8-Pin TXS Decoder & Speaker in a Hornby R3531 M7 0-4-4T

[Rob773]

Has anyone on here successfully fitted an 8-pin sound decoder and speaker in the R3531 M7 0-4-4 tank loco? The loco's instructions suggest there are cut-outs in the side tanks to accommodate these but I have found that the cut-out that seems to be for the decoder is about 2 mm shorter than the decoder PCB and it doesn't fit, yet there is another cut-out in the other tank which would take a speaker!

I am assuming that fitting an R7336 is impossible and am therefore waiting for the R7335 to be released which I believe is a much smaller PCB.

I'd be interested to know if anyone has managed to fit an R7336 and, if so, how?

Thank you.

Regards, Rob

 

[Fishmanoz]

For those like me who don’t keep the R number catalogue in their head, the R7335 is the HM7000-8, 8-pin non-sound decoder.

Then given an 8TXS plus PB has been fitted in a TT:120 08, albeit with a lot of modification, I cannot imagine this fit to be not possible with a little innovation/modification. 

[SteveM6]

I sensed a bit of a grumble that the TXS decoder didn't fit the M7 - not surprising when the loco predates the decoder design by at least seven years.

As Fishy says, ingenuity and modifications to the loco (not the decoder!!) could make it fit.

[Going Spare]

The decoder fitting instructions within the Product Support menu (predating the advent of TXS decoders by several years) states that the tank weight should be removed to provide room for the decoder and illustrates how the retaining screw is revealed.

[Rob773]

Thank you all for your comments, I will revisit the loco instructions and then see if I can find a supplier that actually has an 8-pin TXS in stock!

Cheers,

Rob

[ColinB]

24 minutes ago, Going Spare said:

The decoder fitting instructions within the Product Support menu (predating the advent of TXS decoders by several years) states that the tank weight should be removed to provide room for the decoder and illustrates how the retaining screw is revealed.

Not that I have one of these but I would suspect one of the biggest issues would be adding a Powerpack or suitable "stay alive". Given the short wheelbase of this loco I imagine it would need it.

[Rob773]

Indeed I would predict that this loco would benefit from a power bank, although there are pickups on the rear bogie, as well as the driving wheels. However, I can't imagine that removing the tank weight would be a good idea as this loco is light enough as it is and I'm sure would suffer from loss of traction if the weight was removed.

[Bulleidboy]

I am not going to say this installation is impossible as someone will come along and do it. I have tried twice to install the 8pin TXS sound decoder into this loco and failed. Steve has already explained why there is very little or no room in older loco's to fit the new TXS decoders. It is one of the reasons a number of my loco's have TCS DP2X-UK direct plug-in decoders fitted - no harness to worry about. Even removing both weights it might be possible to fit the decoder on one side and the speaker on the other, but as the chassis and motor take up every millimeter of space in the body there is no room for the harness. The cab roof can be removed (carefully), which provided crew have not been fitted would give some room for a power bank to be fitted, this of course is assuming you have managed  to fit the decoder and speaker. Also I have not explored removing the coal bunker floor - there does appear to be a screwdriver slot, but I was not prepared to risk damaging the loco body. So until a smaller TXS sound decoder appears this loco will have to remain plain DCC operated. There are of course other suppliers of sound decoders for this loco - but at a much higher cost - and they still need to be fitted!!. 

Edited June 5 by Bulleidboy

[Brew Man]

Yes, I recently bought a Bachmann 64XX Panier Tank and there was no way I could fit a TXS sound decoder, principally because it has a 6 pin socket. But apart from that I couldn't see how the bulky 8 pin wold fit. So I bought a 6 pin micro direct plug Zimo fitted with 64XX sound from YouChoos. That fitted neatly. Still going to be struggle getting a SA in there though. Maybe tantalums. They are, as BB says though considerably more expensive than TXS.

[Bulleidboy]

I just did a YouTube search on Hornby M7/Sound - plenty of videos demonstrating the sound, but none on the fitting. One did say sugar cube speaker and small stay alive went into the coal bunker - how do you get into the coal bunker???  The M7 that runs on my layout, I bought from Walking the Dog (he's rarely on the Hornby site nowadays), and it has real coal and the top of the bunker appears firmly fixed, however I do have a new M7 lurking somewhere in the stock cupboard, and it may be that the fake coal and the top of the bunker lift off, as in other Hornby loco's - Hornby Adams Radial. 

Edited June 5 by Bulleidboy

[Rob773]

Thank you very much for your comments. I've gone ahead and removed the weight from the right-hand side tank, as recommended by the instructions in the loco box, and I have managed to fit an R7336 8-pin TXS decoder into it but not with a speaker (I have an R7336 with a broken speaker socket so this is what I've fitted). I tried a speaker with the smallest enclosure and it fits perfectly into the cut-out in the weight in the left-hand side tank, but the enclosure fouls the rear driving wheel when you try to refit the body, so I've concluded there's no way to fit a speaker without removing the left-hand weight (although I've not explored the possibility of fitting one in the bunker under the removable coal load but assume this would require drilling a hole somewhere to poke the wires through!). The loco is now more prone to wheelspin, especially up gradients, but the power pick-up doesn't seem too bad. It traverses my Peco double slips at 25% traction without stalling.