Fuggles Posted February 20, 2020 Share Posted February 20, 2020 I have a Hornby class 71 with a burnt-out control board (don't ask!). I have tried unsuccessfully to get a replacement from Hornby and Peters Spares. They both need a parts number before they can start looking, but I don't believe Hornby have issued a service sheet for it. I am reluctant to bin this one as it is the best running loco in my collection (still OK on analogue but I need it to work in DCC). Any help would be much appreciated. Link to post Share on other sites More sharing options...
JSpencer Posted February 20, 2020 Share Posted February 20, 2020 I would probably just remove the board and directly wire in the DCC chip. 2 Link to post Share on other sites More sharing options...
John Tomlinson Posted February 20, 2020 Share Posted February 20, 2020 Have you tried searching for the service sheet on the Hornby website, or with Lendons of Cardiff who list service sheets and are also spares suppliers? Also try searching Ebay under "OO gauge - Locomotives - 71" and see what comes up. John. Link to post Share on other sites More sharing options...
micklner Posted February 20, 2020 Share Posted February 20, 2020 Phone Hornby 2 Link to post Share on other sites More sharing options...
John Tomlinson Posted February 20, 2020 Share Posted February 20, 2020 I just tried the Ebay search as I suggested, and no 71 spares came up at all. I'd go with Micklner's advice and failing that wire the chip directly as suggested. John. 2 Link to post Share on other sites More sharing options...
Kelly Posted February 20, 2020 Share Posted February 20, 2020 Get a socket harness, and replace the board, and retain the pluggable chip option that way. You could even get a 21pin one if you wanted to add extra functions that the original pcb won't offer with an 8pin socket. 1 Link to post Share on other sites More sharing options...
Guest Half-full Posted February 20, 2020 Share Posted February 20, 2020 There are these on eBay. I used one on a converting a Lima 31, very quick and easy to get going Link to post Share on other sites More sharing options...
Kelly Posted February 20, 2020 Share Posted February 20, 2020 Another option that might be easier to fit inside the body is this. Other manufacturers/versions exist. IMO this is much better than hardwiring the loco, as blown decoders don't mean needing to get the soldering iron out, etc. and conversion for DC is simple too. 1 Link to post Share on other sites More sharing options...
Fuggles Posted February 21, 2020 Author Share Posted February 21, 2020 Thank you everyone for your suggestions. I will certainly make some more enquiries. I never thought of directly wiring the chip. It shouldn't be too tricky. I'll let you know how I get on. Link to post Share on other sites More sharing options...
RAF96 Posted February 21, 2020 Share Posted February 21, 2020 I concur with ringing HCC they may be able to dig out a spare board from a returned loco and you are likely to get it foc. Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted February 21, 2020 Share Posted February 21, 2020 20 hours ago, Fuggles said: I have a Hornby class 71 with a burnt-out control board (don't ask!)... (still OK on analogue but I need it to work in DCC). I have to ask! What exactly is 'burnt out'? If the loco still runs on DC as suggested by your text in parentheses, then what is it that prevents a decoder being plugged into the decoder socket? If there's some very minor damage to the board - a component gone 'phut' or something - yet it is still a functional runner on DC it should run on DCC when a decoder is installed. If so I would suggest continuing to use it. Hornby will eventually get a diagram out and you can replace the board then if you feel it matters. I have had small components burn out in models from Bachmann, Hornby and Oxford in recent years while the model was on DC test before decoder fitting, supply of small surface mounted components is clearly of ultra-cheapo grade! None of this has affected the motor circuit with the decoder installed. The interior lights don't work on one Bachmann Cravens DMU car is all, the others were capacitors letting go, in the RFI suppression circuit which is not required for DCC anyway. 1 hour ago, Fuggles said: ... I never thought of directly wiring the chip. It shouldn't be too tricky... It's actually exceedingly easy, if you are happy with electrical soldering. So, another question; are you able to solder? If not, hardwiring ranges from tricky to well-nigh impossible. 1 Link to post Share on other sites More sharing options...
Fuggles Posted February 23, 2020 Author Share Posted February 23, 2020 The attached photos should help. It was hot enough to burn the roof. Unsure of what exactly had been destroyed I was reluctant to plug in a decoder in case it too was damaged. It might bee that all the circuitry/components do is the lights. Since Friday I have acquired some attachments as per suggestions so I'll try one. I'm very happy soldering. Thank you. Link to post Share on other sites More sharing options...
RMweb Premium spamcan61 Posted February 23, 2020 RMweb Premium Share Posted February 23, 2020 Apropos of nothing really; crikey that tantalum capacitor has certainly let the magic smoke out, the bypassing of R1 may or may not be a contributory factor in its demise. Even industrial rated tantalums do this occasionally (I try and design them out wherever possible) so not super surprising a commercial grade one goes pop occasionally. Link to post Share on other sites More sharing options...
Fuggles Posted February 24, 2020 Author Share Posted February 24, 2020 It was quite dramatic - smoke emitting from the hole on the roof. It's going to need some drastic plastic surgery! Are you suggesting that there should be a resistor at R1 rather than a link? Curious Link to post Share on other sites More sharing options...
RMweb Premium spamcan61 Posted February 24, 2020 RMweb Premium Share Posted February 24, 2020 9 hours ago, Fuggles said: It was quite dramatic - smoke emitting from the hole on the roof. It's going to need some drastic plastic surgery! Are you suggesting that there should be a resistor at R1 rather than a link? Curious There is a resistor under the link if you look at the photo closely; I'm not sure if this is an official modification or somebody's bodge, as I couldn't find a photo online of an unmolested PCB. 1 Link to post Share on other sites More sharing options...
mikesndbs Posted August 15, 2020 Share Posted August 15, 2020 This burnout is super shocking, I note that one of the electrolytic caps has also overheated and must be considered unsafe now! Hornby should be made aware of this as clearly this is/was a very serious fire risk and if as designed could be a product recall issue. I am going to be checking my PCB very carefully for bridged resistors as shown here. I can also see the PCB is cracked, really hope this is a after market bodge. Sorry you have had this happen Link to post Share on other sites More sharing options...
SteveyDee68 Posted August 16, 2020 Share Posted August 16, 2020 Crikey - I have a Class 71 (DC) that has only been test run! Hope this isn't a common occurence! Steve S Link to post Share on other sites More sharing options...
RAF96 Posted August 17, 2020 Share Posted August 17, 2020 17 hours ago, SteveyDee68 said: Crikey - I have a Class 71 (DC) that has only been test run! Hope this isn't a common occurence! Steve S Check for that R1 shorting link. If you have it worry a bit/lot, if not all is probably well. Link to post Share on other sites More sharing options...
bigherb Posted August 17, 2020 Share Posted August 17, 2020 On 24/02/2020 at 19:24, spamcan61 said: There is a resistor under the link if you look at the photo closely; I'm not sure if this is an official modification or somebody's bodge, as I couldn't find a photo online of an unmolested PCB. It looks like a bodge, there is a resistor fitted to mine. 1 1 Link to post Share on other sites More sharing options...
mikesndbs Posted August 17, 2020 Share Posted August 17, 2020 Only a small value by the looks of it 5R6, and I can now see that one of the diodes had exploded as well. One has to wonder what happened Link to post Share on other sites More sharing options...
bigherb Posted August 17, 2020 Share Posted August 17, 2020 1 hour ago, mikesndbs said: Only a small value by the looks of it 5R6, and I can now see that one of the diodes had exploded as well. One has to wonder what happened Looks like a 560 ohm to me. Link to post Share on other sites More sharing options...
RAF96 Posted August 19, 2020 Share Posted August 19, 2020 (edited) I took the liberty of informing Hornby about the problem in case it was a general safety hazard. They think not, as according to Hornby Tech R1 should not have been linked out and it was certainly not a factory mod. The over current resulting was most likely the cause of the burn out, as the resistor controls supply to the loco lighting services. Cab lights are switched by the green wire under control of F1 and each has its own resistor. Edit - these resistors are on the separate cab lights pcbs not the main board. Edited August 19, 2020 by RAF96 More info about cab light resistors 2 Link to post Share on other sites More sharing options...
mikesndbs Posted August 19, 2020 Share Posted August 19, 2020 1 hour ago, RAF96 said: I took the liberty of informing Hornby about the problem in case it was a general safety hazard. They think not, as according to Hornby Tech R1 should not have been linked out and it was certainly not a factory mod. The over current resulting was most likely the cause of the burn out, as the resistor controls supply to the loco lighting services. Cab lights are switched by the green wire under control of F1 and each has its own resistor. Edit - these resistors are on the separate cab lights pcbs not the main board. That's good news indeed! Would you happen to know which resistor controls which lighting please? I am unhappy with the very bright marker lights and almost non existent headcode boxes and am wondering if I could simply swap the feed wires around. Many thanks Link to post Share on other sites More sharing options...
RMweb Premium spamcan61 Posted August 19, 2020 RMweb Premium Share Posted August 19, 2020 On 17/08/2020 at 17:00, bigherb said: It looks like a bodge, there is a resistor fitted to mine. Whoops, the fried components I thought were tantalum capacitors are/were in fact diodes, makes the fry up even more impressive! 1 Link to post Share on other sites More sharing options...
RAF96 Posted August 19, 2020 Share Posted August 19, 2020 (edited) 1 hour ago, mikesndbs said: That's good news indeed! Would you happen to know which resistor controls which lighting please? I am unhappy with the very bright marker lights and almost non existent headcode boxes and am wondering if I could simply swap the feed wires around. Many thanks R4 Rear cab R11 Rear whites R13 Rear reds R12 Front cab R14 Front whites R10 Front reds All as marked on an actual PCB. Still trying to find a part number for the main PCB for you. Edited August 19, 2020 by RAF96 2 Link to post Share on other sites More sharing options...
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