Need help identifying this component and finding a suitable replacemen - Page 1
Forum section: electronics / projects

author: shims506
author_rank: Contributor
timestamp: January 12, 2012, 11:48:43 pm
content: My oscilloscope came in and seemed like the front panel was hit and dented due to shipping. I thought that most of the knobs work except one opened it up and sure it was cracked and looks like a simple fix. Pictures will show the cracked one and the working oneAny one know what component it is and where i can find a new oneon the side it says 30V 3A

author: daedalus
author_rank: Regular Contributor
timestamp: January 13, 2012, 12:05:15 am
content: bottom bit looks like a rotary pot, top bit is a little indecipherable. If it were me I would go google for the scopes schematic, as they are usually available. Other then that, can you describe what the control is for / photograph the wiring more clearly. It may be a simple switch on the same axle as the pot, but cant make it out from the photos.

author: olsenn
author_rank: Frequent Contributor
timestamp: January 13, 2012, 12:06:17 am
content: If I'm looking at the part you were referring to, then it is a potentiometer (a variable resistor). The "30V 3A" just means it is capable, or rather tested to withstand 30 volts and 3 amps of current passing through it continuously... I seriously doubt that much power is really going through that pot, so don't worry too much if your replacement part doesn't meet that spec, just pick something of comparable weight and you should be fine.

author: shims506
author_rank: Contributor
timestamp: January 13, 2012, 12:18:23 am
content: its the knob that changes vertical axis position of the green line, it still work miracoulously even though the two parts are apart strange??? Also its a BK Precision 1590 100mhz quadIs it better to replace the potentiometer?

author: daedalus
author_rank: Regular Contributor
timestamp: January 13, 2012, 12:41:06 am
content: the front bit is definitely a potentiometer, and by the sounds of it this works still so should be ok.The brown bit at the back is what im not sure on. Looking at the similar unit below in the picture, it appears to have 4 terminals on the back, and it looks like the broken one has wiring on the back.This looks like it once mated with the extended shaft out the back of the pot, can you take a look inside the brown bit and see if there are any terminals / connections visible / post a photo of the wiring on the back of it? Im guessing its some kind of switch.

author: shims506
author_rank: Contributor
timestamp: January 13, 2012, 02:10:47 am
content: here are more pictures that might help

author: daedalus
author_rank: Regular Contributor
timestamp: January 13, 2012, 12:41:56 pm
content: sorry I really cant make out what the brown hood is, it does have wiring going to the terminals on the back right?You could always leave it and use the scope as-is if its working, otherwise a look at the schematic would clear up what this part does.If you want a service manual / schematic these guys stock them, unfortunately its not a free download though. I guess it depends how important the fix is.http://www.bkmanuals.com/1501-1600.htm

author: shims506
author_rank: Contributor
timestamp: January 13, 2012, 05:33:41 pm
content: They are both connected and there are wires so I'm not sureI am not willing to pay $65 for schematic if majority of functions work. Thank you for all the help and deadalous by any chance you airsoft? I was just wondering name sounds familiar.

author: daedalus
author_rank: Regular Contributor
timestamp: January 13, 2012, 05:46:58 pm
content: nah, i don't do airsoft, must be someone else.

author: vk6zgo
author_rank: Super Contributor
timestamp: January 14, 2012, 02:59:48 am
content: Back in the day,these things were common--it's called a "switchpot".There are several types:(1)The most common type has the same shaft operating both the switch & the pot,with the switch "off" at one extreme of rotation--usually fully counterclockwise.(2)Another type has the switch operated by another shaft concentric with the pot shaft,so the pot may be used without operating the switch,& vice versa.The switch operation is still rotary,but may sometimes be multi-position.(3)This type,again has a concentric shaft,but the switch is "push or pull on"--again the pot may be in any position.Be VERY cautious,as it was common to turn the mains on & off using a switchpot.If there is another on/off switch,then you should be OK.Examine your front panel.You should be able to determine what the switch does by looking at the associated labelling.You may not even need a Service manual,as an Operator's manual will identify all the controls.You also may be able to reassemble the switch onto the rear of the pot with a little care.VK6ZGO

author: vk6zgo
author_rank: Super Contributor
timestamp: January 14, 2012, 03:27:51 am
content: Well, I Googled,& found a fairly poor pix of the front panel:-From the markings,it looks as if the switch is intended to switch between CH1 & CH3,.There is a similar switch in the CH2 section,marked CH2--CH4.I must admit I'm a bit puzzled as to how a 4 channel 'scope works with only two inputs on the front--maybe on the back?Still,it looks like a nice unit,& if you do reassemble the switch to the back of the pot,even if the switch doesn't work,you've still got a 3 channel 'scope!VK6ZGOPS: On looking a bit closer,it's possible that it just switches the vertical position pot over to CH3,so maybe,you might still be able to useCH3,but not be able to centre it vertically.PPS: It looks like the switchpot is type(2) as in my previous posting.