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Author Topic: Oscilloscope Specs  (Read 8520 times)
KM3F
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Posts: 525




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« Reply #15 on: April 16, 2012, 10:14:21 AM »

If you go to any hamfests, look out for working scopes.
There are good deals if you just keep an eye out.
I got a dual trace solidstate 60 mhz combination, X-Y and Z input functions, 120/12 volt dc small one with two new probes for $120.
All functions work, conditon as almost new.
Just as a fyi, I did a test using a Palamar RF noise bridge generator runing into a 50 ohm load just to see if the scope would respond.
Perfect, it showed a large amplitude noise output from the bridge and nulled out perfectly at 50 ohms and near zero reactance on the bridge dial calibration, to a 'flat line', with the scope's full vertical channel sensitivity settings.
I really would not consider a unit in the EICO or Huh class unless you get it for next to nothing.
Not saying they have no use having had a few, but you will end up wanting one that is much better in the Lab class of unit, later on.
Good luck..
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G3RZP
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Posts: 4957




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« Reply #16 on: April 16, 2012, 02:08:27 PM »

I agree with KM3F. I'd go for Tektronix rather than HP - some HP 'scopes had switch problems as they got old ( Don't we all get problems as we get old?)

We used to say "HP for spectrum analysers, Tek for 'scopes".

That was when we were buying for work. Personally, I think it still applies.
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KA5IPF
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« Reply #17 on: April 16, 2012, 02:49:21 PM »

I agree with KM3F. I'd go for Tektronix rather than HP - some HP 'scopes had switch problems as they got old ( Don't we all get problems as we get old?)

We used to say "HP for spectrum analysers, Tek for 'scopes".

That was when we were buying for work. Personally, I think it still applies.

As far as I'm concerned it does, sorta. Tek makes scopes and HP makes the rest, especially service monitors.

Clif
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K1ZJH
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Posts: 1185




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« Reply #18 on: April 16, 2012, 05:38:10 PM »

HP made spectrum analyzers. Roll Eyes

I agree on the price, I've seen older 35 MHz solid-state scopes being given away on
forums for the asking.  Don't put any serious money into a Heathkit, RCA, WIZ or EICO.

Pete
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KA5IPF
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« Reply #19 on: April 16, 2012, 06:20:40 PM »

I should have been more clear, Tek makes scopes and HP makes the rest of the TEST equipment.

Sheeesh

Clif
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G3RZP
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Posts: 4957




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« Reply #20 on: April 17, 2012, 03:15:46 AM »

Strictly, HP doesn't make test equipment any more. It's now Agilent. But I know what you mean.
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KB1WSY
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Posts: 813




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« Reply #21 on: April 26, 2012, 05:15:01 AM »

So, I opened up my broken Eico 460 scope (no horizontal deflection) and cleaned the rotary Sweep switch with DeOxit -- and now, the oscilloscope is working! Mostly rubbish performance with heavily distorted waveforms, but I tested the functions and they all work. I was even able to connect an Eico 488 Electronic Switch and turn my scope into a crude "dual trace" model! The square waves look more like camel humps, but it's a start. I also applied the audio output from my Ameco Morse code oscillator and the waveform came out nicely: very spikey and that presumably is what you would expect from a simple tone produced by a cheap IC.

After testing the scope I turned it off and carefully shorted the rectifier caps to ground with an isolated screwdriver to avoid getting zapped. The inside of the unit is a real mess. Those that warned me of "drifted resistors and failed capacitors" were, predictably, correct. There was a pool of waxy capacitor gunk on the bottom of the case, where a couple of big, old, 1000V-rated paper caps had leaked, in the HV rectifier circuit. A quick check with my newly restored Eico VTVM showed that around many of these capacitors, the resistances measured are completely different from the factory spec given in the Eico service manual (in some cases, orders of magnitude off). Also, a previous owner has made some odd modifications including removing parts of the original circuit altogether -- cutting the wires that lead to them and leaving the original components stranded, without replacing them with more modern equivalents. In one case, a phenolic terminal strip has snapped in half -- and been "repaired" with a piece of insulating tape! I am amazed that the unit works at all.

As a result of this brief test, I have already learned some cool stuff about how scopes work, despite the crudeness of my unit. Now comes the extensive disassembly/rebuild job. Lots of fun in prospect!!!

73s DE Martin, KB1WSY
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