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Replacement oscilloscope Knobs?

TriodeLuvr

TriodeLuvr

So many electrons, so little time!
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Looking for a replacement for the small red knob shown below. My old scope has four of these, and they're all cracking apart from age. The shaft is a 6mm T18 spline. The knobs are 0.48" (12.2mm) high X 0.395" (10mm) diameter at the widest point.

Scope Knob.JPG

Antique Electronic Supply sells a style that fits the shaft (below), but it's only .305" diameter and will probably look odd on the scope. Does anyone know of a source for replacement that would be more like the originals?

AES Knobs.jpg

Jack
 
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You can try super glue on the knob itself, not between the knob and the shaft.

I once made a knob for a Topward oscilloscope with an orange marette

P1310322.JPGP1310317.JPG
 
These knobs are a tight fit on the splines so they don't slip off when the push-pull switches are pulled out. Over the years, the plastic has shrunk enough to cause them to crack (this scope is about 40 years old). Anyway, even if super glue could hold the cracks together, the knobs would just break somewhere else. Interesting idea about the twist-on connector. :)

Jack
 
Well with all the dead scopes and old tube scopes robbed of tubes one would think there is a pile of knobs available out there. Providing the make and model and the part you need might just get a response from someone with a knob that will work for you.
 
Well, after a lot of searching, it's down to three sources. The originals are 10mm X 12.2mm high. The gray/black/white knobs in my first post are 9mm X 14.2mm. I could probably trim the length on my lathe, but I was hoping this wouldn't turn into a project of its own. So, they'll fit, but not my first choice.

I think the same knobs are available in colors here, but they don't list the shaft size or even if they're splined.
Micro Knobs - Colors
Micro Knobs.jpg
Then there are these knobs, which are essentially the same size as the originals, including the shaft diameter and type. The seller is in Britain, but they'll ship to the US at a reasonable cost. I wish the body color was different, but they're knurled, which I like. They're also "plug N play" for fit and function. I'll probably give these a try.
Eurorack Knobs
Knobs..jpg
Jack
 
Know I've seen the second rype you posted in different colors. Not just the cap. Probably ebay? But it has been awhile since I've looked for knobs there.
 
Lavane said:
Know I've seen the second rype you posted in different colors. Not just the cap. Probably ebay? But it has been awhile since I've looked for knobs there.
Click to expand...
You might be thinking about these:

Davies 1900H Clones

Davies 1900H Clone.jpg

Unfortunately, they're 12mm X 16mm high. Much too large. I haven't found any in this style in a smaller size. If you know of some, please let me know.

Jack
 
I've always looked to eBay when I need specific parts like that.

Other places I've found replacement knobs has been "Tubes and More" website, Mouser, and Digi-Key. Tek may still have them, but I haven't bought anything direct from them.
 
Well, darn. The 10mm knobs came in from UK, but they don't fit correctly. They're so loose, they basically just fall off the shaft. There's no grip at all. I did measure one of the control shafts, and it's definitely 6mm with 18 splines. One thing interesting is that the new knobs only have half the number of splines. Don't know if that's the reason for the problem. Anyone here who might have seen something like this before?

10mm Knob 02.jpg

10mm Knob.JPG

Jack
 
Can't you just get some super glue into the cracks of the old one?
I had the knob for the vent selector in my 2002 Jeep Wrangler split.
I super glued it and clamped it tight enough to keep it together until it dried.
It's been working fine now for about 6 or more years.
I had bought some super glue that had a thin needle on the end of the small plastic bottle. The glue went right into the crack.
As for those knobs you bought, I haven't seen splined knobs like that.
 
I think the problem with glue is that these knobs have shrunk over time. This scope was purchased brand new by me in the mid-'80s. Also, despite the cracks, they were devilishly tight and difficult to remove. Two of them had to be pried off with a screwdriver. Superglue doesn't fill gaps, so the knobs would need to be clamped together after the application. I'm certain they won't be able to be reinstalled after that's done (the process would reduce their circumference even further). FWIW, three of the original knobs were able to be reinstalled in this condition (I had removed them in order to clean the controls and switches). One came apart completely in two halves.

I'm waiting to hear back from the company that sold me the new knobs. Maybe they'll have some helpful info as to why they don't fit. Thanks for your input!

Jack
 
Cant you spread the spline post a little with a flat head screw driver and see if it will make a tighter fit?

Athanasios
 
I'm sure you saw the several sit3s selling replacement knobs for various scopes. Several seemed to maybe have want you needed, but some in gray, not orange. What model and series scope?
 
Nashou66 said:
Cant you spread the spline post a little with a flat head screw driver and see if it will make a tighter fit?
Click to expand...
I remember trying that years ago on a piece of audio gear, but it didn't work well. I'm thinking that a thin wrap of tape over the shaft might work if I can find just the right thickness. Maybe I'll try that later today.
Lavane said:
I'm sure you saw the several sit3s selling replacement knobs for various scopes. Several seemed to maybe have want you needed, but some in gray, not orange. What model and series scope?
Click to expand...
No, I haven't seen those sites. Guess I didn't Google the right keywords. This is a Hitachi V-1050F.

The seller contacted me and said these knobs fit tight on the Alpha clones they sell. I can only think the clones are different enough that they grab the splines in the knob. I made measurements yesterday, and the inner diameter of these knobs at the base of the splines is considerably larger than 6mm. They're not so large that they would fit a 1/4" splined shaft (like Marshall style), but they're definitely not right. I also noticed under magnification that the base of the splines is much narrower than the original knobs. Splines in the originals are triangular, which is how CAD drawings of 18T pots show the shafts. So, I think these knobs don't meet the 18T specification, despite the fact they might grab onto certain Chinese-made pots.

Jack
 
I only see one small Hitachi knob on ebay off of a V-1100A.
The sites I found were for Tekronix mostly.
 
Lavane said:
The sites I found were for Tekronix mostly.
Click to expand...
Some of the red Tek CAL knobs are exactly the right size externally (10mm X 12mm), and they use a setscrew, which would resolve the issue of obtaining the proper grip. However, they have a solid aluminum bushing with a hole for a tiny 2mm shaft. Maybe they could be drilled out to 6mm, but the knobs are tapered. It would be a major challenge to secure the knob on a drill table or chuck it in a lathe without damaging the plastic. Plus, I'm not sure there's enough aluminum in the bushing to do this, and the knobs might not even be readily available. The search continues...

Jack
 
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