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Technical Help Forum
Started by Ray in Waxhaw at 07-21-2008 6:50 PM. Topic has 24 replies.
  
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 07-21-2008, 6:50 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Repairing a CDI box, CX500 '80
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I need help trouble shooting my CDI unit. This is the second one to fail so I'm not interested in spending $160 (Ebay) on another used one that's just as old and may not last long. I have checked the stator according to the book. The only things a little out of spec are white to green wires at 354 ohms but the low coil voltage is high at 110V and the high at 135V. I've got the CDI box enough apart to check the main caps and they both tested good for capacidence. Could they be bad and still test good on a tester? What other components go bad? If I can't fix one of my boxes I'll probably try to build one from the schematic.
Thanks for any help.
Ray
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07-21-2008, 10:02 PM
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hakko808
 
Joined on 05-25-2008
Fargo, ND
Posts 209
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Re: Repairing a CDI box, CX500 '80
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Yes, on the caps. Most common failure on old caps is High ESR (Equivilant Series Resistance). When using capacitance meter only I found good caps read about 20% high. At or below value usually indicated falure
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07-22-2008, 4:24 AM
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Reg in Bristol
Joined on 03-11-2006
Bristol UK
Posts 291
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Re: Repairing a CDI box, CX500 '80
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I've got a couple stripped down for repair
probably/hopefully wont need em as I want to use a TI motor in my bike
but my lad has a CDI CX and thought I'd do it anyway just out of interest
and dig them out when in the mood.
I'll renew the main dump caps as a matter of course whether they tested good or not
and got 1.2uf 400V axial electrolytics locally and cheaply
Ditto the main SCR's, the originals are NEC 5P4J's which I couldnt find easily
so found an ST device which had the same gtv and better spec. (cant recall its number off hand)
I'd suggest checking it has no burnt tracks.
I have found a couple which had this problem and you'll need to either
dig them well out, or trace/test using the diagram and meter
A little while back I did start to put some info on digging them out on my site.
Link below.
see 'CDI autopsy' in the 'tinkerin' section
I dont update it very often, only when the mood takes me, but it may have some info
you find useful
Down to one project/rat bike now, when I get a 'round tuit'
Member of the UK CX-GL MCC at
http://www.cx-gl.org.uk/index.html
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07-22-2008, 5:00 AM
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WisconsinCX
Joined on 07-07-2008
Germantown, WI
Posts 242
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Re: Repairing a CDI box, CX500 '80
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Ray, I have one off a old 78 that I would sell you for a few bucks and shipping. I don't know anything about the part tho.
Would a 78 CDI work on a 80?
Barry
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07-22-2008, 1:51 PM
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Randall-in-Mpls
Joined on 07-06-2007
Minneapolis, MN
Posts 1,090
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Re: Repairing a CDI box, CX500 '80
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Barry,
I emailed you yesterday regarding the CDI and some other parts, but I haven't heard from you.
R
'78 CX500 - The Black Maggot
My mid-life crisis has two wheels.
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07-22-2008, 2:57 PM
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WisconsinCX
Joined on 07-07-2008
Germantown, WI
Posts 242
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Re: Repairing a CDI box, CX500 '80
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Hmmm...didn't get.
Try my secret email at:
rtfbarry at yahoo dot com
I'll check my address in my settings.
Barry
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07-22-2008, 3:23 PM
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Randall-in-Mpls
Joined on 07-06-2007
Minneapolis, MN
Posts 1,090
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Re: Repairing a CDI box, CX500 '80
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Barry,
I just got your email. I'll try to call after I get home tonight.
R
'78 CX500 - The Black Maggot
My mid-life crisis has two wheels.
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07-22-2008, 7:00 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Reg,
Thanks for the advice. The only link I saw took me to the MCC club web site and I couldn't find any section called "tinkerin". Am I missing something, I would like to see what you have?
Thanks,
Ray
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07-24-2008, 4:39 PM
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Reg in Bristol
Joined on 03-11-2006
Bristol UK
Posts 291
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Re: Repairing a CDI box, CX500 '80
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Ray
Just realised my email and site buttons (with the WWW on it) are only visible when logged on
just in case you dont see it, its at
http://myweb.tiscali.co.uk/cxism/
The CDI's are very fixable/reworkable, the only snag is digging the things out of the potting compound in a careful, relaxed, manner.
i've buggered a couple up by hacking away wildly
When theyre dug out, the board has all the components one side and most
but not all, of the tracks on the other
I've been lucky and never had a CDI fail on me but have been brought bikes that have
and never had to repair one for myself so i guess that why its an 'out of interest' job
and I 've never tackled it in earnest.
When I saw what was inside I thought theres no way I'm shelling out £250 for a new one
and you never know how much life is left in a second hand one
BTW
I found the number of the SCR I bought to replace the NEC chip
TS820-600T — STMICROELECTRONICS — THYRISTOR, 8A, 600V, TO-220AB
Same gate voltage but 8A/600V as opposed to the NEC's 5 A/400V
81 pence each and the caps were a similar price. Less then a pound anyway
Good luck with it, I'll be interested to see how you get on
Reg
Down to one project/rat bike now, when I get a 'round tuit'
Member of the UK CX-GL MCC at
http://www.cx-gl.org.uk/index.html
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07-28-2008, 7:08 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Reg,
Thanks for the link, good stuff. I found the SCR you mentioned available through Newark.com. I looked for a suitable cap there. They have a Multicomp MCHV2R2M2WB-1021RH (Newark # 79K3637), is that suitable?
I noticed the raised pairs of resisters and wandered what thy were, you call them trim resisters. I broke one too plus another on the board. My trim resisters appear to have different values then the ones you show in your picture. Should I use the same ones as what I have now or is there a way to detirmine the right ones? Why is their junction wire-wound and why do they stand so far above the board? If I get it working, is it necessary to repot it the way it was? If so, what should I use?
Thanks for all the help,
Ray
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07-29-2008, 8:28 AM
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Anonymous
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Re: Repairing a CDI box, CX500 '80
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Ray
At my current level of understanding and somewhat hazy memory
the tuning resistors were fitted last of all and presume they had the CDI's on test rigs
and chose/fitted resistors to get optimum results.
Finally it was all potted up.
I have two different values each side and without a similar test rig it would be
tricky to establish the ultimate value after changing the caps and SCRs so I'll
just swap like for like when replacing the ones I broke and wont lose much sleep over it
Those Newark caps look fine to me, very similar to the ones I got
Reg
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07-29-2008, 4:50 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Thanks Reg. What about the need for repoting, does it help control heat? Is the third SCR the same part no. as the main two.
Ray
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07-29-2008, 7:01 PM
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Anonymous
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Re: Repairing a CDI box, CX500 '80
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What about the need for repoting, does it help control heat?
Yes that potting compound did a good job of dissipating heat and protecting the components
the drawback is, as you know by now, digging the stuff out again !
When I actually get round to fixing the ones I have here I wont bother potting them until/unless I am pretty damn sure its worth it after some extended testing.
personally I'd rather repair an unpotted/semi potted one once a year cos digging the
buggers out is such a chore
Is the third SCR the same part no. as the main two?
Possibly, maybe, dunno.
Dont have any info to hand but i wouldnt be surprised if it was
I've heard it described as both controlling the advance and acting as an overspeed control
I havent seen the diagram for ages and would have to pore over it to get an idea of its function.
From what I recall, the advance coils are wired in to both sides anyway
plus it is only connected to one channel and when turned on would
short that signal to ground, so for now
I'll plump for the overspeed/governor function.
Reg
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08-05-2008, 6:49 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Thanks. I replaced the main Caps and the resistors and diode that I broke while depoting and tried it. I got fire on one side, the opposite to the one that was working before I worked on it. I also saw some sparking at one of the small caps so I'll look into that tomorrow. There are two types of diodes, the ones that are a cylinder shape that I'm used to and others that look like a drop of ceramic. What is the difference? I broke one of the ceramic ones and replaced it with the other type, will that work? I downloaded a copy of the schematic for this board but it is fuzzy and hard to read the print. Does anyone have a more readable copy they could sent to me?
Thanks for all the help,
Ray
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08-06-2008, 8:36 AM
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Anonymous
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Re: Repairing a CDI box, CX500 '80
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Ray did you change the SCR's?
When I first saw those ceramic diodes I wondered
if they were elderly germanium ones perhaps but as they have the
same forward voltage as silicon ones I now assume they are not.
I'd just replace then with suitable modern ones with the same
or better Vrrm and current rating, the 1N4948/7/9 GP ones look suitable
Reg
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08-06-2008, 6:48 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Although I have them I have not replaced the SCRs yet. I was going to replace one thing at a time to see where the problem was. I'm quite sure my C2 capacitor is bad. I took it out to check about the sparking I saw and it doesn't test well. Unfortunatly the avionics shop at my work where I'm getting help with this doesn't have a suitable replacement for me to try.
Ray
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08-14-2008, 7:00 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Well, I replaced the SCRs, main caps and the C2 cap and it still only fires one side. So I dug out enough of the other box I have to change the main caps. I got it running on that box but not well, maybe slightly better than the it was before. I haven't back to it for afew days.
Ray
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08-14-2008, 10:54 PM
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Harold
Joined on 12-27-2006
Beside Washademoak Lake, N.B. Canada
Posts 350
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Re: Repairing a CDI box, CX500 '80
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I wish I could offer some help, but I don't speak electrical. 
It does sound like you are making progress though
Keep up the good work and keep us posted.
"People are more violently opposed to fur than leather because it's safer to harass rich women than biker gangs."
1978 CX500
1980 CX500 Custom
1981 CX500 Custom
1982 GL500 Silverwing
1975 XL-100
http://www.myspace.com/downwiththebutterfly
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08-18-2008, 7:12 PM
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Ray in Waxhaw
Joined on 06-27-2008
Posts 12
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Re: Repairing a CDI box, CX500 '80
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Has anyone successfully troubleshot a CDI box using the maintenance manual charts on page 17-4, 17-5 with a digital VOM? Some of the numbers on the chart don't make sense.
Does anyone have a copy of the schematic by Charles that is clear enough to read all the small numbers? I have tried enlarging it but still can't read some of the numbers.
Also, my electronics specialist says that the main caps that are original are bi-directional and the ones I have to replace them with are polorized. Does this matter? The new ones are much smaller then the original.
Thanks for all the help,
Ray
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08-19-2008, 9:41 AM
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Shep
Joined on 01-30-2007
Hull.East Yorkshire.England
Posts 1,899
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Re: Repairing a CDI box, CX500 '80
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These are all the pictures I have that may help.I kept them when researching this a couple of years ago but never got round to doing anything with them,
http://www.box.net/shared/b6l2rcuvgx
HTH :)
New Global CX/GL Forum,
http://globalcxglvtwins.hostingdelivered.com/
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08-19-2008, 10:16 AM
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Reg in Bristol
Joined on 03-11-2006
Bristol UK
Posts 291
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Re: Repairing a CDI box, CX500 '80
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Ray
Re the caps:
I'd Carry on regardless.
Its true the electrolytics are polarised but in this case
as its storing a polarised charge and not an alternating one
I'd use tham anyway
Besides Dick and others who have built DIY CDI's used them OK
Size dont matter here, modern caps are probably more efficent than
the ones used back in the 70's
Re the CDI test:
Unless you have the same meters as specified in the manual
forget it.
During resistance and diode tests, meters apply a voltage to the
circuit in question and the voltage applied will affect the result.
The meters used in the manual have a higher output than most
of the ones we use and so will get different results.
Its important to remember that in these tests
the meters are applying the voltage to multiple components not single ones so variations in the input voltage will have correspondingly
different effects on the output.
I suggest you pick out as much of the potting compound as you can and
check for burnt tracks and shorts from your soldering.
got any pics of the job so far? I'd be interested in seeing how your doing
I havent got round to fixing the two I have here.
My sons cleared off with his CX and I dont have a bike to use as
a test bed.
Been busy playing with my beemers and the projects due a Eurosport
(TI) motor.
I'll only go back to a CDI engine if the Euro lump proves to be a
lost cause
Down to one project/rat bike now, when I get a 'round tuit'
Member of the UK CX-GL MCC at
http://www.cx-gl.org.uk/index.html
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