A genuine flaming relay - Page 1
Forum section: electronics / general

author: SeanB
author_rank: Super Contributor
timestamp: February 15, 2015, 10:47:20 am
content: This 40 year old relay recently decided to die, having a brilliant light show from the internal relay contact when it was trying to close. Brilliant yellow orange glow inside the case, and of course no operation of the output. Made in mid 1974.Made by Scharco Elektronic using Siemens parts inside ( all parts look like they were actually made by Siemens, including the relay, capacitors and resistors) and then were assembled in Germany to make this unit. Fixed delay, set by the smaller 47uF electrolytic capacitor and the parallel 75k resistor across it.Uses a transistor type you rarely see these days, a BCY 59 core memory driver, used as a buffer of the capacitor voltage till the relay reaches it's minimum operate voltage. Power supply is a capacitive supply that generates a 24V rail for the unit, smoothed by the big capacitor and regulated by a 24V 1W zener diode.http://pdf.datasheetcatalog.com/datasheet/stmicroelectronics/9042.pdfHand laid out PCB's, with a tongue and groove joint where they join, using solder as a fixing method and as a connector.If you look at the relay contact at the rear you can see where it has worn out and has arced. 40 years of driving a bigger 10W contactor coil has finally killed it.Replaced with a new on time delay relay, and as the neighbouring relay is also the same age I did both at the same time. The shiny coat is the fine oil mist from the adjacent pneumatic systems, which has over the decades penetrated every part of the relay. It also dissolved the glue that originally held the acrylic case to the base.

author: SeanB
author_rank: Super Contributor
timestamp: February 15, 2015, 10:50:10 am
content: Last image....

author: rob77
author_rank: Super Contributor
timestamp: February 15, 2015, 11:49:16 am
content: nice vintage stuffreminds me of the times when i was a boy and instead of dissecting frogs i was "dissecting" old electronics from scrap ('80s)

author: Richard Head
author_rank: Frequent Contributor
timestamp: February 15, 2015, 03:12:44 pm
content: I wonder if the oil ingress had anything to do with its failure?Maybe it would have lasted 60 years in a benign environment.Thanks for sharing.

author: SeanB
author_rank: Super Contributor
timestamp: February 15, 2015, 03:34:49 pm
content: I doubt it, it just was tired after 40 years and around a hundred million operations. The oil mist just protected all the metal from corroding, I think the contacts just wore out electrically from use, and then when the spur got too big the arcing finished it off. This machine used to run 24/7 in it's previous use, and I am still clearing out old product from it every time I work in some of the more confined spaces. There are parts I have never opened even to look, they are still working as well as when new. I am now getting to the point where the next shutdown will likely result in me replacing a row of assorted relays with a single long DIN rail and a load of 11 pin sockets and new 11 pin relays, as there are now only about half of the original ones left in it. only issue is the one relay is a special contact version, so I will have to build it up out of a few cascaded relay units, along with having to get some 20A rated relays for the one section, as there it does draw 15A for heaters. Can't use a SSR as it needs to have safety monitoring contacts, and it runs at 400VAC between phases. the original relays simply run 3 sets of contacts ( out of 4) in parallel to get the contact current down, and they are wearing now, rated 20A AC1 and 16A AC3