Electronics Question (again...)

[Highpower]

Something that has always bugged me about the table power feed on my mill is the POS power indicator lamp on the front of the unit. Unless you are sitting on the floor at eye-level with the indicator - you can't see if the lamp is on or not. Standing right in front of it, looking down at it, you can't see any light so you don't know if it is off or on.  

  Table Feed.jpg (Size: 17.31 KB / Downloads: 108)

The power feed for my knee is a newer design that uses a ring light surrounding the rapid switch button, that is bright enough to see clear across the shop when it is on.  

  Knee Feed.jpg (Size: 19.11 KB / Downloads: 108)      

While I have the table feed apart fixing other issues right now, I want to "upgrade" to the new style switch and power lamp. I have the new switch on order, but these Taiwanese schematics have me befuddled.    
         

The power lights don't come on unless the power switch is turned on. But it looks to me like they are showing the power lamp connected directly to L1 and L2 coming in and not after the power switch. Makes no sense to me.  

Anyway... IF I'm looking at this correctly - it appears that both lamps (new and old style) are fed line voltage through a 33K ohm resistor - is that right?  So if I remove the old lamp from the PCB and solder the new lamp leads to the same terminals, life should be golden... right?  

The whole reason for tearing into this is because the table feed has been getting progressively louder over time. (Growls & howls.) I've tracked it down to the lower bearing on the motor, but I am going to replace both bearings anyway. I'm waiting for the BBT to deliver them any time now...

               

         

[Old Minger]

Rather than second quess the drawing just stick a voltmeter across the PCB where the old lamp originates from. When energized If you get line volts then replace with a suitable lamp or if you get DC then use a suitable DC  indicator.

[EdK]

The worst you could do is blow out the lamp. Just make sure the replacement lamp is rated for the voltage the unit is powered with.

Those "schematics" suck, but it's better than no schematics at all.

Ed

[f350ca]

My power feed has the same POS light Willie. Didn't realize there was anywhere you could see it lit.
The one on the board looks like a neon gas light, haven;t seen one of them in decades. I'd expect the new one is a LED. No idea if the 33k resistor would give the correct drop.

[Vinny]

The light on the old one is a neon. They run at 90v AC and the 33K resistor drops the line voltage to 90V. The schematic for the knee feed looks like the light is also a neon.

What I suggest is to find a neon panel lamp that's small enough to mount to the cover and wire it in without the resistor (the panel lamp will have the resistor built in). Here's a link to some:

http://www.digikey.com/product-search/en...ageSize=25

EDIT:
Almost forgot, the reason the lamp looks to be wired right across the line is because the schematic is of the circuit board, the power switch is not mounted to it.

[EdK]

(03-11-2016, 07:28 PM)Vinny Wrote: Almost forgot, the reason the lamp looks to be wired right across the line is because the schematic is of the circuit board, the power switch is not mounted to it.

Good catch Vinny.

J-1-4 is where the switch would be wired in.

Ed

[Highpower]

(03-11-2016, 02:53 PM)Old Minger Wrote: Rather than second quess the drawing just stick a voltmeter across the PCB where the old lamp originates from. When energized If you get line volts then replace with a suitable lamp or if you get DC then use a suitable DC  indicator.

In my mind the prudent thing to do is to check the schematic first if available, to see if there is anything else that might be further down in the circuit that would be affected negatively, if any other component is changed. That is why quality VOM's have at least a 10K internal impedance. I've replaced a number of various vehicle ECU's in my time due to some kid installing his new 300 watt sound system in his car, and tapping into the first power wire he finds under the dashboard. The parents are never happy to find out the manufacturer won't warranty a $2000 computer on a new car because their kid blew it up trying to do his own install without knowing what he was doing.

But yes, I had planned to check the voltage anyway to see what it was, which turns out to be 58.6 VAC by the way. I'll check the voltage rating on the new switch / light when it arrives, but I'm feeling pretty good about it working since both models have the same resistor in the lamp circuit. (According to the schematics anyway...) The way they show it in the drawings though, the light would come on as soon as the power cord was plugged in - and I know that isn't right.

The good news for now is the new bearings arrived this afternoon and the motor runs nice and quiet again.
It looks like there will be enough room for the new switch / light once the old micro-switch and the push-button plunger assy are removed. But I won't know for sure until I see it.

[Mayhem]

(03-11-2016, 07:48 PM)Highpower Wrote: ...The way they show it in the drawings though, the light would come on as soon as the power cord was plugged in - and I know that isn't right. ...

No - as Vinny pointed out, the input into the circuit board is after the power switch.

[Vinny]

Willie, reread the bottom of my response. I edited to add it and you may have seen it before I saved it.

[Highpower]

Actually, I didn't see it at all Vinny!

I guess I didn't read all the replies before I started typing. <sigh>
Yeah - that makes sense now. I mean why on earth would they show you ALL the wiring on the thing...

Thank you for clearing that up for me. I knew you guys would have an explanation.

90 volts huh? Seems I'm a little short. (No pun intended.) Maybe that's why I can't see the dang thing when it's on?
No matter really. I still like the new style better anyway. Just hope I don't have to dig deeper to get it to work.