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Old 2nd April 2007, 05:45 PM   #21
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A soundcard has its uses, but I have to agree with EC8010 and Tubelab that, for general frequency response measurement and square wave testing, a decent stand-alone, wideband function generator is most useful. In the US, the many Wavetek models have been favorites for decades. You can find these used on on-line auctions or at swap meets, often for well under $50. The picture shows two that I bought at a hamfest for dirt-cheap. The upper unit is a Wavetek 134, whose frequency range goes from <0.2Hz to 2MHz. The lower unit is a US Air Force version of another standard Wavetek model (142?), going from 0.001Hz to 10MHz. You want something that ranges into the low MHz region to give you margin for testing the upper end of frequency response, where peaks and dips can signal resonances and instabilities. The advantages of units like these, in addition to the wide frequency range, include nearly perfect square-wave response, dead-flat output amplitude from well below, to well above, the audio range, and marked dials that give you a quite accurate indication of the frequency. Without a good dial, you’ll be tediously counting divisions on a scope to determine frequency, or resorting to another piece of test equipment, a counter, something you wouldn’t ordinarily need in a basic audio lab. Wavetek made many suitable models in the 110-200 model number range. There are other brands too, of course.
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Old 3rd April 2007, 01:07 AM   #22
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Thanks for all the advice. I'll be on the lookout for a function generator on eBay soon. In the meantime, I'm awaiting this motherfather.

OK, so it ain't a Cadillac, but the price was right. Now I know that I should have consulted the community first, but this was cheap and staring me in the face, so I pulled the trigger.

Now you may advise as to why I should have never purchased this model or bought from this vendor or paid this much, etc., etc.

Also, some advice on how to find the oscillation in my BV amp using the scope would be welcome. Of course, I'll probably need a function generator...

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Old 3rd April 2007, 02:32 AM   #23
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We used to use Hitachi scopes in the factory at work. They were very reliable and worked well. Several hundred of them were run continuously for several years with few problems.

I have also purchased equipment from Avitar at local hamfests. The equipment was clearly marked "non functioning" and priced accordingly. Their description was accurate!
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Old 3rd April 2007, 03:07 AM   #24
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I also have a Hitachi but only a 20Mhz one, Bought for about the same price... Nice and simple to use though and the results are believable. I'm a little sceptical of the need for absolute calibration, I use the "5v" O/p and it does a "5v" square wave, close enough for government work.

So now you have a 'scope you can start probing around, I guess the first thing to do is check the PSU / B+ is clean, at least you dont need any kind of function generator for that. (suitably rated probes though.)

Incidentally whilst musing this, I found a couple of DIY squarewave generators on the internet based on the humble 555 timer. Someone care to venture rubbish they might be?

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Old 3rd April 2007, 07:03 AM   #25
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Kofi, you shouldn't be dissapointed with the Hitachi as long as it's still functional, they work well. My first store-bought scope was a Hitachi V-302B - it served me well, and was very simple to use.
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Old 3rd April 2007, 01:59 PM   #26
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Well done, Kofi. As the others have said, Hitachi made some nice scopes. And the price was right. It should serve you well.
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Old 3rd April 2007, 04:24 PM   #27
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Hi Kofi,
I too have used some Hitachi scopes at vary past places of employment (that's a mouthful) and have generally found them to be reliable and easy to use.

I noted the comment that the contacts on front panel controls need cleaning - in many cases the switches are sealed and cannot be cleaned, however I have also found that with regular use they tend to (self) clean up quickly provided they are not excessively worn.

Get some good probes, for tube work both 1X and 10X probes are useful. Here are some that might suit and are pretty inexpensive:
http://www.hififorless.com/categorie...id=1651&src=10
This probe appears to be very similar (same vendor) as the probes I use at home with my Tek 2245A, and has reasonable performance.
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Old 4th April 2007, 01:51 AM   #28
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Alright! Thanks for all the responses!

I am awaiting the scope and two of the probes that you recommended, Kevin. I also downloaded the manual for the V-1050, which is NOT the V-1050F, but I figure its close enough to get me started.

Also, are there any online resources you know of that would help me understand how to calibrate this thing once I get it? The manual for the HP I was considering was pretty detailed on the subject but the Hitachi, not so much.

Any other first-time-oscilloscope-owner advice would be much appreciated.

Oh yeah-- it seems that the installation of the 1.5K grid stoppers in place of the 330Rs was resulted in a noteable reduction in bass and some grainyness in the highs, but I may just be imagining this. Is this normal for an increase in grid stopper value?

Kofi
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Old 4th April 2007, 02:25 AM   #29
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Quote:
Is this normal for an increase in grid stopper value?
Unlikely. If a grid stopper is too large, you can actually have a reduction in highs.
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Old 11th April 2007, 12:44 AM   #30
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Alright! Scope and probes have arrived and everything appears to be in working order!

So I used the self-calibration lug (.5V) to try and test the square wave and it looks like the sort of square wave Picasso would draw. Its not flat-- its angles quite a bit. I looked for any controls that I thought might help to calibrate and nothing doing.

I'm guessing I need to calibrate the actual probe, then? Also, I can get the probe pin to read the the .5V signal, but not the attached alligator clip. So, there's something else I need to do there, right?

I know this is some basic stuff here, but if one of you would stoop so low there'd be an "Alright! Thanks!" in it for you.

Kofi
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