Not sure if this is a problem specific to my MX-1200 or the way I'm inputting the HEX codes.  My IR database got wiped out in case you're wondering why I'm messing around with HEX codes...

I got the spreadsheet from Anthem, did the drag & drop for every button and all the codes work for single press. Problem is the AVM-70 volume control does not respond repeatedly to press and hold, although the remote indicates IR is transmitting continuously.

[Link: anthemav.com]

Example:

Function: volume up
Device: 856A
Data: 9F
NEC1: 900A 006D 0000 0001 856A 9F60
Pronto classic: 0000 006D 0022 0002 0155 00AA 0015 0040 0015 0015 0015 0040 0015 0015 0015 0015 0015 0015 0015 0015 0015 0040 0015 0015 0015 0040 0015 0015 0015 0040 0015 0015 0015 0040 0015 0040 0015 0015 0015 0040 0015 0040 0015 0040 0015 0040 0015 0040 0015 0015 0015 0015 0015 0040 0015 0015 0015 0015 0015 0015 0015 0015 0015 0015 0015 0040 0015 0040 0015 0015 0015 05ED 0155 0055 0015 0E47

I copied only the long Pronto classic code into the HEX editor, no preamble, and then dropped it on the button.  Works but no repeat - have to press VOL+ 40 times to raise volume 20 dB!

Am I doing it right?

Not familiar with the software for the MX-1200 model. With other URC models click on the IR macro 2 times and it will open up a window allowing you to change the number of repeats.

Neither the repeat count nor "repeat when held" options work. It's the latter I'm after, as you would expect for any volume control.

General question: am I pasting the right code into the HEX editor?

Yes, you are putting in the correct format.

Do you have the original remote still? This happens sometimes and a way to fix it, is to just learn the IR from the original remote.
Sometimes this can happen with the original remote learning as well. In that case you have to try the different methods = learn short presses, learn long presses, learn while feathering the button, learn while blocking the first part of the press, etc....

I encountered the same problem when trying to control a Yamaha receiver with Lirc. It turned, although the receiver reacted properly on the correct signal, it was very picky about the timing between the intro segment and the repeat, and between the repeats. These are the fifth last and the last number of the Pronto Hex. For reference here is the correct signal as computed by IrScrutinizer:

0000 006C 0022 0002 015B 00AD 0016 0041 0016 0016 0016 0041 0016 0016 0016 0016 0016 0016 0016 0016 0016 0041 0016 0016 0016 0041 0016 0016 0016 0041 0016 0016 0016 0041 0016 0041 0016 0016 0016 0041 0016 0041 0016 0041 0016 0041 0016 0041 0016 0016 0016 0016 0016 0041 0016 0016 0016 0016 0016 0016 0016 0016 0016 0016 0016 0041 0016 0041 0016 0016 0016 0622 015B 0057 0016 0E6C

As you can see, these numbers differs a bit, but not very much. You can try if changing these numbers make a difference.

The best thing would be to capture a working repeating signal, without repeat reduction and cleaning, and post it here.

Yes I have the original remote and I started learning codes but it suddenly stopped working (learned a few then would not respond to further attempts to learn the IR). However I tried it again just now and it's working.

This time I tried the "Learn-2" option and it works much better. You short press the button and then it waits for you to long press the button. That seems to have done the trick!

Thank you.

I appreciate the reply but this is over my head. I will save this info for future reference though. Thank you.