Mac 300 no longer 'boots' or resets

[pscandrett]

Hi, I'm having a bit of a problem with a Martin Mac 300 with which I just can't seem to work out what's wrong - can anyone help please?

 

The basic issue is that it won't 'boot'. I'll try to explain how I got here.

 

It started with a pan limit stop/sensor problem. Having had this issue before, which we'd fixed before too, I knew what I was aiming for. In this instance the whole pan sensor/stop assembly had become loose on the screws it was mounted on and rotated - and fixing that was a relatively simple case of tightening the screws and readjusting it. So far so good.

 

Now, as you might know, in order to get to this assembly you have to clear the way through as it's mounted pretty much on the axle of the yoke in the centre of the base where the pan stop bar can hit it. Previously - and so what I did this time too - we'd removed the central mounting unit of the yoke and head from the base (undoing the eight security screws holding it to the base), giving access to the stop and sensor. After adjusting it, I put it all back again... and then the mac wouldn't work.

 

Oh dear, thought I, perhaps I've caught a cable somewhere; however, I can't see any evidence of cables being caught or unplugged or similar.

 

The state of play now is that the mac300 doesn't boot. When plugged in, nothing comes up on the display (and the buttons don't work), the steppers are still 'loose' (ie one can move the head around and about without any resistance as well as colour wheels, shutter etc) and it doesn't reset itself. There is a slight buzz coming from inside the head somewhere - as if a stepper is vibrating slightly - when the mains is plugged in, but that's what it sits there doing.

 

When plugged in, the 5V, 12V, 30V and other 5V LEDs on the mainboard are lit, which is partly what's confusing me - that's indicating to me that the board is powered fine; I have checked and it seems that the stepper chips and all connectors on this board are seated correctly too.

 

Now I'm getting to the stage of not knowing what's going on. I have another, working, Mac 300 which I've opened the base of in order to probe various points to check that all potentials are what they 'should' be (since I don't have any technical documents to tell me what things should be). I've unscrewed the capacitor (which I presume to be the PF cap) to gain more access to the wiring down there. It seems that the potentials on the choc block on the top of the base are the same, and from what access I can get the outputs of the transformers seem to be the same too (but I'm not 100% sure of this without disassembling further). The first board the L/N wires go into - a noise suppressor board perhaps? - seems to be outputting the 'right' things, too, but again it's difficult to tell. I've not looked at the ballast other than a quick check of cables because the lamp striking isn't an issue yet!

 

Another confusing point - and what also pointed me towards cable issues - is that once, but only once, yesterday, when I was reassemling the unit again - the Mac reset fine when I plugged it in - with the exception that the LED display appeared dead. I haven't been able to duplicate this - even a few minutes after its successful reset.

 

I have access to the martin.com/service technical site (I've been on the basic Martin training course) but can't find anything going to this level of diagnosis to help. All the otherwise standard problems I encounter (hall sensors etc) are irrelevant here because this Mac never gets that far now!

 

I do have a supply of some spare parts from a couple of old dead macs; we have a stock of 2xMac300s and 10xMac250+s in total plus parts so if noone can help I think my next line of attack will be replacing things one by one - transformer, this L/N input board, that sort of thing, to try to diagnose the problem... unfortunately these will just be stabs in the dark really now :-( Can anyone advise please?

 

Help!

 

Many thanks

[maeterlinck]

If you are confident that all the cables are in good condition and you do not have any shorts then I would start with swapping or piggy backing the main board in the yoke. It will either reset fine in which case you need a new main board. Or it won't which might suggest a wiring issue.

As a side not you have mentioned metering so I'm assume that you've metered the 3 power rails rather than relying on the LEDs which can appear fine when all is not. As if bad power has killed a board you would not want to kill another, I assume...

HTH

[Richard CSL]

Hi it sounds like you are having a technical nightmare, so what little I can offer is that I have also had many problems in the past with mac 250´s. and the majority of problems , especially on older units , are the link wires, as you know the main board is mounted in the arm of the yoke, crazy idea I know, and it sounds like the display board link wires are cracked.

 

You should also check the main transformer power connector at the bottom of the board, pink, brown, purple wires from memory. If thwese are cracked the display led´s may still show a voltage, but as current is required the wires fail.

 

I know it´s not much , but the alternative costs around 500 pounds to replace the main board..

 

Just a pointer but the wires normally crack at the base of the yoke centre tube. if you pull them gently you can normally find the break.

 

good luck.

[johnhuson]

As all the power appears to be correct in the fixture it sounds like it's just lost it's software some how, could of been a static shock to the board during repair. I would suggest trying re flashing the software in the fixture unfortunately you will need an upload device such as an MP-2 or a DABS1. If you do manage to get hold of such a device you will need to set the fixture to boot mode by moving the link PL121 on the main board, this will force the fixture to look for new software. Once the upload is complete return the link to it's original fixture and then re-power the fixture.

 

It may not work but it sounds a likely scenario to me and will do no further damage if it's not the case.

[pscandrett]

As a side not you have mentioned metering so I'm assume that you've metered the 3 power rails

Many thanks to all who've replied and thank you for the suggestions, particularly to focus on the cables. That was going to be my first line of attack - to look at the power looms in particular and try swapping them out.

 

I'll start off with the good news... I've managed to fix it, after a bit of a worry! :-)

 

To cut a long story short, I metered the power input cables into the mainboard from the transformer on the base on both the broken Mac 300 and a known good Mac 300. I also did the same thing for a Mac 250+ (bearing in mind that generally the whole thing is identical) and worked out what the voltages 'should' roughly be. Rather bizarrely, it seemed that most of the voltages on the broken mac were similar to the good ones, but just all plugged in wrongly - in other words the transformer was outputting the right voltages, but they were being fed to the wrong places on the mainboard.

 

Comparing the voltage differences between the 'wrong' feeds and comparing them to the voltage differences of the 'right' feeds explains why the supply LEDs were illuminated correctly; some of the potentials between feeds were within, say, 10% of the 'correct' differences and so an LED/circuit that was expecting 9V and got 9.6V would probably have lit. Consequently, to fix the problems with the mac, I analysed what was presented from the transformer and 'just' swapped the cables round on the outputs of the transformer - the purple ones were transposed, as were the orange ones.

 

What's really, really confusing me is that a) I hadn't unclipped those outputs of the transformer along that side nor indeed the connector on the mainboard and b) the Mac has appeared to work fine for all the time we've had it - somehow it's been operating on the wrong voltage differences. These voltage differences were, by and large, clearly similar to the desired potentials, however; I can only assume that when I clonked the base when I was fixing the pan sensor and/or the tolerances of the supply from the transformer increased it was sufficient for the unit to finally complain about it all. The puzzle is compounded by the fact the grey, purple and orange wires on that side were numbered in sharpie, implying someone has disassembled it in the past and put it back together again; presumably they put it together wrongly. Fortunately, nothing appears to be damaged and I've run it on test for a while now and it seems OK.

 

From what I can see, it's a miracle that the Mac ever worked in the first place, let alone reliably (which it's been up until now)! I'll certainly bear in mind some of your suggestions for future diagnoses of faults (particularly the cable wear ones, thanks) but for now I can breathe easier again.

 

Thanks for your help!