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sharris

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  1. It should be possible to find out what resistance mat is used if you have a multimeter. Make sure the unit is unplugged and connect the meter between the two track terminals and set it to the resistance range (if you can select ranges on the meter 0-1000 ohms or something similar). Switch the 'resistance' switch to 'high resistance' and wind the control knob to full speed - the multimeter should now show the resistance between the wiper position which should be at one end of its travel, and the opposite end of the mat. You may have to go full forwards and full reverse to get the proper resistance - you need the bridge rectifier reverse biased so it is high impedance and doesn't appear in the overall circuit impedance - choose the forwards/reverse measurement with the higher value.
  2. After a day or two of track making I seem to have ended up with a pile of plastic spiders - the sprues that Exactoscale chairs come on. Has anyone come up with a David Attenborough friendly way of reusing or recycling them?
  3. It could also be a failure of the resistance switch or an open circuit at the lower end of the resistance mat. In low resistance mode the 'bottom' end of the resistance mat is left unconnected and the mat is purely a series resistor making it a current controller. In high resistance mode the lower end is connected to the 0V line making the output voltage proportional to the wiper setting- I.e. Voltage control which should give better slow speed control. Any break in the lower end of the mat or the switch will result in it reverting to low resistance rocket mode.
  4. Mods: can you remove this copy please -accidentally duplicated when the RMWeb server timed out.
  5. Are C&L EM gauge templates actually P4 templates shrunk a bit? Measuring templates for a 60' track panel Printed from Templot: 240mm (well done Martin!) EMGS template: 238mm C&L Template: 230.5mm 230.5/240 = 0.960 18.2/18.83 = 0.967 Is it Coincidence that the ratios are so close?
  6. To quote ZZTop, She's got legs... Each of the four modules has one pair of legs, except for one (the first to be put up) that has two pairs. Legs are 2" wide pairs of 6mm ply strips with 6mm spacers at top, middle and bottom and attached to the boards with M6 bolts. While most boards only have only one pair of legs, I've drilled them all to accept 2 pairs. This is a cunning plan that means I can set up any two adjacent boards to work on them in my workshop (which is exactly long enough to accommodate 2 boards) while using the leg cross bracing to support the other two boards. This is also the reason I decided to bolt the legs to the outside rather than the inside of the board sides. Next steps are to glue and screw the remaining top surfaces (so far I've only done two) - then time to lay down the Templot templates so I can work out where the cross-bracing can go without getting in the way of point motors. Those with eagle eyes might notice a kink in the boards in the first picture- this is down to the lack of levelness in my lounge floor- at some point I'll have to get to height adjusters for the legs.
  7. Might work as-is, and as you say, it's a cheap solution, but with a minimum Hfe of 1000 vs the combined original of 2000, you *might* not get the same maximum current capability with the components as specified and you may want to reduce the speed control pot and resistor values by about half. I say *might* because these are minimum specified values and if you get a good one the gain might be somewhat higher and it could work to the full power of the original anyway.
  8. I know it's rather late in the day (8 years late!) but since JohnnyDMonic just re-opened it, it's the first I've seen. I'm surprised by the small value of the capacitor to the left of the LM317 - I would expect something much larger, more like 1000uF, to smooth the output of the bridge rectifier to DC before applying it to the regulator, in-fact, as you have with the second (13 July) minimal LM317 design you showed. If I couldn't find a ZTX450, the 2N3055 would not be a suitable substitute. The darlington emitter follower, which the two transistors create in this circuit have a current gain which is the combined gain of the two transistors. 2N3055s have a very low current gain (typically specified as 20-70) while the ZTX450 has a higher gain (typically 100-300) - worst case a darlington made from a pair of 2N3055s would only have a gain of 400, while a ZTX450/2N3055 would be 2000. The ZTX450/2N3055 combination has a higher input impedance which better suits the component values for the speed and inertia control pots, and surrounding resistors and capacitors. Replace it with a 2N3055/2N3055 pair and you'd have to reduce the values of the resistors considerably and increase the capacitor values - and you'd need a bigger box! Incidently, Wikipedia tells me that 2N3055s are widely counterfeited with underpowered dies inside the packages, so you might want to buy from a reputable supplier rather than a random Ebay seller.
  9. Occasionally they are real - I've had them call me a few times for real over the years, usually within seconds of me making an unusual sequence of transactions or a transaction from an unusual place, and a couple of other times when they've been suspect, and the skilled fraudsters can be quite convincing. Bank cards have an enquiries telephone number printed on the back - take the details of the caller and tell them you will call them back on the number on the card to confirm.
  10. John, if you're going to be seeing Phil again soon, please pass on my condolences.
  11. TrustPilot appear to do two things with their scores: 1. they weight them with a depreciation factor so that more recent scores have more of an effect than older scores, although in this case with consistent 1 star rating the weighting doesn't really affect things that much. 2. they use a Bayesian average. It's kind of like a starting point that uses pre-existing knowledge (i.e. it's an estimate of what companies are usually like - TrustPilot seem to think an average score for a company is between 3 and 4 stars). This is a statistical method that can be effective for small datasets, but it won't be an effective representation of the data if it is systematically different to the larger community. In the case of TrustPilot they say the effect is to stop a company being completely trashed or completely exalted by a single bad or good review - effectively TrustPilot gives away a few moderately good scores for free to start with. As more and more reviews are added, the effect of this 'preset' will wear off. With only 10 reviews, I think it hasn't completely worn off yet, so CooperCraft is still free-loading points from an expectation of it being an average company rather then entirely on its own merit. TrustPilot's explanation: https://support.trustpilot.com/hc/en-us/articles/201748946 And the science bit: https://en.wikipedia.org/wiki/Bayesian_average
  12. About time any reference to Slaters 4mm wagons was removed from his site too, now that they're prominently displayed in Slaters manufactured boxes on Eileen's and H&A's stands at shows. (Also time Slaters added the MR wagons back into their own site too!)
  13. There was a march, I was on it - it was very good natured with no fractiousness that I was aware of (I found that comment untoward); it did, however mean some tube stations had to close for a while due to overcrowding. I was at AP today- maybe because some of the best layouts I'd seen before, it didn't give me a real "wow" effect. Burntisland and the Cambrian one (guides had sold out and I can't remember the name now) were my standout features, along with seeing most of the Slaters 4mm wagon range in the flesh being sold again by Eileen's and H&A. I did however have a 'careful now!' moment seeing Dapol's 7mm offerings which were quite tempting.
  14. Agreed, Jol - one of the other benefits of small suppliers keeping things in house is that for clumsy klutzes like me, if I break or lose a casting or something from a kit, I can email John at LRM (for example) and ask if I can have a replacement bit and he might be able to send a spare one from stock, or from the caster's next batch. It is quite possible that these parts would not be economical to sell in enough quantity on their own if a 3rd party was handling orders and had to be pre-stocked with them.
  15. Of course, you'd have to supply us with an endless stream of (mostly) awful films into the bargain.
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