Can anyone help me with some Tone burst tests?

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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 :confused: ), 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.:)
 
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?ViewItem&category=45005&item=3873850979&rd=1&ssPageName=WD1V

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=45005&item=3877983194&rd=1&ssPageName=WDVW
 
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
 
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
 
I tried Photoshopping that pocture but its not sharp enough to start with.... You might want to get a sharper pix or write the guy and ask whats on it. It does look like the left hand banana jacks are a trigger input though and you may be able to use that same signal to trigger the scope. That genny is a 1964 model but all GR stuff was built extremely well! Consider that it may also be a tube model.... I say write and ask first..... Test gear that old thats vacuum tube based usually requires alot more TLC to put back into shape.

Mark
 
i can't imagine not having a 'scope but for your required measurement i would think any computer sound card and some freeware would all you need to create tone bursts and see clipping levels, at least with a few audio preamp/attn thrown in to get the levels right
 
"i would think any computer sound card and some freeware would all you need to create tone bursts and see clipping levels"


The main thing is that the tone burst genny has to also trigger the scope.... or have the ability to be triggered by an external source.... this is probably not something that freeware or a standard computer is going to be able to do. There may indeed be a specialized card to fit into a computer that gives all the same facilities that a bench type burst genny will allow.

Mark
 
The guy selling it was a mass parts broker, might not know much, I will write and see.

You guys bring more interesting info... I thought that the output of the generator would trigger the scope, but now it seems you are saying there is an additional mechanism that does a "pre-trigger" ? I am not sure how to interpret your statement not knowing much about these test equipments. :cannotbe:

I have already bought it so I will have to rough it out, if it does not work, I sell it back on eBay or whatever....

Eva how much is the Hamheg?
 
In storage mode the input waveforms are continuously converted to digital values and stored on a circular RAM buffer

In normal trigger mode the oscilloscope starts displaying the waveforms from the RAM address that was being written when the trigger event happened. In pre-trigger mode it starts displaying data captured some time before the trigger event and in post-triger mode it waits for some time and then starts displaying the data being currently captured

This is very basic functionality for storage oscilloscopes. I think the HM407-2 is not particularly powerful for today's standards. It was the cheapest storage model from Hameg 5 years ago when I bought it and it costed approx 1.500 euro [brand-new]
 
"In storage mode the input waveforms are continuously converted to digital values and stored on a circular RAM buffer"

Actuually there are several other types of storage that do not involve digital conversion and storage. One is the "Wire Mesh" type(Tek 7633) and the other is the "Flood Gun Type(Tek 214).

K-Amps, The 7633 has all the normal modes of storage operation as most of the later digital stuff does. The only drawback to CRT storage is that the trace on the Flood Gun type crt's can only be saved for about an hour or so, where the Wire Mesh type will hold it for quite a few hours to indefinately.....

Mark
 
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