Martin-369195 Posted February 6 Share Posted February 6 Can anyone advise on a suitable replacement for the power supply in a Digital Sound TT:120 set?This is from the HM7000 manual:WARNING… Other Power Sources… Laptop Type Power Bricks and Batteries etc… Generally speaking, the HM7000 decoders will work with any 14VDC – 16VDC regulated power supply. The decoders are however rated up to 27V, so higher voltages could be used…. Do not exceed 20V.DCC Concepts have https://www.dccconcepts.com/product/18v-dc-at-2a-uk-a-medical-grade-power-supply-for-dc-dcc-systems-2-5mm-dc-plug/ (18V, 2A)MegaPoints stock https://megapointscontrollers.co.uk/product/12-volt-8-amp-silent-regulated-power-supply/?v=79cba1185463 (12V, 8A)My very, very limited understanding is that more locos need more amps so the MegaPoints has the amps, but not the volts whereas the DCC Concepts has the volts but not the amps.Are there other, more suitable alternatives?Cheers,Martin Link to comment Share on other sites More sharing options...
96RAF Posted February 6 Share Posted February 6 The Hornby 4-amp brick is suitable to run most size layouts. Mine runs a single garage sized 00 layout.You should estimate your total load by averaging the highest current draw of all your expected on-track locos and all the accessories you intend to drive from track voltage, i.e. those without their own power supply like HM6010 modules.Once you have the grand total you can look for a solution.The important thing to look for in a power source is short circuit and overload protection. Some laptop supplies do not have any. I am not sure what medical grade power is. Link to comment Share on other sites More sharing options...
Martin-369195 Posted February 6 Author Share Posted February 6 Thanks 96RAF.R7337 (https://uk.hornby.com/products/hm7020-psu-solution-harness-digital-15v-4-amp-transformer-r7337) fits the bill and appears to have a 2.5mm jack to connect to the TT:120 TT8029 Digital Power Connecting Track 166mm supplied in the set.Does anyone know the limit of the set supplied transformer - how many locos (ignoring lit pullman coaches)?Martin Link to comment Share on other sites More sharing options...
Fishmanoz Posted February 6 Share Posted February 6 Two reliably, sometimes three. That’s digital set, not analog where experience says sometimes none. Link to comment Share on other sites More sharing options...
ateshci Posted February 6 Share Posted February 6 A current Hornby HM7000 sound loco ( full blast and at the slip limit ) will draw 250-300mA at most. Link to comment Share on other sites More sharing options...
ntpntpntp Posted February 6 Share Posted February 6 R7337 is the bundle Hattons were knocking out at £25 before they closed. I bought one (for other purposes actually hoping it would be AC output but it is DC). I usually reckon on 500mA per train as a convenient high estimate (of course the actual current draw will vary for different mechanisms and loads). I have some ancient N gauge locos which do draw 400mA. In most cases the draw will be a lot less with modern models. Never load up a power supply to the max, always leave some headroom. R7337 should easily handle half a dozen trains running at the same time. Keep in mind that other stationary DCC trains will still be drawing a little current for lights and sounds, and don't forget coach lighting adds to the load. As has been said above, appropriate short circuit protection is very important - there's no point having an 8 amp power supply if it will happily keep sourcing that current under fault conditions and cook your wiring or models. Link to comment Share on other sites More sharing options...
ateshci Posted February 6 Share Posted February 6 I've found it very convenient to establish sectors where the supply is protected by a Polyswitch (self resetting PTC-type fuse) rated 1,5A. It trips @ 3A rather fast and that current is tolerated by the rather flimsy pickup blades and what have you in TT Link to comment Share on other sites More sharing options...
96RAF Posted February 6 Share Posted February 6 The digital PSUs have a 6.3mm jack and the analogue PSUs have a 5.25mm jack. The two are obviously not interchangeable but Hornby have two different adapter cables the link their respective PSU to the power track twin-pin input. Link to comment Share on other sites More sharing options...
Iron Body Posted March 8 Share Posted March 8 (edited) Taunton Controls sell a 15v 5A PSU for £42, a bit cheaper and more powerfull than the Hornby one. They do a OO and an N version, not sure which is better for tt120. https://tauntoncontrolsltd.co.uk/product-category/accessory/ Edited March 8 by Iron Body Link to comment Share on other sites More sharing options...
LTSR_NSE Posted March 8 Share Posted March 8 Confirmation that those Taunton PSUs include short circuit & overload protection, would be needed before recommending them for TT:120 use. The specs/instruction sheets for the Taunton controllers mention the protections being included - but a sheet for the PSUs doesn’t appear to be readily available. 1 Link to comment Share on other sites More sharing options...
96RAF Posted March 8 Share Posted March 8 The Taunton power supply does not specify its output as dc or ac but the controller hook up diagram talks about an ac supply. That is no good for Hornby kit and you would also need to confirm with them about self protection and overload as that also appears to be a function of their controller. The transformer is represented as isolating only meaning it prevents main potential appearing at the output. You will also have to devise a suitable connection twixt transformer and track. Link to comment Share on other sites More sharing options...
Iron Body Posted March 8 Share Posted March 8 4 hours ago, 96RAF said: The Taunton power supply does not specify its output as dc or ac but the controller hook up diagram talks about an ac supply. That is no good for Hornby kit and you would also need to confirm with them about self protection and overload as that also appears to be a function of their controller. The transformer is represented as isolating only meaning it prevents main potential appearing at the output. You will also have to devise a suitable connection twixt transformer and track. Yes, I just came on board to make the same points. Sorry I didn't expand earlier. I use their 511 master controller as a separate DCC controller which the PSU is designed for. The 511 has its' own protection so the PSU does not need it. My 3 locos have HM7000 decoders which the 511 drives nicely in parallel with the app. So two people will be able to work the layout at once. (That is when it is ready..) 1 Link to comment Share on other sites More sharing options...
Iron Body Posted March 8 Share Posted March 8 19 minutes ago, Iron Body said: Yes, I just came on board to make the same points. Sorry I didn't expand earlier. I use their 511 master controller as a separate DCC controller which the PSU is designed for. The 511 has its' own protection so the PSU does not need it. My 3 locos have HM7000 decoders which the 511 drives nicely in parallel with the app. So two people will be able to work the layout at once. (That is when it is ready..) Just looked at the PSU itself and it says the output is 15VAC, so the output is AC. And is thermal protected, but not overload. Link to comment Share on other sites More sharing options...
96RAF Posted March 8 Share Posted March 8 1 hour ago, Iron Body said: Just looked at the PSU itself and it says the output is 15VAC, so the output is AC. And is thermal protected, but not overload. No good for direct supply to the track per the Hornby brick plus adapter cable. It can only be used with the ZTC controller, which could power the track. Link to comment Share on other sites More sharing options...
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