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I have just refurbished and calibrated my 7603.
The frame itself showed 2.5ns rise time and bandwidth was 140MHz.
With 7A26 system rise time is 3ns and bandwidth seems to extend to 130MHz. Small dip around 100MHz?
Now I have 4 channel >100MHz ”old school” scope in my lab.

But I have also 7B87 and using high sweep speeds (<5ns/div) horizontal linearity is poor.

Has anybody tried to improve the horizontal amplifier to have a bit better performance?

Regards,
Jouko

Hello there: Very fine to yave these mainframes.

I have the similar 7904, with 7B92A HOR plugins,

HOR LIN is fine, however at the fastest sweep rates first CM of sweep start has some slight aberrations.

I think that is normal.

IF the fast rate sweeps of you HOR are nonlin, either the 7B87 OR the mainframe HOR 7603 amps may be the culprits.

More likely it is the plugin.

Did you HOR cal the 7603?

RE 7B87, try in another TEK 7000 mainframe? Was it calibrated?

Scope photos of the nonlinearity on the fast rate as well as linearity on slow rates, (with calibrator or function gen signal) will get you fast get advice.

Bon Courage,

Jon

On Mon, Mar 8, 2021 at 05:50 PM, Jouko Koskinen wrote:

But I have also 7B87 and using high sweep speeds (<5ns/div) horizontal
linearity is poor.

The faster rates of the 7B87 are too fast for the 7603, by far: Fastest calibrated hor. sweep is 5ns/div. 7B87 goes down to 1 ns/div (with 10x multiplier).

Raymond

The fastest sweep the 7603 is "specified for" is 5ns/div which is obtainable with a 7B53A set the highest sweep (.05us/div) with the x10 multiplier engaged.

I'm amazed you find the 7B85 or 7B87 work well with the 7603 as I thought the delay line in the 7603 was too short for these.

FWIW if you are looking for detail in a sweep at faster than 5ns/div then you also need a (much) faster vertical amp.

David

On Mon, Mar 8, 2021 at 11:18 PM, David C. Partridge wrote:

I'm amazed you find the 7B85 or 7B87 work well with the 7603 as I thought the
delay line in the 7603 was too short for these.

I guess that depends on what you call "work well". You just won't see (part of) the triggering edge but otherwise, the image is fine.

Apart from it possibly being a nice exercise, I don't see the merit in trying to improve Tek's 7603 design. 7704's and 7904's are very affordable these days. Yes, they're a bit wider.

Raymond

There are faster frames frames available.
What I like in this 7603 is the large screen. Therefore I thought about this exercise.

This CRT is without distributed deflection. Seems to be that all the faster tubes use distributed approach at least in vertical.
I assume this is limiting the vertical response. Am I right?

BR,
Jouko

Definitely trade-off in scopes CRT

BW ><display size
BW><cost
acelleration voltage
topology of CRT

Jon

The 7603 large CRT is useful for Spectrum Analyzers, but limited BW 100 MHz

Wide bandwidth example 2467B or 7104, 400 and 1 ghz BW, microchannel plate CRT but smaller display

Jon

On Tue, Mar 9, 2021 at 09:09 AM, Jouko Koskinen wrote:

I assume this is limiting the vertical response. Am I right?

Close. It's a combination of bandwidth and sensitivity. A good explanation is given on Tekwiki: "Distributed deflection plates".

Raymond

On Tue, Mar 9, 2021 at 12:19 PM, Jean-Paul wrote:

Wide bandwidth example 2467B or 7104, 400 and 1 ghz BW, microchannel plate CRT
but smaller display

I guess that the screens of the 2467 and 7104 are smaller not so much because of BW requirements but because the angle of incidence of the electron beam varies more across a larger screen, affecting the "transparency" of the microchannels and thereby the MCP's gain across the screen.
The 2445B and 2465B, both with 400 MHz BW, have a larger screen size, as do the 400MHz and 500 MHz instruments in the 7000 series (7844, 7854, 7904(A)). Smaller screen size allows higher brightness (writing speed), witness models like the 7904 option 4, with its smaller (4 x 5 cm, instead of 8 x 10 cm) graticule. 24 kV total acceleration potential helps as that model...
Analog storage CRT's often have a smaller screen as well (7613/23/33 vs 7603!).
BTW: Models like the 2430/32/40, with their modest BW requirements, use the same complex CRT as the 2445 and 2465. I guess that's to do with CRT availability...

Raymond

On Tue, Mar 9, 2021 at 09:09 AM, Jouko Koskinen wrote:

What I like in this 7603 is the large screen. Therefore I thought about this
exercise.

The 7603 works well with a 7S14 sampling plugin. 1 GHz BW, two 50 Ohm channels only but a P6202 FET probe can provide Hi-Z input. The non-A (so, plain P6202, not P6202A) has its own power supply.
High BW, low input capacity, easy-to-operate sampling plugin, 350 ps rise time, and all that in a 7603, you can't lose!

Raymond

Hi Raymond,

I already have 7S14. Have to look into FET probes.
Thread "Sampling with 7S14".

BR,
Jouko

Hi , if my memory serves me correctly the P6202 FET probe is only 500MHz so you will likely need a P6201 and an 1101 psu for maximum B/W
Brian

On Tue, Mar 9, 2021 at 02:55 PM, Brian wrote:

Hi , if my memory serves me correctly the P6202 FET probe is only 500MHz so
you will likely need a P6201 and an 1101 psu for maximum B/W
Brian

Absolutely, Brian. For full BW you need (something even faster than) the P6201. I was thinking about the convenience of having an "integrated" power supply, as opposed to needing to hunt for an 1101. I should have mentioned that but thanks for bringing it up.

Raymond

Raymond

Hi Raymond?I cant afford better than the P6201 and a home made 1101 substitute , if I need better I have a P6056 and P6057 resistive probes but of course no Hi-Z input?
Brian

On 50 Ohm WB plugins we use a direct connection with BNC/coax or a Zo Probe like P6156.

The FET probes are huge, costly, have DC offset and VERY easy to damage the input FETs. Seldom of practical use.

Best Ref is the Tek Circuit Concepts book Oscilloscope Probes

Kind Regards

Jon

On Tue, Mar 9, 2021 at 03:01 PM, Raymond Domp Frank wrote:

Absolutely, Brian. For full BW you need (something even faster than) the
P6201. I was thinking about the convenience of having an "integrated" power
supply, as opposed to needing to hunt for an 1101. I should have mentioned
that but thanks for bringing it up.

Further to this, AFAIK the OP wasn't looking for 1 GHz BW as such, but looking for a significantly faster time base and vertical BW. Even the P6201 "only" achieves 900 MHz "on its own".
Talking about convenience: I often prefer using a 7A29 over a 7A19, even at around 500 MHz, because of the former's variable attenuation knob - and resettable overvoltage protection...

Raymond

On Tue, Mar 9, 2021 at 03:05 PM, Brian wrote:

Hi Raymond?I cant afford better than the P6201 and a home made 1101
substitute , if I need better I have a P6056 and P6057 resistive probes but of
course no Hi-Z input

Hi Brian,
I love the P6201 and actually prefer it over the P6202 because of its handling convenience. I have the luxury of several 'scopes with probe power sockets. Still, I have modified two P6202's (the ones with permanently connected power supply) by cutting the power wire somewhere near the middle and inserting a Lemo male/female plug set like Tek used for probe power. That way, I have a stand-alone probe power supply to use with a P6201, should a probe power socket be absent, in the process converting the P6202's to P6202A's (?)...

Raymond

On Tue, Mar 9, 2021 at 03:11 PM, Jean-Paul wrote:

On 50 Ohm WB plugins we use a direct connection with BNC/coax or a Zo Probe
like P6156.

The FET probes are huge, costly, have DC offset and VERY easy to damage the
input FETs. Seldom of practical use.

I have P6056/6057's and FET probes - and a P6230. Guess which one I use most.

Raymond

I like the P6201 also , I'm lucky enough to have 4 complete sets . I have not used them with a 7S14 though only the resistive probes . I have a 7S14 acquired long before the P6201's but the sampler has not been used that much for a while as I have since purchased 2 x 7104's along with some 7A29's and 7A19's . I also like the 7A29 over the 7A19 as its much easier to reset the input protection than keep replacing fuses that are really hard to find .
Brian

Hi Raymond?Would I be anywhere near right if I suggested the P6230 -- is that the one providing DC offset . If I am wrong then I would gp for the P6056/6057?
Brian