Corning LSE vortex mixer repair -- triac speed controller - Page 1
Forum section: electronics / repair

author: raphy
author_rank: Newbie
timestamp: October 01, 2023, 05:43:06 pm
content: I have a broken vortex mixer (a device to thoroughly mix samples in a biochem lab).It appears the triac speed control is not working. The 2 switches work and by-passing the speed controller (KBMS-13BV) the mixer spins at full speed.How can I check that the speed controller is for sure broken?And can I replace this triac with a pot?ninja edit.

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: October 01, 2023, 07:46:03 pm
content: Quote from: raphy on October 01, 2023, 05:43:06 pmNo, absolutely not. A triac is a switch. A pot is a variable resistor. Any pot will burst into flames in that position.A device like that is bound to have something called ahttps://en.wikipedia.org/wiki/Phase-fired_controllerSince you had the ask the question above, I assume you have no experience with electronics. Messing with mains-powered electronics is 100% not something a layman can or should do. To service and diagnose this, one is going to need a minimum of equipment like an isolation transformer, an oscilloscope and a mains rated multimeter. Your best option is to take this to a repair shop. It should set you back around 50-70$.

author: fzabkar
author_rank: Super Contributor
timestamp: October 01, 2023, 09:44:11 pm
content: Datasheet for KBMS-13BV:https://acim.nidec.com/drives/kbelectronics/-/media/kbelectronics/documents/triad-fan-controls/data-sheets/kbmc-kbms-data-sheet.ashx?la=enSince bypassing the control enables the motor to run, I would deduce that the control is faulty. A quick Google search finds replacement controls for US$14.50 plus freight.

author: Ian.M
author_rank: Super Contributor
timestamp: October 01, 2023, 11:30:46 pm
content: There's a good chance its cheaply fixable: Unless subjected to severe overloads TRIACs generally fail shorted rather than open, so if the TRIAC is bad, I'd expect uncontrolled full speed, but you have nothing unless its bypassed. Therefore look for a bad connection and also check if R1 has failed open or C1 has failed shorted, and check the effect of turning R3 the min. speed trim, which could point you towards an open circuit Speed Adj pot (R4). If its anything trickier, replace it.As you lack experience, to stay safe, do not attempt to make *ANY* measurement or adjustment, or even handle the board, with it plugged in to the mains.

author: MathWizard
author_rank: Super Contributor
timestamp: October 04, 2023, 07:20:22 am
content: What's the point of the DIAC in that circuit ?

author: Ian.M
author_rank: Super Contributor
timestamp: October 04, 2023, 07:39:25 am
content: The DIAC prevents the TRIAC turning on till its breakover voltage is reached, then provides a 'snap' action (negative slope resistance) so the TRIAC gets a good pulse of current to turn it on quickly. Its breakover voltage sets the level C1 must charge to, to provide the phase angle delay before firing.

author: fmashockie
author_rank: Frequent Contributor
timestamp: October 04, 2023, 01:47:17 pm
content: Like others have said, if the unit works bypassing the speed control, then it is likely the speed controller KBMS-13BV that is the issue. You're not going to be able to fix the controller - they are not designed to be taken apart and serviced. Just by a new one (I see them available from a variety of vendors for anywhere from $10-$20).Alternatively, I work as Lab Instrumentation Engineer for a biotech company. Vortexers are easily acquired used for cheap. Sometimes you can find them for as low as $20 if you get them at auctions. So depends on how much time/money you want to invest to fix this.