Can anyone help me with some Tone burst tests? - diyAudio
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Old 28th February 2005, 01:47 PM   #1
K-amps is offline K-amps  United States
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Question Can anyone help me with some Tone burst tests?

I need to measure the dynamic power of my modded Amplifier. I am guessing that I will need to use 10ms and 100ms tone bursts.

I just got a TEK Oscope, (but have not used Oscopes before ), it is the following model:

TEK 7904 Oscope with the following plug-ins.

7A11 amplifier with built-in FET probe
7A26 dual-trace amplifier
7B53A dual time base
7B85 delaying time base

I have a signal generator but I do not think it can do bursts. !!Is there anyway I can rig something up to do "Dynamic Music" tests to observe the increase in clip level using different capacitors in the PSU?

So far I have only done Clip tests with steady sinewaves.

thanks in advance.
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Old 28th February 2005, 05:51 PM   #2
K-amps is offline K-amps  United States
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Maybe the post was too long... lets try again, Ok... How to do Dynamic power tests in Amps using your homebrew Oscope.... Anyone?

Sy and Jackinnj help a little on another post but they gave me too much credit for basic Oscope knowledge..
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Old 1st March 2005, 12:45 AM   #3
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I have never done this but if you have access to a storage scope it should be easy.... If you have the scope set on single trace mode and use a pulse from the tone burst generator to trigger the single trace sweep and then store it visually on the screen then it should capture the maximum peak to peak voltage that the amp is capable of. I have a 7633 storage scope here but no tone burst generator. There are usually clean 7633 scopes on E-bay in the $100.00 range and you can use your 7904 scope plug ins for the 7633 as well. Be sure that any storage scope you purchase has a good crt!!! BTW: I also use a 7904 here at home...among others. I am actually more into restoring test equipment than I am into audio....

Where are you located in Indiana... I used to service alot of movie theatres in the northern part.

Mark

See this and similar.........

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WD1V

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW
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Old 1st March 2005, 01:16 AM   #4
K-amps is offline K-amps  United States
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Thanks Mark... I live in Fishers, thats NE Indy.

In post number 1 you probably read the 7904 modules I have, If I buy this:

http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WD1V

(The CRT is dim he says... but it's $25... what do u say?)

AND this


http://cgi.ebay.com/ws/eBayISAPI.dll...r4_PcN__Stores


Will I have all I need ?

Thanks!
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Old 1st March 2005, 01:18 AM   #5
K-amps is offline K-amps  United States
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Noobie question, whats the diff between a 7904 and the 7633 storage scope? I am guessing the 7633 can "freeze data", but I heard only digital scopes can do that.
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Old 1st March 2005, 01:40 AM   #6
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Its best to try get one that the seller says is decently bright. That one in the picture does have a dark green filter on it and that may be causing some of the darkness to the trace. I took the filter off of mine. Some of the TEK scopes have an internal CRT bias adjustment and that can be cranked up(usually at calibration time) as the tube ages and dims but the storage tubes are another story and without pulling the manual out I'm not sure that they have similar crt bias pots in them. How that work though is utterly incredible too! The electrons write the trace onto a very fine wire mesh and the charge thats stored on that wire mesh is displayed on the phosphor screen. This stored trace can be set to last for several hours. These scopes can also be used as "normal" scopes but the traces on these are not usually as sharp because you are writing through that wire mesh.

The 7904 was one of the very best standard scopes that Tektronix ever made, and one of the last ones. The main frame has a 500 mhz bandwidth with the right plug ins. I use my 7904 as a 250 mhz scope with the plug ins that came with it, mine is an ex T.I scope. The difference between the two is that the storage scope has a trigger mode in that the tone burst generator could be set up to trigger a single sweep of the screen. The storage crt then can be set to retain this single trace which should contain your tone burst and hence peak output level. These scopes use all the same plig ins as the 7900 series does so if you can find just a decent mainframe only then you may be money ahead...... Hope this helps....

The last theatre booth install job I did was several years ago in Greensburg. Comming back to all that humidity almost killed me!

Mark
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Old 1st March 2005, 01:41 AM   #7
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The obvious approach is to use an oscillator, timer IC or PWM IC to periodically mute and un-mute the output of the signal generator

There are also some computer programs capable of generating tone bursts with adjustable tone frequency, length and period, SpectraRTA is one of them

I use 10:1 burst testing to check things like amplifier stability at minimum load and clipping behavior without generating too much heat or requiring huge power resistors
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Old 1st March 2005, 01:42 AM   #8
K-amps is offline K-amps  United States
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Thanks Mark, you have got me 90% home. ;-)

Now on for a search for a 7633 with a good screen.
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Old 1st March 2005, 01:44 AM   #9
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Does your tone burst genny have a trigger or extra pulse output on it? Most do, mainly for this purpose.

Mark
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Old 1st March 2005, 01:46 AM   #10
K-amps is offline K-amps  United States
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Not paid for it yet so I cant say,

http://cgi.ebay.com/ws/eBayISAPI.dll...r4_PcN__Stores
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