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Old 6th April 2006, 09:28 AM   #21
mzzj is offline mzzj  Finland
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Quote:
Originally posted by Clipped


ive been meaning to get a scope, but just kinda afraid it wont see enough use to make it feasible....any recommendations for a good cheap one?

thanx
Second-hand textronix 465 could be a good deal, but I have no idea where to buy 2-hand scopes in Thailand

Brand new Instek GDS-820C digital scope is around 1000 euro, looks usable on specs.
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Old 6th April 2006, 12:05 PM   #22
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With the amp on, measure the DC voltage on all pins of the muting transistors. The black meter lead will be grounded to the RCA shield ground. Post your results.

When you reinstalled the transistors, did you reinstall them with proper orientation? Generally, pin 1 of the transistor goes to the square pad. On all of the orions amps of that model that I've seen, the muting transistors are installed backwards from this. This is only true of the jfets. I believe all 3 jfets are installed this way but I know the 2 muting jfets are installed this way (I'm not sure of the one near the power supply).

Tektronix makes great scopes. The 400 series scopes are rugged and can be repaired relatively easily because most of the parts are generic and still available. Don't buy a 2400 series scope. They have hybrid modules that fail and are no longer available as a new part.

Although it's nice to have a 100 meg scope (like the 465 -- the 465 and 465B scopes are very good), it's not necessary for audio work. I used one of the 5000 series Tek scopes (only a 2 meg scope) for several months and it did everything that I needed to do. If you can find a 10, 20, 50 meg scope in good working order, it will work well for troubleshooting audio and power supply problems.
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Old 6th April 2006, 12:19 PM   #23
lndm is offline lndm  Australia
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A very cheap scope can be done in software. Basic audio is not very demanding of a scope and a soundcard can perform adequately. A preamp is a good idea to protect the soundcard. (There are kits to do this)
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Old 6th April 2006, 01:39 PM   #24
anatech is offline anatech  Canada
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Have a look at the 20 MHz Kenwood 'scopes. The oscilloscopes these days will do eveything you need. I started with a 500 KHz Stark for army surplus. Get a new one for what they cost. You will find you use it often.

-Chris
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Old 6th April 2006, 02:13 PM   #25
clem_o is offline clem_o  Philippines
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Hi all,

Leader or Iwatsu, as additional possibilites. We use several Leader units in our labs, as they are fairly inexpensive - most of the problems are associated with contact corrosion.

I tend not to like the sound-card solutions because they won't show DC.

my 2c :-)

Cheers!

Clem
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Old 6th April 2006, 08:21 PM   #26
anatech is offline anatech  Canada
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Hi Clem,
I agree with your statements.

Making a correct attenuator for your sound card input is not easy. You need a scope or accurate meter with good HF response. I'd suggest an HP 34401a (-3dB @ 300KHz) or equiv. for this.

Just buy a 'scope. The sound card thing has other uses.

Anyone check out the new Agilent 3000 series. I am going to test one, it's a DSO with FFT math built in. Less than $2000 CDN. Don't ask me how much my Philips PM3070 cost.

-Chris
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Old 6th April 2006, 11:47 PM   #27
lndm is offline lndm  Australia
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The above comments are fair (admittedly I do have a scope). A sound card is also good for FFT - fairly high res spectrum analysis, and CSD plots.
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Old 7th April 2006, 02:21 AM   #28
clem_o is offline clem_o  Philippines
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Quote:
Originally posted by anatech
Anyone check out the new Agilent 3000 series. I am going to test one, it's a DSO with FFT math built in. Less than $2000 CDN. Don't ask me how much my Philips PM3070 cost.
Hi Chris,

Ouch!! :-)

Lower-cost option: get the lowest-end Tek, add the computer comms module. Do the FFT on the computer (that is, if FFTs are only to be used occassionally).

Admittedly, the sound card will have better amplitude resolution, owing to the 16bit AD. Sampling rate is limited though, save for the more expensive ones - if you work only in the audio band...

Cheers!

Clem
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Old 7th April 2006, 04:26 AM   #29
anatech is offline anatech  Canada
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Hi Clem,
If I can get away cheaper and still have a great reliable product then I will.

Sound cards will generally not show harmonics over 20KHz that I've seen. Attenuator is a pain. My current 'scope cost over twice that of the Agilent, but I'm hurting for money so I only want to spend it once. The Philips has failed a few times now. Expensive POS.

Since I need a 'scope and I would love usable FFT, I hope to combine the functions.

-Chris
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Old 7th April 2006, 04:36 AM   #30
clem_o is offline clem_o  Philippines
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Hi Chris,

Some of the new sound cards boast 192KHz sampling with 24-bit ADCs. A proper FFT should be able to show harmonics a fair bit beyond 20KHz, assuming the manufacturer didn't put in a non-programmable anti-alias. I have to admit though I've never tried them new-fangled cards...

Cheers,

Clem
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