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Gina, Paul, thanks for the advice, appreciate it. You know in the classroom I often remind pupils to confirm the output from the bench supply with a voltmeter and not assume it will kick out what the dial is set to. I should have taken my own advice. I need to be more respectful with this stuff or I'm going to lose some expensive kit. At the end of the day I think you are right in that I was just unlucky with this one, it wasn't meant to be my "forever" psu as Kirstie Allsop would say The new one is humming gently in the background and the my little panel meter shows a steady at 13.8V. I'm happy, and I've learnt something new about power supplies. Jim

Paul, yep I don't think I'd embarrass myself now by taking it into Maplin, I should have done that in the first instance - I'm too impatient at times. I may ask the technicians at school to take a quick look at it, if there is no easy fix then I'll chalk this one down to experience. I'm just so relieved that the mount wasn't damaged. Overall what is your experience with this line of psu regarding reliability? I was happy to go for a like replacement given the comments from other SGL users (above) and I must admit, I do like the build quality of it. Jim

Thanks for that, I must admit I've always had good a experience with Maplin, they do tend to be very reasonable. I've been a bit silly though - I opened the faulty psu to have a look inside. The variable resistor you described was there (2 x) one I believe to control the regulated output the other not sure - part of the regulation circuit. Could not see anything obvious - capacitors all looked good as was the external fuse. On the back panel it says there is also a internal fuse but I couldn't spot it - maybe a thermal fuse on the transformer - something was wrapped in heat-shrink coming off the transformer. I may yet have a word with Maplin to see if there is anything they can do but I'd need to let them know I've opened it - I think that will the killer - ach well lessons learned. Jim

Picked up a new psu all is well, looking like clear skys tonight as well - one happy astronomer Jim

Thanks Gina. There is a Maplin store in Dundee, I'll take a drive in tomorrow after work and pick up a replacement. This time I'll make sure to do two things - measure the output voltage and keep the receipt! Jim

Thanks Steve and Steve, good to have positive confirmation on the psu's normal output characteristics. In one respect, it looks like I've been lucky that the mount hasn't suffered, I suspect it has been operating like that for some time. Also ironic that the work I've been doing on the observatory was to install a control panel - few switches for the mount and ancillaries and a panel meter to monitor the supply to the mount. I should have known better but that is the first time I have checked the supply output. That little panel meter could well have just saved my mount from being fried! It may be cloudy tonight but I'm happy Jim

Yes you want to avoid any trip hazard, I only have a few metres to walk to mine but its always with trepidation as my eyes adjust to the dark - I've walked into the washing line a few times too many! Looks like the rotovator is the way ahead with the grass cut before. How are you planning to level out the path once the rotovator churns it over - would the tractor bucket smooth it over? Jim

I've never used one of those things Gina but I would imagine that as you say it may well not like long grass. My petrol lawnmower often stalls if I try to go over grass of any length. Be careful with it. If the rotovator doesn't work you could try spraying the grass with weedkiller then laying the fabric direct on the top once it has died backed. It would of course mean you'd have to use a raised edge each side to act as a border. Maybe not ideal but it may save a lot of work. Jim

Yes it's got to be goosed I'm afraid. A no load supply of 21.5 V against a regulated output of 13.8 V is just a little too high of a margin for comfort. Time to look for a new psu, I'll consign this one to use in the garage for less sensitive tasks. Just out of interest, the AZ's manual advice on power supply is copied below. It suggests a max of 16V, looks like they built in a reasonable margin thankfully. Off to look for a new psu. Jim from AZ EQ6 ops manual: "Output Voltage: DC 11V (minimum) to DC 16V (maximum). Voltage not in this range might cause permanent damage to the motor controller or the hand controller. • Output Current: 4A for power supply with 11V output voltage, 2.5A for power supply with 16V output voltage. • Do not use an un-regulated AC-to-DC adapter. When choosing an AC adapter, it is recommended to use a switching power supply with 15V output voltage and at least 3A output current. "

Funny my initial thought (hope) was that what I was seeing was a no load voltage (supply emf) and that it would drop once connected to a load; what AndyG describes as regulated on load. But the same voltage was measured under load both on the mount and on bench load. Not a calibration or meter setting issue , I wish it was a simple mater of fat fingers (has happened before) but not this time. Under bench load and while supplying the mount the voltage read 21.5V and didn't drop to the expected 13.8V. Now the mount was only loaded lightly with my SW 80mm but even with slewing on both axis the voltage held at 21.5V. I checked the mount after using a power bank and it all worked well, no harm done. The mount itself must have an internal voltage regulator. Just thinking if the XM21X supply is regulated on load it may well be that a heavier mount load would see the voltage supply regulated to 13.8V. I suspect that its been operating like this since I got it and the mount clearly hasn't suffered any harm. Some more investigation needed I think when the mount is properly loaded up. Jim

I've been working on my electrics in the observatory, getting things more permanently wired up now that I've got a main supply installed. As part of the setup I installed a little panel meter to measure the voltage and current on my dc supply (Maplin XM21X). I gave it a wee test run and to my horror rather than providing a regulated 13.8V it was supplying a regulated (I think) 21.5 V. I've had this power supply for the past year, bought from Maplin, and it's been powering my AZEQ6 without any problem; until now I've haven't put a voltmeter across it so it may well be just a recent fault (I hope it is at least). The receipt for it is long gone (habit of mine not keeping receipts), so I'm not really sure what I can do with it now; I'm assuming that there is no internal adjustment to be made. I guess I could drop the voltage externally but it makes me wonder what else may be wrong with it. I wonder if anyone else has had similar problems with the XM21X, I know it's a popular power supply. Jim

Oh that must be so frustrating Gina, you have to wonder why they would do that. Jim

Thanks Gina I get a real kick of maintaining and driving it. It's a bit like the astronomy - challenges to be overcome, problems to be solved - I'm always happiest when I'm working on something. Jim

Bricks or stone should work well in holding down the fabric, good thinking. An advantage of your plan for a wider path should mean less of a trip hazard I guess as you won't be so tempted to walk off the path itself. Here's my other diversion Gina, a 1967 MGB. She's one year older than me and in better condition! I guess a little bit like your tractor the maintenance is fairly straightforward, greasing and annual oil change in the main. What I have found is that if I run the car regularly it tends to be more reliable - no electronics, no ecu, abs, or power steering - just twin carburetors spring leaf suspension and lots of fun. These old machines are great and well worth preserving. Jim

Gina I don't think you need to use pegs to tie the fabric down, at least the stuff that was laid by the builders around my house has no ties - just held in place by the weight of the stones above. Having said that if you're laying such a large area maybe staking it down would be a good idea just to stop the breeze catching it as you are working. I wouldn't go for anything fancy, a nail with a broad head or a clothes peg would do, lift them out once you got the stone down. Love the tractor Gina, she is a beauty, do you do anything in the way of routine maintenance to keep her going?

Jings, I've just looked with envy through the "Show Me Your Eyepiece Case" thread - left thinking I'm not a proper astronomer until I own a few Naglars. Now Gina goes and tells us that she has a tractor!!!! And I thought I had arrived when I got a wheelbarrow with a pneumatic tyre instead of one of those hard things you got on your first bike as a kid. Jim

You've made good progress on the structure of the observatory Magnus. I'm looking forward to following your progress and learning about the automation. Jim

One way of removing the trip hazard would be to increase the height of whatever you use to define the edge of the path. A small knee high fence may work - trellis panel, picket or even conifer hedge. Starts adding to the overall cost though but you could add it as and when you were ready. Jim http://www.homebase.co.uk/en/homebaseuk/forest-picket-fence-edging-485567

Gina have you already ruled out something like pea shingle - I find it comfortable under foot because of the small grain size it yields easily around your feet when walking on it. I wouldn't have thought ice would be a problem on it either - its doesn't act as a continuous surface so any ice would be localised and break up. Unlike bark it won't be wind blown, picked up by birds nor carried by your foot into the house. I think for your particular need a pea shingle path would potentially be a cheap option and relatively straightforward to install. Cover the path with anti weed fabric, hammer in some stakes and nail in some lengths of batten either side to act as a retaining wall for the shingle. Jim