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Re: 7704A - Option 9?

 

As I recall, it was all done with a greatly relaxed transient response. Compare the overshoot specs. The hardware is the same.
Re: [OT] Shocks in a large market. How to check ESD direction?

 

How do you make one?

On Mon, May 6, 2024 at 12:41?AM jspencerg via groups.io
<jspencerg@...> wrote:

It is easy to make an electroscope. Walk around store with your finger on the electrode and observe when you get charged. Wear a foil hat if you don't want to answer any questions.
Re: 7704A - Option 9?

 

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
Re: 7704A - Option 9?

 

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

On 5/5/2024 9:17 PM, n4buq wrote:
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
7603(?) Restoration

 

About a year or so ago, I found a website (possibly youtube video) where the guy performed an electric and mechanical restoration on a 7000 series scope (I think it was a 7603 but possibly 7613, 7623, 7633). The scope looked almost brand new and I would like to review that material if possible. Does this sound familiar to anyone here?

Thanks,
Barry - N4BUQ
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
Re: 6C10 Tube

 

The Type 549 uses a 6GF5 in the HV supply, also the "almost" compactron 8608 in the vertical output section.
Re: 6C10 Tube

 

The 6AC10 has an amplification factor of 62 for each section (like a 12AT7). The 6C10 is 100, as you pointed out, like a 12AX7.

They work perfectly in a Heath HO-10, probably in other instruments, and are around $7 instead of $100 to $200 (ridiculous)...
-Charles
WTB: 453 rear cover plate

 

I recently got a 453 that needed some work to get going but it’s missing the rear cover plate. It’s an early one that has a separate power cord. If anyone has a parts unit that would let just the rear cover go please pm me.
Re: Experiences / Improvements with 1L5

 

You could also upload them to TekWiki at .

Regards,
Dave Wise
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Karl Goedecke <karl@...>
Sent: Sunday, May 5, 2024 2:56 PM
To: tekscopes@groups.io <tekscopes@groups.io>; tekscopes@groups.io <tekscopes@groups.io>
Subject: Re: [TekScopes] Experiences / Improvements with 1L5

Hi Benedikt,

I've scanned about 10 pages of pencilled schematics and notes about the 1L5 modifications. I'm trying to make them useable and add schematic refs.

I still want to do some explanations as well.

Can you email me so I can get your email? I can't use the Tekscopes link; it's in Outlook, which I don't have.

Karl G
Re: Dennis Tillman Tek 575 Curve Tracer Adapter PCB?

 

I hope so too, I have a 575 that I want to set up as a dedicated tube tester. I’ve been watching this thread with great interest.

Haven’t found a decent 576 that’s affordable yet.
Re: Keithley anyone?

 

It took me a very long time to find an original manual and probe for my 610B electrometer.

I was thinking of starting a Keithley group but it's hard to gauge how much interest there would be.

DaveD
KC0WJN

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.
Re: Keithley anyone?

 

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.
Re: [OT] Shocks in a large market. How to check ESD direction?

 

It is easy to make an electroscope. Walk around store with your finger on the electrode and observe when you get charged. Wear a foil hat if you don't want to answer any questions.
Re: Experiences / Improvements with 1L5

 

Hi Benedikt,

I've scanned about 10 pages of pencilled schematics and notes about the 1L5 modifications. I'm trying to make them useable and add schematic refs.

I still want to do some explanations as well.

Can you email me so I can get your email? I can't use the Tekscopes link; it's in Outlook, which I don't have.

Karl G
Re: 6C10 Tube

 

6C10s are three 12AX7 sections in one envelope. For many applications, the 6AC10 will work fine, it's three 12AU7 sections in one envelope. Not only do the AudioPhools like them, guitar amplifier builders are smitten too, and many hifi amplifiers and tuners use them. Compactrons were a last ditch effort to reduce vacuum tube overall cost and size, and buy time for developing solid state equipment. For this reason, they tend to be more rugged and longer lasting so people won't be? so annoyed at replacing them when only one section has failed.

?? Bruce Gentry, KA2IVY

On 5/4/24 16:11, Tom Lee wrote:
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: TekScopes@groups.io <TekScopes@groups.io> on behalf of Tom Lee <tomlee@...>
Sent: Saturday, May 4, 2024 12:24 PM
To: TekScopes@groups.io <TekScopes@groups.io>
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
Re: Dennis Tillman Tek 575 Curve Tracer Adapter PCB?

 

Dennis used to sell these from his table at the Ham swaps. Hopefully he will be attending them again soon.
Re: Keithley anyone?

 

I have 610B; we used those to measure the triboelectric charges on toner way back when laser printers were in vogue.

I am surprised to find that there is no Keithley groups.io group.

DaveD
KC0WJN

On May 5, 2024, at 08:34, Joel Setton via groups.io <setton@...> wrote:

?Hi,

I also have a few Keithley instruments :
- one 480 Picoammeter, works great
- One 616 digital electrometer which was "flaky" when I got it. I have since replaced the dual FET (Q301 A/B) in the Autoranging Amplifier. I also installed a standard BNC with an isolated mount to replace the input Triax connector, which was missing when I bought the unit.
I replaced the op-amp on the input board with an LM308. The original chip was the source of low-level AC oscillations, which resulted in unstable readings.
I also designed a small board with a 68HC11 which plugs into the QA408 socket, which normally carries the LSI-2 chip on the logic board. This was done as a protection against a potential failure of the original SL35155 chip, which is pure unobtainum.
Now the 616 is future-proof and it works great !
I even sold a few of these replacements boards for the SL35155 on a popular auction site. If anyone is interested, just drop me a PM.
- I also have a 261 Picoampere source, which was the cause of countless headaches because of erratic drift. At first I thought it just needed to be calibrated, but weekly recalibration is not what you expect to do ! Finally, I found that the 200-ohm calibration potentiometers were prone to random changes in cursor resistance, and since cursor current is several milliamps, this resulted in degraded accuracy. I couldn't find any replacements for the pots, and concluded that the design of the power regulator with these potentiometers was inherently flawed. One day I decided to bite the bullet and I designed a new regulator board, using good cermet trimpots in a scheme where the cursor current is close to zero. This performed exactly as expected, and I have not seen any significant drift in output current ever since.
If anyone is interested in the new regulator design, I have schematics and a few blank PCBs available.

That's all !
Cheers,
Joel
Re: [OT] Shocks in a large market. How to check ESD direction?

 

On Sun, May 5, 2024 at 05:01 AM, cheater cheater wrote:

anyways, does anyone know how to measure the direction of esd? some sort of galvanometer?
Gold leaf electrometer

--
Jim Adney
Madison, WI USA
Re: 6C10 Tube

 

On Sat, May 4, 2024 at 05:16 PM, Morris Odell wrote:

The 556 is the only one I've experience of but I can't remember which tube it uses.
From TekWiki: The 6M11, a pentode/dual triode, used only in the 556

--
Jim Adney
Madison, WI USA
4141 - 4160 of 208544