Any electronics wizard in here?

[Exuptoy]

Whats a lamp limiter? Does it regulate the fault current through a lamp instead of blowing a fuse?

 

[WorkshopChris]

Yes useful for initial power up and testing. I made one with a rotary switch to alter lamp wattage.
http://www.vintage-radio.com/projects/lamp-limiter.html

 

[Exuptoy]

That is superb and very basic. I used a similar idea some years back when the fuse in an old Ford Fiesta would keep blowing. I connected a spot lamp soldered to the legs of the fuse and it lit up the lamp instead of blowing the fuse. It turned out that there was a chaff in the wiring in the tailgate and when you opened it the fuse would not blow and the lamp would not illuminate. Clever.

 

[gaz1]

i thought i recognised those pics

its a kbmm-255d board

http://www.kbelectronics.com/manuals/kbmm_smt_manual.pdf

or the solid state schematic down near bottom

http://www.kbelectronics.com/manuals/KBMM_thruhole_manual.pdf

ive got some of the other boards for some projects in mind

 

[WorkshopChris]

The pdf appears to confirm the logic that the devise is a 25a 600V diode.

 

[Exuptoy]

Cheers guys. Although the one I have is the 240D not the 255D. I think the only difference is mine is rated to 2HP max not 3HP.
Found my manual but not the PDF. Do you think we can safely assume that the rating of the Diode will be the same or should I plump for the 15a at 600v as my motor is only 0.5hp and maxed out the unit is only rated at 12a full load at 240v or 16a with the optional heatsink? So maybe the 20a is more suitable to cover all eventualities?

http://www.kbelectronics.com/manuals/kbmd_240d_manual.pdf

 

[Exuptoy]

So it this what I am looking for 20a @ 600v?

http://www.littelfuse.com/products/...fier-diode/dxx15l-dxx20l-dxx25l/d6015ltp.aspx

Is it even a TO-220L switching thyristor I need? If so I'm sure I could find a local equivalent from the PDF below.

http://www.littelfuse.com/~/media/e...ristor_dxx15l_dxx20l_dxx25l_datasheet.pdf.pdf

This
http://www.ebay.co.uk/itm/D6020L-Di...676208?hash=item2ef64c1270:g:kT4AAOSwHsRYEQ1g

or this
http://www.ebay.co.uk/itm/DIODE-STA...150006?hash=item3f273b7e36:g:DqAAAOxyDEVSa8D9

 

[Exuptoy]

The pdf appears to confirm the logic that the devise is a 25a 600V diode.

Rectifying or standard?

Scratch that, we've agreed it was a power diode right? So it's rectifying?

 

[Exuptoy]

Looking at the manuals again I have a feeling I know why the diode may have blown if it wasn't caused by condense in the box.
Please bear in mind that this set up on my door has existed for over 10 years, BUT because the drive was capable of reverse as well as forward (even if it wasn't equipped) with the reverse switch with combined 10ohm 50 watt braking resistor allows the motor voltage to be dissipated through BR and dynamically brake the motor.

I decided when I built the 2 contactor / remote interface to use the interposing relays (my contactors) to swap the armature winding cables to achieve forward and reverse, and in fact when you power up the drive, instead of it soft starting the motor immediately, it is sat there awaiting me to introduce the down winding or up winding depending on the position of the door. One thing the manual implicitly warns of is the use of a switch or relay in series with the armature windings may cause catastrophic failure and heavy arcing.
I hope this repair fixes my drive but I fear I may have to review my set up to incorporate the I1 / I2 contacts to inhibit the drive and cut the power to the armature when the change over is being done. I could always use the relay contacts to control the interrupt. I'll have to take a note of the wiring config of the remote and contractors and revisit this.

 

[WorkshopChris]

OK i have looked through the circuit and cant see anything obvious that would cause a short that would trip a mcb without showing any visible damage.
Most of the components on the pcb are all control and timing not much in the supply line after the rectifier.
It wouldn't be a build up of damp carbon in the motor could it.

 

[Exuptoy]

Anything a possibility mate but at the point where the juice trips, all I've done is turned on the control, at that point the armature cables are dead ended at the N.O. contacts of the forward reverse relay so I would suspect not. Favourite for me is condensation on the metal case directly above the transistors.

 

[Exuptoy]

Well, I got my Teccor 20A 600V power diode today. It was here when I got in from work. I removed the old scrap from the board and fitted the new component and it powers up without knocking off the juice. I just got back in from the garage after re-installing and reconnecting the remote interface and switching box and the door works as before.

Thanks for all your help guys. It's most appreciated.

Right then guys, then next thing I need to check out is the speed control. It has never worked since installed. I have checked the 5k pot and at zero it reads around 1 ohm (I think, from memory, it may have been 100ohm) and around 4700ohm at full scale so I think the pot works fine but I have no speed control when operating the pot, only max speed when running. If I adjust the min and max trim pots there is no effect but if I adjust the accel or deccel trim pots then the ramp up to speed or ramp down to stop does adjust the motor speed until it reaches v-max.

The actual unit installed is this one.
http://www.kbelectronics.com/manuals/kbmd_240d_manual.pdf

....but the board fitted is actually marked up KBMM and the PDF contains the general circuit layout which is below although I do not have the extras fitted.

http://www.kbelectronics.com/manuals/KBMM_thruhole_manual.pdf

It's not too important now the door is operational once again but it would be appreciated if I could get some more feedback.
Thanks again.
Lyn

 

[Seadog]

If you can get to the PCB easily I'd suggest measuring the voltage on pin 2 of the LM358 ( negative lead to 0V), take care not to short between adjacent pins though. Varying the speed should adjust the level on this pin. If that is OK then check pin1 to 0V and you should see a change there. If not it would suggest that one of the op-amps has failed which means changing the IC. If you don't see a change at pin 2, then there is something wrong with the resistance chain at the front of the op-amp, maybe the max or min pot is faulty.
Set the meter range so that it'll indicate up to 12V dc.

 

[Exuptoy]

Cheers dude. I'll take a look one evening this week.