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Totally makes sense.? I was refuting Jean-Paul's assumption that the 20 pF was across the 50 ohm input.? We agree.? Thanks, Tom.? ? ? ? ? ? ? JimSent from my Verizon, Samsung Galaxy

The 81 errors are related to CTT (non-)calibration. Not unexpected, since you replaced the option board. This was discussed a while ago in this group. The 86 error quite likely is linked to the same.

Chuck, with known good CTT board exchanged for the one in the failed scope, all cables properly reattached. A5 board is know good and had no SMD leaky caps. Only, partial success, CTT works but the

Sr. Marullo, Keep scope inputs away from TX or exciter outputs, there are various techniques to monitor the modulatiion, power etc. using directional couples and splitters. A power rated load may have

/g/TekScopes/photo/260052/0?p=Created,,,50,2,0,0 Done. It’s there, but now it’s not moving no matter the position of the Hold-off knob.

Ok, I looked at the picture. Could you try this: Select Ch1 only, put the Ch1 input to GND, and at 5mV sensitivity. Select Line trigger and set the timebase at 10ms/div. Curious how that looks like.

On Tue, Feb 23, 2021 at 07:13 AM, satbeginner wrote: Interleaved. > > Hi, > > A while back I asked you to put a temporary (very short) ground in between the > attenuator output and the amplifier input

The 485 has two attenuators, the normal 1Mohm attenuator used with traditional "high impedance" probes, and a separate 50ohm attenuator. A relay connects the input from the BNC socket to either one or

A high power through attenuator (probably with cooling fins!), or a 20dB coupler which taps off 1% of the power going through it.

Thanks Tom, Just repeated my measurements with the 7603 frame. 2.5ns is more correct value (timebase calibration issue with fastest sweep and 10X). This corresponds to 140MHz. I measured also frame

Hi Jim, Lower frequency scopes merely throw a 50 ohm terminator across the input to provide a 50 ohm mode, but the 485 has two separate attenuator sections, one for 1M, and a different one for 50

Mike, I DID all the recommended tests except for the one involving a diff amp, which I don’t have. Ozan suggested that I use the “INVERT” and “ADD” trick, although it was not as good. I

Well, 20 pF is about 22.7 ohms at 350 MHz, so that would affect the 50 ohm input. So I assume Tek left the 20 pF shunt cap off the 50 ohm input. Jim Ford

Hi Jeffrey, First link inside EEVBlog is dead, but the second seems really good: http://www.emcesd.com/1ghzprob.htm Already bought, hope it will work thanks. Giuseppe Marullo IW2JWW - JN45RQ

Non, non et non. I gave you the upper bound on the input capacitance implied by Tek's input VSWR spec. That number is 5pF. It's irritating that I do this work for you and you simply ignore it. That

Hi John, Trying to get them from Ebay, I asked the seller specific conditions/photos and I will claim the money back if they are not in good order. Anything specific to ask to be checked, like the

Rebonjour, the 485 spec is 50 Ω /1 MΩ//20 pF https://w140.com/tekwiki/wiki/485 I assume the 20 pF applies to either Zo. Best measurement of Cin is the classic TEK 130 LC meter, very easy to use and

Hi, A while back I asked you to put a temporary (very short) ground in between the attenuator output and the amplifier input to find where the ripple is picked up. I'm not sure if I saw feedback on

I should add that I don't fully understand the reason for your question, though I was happy to answer it. The 485 is a 350MHz scope, and so one would naturally expect the input RC time constant to be

Dear Chuck: I swapped only the U5930 of the OPT boards, as it was easy and socketed, the EEPROM. No change. I am just now removing and exchanging the OPT bd of known good unit to fault unit. Will