Author Topic: HELP!!!  (Read 22785 times)

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
HELP!!!
« on: September 25, 2010, 05:51:32 PM »
Hi guys,

Does anyone out there have a schematic daigram for a HF mini lathe model 93212? I was working on my latest project this weekend and my lathe motor stopped turning. I thought perhaps it was the fuse or my end of travel limit switch, but no..... :zap:
I think the drive circuit has a problem. The booklet that came with the lathe has no information at all about the drive circuit, so I wonder if anyone out there has reverse engineered their unit, I'm willing to pay for a copy if anyone has the info I need. :wave:
I feel like a 22-year old, but my wife won't let me have one.

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #1 on: September 25, 2010, 06:17:20 PM »
Hi
several months ago I reverse engineered the FC250J board in my Clark CL300M lathe
(its a Sieg C3 mini lathe)

the latest version uses a XMT.... series controller  that I think has been used in some mini mills

If your control pcb looks like one of the pictures
I'll send you the info I have

    John

« Last Edit: September 26, 2010, 08:36:08 AM by John Swift »

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #2 on: September 25, 2010, 07:37:13 PM »
Hi Grinder ,

I have had a look at the manual for your lathe

the nearest to the FC250BJ/110v  controller you have I can find on the  web is
 that circuit for a FC350BJ/110v

hope this helps


 John


« Last Edit: September 25, 2010, 07:49:36 PM by John Swift »

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
Re: HELP!!!
« Reply #3 on: September 25, 2010, 08:24:12 PM »
Hi John,
Thanks  a billion for the info. The photo of the board looks exactly like the board in my lathe. I'll have to take it apart to be sure, but it is very similar.
I'm trying to repair a worn clutch in my lawnmower...two wedge pices that slide into a tapered gearwheel, and I was midway through turning down an aluminum plate to hold the gear when power went off. I have a limit switch to prevent the crosslide drive from running into the chuck, and I thought perhaps it was giving me a problem, but I still hear the interlock working.

What you have there is some great info, thanks again :beer:
I feel like a 22-year old, but my wife won't let me have one.

Offline 75Plus

  • Hero Member
  • *****
  • Posts: 624
  • Country: us
Re: HELP!!!
« Reply #4 on: September 25, 2010, 08:38:32 PM »
Grinder, Check the choke just below the yellow relays. That's the thing that has enameled wire wrapped around a toroid. I had a similar failure and found that the choke had broken loose from the circuit board.

Joe

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #5 on: September 26, 2010, 08:29:29 AM »
Hi Grinder ,

 If you need to test the speed control pcb , try this test circuit


I have used it when working on my controller

ps the motor brushes are not too short are they ?  new ones are about 0.55" (14mm) long

                   John



pps not sure of circuit downloaded for FC350BJ   (fc350 3 in earlier previous post)

on my FC250J/240v  pcb terminal P4 is connected to a 10K resistor , not to P1

linking P1 and P4 or not , changes the level of the motor voltage feed back

on my lathe the maximum speed in reverse is half that in forward

see "part fc250 main pcb"
« Last Edit: September 26, 2010, 12:20:55 PM by John Swift »

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #6 on: September 26, 2010, 01:51:19 PM »
Hi Grinder ,


   even more info

the circuit of my FC250J/240v control looks like a cutdown version of
your control without the overload protection circuit


      John


« Last Edit: September 26, 2010, 01:52:54 PM by John Swift »

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
Re: HELP!!!
« Reply #7 on: September 26, 2010, 05:30:50 PM »
Hi John,

I took out the PCB today, and it looks like the damage is more than I first thought. There is a row of pots along one side of the board, and between VR1 and VR2, I noticed a sooty deposit around the SMT resistors, and one small electrolytic cap has a blown pressure relief on top. I'm thinking now that I should try to replace this board, and tackle the repair when I have more time. You have some great information though, thanks again
I feel like a 22-year old, but my wife won't let me have one.

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #8 on: September 26, 2010, 06:29:24 PM »
Hi Grinder ,

if you have not had much practice with SMT boards , get an old computer board to practice on first

my board and others I've helped on the model-engineer.co.uk forum   , have had faulty capacitors
(thread :-  speed control pcb for clarke cl300 lathe)
some measure ok for capacitance but the ESR is high ( several ohms instead of half an ohm at most)

with luck the deposit is from the capacitor ( is it C9 a  1uF 250v electrolytic  by any chance ? )

if its one of the one's I suspect , it's been heated by R1B in the photo (0.34 ohms  5w)
hot capacitors have a short life  - i've changed a few in  switch mode power supplies inside of  TV set top boxes and LCD monitors
the electrolytic capacitors are easy to replace
the SMT components under the protective laquer are more difficult

   good luck


        John
« Last Edit: September 27, 2010, 06:24:09 AM by John Swift »

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
Re: HELP!!!
« Reply #9 on: September 27, 2010, 12:23:01 PM »
Hey John,

I just saw your pic, and the cap that blew is the one to the right edge of the red box (C12). The board you show there is practically identical to my board, and the sooty deposit was over the SMT resistors in the box. If I can't find a replacement, I may just go in and change all the IC's and hope for the best. I do work with a lot of electronics stuff and feel capable of repairing this board, but most of the work I do is thru hole.

Thanks again for all the info
I feel like a 22-year old, but my wife won't let me have one.

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #10 on: September 27, 2010, 01:11:22 PM »
Hi Grinder

  I think I have identified your board

the capacitor is on the output of the +12v regulator

I've captured the web address from my screen
for some reason I failed to copy it to this reply

(the info is from John Gerling at Gerling laboratories)  

the only problem in changing the LM2902 / LM324 quad op amps
will be if the pcb laquer has glued them to the board

          John
« Last Edit: September 27, 2010, 02:19:02 PM by John Swift »

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
Re: HELP!!!
« Reply #11 on: September 28, 2010, 01:02:24 PM »
Hi John,

You're right about the laquer holding those parts to the board.
I found some SOIC's, but had a hard time cleaning off the gunk in order to get good thermal contact (seems like they put an extra couple coatings on this one). I think my best option is to get a replacemant board and work on this one after I get the old components off. Do you know af any solvent for this stuff? It feels like polyurethane (maybe). I wonder if acetone, MEK or even turpentine will soften it enough to wipe off?
I feel like a 22-year old, but my wife won't let me have one.

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #12 on: September 28, 2010, 02:18:44 PM »
Hi Grinder ,

the nearest  Sieg board I've worked on is a FC250JSMD
the board looked like the laquer had been applied with a tar brush , nice and thick !

 the only components I changed was some of the electrolytic capacitors
heat from the soldering iron freed the laquer so I was lucky
( 60 / 40 solder across both connections , I only use lead free when I have to)

my first thought would be  to try cellulose thinners , but would test it out on an old computer board
to see what it does to the components , just incase !!!
take a picture of the pcb ,the markings may come of the board
if you remove the presets from board
you can wipe the dissolved laquer of the edge and away from the wire ended components

the only  time I had a problem removing surface mount ic's
was when the red glue used to hold the ic's before soldering , worked too well,
the copper track come away  with the ic

I would start with the easy bits first
change the through hole components first
the electrolytics and semiconductors in the + & - 12v power supply
since C12 decouples the +12v regulator

without the mains supply , it may be worth using a bench power supply set to +&- 15v to test the onboard regulators
and prove the ic's are faulty or not

to remove the ic's , I would cut the legs off first as close to the epoxy body as possible
with some high quality ,flush cutting side cutters or dremmel type of cutter

then you can remove the legs from the board one by one

If the laquer proves easy to remove
a soldering iron with a bit to heat all 14 pins would be quicker

the chip resistors are marked with three digits but the capacitors are not marked at all !
I'm not sure if the value of the chip capacitors is shown on all positions , on the circuits off the web
it looks like they are all 0.1 uF

 NOTE :--  with your FC250BJ board
some of the resistors , setting the gain of some of the op amps will differ from the values on the FC350BJ boards


                                      John
« Last Edit: September 28, 2010, 06:35:44 PM by John Swift »

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #13 on: September 28, 2010, 04:38:07 PM »
Hi Grinder

just looking at the two versions of the FC350BJ controller i've downloaded

it looks like in one version the capacitors on the input and output of the regulators
have been exchanged.

is it the one of the circuit diagrams thats wrong or one version of the pcb ??
looks like one pcb !

usually the capacitor on the input side the capacitor is the larger of the two

see the pictures


                 John
« Last Edit: September 28, 2010, 05:08:29 PM by John Swift »

Offline grinder

  • Jr. Member
  • **
  • Posts: 22
Re: HELP!!!
« Reply #14 on: September 29, 2010, 12:59:38 PM »
Hi John,

I'm not able to look at the board now, since I'm actually at work, but I'll take a look when I get home. I've seen both combinations of capacitors on low voltage power supplies before, and I don't know that it makes an awful lot of difference, depends who you talk to. I prefer larger caps on the input side, so that the output side discharges first. These low voltage regulators work great, but they don't like it if the voltage reverses on them. So I always try to arrange it so that smaller caps (or a faster time constant) is on the output side. :beer:

Stan
I feel like a 22-year old, but my wife won't let me have one.

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #15 on: September 29, 2010, 03:21:03 PM »
Hi Stan ,

the only danger with a small reservoir capacitor and a large capacitor on the output
is when the stored energy discharges the wrong way through the regulator

the protection diodes shown in the diagram are also helpfull
with multiple power rails if there is a loss of input to one regulator

(hot swopping of power supplies and amplifier modules is all ways good fun !! )


     John
« Last Edit: September 29, 2010, 03:34:04 PM by John Swift »

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #16 on: September 30, 2010, 02:38:16 PM »
Hi Stan
just tested cellulose thinners on the edge of a sieg pcb and it does remove the laquer
I would expect acetone to work as well

not wanting to disassemble the board I've not tested it on the components

hope it helps


    John
« Last Edit: September 30, 2010, 02:40:03 PM by John Swift »

Offline John Rudd

  • Hero Member
  • *****
  • Posts: 2525
  • Country: gb
Re: HELP!!!
« Reply #17 on: October 01, 2010, 03:40:37 AM »
I would avoid getting solvent on the component side, it will remove the ink used for marking items like capacitors.....

Celly thinners is probably better suited than acetone as it is slightly less volatile...

2 cents supplied...
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

Skype: chippiejnr

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #18 on: October 01, 2010, 06:59:32 AM »
 Hi John 
you are correct ,  it would remove the markings

but if the solvent  helps removing the ic's without damage to the pcb , I would use it  ( we need to save the pcb at all costs)

since I would change the electrolytic capacitors any way ,  the loss of the markings isn't a problem

but as in earlier posts I would have tried the easy bits like the power supply first

        John

Offline John Rudd

  • Hero Member
  • *****
  • Posts: 2525
  • Country: gb
Re: HELP!!!
« Reply #19 on: October 01, 2010, 07:33:29 AM »
Sure thing John.......
If ic's are to be changed I'd be inclined to add ic sockets of a decent quality as an aid to any future troubleshooting ( much easier to change a chip that is socketed than soldered direct). Assuming we are not dealing with smt devices... :doh:

Umm, just checked one of the fotos....They are smd devices...

Ok, no problems..You can either butcher the chip by cutting the legs and then removing the left overs...or you could fashion a desoldering bit from a piece of copper bar to fit on your big soldering iron..

(Without sounding patronising or teaching granny....you need to be quick in unsoldering/reflowing...prolonged application of heat will inevitably impair the bonding of the copper traces to the board...But I'm sure you know this already  :D)
« Last Edit: October 01, 2010, 07:38:11 AM by John Rudd »
eccentric millionaire financed by 'er indoors
Location:  Backworth Newcastle

Skype: chippiejnr

Offline John Swift

  • Sr. Member
  • ****
  • Posts: 344
  • Country: england
Re: HELP!!!
« Reply #20 on: October 01, 2010, 09:07:16 AM »
Hi John
I agree cut the legs off first , but on these boards the lacquer may have glued the body to the board

antex do a kit of bits for SMT work , but so far I have  have removed up to 18 pin SMT ic's with the standard 1/8" bit ok

the only problem board I had  the dot of glue under the ic was too good and bonded to the copper print better than board :(
fixed with some 30 awg KYNAR wire  :D

most other makes of boards survive two or three repairs to the same part before you need the kit of replacement lands and via's
but I don't have the funds for the tools or parts for that

if you go to www.repaircontrol.com
you will find some info on these boards and one one page John Gerling considers faulty smt ic's to make a  board  not repairable

not repairing seig boards as a business I see it as a challenge


                       John

ps   I recommend any one who has not  worked on SMT boards to practice on an old computer board or something first
« Last Edit: October 01, 2010, 09:12:38 AM by John Swift »