Re: Switching a Tek TDS 5204 to 50 Ohms input impedance - Strange!


Hi Raymond , I have several 7A19's and so far not blown one of the input fuses , I hope I dont ever as I gather that they are rather hard to find , fortunately all the 7A19's I have purchased have had intact fuses and came complete with the spare ones inside if memory serves me well . I've not had that much luck with 7A29's , even with ones that still function , the input attenuator is often damaged such that the input inpedance is no longer constant when changing sensitivity . Fortunately my 7A29P that I purchased for my 7912AD doesnt suffer from that .
I am not 100% sure that the TDS series would exactly follow that original observation but I feel certain that it would in order to protect the input termination , its the only way that gives best protection for it . Later instruments are always more expensive so I would expect the cost of repairing the input termination out of warranty to match the cost of a new instrument . For a modest TDS744 diy replacement of the input hybrid costs in the region of 100GBP , without labour or factory overheads , if they would still do it -- imagine the likely cost if TEK did it


On Monday, 15 June 2020, 23:45:45 BST, Raymond Domp Frank <@Raymond> wrote:

On Tue, Jun 16, 2020 at 12:27 AM, Brian wrote:

Hi Raymond , I have a couple of TDS's , a 744 original version and a 420A .
Both are protected on the 50R input setting so I would expect all others to be
the same . I have noticed this behaviour when using the 50R input and until I
got used to it having wondered what was happening at first I much prefer it to
the action taken by the 7A29 7k plug-in which just disconnects the input - and
you need to disconnect to reset it.Regrettably I am just a hobbyist pensioner
nowadays so my experience with anything newer than a TDS744 is zero , give me
500 series or 7K series even a 661 and I am happy
Brian Skilton
Hi Brian,
I have had several TDS 4xx and 5xx 'scopes and never experienced this behavior. I'm *that* careful - or lucky...
Nowadays, my only 'scope in that range is a TDS3054 (actually, a modified TDS3032) and I've never tried...
The 7A19 blows an input fuse if overloaded, the 7A29's behavior is much more user-friendly, being resettable.
I love 7K mainframes and I would never think "*regrettably*, I'm a hobbyist pensioner"...
Of course, some things can only be done with the newer stuff but I'm quite happy improvising.


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