[Coco] RGB to VGA boards, test equipment needed

[Gene Heskett]

On Sunday 06 September 2015 16:19:14 Kandur wrote:

> Would these pocket oscilloscopes do for checking video signals?
> If yes, wich one is better? Are there any others under $100?
>
> http://tinyurl.com/p9jx2ec
>
> http://tinyurl.com/ommymqs
>
I have one of the latter, and the answer is firm no for either.  They do 
not sample at a high enough rate to show you anything but a very poor 
caricature of what the video looks like.  And they will alias to beat 
the band when the repetition rate is some near close to synchronous 
ratio of the sampler frequency.  Decent enough for audio, but get much 
above an audio signal and their warts are pretty obvious to the trained 
eye.

Some of the older analog stuff, with triggered sweep and at least 20 Mhz 
of bandwidth will spend .1% of the time lying to you than one of the 
above will, and because they are analog, often under priced on ebay.
I have one of these:

<http://www.ebay.com/itm/Hitachi-V-1065A-Portable-Two-Channel-Analog-Oscilloscope-100MHz-R-Type-w-Handle-/181840967212?hash=item2a5690f62c>

for about 24 years now, works well and has not gone out of calibration.  
And I stole it for $1200 at the time I bought it used in '91.  New at 
the time was $2790.  Under $200 s/b a good price.  Quality stuff IMO.

Stay away from the older tektronics stuff, full of proprietary inhouse 
parts that you cannot buy except buying another scope in hopes it 
contains a good part you can use.
 
Cheers, Gene Heskett
-- 
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