Vintage Synth Repair

OK well, now, the synth is repaired and the owner has it now. The corrosion split a trace next to some solder points, but not the ones going to the solders themselves.

Brian Davies a \ufffdcrit :

Hi John

Yes I take your point, semiconductor leads generally are made of some sort of ferrous material, most probably steel and sure this can rust. However these are mostly plated in order that they take solder without trouble. The plating could be anyone of several metals, tin, silver, or even solder itself. I have to say that in 50 years as a test and servicing engineer I have never come across the effect you mention. That is not to say that the problem doesn\ufffdt occur only that I\ufffdve never seen it. Such corrosion problems can occur in tropical climates but normally where equipment is known to going into such climates the manufacturer would coat the board with a tropical varnish.

What I have found, on many occasions, are problems associated with components plated with nickel. Nickel seems to deteriorate with time and soldering nickel plated components can be impossible. I have in stock a quantity of nickel plated solder tags, in order to use these today \ufffd they are at least 40 years old \ufffd I have to scrape off the plating down to bare metal and then tin them with cored solder prior to using them.

I had occasion to have to sort out an intermittent fault on a Kawai keyboard only four days. The reported fault was intermittent switching on. Even when the piano did come alive it rarely stayed on for more than a few minutes. I traced this to a dodgy solder joint on the power input jack socket, the pins of which had clearly been nickel plated. I ended up re-soldering several joints around this component and this cured the fault. However there was no visible sign of any corrosion.

Regards

Brian Davies G3OYU

www.g3oyu.co.uk

From: vintagesynthrepair@yahoogroups.com [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of John Brewer
Sent: Friday, 27 January 2006 14:16
To: vintagesynthrepair@yahoogroups.com
Subject: Re: [vintagesynthrepair] Roland RD-300S trouble

Hi Brian,

I think rust was a generic term intended to mean corrosion. However, just for an exercise, take a magnet and a selection of transistors and diodes and you will find you can actually pick some of these devices up. I discovered this when I found a diode hanging off of my magnetic screw driver.

Over the years, salts in the tinning used on these leads will leach out and react with the wire and solder causing corrosion and failed joints. A joint can look perfectly OK but you can put your Ohmmeter on the wire of a diode and get an open circuit at the next connection point on the card.

This leaching can also spread and destroy thin circuit tracks,reducing them to the texture of lace curtains and causing a high resistance or open circuit. I hope this helps.

JohnB

----- Original Message -----

From: Brian Davies

To: vintagesynthrepair@yahoogroups.com

Sent: Thursday, January 26, 2006 9:46 PM

Subject: RE: [vintagesynthrepair] Roland RD-300S trouble

I\ufffdm a bit puzzled and no one else seems to have picked up on this, solder cannot rust it has no iron in it! So just what do you mean by the solder has rust on it? Note also that the PCB tracks are made of copper and they are either tin plated of solder plated or varnished so again they do not contain iron ergo they also cannot rust.

Regards

Brian Davies G3OYU

www.g3oyu.co.uk