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Hi Harvey,

That's been my belief as well. Years ago a friend and I compared our two 7704A scopes, one with opt. 9 and one without. We couldn't identify any obvious differences in circuitry. Of course, Tek could've selected some critical devices for the opt 9 mainframes, but since we couldn't see any references in the documentation that suggested that this was going on, we discarded that theory. I remember reading a sentence somewhere that the opt. 9 units were calibrated for higher bandwidth, seemingly implying that all they did was effect a different tradeoff during calibration between transient response (or frequency response flatness) and bandwidth, allowing some degradation in the former for a boost in the latter.

That said, the non-opt 9 scope didn't have significantly worse bandwidth (IIRC, it was around 230MHz or so anyway), so the difference was 10-15%, or within tweaking range of each other, as you surmise. It's probably the case that many (maybe most) non-opt 9 units can be tweaked to hit 250 MHz.

--Tom

From: "n4buq" <n4buq@...>
To: "tekscopes" <[email protected]>
Sent: Sunday, May 5, 2024 8:17:28 PM
Subject: [TekScopes] 7704A - Option 9?

Does anyone know what was done to the 7704A for Option 9 (250MHz BW)? All I'm
finding is the definition but not what changed to accomplish that. The sticker
on the back of one of my 7704As states such and I'm curious what was changed
for that option.

Thanks,
Barry - N4BUQ

Hi Harvey,

That's been my belief as well. Years ago a friend and I compared our two
7704A scopes, one with opt. 9 and one without. We couldn't identify any
obvious differences in circuitry. Of course, Tek could've selected some
critical devices for the opt 9 mainframes, but since we couldn't see any
references in the documentation that suggested that this was going on,
we discarded that theory. I remember reading a sentence somewhere that
the opt. 9 units were calibrated for higher bandwidth, seemingly
implying that all they did was effect a different tradeoff during
calibration between transient response (or frequency response flatness)
and bandwidth, allowing some degradation in the former for a boost in
the latter.

That said, the non-opt 9 scope didn't have significantly worse bandwidth
(IIRC, it was around 230MHz or so anyway), so the difference was 10-15%,
or within tweaking range of each other, as you surmise. It's probably
the case that many (maybe most) non-opt 9 units can be tweaked to hit
250 MHz.

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070


On 5/5/2024 6:39 PM, Harvey White wrote:

I just spent a little time going through the (printed) manual. Mine's
revised as of 1981 and does cover the option 9 scopes.

I don't see anything on the schematic about option 9.? Easy to miss,
though.

What I do see is that the adjustments are slightly different, testing
the vertical amplifier at 280 Mhz rather than 230, with different
tolerances on the risetime, etc.

I suspect it was a tradeoff between overall flatness and bandwidth,
performed by adjustment.

Harvey

I just spent a little time going through the (printed) manual. Mine's revised as of 1981 and does cover the option 9 scopes.

I don't see anything on the schematic about option 9.? Easy to miss, though.

What I do see is that the adjustments are slightly different, testing the vertical amplifier at 280 Mhz rather than 230, with different tolerances on the risetime, etc.

I suspect it was a tradeoff between overall flatness and bandwidth, performed by adjustment.

Harvey

Does anyone know what was done to the 7704A for Option 9 (250MHz BW)? All I'm finding is the definition but not what changed to accomplish that. The sticker on the back of one of my 7704As states such and I'm curious what was changed for that option.

Thanks,
Barry - N4BUQ

On May 5, 2024, at 18:51, jspencerg via groups.io <jspencerg@...> wrote:

?Yes, I'm surprised about the lack of traffic on forums and YT about the old keithleys. I have working 2000 dmm, 236, and 610C units. I am getting into the fix with a 619. I was lucky to get a printed manual for the 619. I intend to have another go with my 228 after further honing of my chops.

Thank you, Dave. I’m wondering whether that 6C10 was used in a production instrument or an in-house fixture. I just checked the web and it commands crazy prices on eBay. Audiophiles have clearly fallen in love with its triple-triode sonic magic.

Tom


Sent from an iThing; please forgive the typos and brevity

On May 4, 2024, at 12:58, Dave Wise <d44617665@...> wrote:

?I don't know which scope used compactrons. I do know a cal fixture sort of did.
From my notes:

Tektronix 067-0502-01 Amplitude Calibrator.

The voltage regulator originally used the 6GE8/7734
signal pentode/power triode, but later switched to the 6G11
signal pentode/beam power tube, triode-connected in a purpose-built adaptor.

Besides the 12BU pinout (6AL11 and 6G11) the adaptor is made for,
the 12EZ tubes (6AD10 6BF11 6BY11 6T10) can probably work,
with a new adaptor.

Dave Wise
________________________________
From: [email protected] <[email protected]> on behalf of Tom Lee <tomlee@...>
Sent: Saturday, May 4, 2024 12:24 PM
To: [email protected] <[email protected]>
Subject: Re: [TekScopes] 6C10 Tube

I’m curious: which Tek scope used compactrons?

Cheers
Tom
Sent from an iThing; please forgive the typos and brevity

On May 4, 2024, at 11:23, Bill Riches via groups.io <bill.riches@...> wrote:

?Help! I am looking for a 6C10 tube.
73,
Bill, WA2DVUCape May, NJ