Tag: plague

Sony Discman D-121 Pt:2

Assessment and fault finding… will it work?

My recent purchase of a Sony Discman D-121 from EBay has arrived. Just as described it wasn’t really working so I decided to give it a once over to check condition.

Cosmetically sound

Cosmetically it’s in very good condition, open the battery compartment and it’s a different story, definite signs of corrosion and at this point I’m thinking the worst. I put two batteries in to check, the display comes on and shows some strange indication of “HI VOLTS” even though all I have are the two AA batteries in. Strange.

Corrosion on contact
On the board as well

I do manage to play one song but that’s it, any slight move and it skips and hops and shows a raft of other error messages that don’t Instil any confidence into me that this is going to have a good outcome. Then the CD drive motor breathes its last. That’s it….kaput.

Greasing the worm gear
Strip down

So I open up the unit, and put the circuit board under the microscope. The area around the corroded battery terminal has progressed on to the board and a couple of the circuit board tracks have been totally destroyed. A few components look to have issues and have some spurious test results. A check for continuity with the multimeter confirms that one track is dead and another is intermittent at the very least.

Under the microscope

I clean the offending section of the circuit board with IPA and this just confirms the issue, but at least it looks cleaner. If this had been the only issue I’d have happily soldered in a couple of thin wires to the undamaged track to ensure a reliable continuity.

Damaged tracks
Bad corrosion

A further look around the board, and there’s nothing blatantly obvious, but seeing this unit was produced in 1993 it’s now in its 31st year of use I also suspect the capacitors (of which there are many) may well be of that era of suspect capacitors I discussed on a previous post. Read here: Capacitor plague

The main drive motor is known to fail after time and a sure sign is if the CD jumps when moved off the horizontal, apparently this is due to bearings becoming misshapen due to use.

This unit therefore is beyond economical repair for me, and I’m not going to progress it any further. The good news is that I can use the unit for spares and as a number of these older units have interchangeable parts, I’m hopeful that as I have a few more units turning up later this week they may have a willing donor.

So the recycling goes on, and that’s always a good thing.

Happy day to you all.

Capacitor plague

What the heck is that?

Blown capacitors

Photo copyright : Wikimedia Commons

For many this is old news and pretty much everyone involved in electronics is aware of this problem that swept through the industry in the mid to late 2000s. Chances are you may have such a unit in your home that has either luckily survived the issue to still be working, or may well be not working and assigned to that part of the house (Normally the loft) where it left until the day you move premises and visit the local tip.

Those of us that number a great many who like to tinker and repair old machines and equipment from this era are still seeing the back end of this issue to this day, its fairly easy to deal with and those that especially work with old computer motherboards and graphics card notice issues the most, its an interesting back story and ill try to cover it as best as i can in this post.

What is a capacitor?

  • A capacitor is a device that stores electrical energy by accumulating electrical charges on two closely spaced surfaces that are insulated from each other. It is like a little battery but thats where the similarities end, as a capacitor distributes energy in short bursts rather than a battery that is distributing power linearly. Originally known as the condenser, the capacitor is used within a circuit to add capacitance to that circuit.
  • Capacitance is the ability of a component to store an electrical charge – (Simple version)

What was the issue?

  • The issue was with Electrolytic capacitors produced between 1999 and 2007
  • The origins of the issue was with the use of water based electrolytes developed during the late 90s. These capacitors using this type of electrolyte were found to be exceptional components when used in power supply circuits. The problem was that the water based caps produced aluminium oxide when reacting with the capacitor “Can” and that reaction was Hydrogen. The Hydrogen built up until the stamped vent on the top broke. Resulting in a failure within the circuit.

It was only in the mid 2000s when the plague really set in, some of these capacitors would have had hundreds of thousands of hours of use and even though they would have passed initial testing protocols they were doomed to fail, and that just so happened to be in the mid 2000s.

The Blame game

It was around this time with exceptional failure rates on certain items and claims being raised against major players in the electronics industry that deeper investigation took place.

Findings

  • The cause of the failures was due to a mis-copied formula, in 2001 a scientist working for a major corporation that made these type of capacitors stole a mis-copied formula for the capacitors electrolytes. He then took this faulty formula to another company. That same year the scientists staff where he previously was employed left that company, again with the stolen formula and started their own company in Taiwan producing immense amounts of faulty capacitor electrolytes.
  • No one was ever really brought to justice for the failures, no one company ever really came clean over the issue, the tech companies tended to absorb the cost of repairs and the end result was probably that the consumer paid in the long run…nothing changes there then!

When this started to occur, many individuals in the industry jumped on the band wagon to repair these items, many selling capacitor kits for certain brands to allow those who were willing, to make their own repairs.

Today the issue still occurs but it is not so prevalent, older circuitry does still throw up some classic blown capacitors and these are fairly simple to replace, some smell quite fishy as well, so sometimes a good sniff of a circuit board can alert you to a blown capacitor…very strange!