Editing CVs on Hornby Decoder

[Ian-375106]

I have just acquired a OO Bachmann class 37 loco fitted with a Hornby 21 pin decoder.

CV 7 reveals it to be version 134. Is this a a TTS decoder?

I am using a Bachmann dynamis controller.

I need to balance the volume levels on some of the functions by changing the values of CVs.

Where can I get the list of CV addresses for this decoder?

Are all decoder CV addresses the same? i.e NRM standard

Also, I cannot read CV 2. (Start voltage" I just get the message "error on reading" is this normal for this decoder?

[Ian-375106]

[Ian-375106]

[96RAF]

Hornby had a 21 pin Sapphire non sound decoder which came with an 8/21 adapter harness.

Their early sound locos, pre-TTS/TXS were ESU 21-pin.

All TTS decoders were 8 pin.

The newer TXS decoders can be 8, 18 or 21 pin.

Sapphire, ESU and TTS all had dark PCB’s and TXS has a white PCB.

CV2 should be readable on Sapphire and ESU decoders as well as TXS.

If your decoder is TTS it will be 8 pin and an adapter 21/8. To confirm it is TTS read CV159, which is the sound chip ID.

R8249 is a basic 8 pin non-sound decoder upon which TTS was based.

[P-Henny]

To confirm that the brand is indeed a Hornby, what is the value of CV8. For Hornby it should be 48 (see NMRA code list below for CV8). Confirming that it is indeed a Hornby would really help to narrow down exactly what it is, because as 96RAF says, the ONLY 21 pin decoder Hornby have ever done to date, is the R8245 Sapphire which is a non-sound decoder. Being 21 pin means it cannot be a TTS, the only 21 pin sound decoders Hornby have ever used historically (pre-dating TXS) was a ESU Loksound 21 pin. This decoder would read 151 for CV8, not 48 even though it was a Hornby factory fitted decoder.

appendix_a_s-9_2_2_5.pdf

With regard your supplementary query "Are all decoder CV addresses the same? i.e NRM standard."

Some CVs are NMRA defined standard, whilst others (the majority) are Manufacturer defined. This NMRA document linked below lists which are which:

S-9.2.2 2012.10.doc - s-9.2.2_decoder_cvs_2012.07.pdf

If the fitted decoder was a R8245 Sapphire, then the manual for it (contains CV info) is linked below:

R8245 Sapphire Loco Decoder Manual – Hornby Support

Noting that the decoder is very unlikely to be the R8245 Sapphire because the manual above states that CV7 is 10 and not 134. Plus, of course, it is not a sound decoder, which realistically eliminates it as being a possibility.

The internet page linked below may assist with your research.

JMRI decoder identification

EDIT: The intermediate posts that were held back for approval were not visible when this reply was written.

It appears that the decoder was an 8 pin one after all and not 21 pin as stated in the O.P.