Using HM7000 with Accurathrash 8-ohm speaker

[Philip-380655]

Has anyone got any experience using the HM7000-21TXS with Accurascale's Accurathrash 8-ohm speaker?

I have an Accurascale Class 37 which works just fine with a 21TXS chip (bar some lighting issues which I can live with) and the supplied sugarcube speaker. The loco also has an onboard speaker but it's not clear if that functions when the sugarcube is plugged in.

I would like to replace the sugarcube with an 8-ohm Accurathrash speaker to get more of that nice bassy tractor noise. I disconnected the sugarcube from the chip and plugged the Accurathrash into the speaker socket on the Class 37's PCB. All appeared well for a couple of laps of the layout until the loco suddenly stopped, its lights went out, and it remained unresponsive for quite some time. I was convinced I'd blown the chip somehow but it did eventually come back to life - after I'd removed the Accurathrash. Meanwhile my phone maintained its Bluetooth connection to my HM6010 accessory controller which continued working just fine.

I am now worried that using the Accurathrash by plugging it into the PCB might damage the chip. Since it's an 8-ohm speaker I'd guess that connecting it directly to the chip - as the original sugarcube was - should be OK but I'd have to remove the existing connector and solder it to the pads on the chip. I'm happy to do that if that's the solution but I'd like to be sure I was doing the right thing.

So, if anyone has experience of this I'd be grateful to hear about it!

Edited August 17 by Philip-380655

[96RAF]

Generally if a 21-pin decoder is used with a loco provisioned speaker then the external plug in speaker should not be used as you are connecting both speakers which will result in a different impedance depending upon how the loco speaker and Hornby speaker are wired - series or parallel. The decoder manual states that the sound amp has enough oomph to drive greater wattage speakers at 8 Ω.

[ColinB]

I assume it is the 8 ohm you fitted, they do do a 4 ohm one. It should be alright as it is still 8 ohm. Now if it was the Accurascale sound decoder you did have to turn the sound down but you are using a HM7000. I was going to fit one of those to my class 73 but they had run out when I went to order it.

[Philip-380655]

Just a quick follow up to this. I now believe the sudden stop problem I had with my Accurascale 37 was actually a Bluetooth glitch. However for peace of mind I have removed the factory-fitted speaker, which turned out to be a relatively easy thing to do, and re-fitted the 8-ohm Accurathrash on its own via the PCB socket. All is now well and I'm getting that lovely tractor rumble. No sign of any sudden stops or other worrying stuff.

[96RAF]

Interesting comment in the latest Roads&Rails email . . .

 

[ColinB]

4 hours ago, 96RAF said:

Interesting comment in the latest Roads&Rails email . . .

 

There was a bug in the class 37s sound decoder implementation. On the early one I bought, no problem at all, the later one kept resetting itself. It appears they got the volume wrong so the extra current trips the decoders, there was a CV you adjust to make it work reliably. I have never opened the later class 37 up to see whether it is an 8 ohm or 4 ohm speaker. A 4 ohm speaker would explain a lot.

[LTSR_NSE]

Who is going to purchase an after market speaker for an Accurascale loco? (Aside from a tiny second hand market)

Since those models come with lifetime warranty, if an incorrect speaker is factory-fitted, surely a correct replacement would be available if customers contacted AccuraSupport!?