Author Topic: First oscilloscope dilemma  (Read 14010 times)

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Offline picofaradTopic starter

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First oscilloscope dilemma
« on: September 15, 2013, 06:37:59 pm »
Hello there,
I need an oscilloscope, but since I'm a beginner and due to the economic crisis, I don't want to spend much money.
So, following Dave's advices I started searching around for analog scopes and I found two in my area:
 - the first one is an old italian scope made in the '70s. Single channel, 10 MHz. Fully operational. The seller would give me all the schematics and complete manual. Price: 50€;

 - the second one is an Hung Chang 5502. Dual channel, 20 MHz. The scope shows a small linear trace in the center of the display, but the seller said that he doesn't know how to use it, so he sells it as not working. Seems to be hard to find the manual and schematics. Price: 50€;

The dilemma is: if I get the first one, I would have a working scope with manual and schematics, but it's nearly 40 years old and it's single channel, that for the moment it's enough to me;
if I get the second one, it could be both working and not working, but it's dual channel and 20 MHz. Besides, if the second one is not working it could be both a broken cap (so I might probably fix it) and something else (I'm not too good in troubleshooting).

What do you recommend to do?

P.S. As always, sorry for my english. :)
 

Offline envisionelec

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Re: First oscilloscope dilemma
« Reply #1 on: September 15, 2013, 07:39:25 pm »
Hung Chang 5502 is also Protek 5502.

Not exactly the same model number, but I bet it's close.

http://www.eserviceinfo.com/equipment_mfg/Protek_35.html

 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #2 on: September 15, 2013, 07:56:46 pm »
Thanks for the info.
The italian one is a Unaohm type G49.

Here there are some pics and info.
http://www.radiomuseum.org/r/unaohm_oscilloscopio_g_49.html?language_id=2

 

Offline Stonent

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Re: First oscilloscope dilemma
« Reply #3 on: September 15, 2013, 08:34:47 pm »
Honestly, I'd take a chance with the second one.  Lets say for instance one channel is completely dead. You still end up with a 1 channel scope with 2x the bandwidth of the other scope.

Second, you know the screen is good, so you can eliminate that as being an issue.  It comes on so the power supply is at least functioning to a degree.

The old 70s scope could potentially have parts inside it that don't exist any more.

Also the Hung Chang / pro tek scopes are all over the place rebadged by other companies such as BK, Tenma, I think even LG may rebadged it as well.
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Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #4 on: September 15, 2013, 09:02:14 pm »
Mmmmm, so I should have a chance with the Hung Chang.
The problem is that I'm a beginner and I don't have so much experience in troubleshooting (only repaired few pc monitors and TVs, I prefer to make my own projects).

That's an image of the Hung Chang:


As you see, there's only a small trace on the screen. The scope seems to have all the pots and switches. I thought that the strange vertical position of the trace can be due some rotation of the vertical position pot made by the seller trying to understand if it works, but I have no idea about the width of the trace.
 

Offline sync

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Re: First oscilloscope dilemma
« Reply #5 on: September 15, 2013, 10:24:39 pm »
Unfortunately you didn't set your country. So i don't know where you live.

The Hung Chang is broken. It probably can be fixed. But to repair an oscilloscope often a second, working oscilloscope is needed. Also often needed are the schematic/ service manual, a (function) generator and experience in repairing. 50€ is too much for this one. IMHO even for a full working one 50€ is a bit expensive.

Regarding the other scope. Don't buy a single channel one. It's not enough.
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #6 on: September 16, 2013, 10:18:54 am »
I'm from Italy (now I setted the country).

How do you know it's broken?
As I said, I can fix it only if the repair is easy (caps, resistors, inductors, maybe transistors).
Regarding the price, maybe I can ask the seller a lower price (30€ ?), since I don't know if it's working.
 

Offline mzacharias

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Re: First oscilloscope dilemma
« Reply #7 on: September 16, 2013, 10:40:34 am »
I agree the Hung Chang is probably broken, and probably a complete waste of money. The other scope is a recurrent sweep type. You should at least get a triggered sweep type. Stay patient and keep looking. Neither of these two scopes are for you.
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #8 on: September 16, 2013, 10:52:08 am »
Thanks for all the replies. I'll keep looking.  :)
 

Offline EEVblog

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Re: First oscilloscope dilemma
« Reply #9 on: September 16, 2013, 11:10:24 am »
Yep, I agree, keep looking, one will turn up.
Do you have any local classifieds like the equivalent of craigs list?
Set up ebay serachs so you get alerted when a new scope pops up.
 

Offline EEVblog

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« Last Edit: September 16, 2013, 11:14:52 am by EEVblog »
 

Offline M0BSW

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Re: First oscilloscope dilemma
« Reply #11 on: September 16, 2013, 11:59:41 am »
You should  ask the colleges around or near you to, I know this works as I just got a Tek 2465 from a college, for £200. UK, and they were going to bin it, its perfect and in perfect working condition, so ask, they can only say no.
no one would or will tell me how to delete this account
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #12 on: September 16, 2013, 12:24:22 pm »
Thanks for the reply, Dave.
The HP oscilloscope seems very good. Only some glitches an jitters on some horizontal and vertical scales combinations. The seller says also that at very high frequencies, the waveform is distorted horizontally. It seems to be manufactured on late '70s: would it be hard to find replacement parts, like the old italian mentioned in my first post?

The other one, Kenwood CS-1025, it's good but the auction begins from 95 €, the price can raise too much.

My school still keeps all the broken scopes. They prefer to have a full room of non-working gear rather than give it away. I guess that this condition is due to the messy burocracy in my country.
 

Offline EEVblog

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Re: First oscilloscope dilemma
« Reply #13 on: September 16, 2013, 12:41:49 pm »
The HP oscilloscope seems very good. Only some glitches an jitters on some horizontal and vertical scales combinations.

Likely just some dicky switches that need a clean, as I showed in the Hameg video.

Quote
The seller says also that at very high frequencies, the waveform is distorted horizontally. It seems to be manufactured on late '70s: would it be hard to find replacement parts, like the old italian mentioned in my first post?

Sorry, don't know the model off-hand.

Quote
The other one, Kenwood CS-1025, it's good but the auction begins from 95 €, the price can raise too much.

Ah, I didn't see "starting price".
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #14 on: September 16, 2013, 01:16:13 pm »
Now I'm focused on the HP 1222a. Anyone has any info about it? I found that actually is from early '80 (the schematic says 1982).
 

Offline PA4TIM

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Re: First oscilloscope dilemma
« Reply #15 on: September 16, 2013, 01:29:46 pm »
For an old scope, the 70's is a good periode. Most low frequency scopes were  build with just transistors and some opamps. Later they started using special ICs for things like readout, cursors. Most scopes from the 50's to end 70's are rather easy to repair but most times you need a  second working scope to repair a broken scope.

I would go for the HP. They are good. I have a HP122AR (got it for free) from the 50's, this is never repaired and still perfect. Only had to clean the switches and reform the caps. I had a HP-1740A (100 MHz including probes I bought it for 100 euro including transport), that worked but got a problem. Somebody had repaired it before me and forgot some screws so the pushbuttons wobbeled the whole mount and killed a solderjoint. A while later the floodgun got problems, burned a resistor, this was caused by a bad  cap. I gave it to a friend 2 years ago and it still works perfect. I bought a 200 MHz 7704 and a 100 MHz 7603, both working scopes with plugins  for a total of 125 euro. A 150 MHz 2445B working for 125 euro, A Tek miniscope for 40 euro, but all my other analog scopes I got for free (around six Tek 5XX models, a 453, two 1 GHz Philips samplescopes, a 75 MHz Philips, a 100 MHz fairchild, a few very old 50's  Philips scopes (from the top of my head, and I'm not searcing, in fact, I never look on ebay or other sites, only looking if people ask advise, like the links given here by Dave.

So again, just be patient.

But just be patient, there are lots of cheap or even free scopes, but most times not on that legal gambling site were you do not buy but win scopes, and like with most gambling, you often pay more then you win  , >:D


www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
www.schneiderelectronicsrepair.nl  repair of test and calibration equipment
https://www.youtube.com/user/pa4tim my youtube channel
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #16 on: September 16, 2013, 04:22:58 pm »
I have a HP122AR (got it for free) from the 50's, this is never repaired and still perfect. Only had to clean the switches and reform the caps. I had a HP-1740A (100 MHz including probes I bought it for 100 euro including transport), that worked but got a problem. Somebody had repaired it before me and forgot some screws so the pushbuttons wobbeled the whole mount and killed a solderjoint. A while later the floodgun got problems, burned a resistor, this was caused by a bad  cap. I gave it to a friend 2 years ago and it still works perfect. I bought a 200 MHz 7704 and a 100 MHz 7603, both working scopes with plugins  for a total of 125 euro. A 150 MHz 2445B working for 125 euro, A Tek miniscope for 40 euro, but all my other analog scopes I got for free (around six Tek 5XX models, a 453, two 1 GHz Philips samplescopes, a 75 MHz Philips, a 100 MHz fairchild, a few very old 50's  Philips scopes (from the top of my head, and I'm not searcing, in fact, I never look on ebay or other sites, only looking if people ask advise, like the links given here by Dave.

Nice collection, you're very lucky!
 

Offline Sigmoid

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Re: First oscilloscope dilemma
« Reply #17 on: September 16, 2013, 04:34:09 pm »
I entertained the idea of getting an old HP storage scope, those are awesome, with that oldskool heavyweight cold war feel to them... XD
But unfortunately in the end reality won, as the thing is about the size of my entire workbench. :D So I went with a Rigol. How uncool.
 

Offline edavid

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Re: First oscilloscope dilemma
« Reply #18 on: September 16, 2013, 04:43:56 pm »
Now I'm focused on the HP 1222a. Anyone has any info about it? I found that actually is from early '80 (the schematic says 1982).

That was a low end model, which has particularly bad switches and pots.  So, I wouldn't count on getting them working perfectly.  Also, it's pretty darn slow.  On the other hand, it's fanless, which is very nice if you need to use it in your living room.
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #19 on: September 16, 2013, 04:55:49 pm »
Also, it's pretty darn slow.

What do you mean?

EDIT: just discovered that the seller is the user ddavidebor in the forum!!!
« Last Edit: September 16, 2013, 05:04:42 pm by picofarad »
 

Offline van-c

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Re: First oscilloscope dilemma
« Reply #20 on: September 16, 2013, 05:09:52 pm »
The suggestions from Dave and others about being patient are the best advice you could get.  Remember, as happy as you might be once you finally buy that first scope, the person selling it is probably equally happy, if not happier, to have finally sold it.  And there are lots of sellers out there.

I would also offer this advice:  Don't be afraid to ask the seller if there is anything about the scope that you should know before buying it.  Ask if, to the seller's knowledge, any parts inside the scope been removed, scavenged or replaced.  Often a used scope becomes a parts donor and known faulty parts are put back in after working parts are removed.  Of course the seller may not be honest enough to tell you if you ask, but he is much more likely to tell you if you ask than if you don't ask.

Good luck.

--Van
 

Offline edavid

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Re: First oscilloscope dilemma
« Reply #21 on: September 16, 2013, 05:18:55 pm »
Also, it's pretty darn slow.

What do you mean?

Only 15MHz spec, and don't expect better than that.
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #22 on: September 16, 2013, 06:38:14 pm »
Also, it's pretty darn slow.

What do you mean?

Only 15MHz spec, and don't expect better than that.

I mostly work with audio stuff. I think that 15MHz it's enough for what I have to do.
 

Offline picofaradTopic starter

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Re: First oscilloscope dilemma
« Reply #23 on: September 16, 2013, 09:15:45 pm »
And what about a Tektronix type 454? The auction starts from 25€.
 

Offline Msusec

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First oscilloscope dilemma
« Reply #24 on: September 17, 2013, 02:03:42 am »
Hello!

The same question, but another person!

So i would like to buy my self a new oscilloscope.
i can chose between :
 - Hameg HM400( because i love analog scopes )
 - Rigol DS1102E
 - Tektronix TBS 1152
because they all are in range of 460€ max.

so which one should i buy?

thanks for Helping me.
 


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