Products > Test Equipment
HP 1741A oscilloscope - restoration project
MuchMore:
Hey
I am new to this Forum, so I guess a short introduction is necessary:
I am:
- a mechanical engineering student
- 22 years old
- from Austria (not Australia :) )
- (have) some experience in electronics
- quiet frustrated with my first oscilloscope
Now to my Problem:
I recently bought my first oscilloscope an HP 1740. After some testing I figured the time/sweep assembly must have some bad switch/contacts. I carefully removed the main sweep board and immediately saw that there was someone in before me. After cleaning the contacts I spotted that one "flyleg" was bend so I brought it back to the standard position and recognized the metal was very weak, after a closer "look" it snapped off......
does anyone have a good idea how to fix "my" mistake?? replacing the leg seams quite difficult. And I guess HP does not sell replacement parts!?!
P.s.: All remaining grammar mistakes are placed on purpose, to ensure an pleasing reading experience...
tekfan:
Hi! Welcome to the forum.
Probably your best bet on replacing the switch wiper is to find a similar sheet of metal and make the part yourself.
The sheet metal is very thin so don't expect your local hardware store to have it in stock. It also must be quite springy so it doesn't deform when you turn the switch.
You can ask in the hardware stores if they know where you can get spring steel sheet (''federblech'').
You can also try to find a mechanical clock because the spring inside the clock is just the right material. It may be too thick but still worth a try. If you have a mechanical egg timer it probably has this type of spring inside. The only thing you need to do is to cut and bend it into the correct shape. You could also try to find a watchmaker or jeweler and as if he's got some similar metal.
To disassemble the switch to get the wiper contacts out you will have to do the following:
On the other side of the switch there are several marks where the two halves of the switch were sealed together by melting the plastic. You will have to carefully remove this plastic dimples so that the two switch halves can be separated. You can even try to drill out the plastic. Just be careful not to damage the rest of the switch.
Once you have the switch apart you can remove the broken wiper contact and another one so that you know the exact shape of it.
To put the two halves together you will probably have to use some sort of glue. It's easier to remove afterwards if it needs repair again.
Here you can see the 4 melted plastic dimples that hold the two halves together:
HackedFridgeMagnet:
Yes very light spring steel.
I did one with a banana plug and an angle grinder, It worked but would have been no good, long term.
I then got some spring steel and was set up to fix it when somebody gave me another scope which I then cannibalised for parts.
MuchMore:
Hey
thanks for the fast replies.
After some thinking I remembered that there was a useless Battery Tester in my drawer.
And sure enough there where two flylegs inside.
The idea of removing the molten nipples is risky, since the plastic is soooo old I fear it will shatter while Drilling.
I came up with the idea of removing a pocked, with a dremel, on the front big enough to fit the new flyleg and glue it with epoxy.
However if I mess this up it is over...
Since the new flyleg is at least coated with copper is it a longtherm issue off rupping on the goldpats?
I could get a Nickel-solution to make it like the other once..??
P.s.: some rant from me: I HATE THE IMPERIAL SYSTEM, now I can go to an expensive hardware store to get does *** Hex keys that will fit the screws inside the knops. |O
vk6zgo:
The problem with the Imperial System is all the little inconsistencies,like the fact that US Gallons are smaller than British/Australian ones,so that a "44 Gallon drum" in Oz translates to a "55 Gallon drum" in the USA.
They are both,thankfully,near as dammit to 200litres.
Old Brit type equipment is likely to have Whitworth,UNC,UNF,BA (AAARRRGH!),or BSF (double AAARRRGH!) screws,while the smaller screw sizes used in US equipment are of a incomprehensible & completely incompatible series.
In the larger sizes,UNF is pretty much common to both,some UNC,SAE,& Whitworth are compatible in very large sizes.
Even metric screws have weird things,though.--- small Japanese metric screws were different to the same nominal size German screws---though this may have been sorted out in more recent times.
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