OFF TOPIC QUESTION Fluke/Philips PM3350A scope
On Friday last I was at the local surplus store, which is giving up after 30 years, and ran across a Fluke/Philips PM3350A scope in fantastic condition. I bought it for a modest $40.00.
I have downloaded a User's Manual but it is rather silent surrounding my question. Perhaps I have overlooked the information I seek.
It’s silly - all of the analog and digital functions of this scope seem properly functional. Of course, I need to play with it and learn its menus, but it appears to be in excellent condition.
The one exception is the “Scale illuminator”. Turning the knob does nothing and out of all the features and functions of this scope that is surprising. To the best of my knowledge the User’s Manual is silent on the scale illuminator except to mention its location.
Does anyone know if the illuminator only works under certain settings or conditions which I haven’t stumbled across yet?
Is it a side illuminated graticule like 500 series Tek scopes employing little lamps, or a CRT flood gun similar to the old HP 180 series?
As long as I am asking for your indulgence for my off topic questions does anyone have an original printed User’s Manual for this scope which you no longer need?
You are most welcome to PM me.
Thanks for you time and consideration.
The schematics show that the graticule illuminator is a simple circuit, not controlled by software. The front panel pot drives a couple of transistors that, in turn, drive the bulb. Just a standard old-school analog circuit.toggle quoted messageShow quoted text
As Toby suggests, first check the bulb. That's by far the most probable problem. And if it turns out not to be the bulb, it will be trivial to find the problem.
In too many scopes, replacing the bulb involves more disassembly than one would prefer. If that is the case here, you may wish to consider replacing the bulb with an LED so that you won't ever have to go through the hassle again.
Btw, If you only have the user manual, you'll want to download the service manual.
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford, CA 94305-4070
On 10/4/2020 09:06, ken chalfant wrote:
I have one of these scope's and the scale illuminator works in all
positions. Your lamps, pot or the regulator may be faulty.
On mine the shaft of the illuminator is broken and the knob is missing. If
some kind soul has a spare pot and knob I would be interested in buying
same. Both are a European type not available in the US.
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This series of Philips scopes is terrific, I have used them for many years, and find them very easy to use.
You have hit on the *one feature* that is only *so-so*, the scale illuminator. If you turn the lights off in the room,
you may be able to see it, if not, it is a single miniature lamp, sitting op top of the CRT in a clear plastic wedge.
Pop off the top cover and you can see it plainly. It might be burned out.
I can't recall the exact lamp type, might be a 327 (the number is on the lamp), but it's a T 13/4 midget flanged type, but as you might guess that *single lamp is just not very bright.* I have tried numerous tricks to try and improve it (metal foil on the clear plastic to try and increase the light trapped inside, brighter lamps, etc.), but it makes only a slight difference.
other than that one issue, it is an amazing series of scopes that hold their cal well, and the Auto-Set features saves a lot of time.
all the best,
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)
I am willing to try and 3D print a replacement.
With best regards
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