mbullyb Posted December 12, 2015 Report Share Posted December 12, 2015 Hi, ive just replaced a tachometer that didnt work in my Spitfire 1500. I brought the replacement tacho off ebay and it was sold as working. Ive connected it up as per the original but as soon as the ignition is switched on the needle moves to the 70 position and remains there, any ideas? I have two green wires which connect to the spade terminal, a white and black wire to the bullet terminal and two black wires to the body earth? Thanks Mark Link to comment Share on other sites More sharing options...
SpitFire6 Posted December 12, 2015 Report Share Posted December 12, 2015 Hi, Should be green (12V-Ignition) to a terminal. Should be black (ground) to body. Should be green/grey (-ve of coil) to a terminal With just the green and black connected the needle should not move. If the two wires are on the correct terminals and it does not read zero; it's kaput. If it is faulty the few electronics inside could be fixed by a competent electronics person. Suspect a cap has gone short. Cheers, Iain. Link to comment Share on other sites More sharing options...
SpitFire6 Posted December 12, 2015 Report Share Posted December 12, 2015 Suspect C2. Cheers, Iain. Link to comment Share on other sites More sharing options...
mbullyb Posted December 12, 2015 Author Report Share Posted December 12, 2015 Thanks Iain Thats a useful diagram. i might give it a go myself or see if i can find a local electrons shop. Regards mark Link to comment Share on other sites More sharing options...
John Bonnett Posted December 12, 2015 Report Share Posted December 12, 2015 Thanks Iain Thats a useful diagram. i might give it a go myself or see if i can find a local electrons shop. Regards mark Failing that Mark, Speedy Cables will repair it and it will come back like new. Link to comment Share on other sites More sharing options...
rlubikey Posted December 13, 2015 Report Share Posted December 13, 2015 I think all 1500 Spits had voltage-driven tachos. Iain, your diagram is for a current-driven one (has a feed *and* return to points). Here's a voltage tacho. Ignore the extra resistor (in red) which is for converting from 4-cyl to 8-cyl. Richard Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 13, 2015 Report Share Posted December 13, 2015 For components try Maplins or RS components pete Link to comment Share on other sites More sharing options...
mbullyb Posted December 19, 2015 Author Report Share Posted December 19, 2015 Hi Richard, thanks for the correct diagram. ive had the back off and that looks spot on. Pete, I'll give maplins a try. Many Thanks Mark Link to comment Share on other sites More sharing options...
SpitFire6 Posted December 19, 2015 Report Share Posted December 19, 2015 Hi, Apologies Mark for posting the wrong schematic. No idea what the chip is. A triple 5? Hope the schematic gets you sorted & Sorry. Iain. Link to comment Share on other sites More sharing options...
mbullyb Posted December 19, 2015 Author Report Share Posted December 19, 2015 No worries Iain, Can anyone advise what type and voltage rated capacitor will do. At Maplins I can find a number of 0.022 uF and 47 uF capacitors but none rated at 12v? Thanks Mark Link to comment Share on other sites More sharing options...
Simon Posted December 19, 2015 Report Share Posted December 19, 2015 Have you taken it apart to see what type, shape and markings of capacitors are currently fitted as there are different types for different purposes, also some are polarised such as electrothic so you need to ensure you get them round the right way. Looking at the diagram 47 uF is polarised and most likely electrothic, the other are probably standard ceramic. I use CPC as they have everything and also free del do a search here http://cpc.farnell.com/components-passive_capacitors Can you take a pic of them? Link to comment Share on other sites More sharing options...
mbullyb Posted December 19, 2015 Author Report Share Posted December 19, 2015 They have no writing on them at all, just coloured stripes Link to comment Share on other sites More sharing options...
Pete Lewis Posted December 19, 2015 Report Share Posted December 19, 2015 Bit of thread drift In my day coloured rings were on restistors the colours and bands code the rating then capacitors were called condensers and valves had a 6v heater and 90v ht portable radio needed a barrow due to battery weights if you went to sleep listening to the goon show on a crystal set the earphones made your ears flat then came along a transistor one xb104 would run a small speaker .....from a new idea a pp3 battery now wheres that got me pete Link to comment Share on other sites More sharing options...
Simon Posted December 19, 2015 Report Share Posted December 19, 2015 Yes the coloured stripes indicate they are actually resistors. They rarely fail. Is there any obvious damage to any components or any leaking? Check the reverse solder side for any joints that look bad or are broken. If you can post some clear pics then I can tell you what you need. Link to comment Share on other sites More sharing options...
rlubikey Posted December 19, 2015 Report Share Posted December 19, 2015 Mark, check out https://en.wikipedia.org/wiki/Electronic_color_code#Capacitor_color-coding (or use your favourite search engine to look for similar explanations). Choose a voltage rating in excess of the highest voltage it will ever see - I would choose double or more as this will make the component 10-times more reliable! Iain, the chip is a Texas custom job for Smiths. I searched loads of data books and never found it! I'm trying to remember the name of the TSSC Model Officer (can't remember the model either) who found the part, drew the diagram *AND* the component to change to convert the number of cylinders. Richard PS: Simon, capacitor values used to be marked with colours too. Mark, give us a picture of the component/circuit board if you need help identifying it. Link to comment Share on other sites More sharing options...
KevinR Posted December 19, 2015 Report Share Posted December 19, 2015 Polyester capacitors are marked with colour bands Link to comment Share on other sites More sharing options...
mbullyb Posted December 20, 2015 Author Report Share Posted December 20, 2015 Heres some pics https://www.flickr.com/photos/138682070@N02/23761434822/in/photostream/ https://www.flickr.com/photos/138682070@N02/23761196392/in/photostream/ https://www.flickr.com/photos/138682070@N02/23869577235/in/photostream/ Thanks Mark Link to comment Share on other sites More sharing options...
rlubikey Posted December 20, 2015 Report Share Posted December 20, 2015 Heres some pics https://www.flickr.com/photos/138682070@N02/23761434822/in/photostream/ https://www.flickr.com/photos/138682070@N02/23761196392/in/photostream/ https://www.flickr.com/photos/138682070@N02/23869577235/in/photostream/ Thanks Mark Lovely "Liquorice Allsort" polyester capacitors! OK, that first one - the wide red band is actually two reds - so it's red, red, orange, or 2, 2, 3. That's 22 and three noughts, giving 22,000pF (colour stripes and surface-mount capacitor values are givien in picofarads) However, it's more sensible to refer to this value as 22nF or, as on the circuit diagram above, 0.022uF - it's just different ways of saying the same value! The second one is brown, black yellow or 1, 0 followed by 4 noughts (i.e. 5 noughts in total) which gives 100,000pF. As above, it's more usual to say 100nF or 0.1uF. In both cases, the last two bands are black, red. So it looks like the tolerance is 20% (black) and the red means it's 250V (I had to look that one up!). I wondered why the voltage rating was so high. Polyester capacitors just aren't made in very low voltages, but it may also be because that first one is seeing all the spikes on the ignition so the designers chose a robust higher voltage part - and made all the others the same!!! You don't *have* to replace them with polyester, but it would be a good choice for this application. Hope this helps, Richard Link to comment Share on other sites More sharing options...
mbullyb Posted December 21, 2015 Author Report Share Posted December 21, 2015 Thanks Richard, much appreciated. Order has now been placed, i'll let you know how i get on Regards Mark Link to comment Share on other sites More sharing options...
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