You'd be surprised...)

Make sure your power supply provides a minimum of 2A continuous current. Some PSUs can be very "optimistic".

On the 6128, you don't need a 12v feed for anything except the 3" disk drive. So it can be omitted for testing.

Earth yourself to prevent static damage or better yet, get an anti-static strap. It's a 30 year old machine remember...

Now carefully remove the case.. Be VERY careful with any keyboard membranes. You CANNOT buy these anymore.

Btw: eBay is The best source for spare chips and other replacement components that I have found

The obvious things on the board to look for first are:

1: check the 5v power and 6pin display sockets for dry solder joints. A dab of fresh solder will fix this.

2: check the rest of the board for dry joints too. This can be tedious but is worth it in the long run. Never touch the soldering iron tip to a joint for longer than 2 seconds to avoid damaging sensitive components.

3: Check for any damaged or leaking capacitors. Check the ceramic ones too, in case a previous owner has knocked one. Remember to replace any capacitor with a product of equal or higher voltage rating. Equal ones are now frequently physically smaller than the 1980's originals.

4: examine all resistors for signs or damage or discolouration. check resistance with multimeter and replace as needed.

5: Examine all the chips for any corrosion, damage or discolouration.

The main Z80 cpu can be replaced for £3 and is always socketed. The rest can be sourced for between £2 and £6 each from eBay, if you look around. Capacitors and resistors are too cheap to be even worth mentioning. The gate array (40007, 40008 or 40010) is the only expensive part at between £9 and £15. (Suppliers market for those unfortunately..)

The most common fault is probably someone having plugged a 12v PSU into the 5v socket. This usually fries some or all of the ram (memory) and may sometimes damage a few ceramic capacitors along the way too.