continuous sweep

[Triforce]

Hi,got a teaser here!
M/C started to give a constant sweep cycle without stopping.
On investigation found it to be the M.P. chassis.
We have O.O.R. control boxes wired in to the m/c`s to give automatic sweep reverse on the event of an off spot pin,with the table returning to 0 degrees.
I arrived on site to find that the O.O.R. box was burnt out with the M.P. chassis giving constant cycle.So I transferred the M.P. chassis to another m/c to find that the fault had transferred.
I assumed it to be the M.P. chassis at fault.So I changed the sweep A.B.contactor-still the same.
I then checked all the pins on the C1 circuit-all ok and positioned correctely-still the same.
C.B.1;C.B.2;C.B.3 all ok.
Al relays ok:-S;M;M2.
The chassis is a 9800 with a mark v p.c. board.
All interconnecting wiring looks ok.
Was it the O.O.R. box shorting out, to cause the fault on the m.p. chassis or visa versa?
I`m puzzeled!!!

[JimDorsin]

Re: continuous sweep

I dont have any EXP with that specific OOR reverse device, but did you by chance check your sweep run button on the chassis??

[Tablejam]

Re: continuous sweep

You did not mention if you swapped boards.

[Triforce]

Re: continuous sweep

Yeah Tablejam,I forgot to mention I also changed the p.c. board over to elimanate it.
I did check the sweep button on the side of the chassis,Jim.It`s ok.
Now you see i`m running out of options!
It`s the first time in my 15 years that i`ve come across this fault.You think you have everything covered then a fault like this raises it`s ugly head!

[JimDorsin]

Re: continuous sweep

I am not sure what differenced may be in the chassis to for your 220 power over there. Not sure I can be a bunch of help.

[Andrew]

Re: continuous sweep

The OOR device probably piggybacks the sweep run output of the board (which also connects to the sweep run switch and runs through the sweep switch back to the contactor).

I guess if something catastrophic happened to the OOR device, it could do damage to the sweep output of the board. It would have to be pretty bad though (like putting 220V up the sweep output). But I expect that would equally damage the contactor too.

Another shot in the dark:

Does the other machine (on which the chassis now sits) also have an OOR device? If so, can you tell if it's activating? Can you disable it (turn it off)? I'm wondering if the problem is actually the offspot input and not the sweep output causing the otherwise working OOR device to make the sweep run. Is the sweep running backwards?

[Triforce]

Re: continuous sweep

Thanks for the replies!
The chassis in question has the fault described,no matter what m/c it is connected to with a fully functional O.O.R. sw`connected to that m/c.
I just don`t know whether the cooked O.O.R.sw`caused the fault on the chassis or the other way round?
I have since fitted a new O.O.R sw` to the problem m/c with a different M.P. and everything works fine.
So I still have this M.P. chassis with continuous sweep run,having changed the p.c. board;contactor;3 relays;all C1 pins checked & C2;CB1,2,3 checked and sweep button,table,and cycle buttons checked.
The only thing I have`nt changed is the table contactor,but I would`nt have thought it would have affected the sweep circuit?
Will be on the fault tomorrow,so will keep you posted if I fall on it!

[JimDorsin]

Re: continuous sweep

is the sweep contactor pulling in when you get the continous sweep?? need to acertain if this is a low voltage or high voltage fault... (most likley low, but better to eliminate the easy forst)

[Fudge]

Re: continuous sweep

On our M.P's we have diodes protecting the board they are located under the M.P board. Try checking these to see if one of them has gone there should be 3 one for each motor. Worth a shot.

[Fudge]

Re: continuous sweep

Sorry forgot to mention had this problem before and this was the fault replaced the diode sorted the problem.

[triac]

Re: continuous sweep

I don’t have MP chassis, but I do have the MP schematics.

If the “S” relay is energized during a continuous sweep, I see 1 of 3 possibilities.

1.) Defective sweep switch on the chassis. Disconnect the wires to this switch and do a continuity check across the terminals without pushing switch….you should have no continuity.

2.) Defective varsitor going to ground (earth) coming from the relay coil A2. Although it is supposed to go to ground, there should be a lot of resistance or no continuity to ground. Disconnect and retry chassis.

3.) C2A-21D has shorted to ground. You can do a continuity check on this to ground, but if either items 1 and 2 were grounded….they would need to be disconnected, because if either the varsitor or sweep switch were grounded, you would get some continuity.

Items 1,2 and 3 are all tied together. A grounded wire from either component or the component being defective will cause a continuous sweep.

I suspect item 2 (the varsitor) to be the culprit by the circumstances that you described.

Triac

[Andrew]

Re: continuous sweep

Originally posted by triac:
I suspect item 2 (the varsitor) to be the culprit by the circumstances that you described.

<font size="2" face="Verdana, Helvetica, sans-serif">Great suggestion, Triac, as usual. [img]/content/btubb/images/%%GRAEMLIN_URL%%/143.gif[/img]

[Triforce]

Re: continuous sweep

Thanks for the excellent info guys!
I checked the diodes as Fudge mentioned and found that the one that comes from the relay coil A2,as Triac mentioned was at fault!
There was total continuity between the varsitor and ground so I dissconnected it as Triac mentioned and then tested the chassis.
It got rid of the continuous sweep fault!
New problem has now arose on the m/c that give the original fault on the M.P.!
A good M.P. that was fitted a few days ago started to give the continous sweep problem again!!O.O.R.sw` ok along with everything else previously tested.
So I preceeded to test the varsitor that was defective on the other M.P. chassis to find that this one was also defective!
I then disconnected it like I did with the other one and tested it on a different m/c-puff of smoke from the p.c. board!
On checking the p.c. board the resistors no`s 67 and 68 where frazzled!
Not to sure what else might be now defective,but will look into replacing the resistors for now!
Getting back to the problem m/c.The only other thing I can see that is iffy is a buzzing shuttle solenoid.
Surely can`t be owt to do with that!
I`ll keep plugging on!
Thanks again for the input guys!

[Andrew]

Re: continuous sweep

You should replace the varistor with a new one, not just remove it. It protects the rest of the circuit from damage.

It is likely that something (like the OOR device) is producing high voltage on the sweep circuit.

What is the status of the OOR device on the original machine? Is the dodgy one still fitted, or did you replace it?

Andrew.

[Triforce]

Re: continuous sweep

The OOR device is good on the problem m/c.I changed it last week when the other one cooked!
I personally tested it yesterday and it works fine.
I think I might dissconnect the OOR device on this m/c only to see if fault dissapears and then take it from there.
I only dissconnected the varistor temporarily to see if fault dissapeared on problem chassis,as Triac stated in no.2 suggestion.
Was by no means going to leave it dissconnected permanently!