Anyone know what part this is - Page 1
Forum section: electronics / general

author: dralthi
author_rank: Contributor
timestamp: April 30, 2018, 11:11:04 pm
content: Hi, I'm trying to reverse engineer this 24 VDC surge suppressor. I believe those silver through-hole components are Zener diodes but I am not sure a) What type they are b) What is the package c) Where to buy them?Any help would be greatly appreciated.

author: Brumby
author_rank: Unknown
timestamp: May 01, 2018, 04:42:30 am
content: Somebody else may recognise them - but they look like a heatsink to me. What is underneath is the question.My first question is: Are they a 2 terminal device?My next would be ... can you take a shot from the right of that picture so we can read what the silkscreen says? This often gives hints on the component.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 01, 2018, 05:07:52 am
content: I'm going to guess some MOVs in a strange package.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 01, 2018, 05:52:47 am
content: If you are referring to the cylindrical components, they are just fuses.They even have "F1" & "F2" printed on the PCB.The three devices in a rectangular package with moulded fins have V "something" marked on the PCB.If they are zeners, they will look like diodes in the forward direction.

author: dralthi
author_rank: Contributor
timestamp: May 01, 2018, 01:00:02 pm
content: THanks for the response....I have attached another picture to help folks identify the component in question.

author: krish2487
author_rank: Frequent Contributor
timestamp: May 01, 2018, 01:41:37 pm
content: Looking at the overall layouti.e huge copper planes, finned devices and fuses.I am tempted to guess they are TVS diodes on the input stage of a power converter.They look remarkably similar to these.http://www.littelfuse.com/products/tvs-diodes/leaded/ak10.aspx

author: dralthi
author_rank: Contributor
timestamp: May 01, 2018, 02:59:01 pm
content: TVS or Zener?

author: @rt
author_rank: Super Contributor
timestamp: May 01, 2018, 02:59:53 pm
content: SMT selenium rectifiers

author: dralthi
author_rank: Contributor
timestamp: May 01, 2018, 03:14:27 pm
content: Realy?

author: dralthi
author_rank: Contributor
timestamp: May 01, 2018, 03:18:15 pm
content: Actually, I think it's not bi-directional because of the color coding printed on the terminals.....

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 02, 2018, 03:54:26 am
content: Quote from: @rt on May 01, 2018, 02:59:53 pmFirst thing I thought of, they look like seleniums.The color marks probably are for some identity or QC marking, they are perpendicular to the leads.

author: Brumby
author_rank: Unknown
timestamp: May 02, 2018, 04:00:54 am
content: Quote from: Cyberdragon on May 02, 2018, 03:54:26 amI'm not seeing that.I'm curious as to the underside of the PCB. Seeing the track layout could help.

author: TerraHertz
author_rank: Super Contributor
timestamp: May 04, 2018, 12:44:04 am
content: They remind me of the devices used in CRT TV sets to drive the tube degausing coil. Two varistors, one positive temp coefficient, the other negative coefficient. When cold, current sent to the coil. On warming up (from the current passing through them) the coil current reduces smoothly to nothing.Point being, they were constructed as two disks of material held by spring pressure between three metal plates.The things in the picture look like there are rectangular plates of some material, held in a stack of alternating metal and active material. Looks like they rely on the shrink-plastic to apply the pressure. And the metal layers are thick, to absorb transient thermal energy? Also to keep the pressure even across the surfaces.I also see one and probably two of them have one terminal connected to chassis ground.Given that it's a 24V DC transient protector: two slo-blow fuses, would be on the DC plus and minus rails. There are three mystery components, so they'd be arranged as two DC rail to ground protections, and one differential (between Plus and Minus.)I'm guessing they are MOVs, done with a stack of thin MOV compound, stacked between thick metal contacts for better energy pulse survivability, and maybe also to get the right breakdown threshold.Their job would be to clip transients, for long enough to blow the fuses.