Troubleshooting circuit board

Thread Starter

amtrakusa

Joined May 28, 2019
18
Greetings: Amateur here, but with 50 years of electronics history. This circuit board is for a medical adjusting hospital bed. It has eight relays (24v - model no. 1055030). They are very basic relays. When testing them I get continuity across both poles with no voltage applied. I would expect closed on one side and open on the other and then when voltage is applied I would see the reverse. Anyone have knowledge on this symptom? A little more information on the board. 3 of the motors on the bed work OK. The fourth motor either has bad relays or source voltage for the relays from the processor is missing. Bed has 4 separate motors, 2 relays per motor. At this point I'm just trying to clear the relays as the problem. Many thanks!
 

MrSoftware

Joined Oct 29, 2013
1,676
Edit--> Oops you did post the model number. See if you can find the datasheet for the relays online. That will tell you exactly how they should work, and you can compare that to what you're seeing.

Also connect one side of your multi meter to ground, use the other to probe the relay output pins when someone operates the bed (if it's safe). Compare a known working relay to one that you suspect is dead.
 

killivolt

Joined Jan 10, 2010
754
Greetings: Amateur here, but with 50 years of electronics history. This circuit board is for a medical adjusting hospital bed. It has eight relays (24v - model no. 1055030). They are very basic relays. When testing them I get continuity across both poles with no voltage applied. I would expect closed on one side and open on the other and then when voltage is applied I would see the reverse. Anyone have knowledge on this symptom? A little more information on the board. 3 of the motors on the bed work OK. The fourth motor either has bad relays or source voltage for the relays from the processor is missing. Bed has 4 separate motors, 2 relays per motor. At this point I'm just trying to clear the relays as the problem. Many thanks!
Trash Compactors work in a similar way, forward and reverse voltages my guess is they only open when the motor reaches the maximum limit or vice versa on the other end probably uses a worm gear. Normally closed when open and open when closed.

kv
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
Thank you sirs!

Mr Software: that is another option I'm hoping to avoid. I do have another bed that works and can remove the board from there and do comparative checks. Problem is the only time to access the only other working board is limited due to usage. Also, it is impossible to to testing on the board while it's installed because it mounts in tight access underneath the bed.

MaxHeadRoom: there is other identifiable numbers on the relay,
OKS2C-SDC24V-S
12A 28VDC
15A 125VAC
E051180
along with > 1055030
Also the circuit board is a LINAK WK2 94V0
and lastly there is a white sticker >> * SLRSZ0043K060205Z * 00CB9C00E004-G-2 CHINA
phone broke yesterday so no pics currently

killivolt: that's a thought I had not considered and may be what is going on here except that the diagram for the relay's schematic online show it to be a simple spdt switch so one side should be closed when not energized and the other open. Then energized it should (I'm expecting) reverse. All 8 of these relays have continuity between the input terminal and both of the relay's output terminals when not energized.
 

MaxHeadRoom

Joined Jul 18, 2013
20,023
Have you checked the underside of the board, solder side,?
I have found that in many cases with this type of relay it is often the foil has come away from the pin or become unsoldered, or even blown.
Max.
 

killivolt

Joined Jan 10, 2010
754
killivolt: that's a thought I had not considered and may be what is going on here except that the diagram for the relay's schematic online show it to be a simple spdt switch so one side should be closed when not energized and the other open. Then energized it should (I'm expecting) reverse. All 8 of these relays have continuity between the input terminal and both of the relay's output terminals when not energized.
I thought it would be a simple circuit, but Max will help you out.

Good Luck,

kv

Edit: If you can provide the right info to him, he is very knowledgeable about these circuit motor controls.
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
Thank you kv!

Yes Max, I checked the board with 2 pairs of reading glasses on looking for any slight defect or burn and it's a clean well built board. I'm going to jump at it again tomorrow morning. Something about those relays isn't adding up. I'll try to activate them with a 24v dc supply and see what I get.

Note for all, this control box sells for $650 so I'm just seeing if I can save my boss some money with a $2 relay or whatever. Cheers!
 

bwilliams60

Joined Nov 18, 2012
1,259
Can you disconnect the relays from the board and test them? If that one is disconnected and you still test continuity on both terminals, it would seem to be a shorted relay, no? Sounds like you are on the right track.
 

MaxHeadRoom

Joined Jul 18, 2013
20,023
If you suspect any and remove for testing, it might pay to pick up a stock and just replace them anyway while you have them out.
Max.
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
bwilliams: removing them would be quite a trick, they are flat on the circuit boards all jammed next to each other. still trying to locate a 24v power supply

max: yes stock acquirement would be nice, I found some site selling then for $0.10 - 0.20 apiece . just need to verify they are the problem:eek:
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
View attachment 185684 View attachment 185685
c.b. #3.jpg
Managed to upload 3 pics using my wife's phone. I noticed some gunk on the backside of the board where the relays are attached. I cleaned with acetone around the relay's solder points used for motor 4. (no change) In the bottom pic the top two relay's are the ones not activating. Also, anyone know what the 4 black barrels in the bottom of pic 1 are for? I am assuming voltage transformers due to 120v leads run direct to them. Also 2 of those creatures have continuity, two do not.
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
So, I do not know if all 3 pics came through. I have 2 bullets on the previous message which say, "view attachment 185684 and -685," but when I click on them I get a "no permission to access" message, prolly due to me being a newb.
 

Thread Starter

amtrakusa

Joined May 28, 2019
18
Those 4 black barrels to the right in the pic with the relays are the plug-in terminal ports for the foot pedals that operate the bed.
 
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