R&S HMP4040 knob - Page 1
Forum section: electronics / repair

author: seavan
author_rank: Contributor
timestamp: June 11, 2025, 01:26:32 am
content: I am thinking of getting HMP4040 off the ebay. It's missing a knobhttps://i.ebayimg.com/images/g/jrIAAeSwAbRoSDLf/s-l1600.jpgand I cannot find parts catalog anywhere. Would appreciate any help.

author: D2236
author_rank: Regular Contributor
timestamp: June 11, 2025, 03:06:01 am
content: It looks like the shaft of the encoder is snapped off. I replaced a missing knob with this from eBay. It is a bit of a tight fit on the shaft, but it works. This looks better than the original knob for me.https://www.ebay.com/itm/235973093884

author: seavan
author_rank: Contributor
timestamp: June 11, 2025, 03:36:44 am
content: It does look like the shaft is snapped off. Thank you for pointing out. I need to either find the original part or maybe 3d-print it. If it's not too much trouble, can you take a photo without the knob?

author: D2236
author_rank: Regular Contributor
timestamp: June 11, 2025, 04:03:20 am
content: I can take pictures, but it may be easier just to replace the whole encoder. They most probably use a common available part for this. Hopefully, someone in this forum did a tear-down and can provide a part number for you.I guess it may be possible to drill into the rest of the remaining shaft and glue something in order to extend it, to make some suitable shaft. The problem may be that the encoder itself got damaged when the shaft was snapped off. This will require replacement to get the unit working again.

author: seavan
author_rank: Contributor
timestamp: June 11, 2025, 04:24:04 am
content: If I can find the part number, replacing is the best option. I went through all tear down videos that I could findI am afraid, it maybe not just the shaft but the encoder broken too.

author: D2236
author_rank: Regular Contributor
timestamp: June 11, 2025, 04:30:50 am
content: Put out a request in the forum for the part number or type. Someone may know of a suitable replacement.

author: dew
author_rank: Contributor
timestamp: July 08, 2025, 10:56:40 pm
content: Sorry I snatched that one, but I have more of those encoders if anyone needs them.

author: D2236
author_rank: Regular Contributor
timestamp: July 08, 2025, 10:59:10 pm
content: Any part numbers visible on them?

author: dew
author_rank: Contributor
timestamp: July 08, 2025, 11:08:22 pm
content: It's an Alps mechanical encoder. No part numbers on them. I got a few of them in China, but seems to be a real Alps encoder. Neither Alps website nor vendors like Mouser, Digikey, Arrow, etc. have those that HAMEG was using. They are probably end-of-life parts. I had to buy them by trial and error method. Got a shorter shaft models first. Had to wait over a month each time.As close as I could get to the right one on Alps website:https://tech.alpsalpine.com/e/products/category/encorders/sub/01/series/ec11e/

author: D2236
author_rank: Regular Contributor
timestamp: July 08, 2025, 11:35:01 pm
content: I wonder if these may work?https://www.mouser.com/ProductDetail/Same-Sky/RIC11-22S10D5S-TH?qs=HoCaDK9Nz5fxypdms%252BmQUg%3D%3D

author: dew
author_rank: Contributor
timestamp: July 09, 2025, 04:35:39 am
content: These might work, but they are lacking four additional mounting points. Their shafts are sticking out above a flat face of a rather heavy unit. I fixed at least three of those units with broken encoders. Most of the time, the encoder snaps in half. If you install this type, it might rip out tracks on the PCB instead. And they can simply be broken while you are moving something in front of the unit, even if your hand is empty.Those I use have a 12mm shaft, 15 PPR resolution, and 30 detents. Feels just like an OEM part. At least I can't tell the difference. But resolution and number of detents, even though they can change the interface feel, are not critical.

author: pdenisowski
author_rank: Super Contributor
timestamp: July 09, 2025, 11:37:59 am
content: The HMP4040 is currently in production, so you might want to contact R&S and see if you can order the knob/shaft as a spare part.

author: dew
author_rank: Contributor
timestamp: July 10, 2025, 02:51:32 pm
content: I bet $10 (or one of those encoders) that R&S won't sell either the encoder or the board it's mounted on.

author: D2236
author_rank: Regular Contributor
timestamp: July 10, 2025, 10:03:50 pm
content: I will be surprised if they are willing to sell these parts. More than likely, you will be asked to send the unit for repair. $$

author: ps1734
author_rank: Newbie
timestamp: September 07, 2025, 04:23:54 am
content: Looks like Alps Alpine series EC11J which is obsolete. You can find Bourns makes a replacement under PEC11J series. Perfectly matches the footprint shown in the images above. Just need D shaft knob instead.I just bought one of these broken encoder shaft HMP4040 from the same ebay seller. Once I get it and tear apart, I'll update here with results.Edit: My HMP4040 arrived and the bourns encoder will work great. I ordered this one: PEC11J-9215F-S0015