Date   

Re: Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book

 

Hi Jeffrey,
Apologies for not responding until now but I have been overwhelmed with the response for Peter's book and I finally have the time to respond to the email I didn't have time to reply to until now.

I think from what I have read that PayPal must have changed the wording of their choices to "Trusted Recipient" instead of "Friends and Family". They have changed a few other things to make it more difficult to figure out how to answer their questions to avoid all their fees completely.

You payment was eventually released but PayPal charged me a $2.00 fee. I would appreciate it if you could send an additional $2.00 since I was only charging everyone
Peter's cost for his book: $30.00;
USPS media rate mail for postage: $4.00;
Shipping supplies I bought (book mailer boxes, labels, and tape) $2;
My time (packing up the books, printing labels, multiple trips to the P.O to get the cheapest rates, etc): $1.
That was how I came up with the $37.00 total for each book.

What I forgot to include was the 40+ hours it took to get everyone's names and addresses, answer all the emails, locate missing payments, keep track of the orders, match the orders to the payments, deal with PayPal screw-ups, and double check that I got every order correct.

In the end I think I probably made less that $5/hour and that is something for me to think about before I come up with another one of my bright ideas.

Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jeff Dutky
Sent: Monday, November 23, 2020 8:31 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Why you MUST USE the PayPal "FRIENDS and FAMILY" option for Peter's book

Dennis,

If PayPal had offered me the option to use "Friends and Family" or "Gift" (or any option, for that matter) during my transaction, I would have used it without hesitation. PayPal's web interface never offered me any kind of option to categorize my payment. It is also not offering me the option to cancel the payment, and is saying that I can not confirm receipt of the order until 48 hours after the payment was made.

Since I can't cancel the payment I will confirm the order as soon as PayPal allows me to do so. I hope this all works out, and I appreciate the effort that you have expended. I'm just frustrated with PayPal.

Thank you again for the effort you have put into this process.

-- Jeffrey Dutky







--
Dennis Tillman W7pF
TekScopes Moderator


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Brian
 

Hi DaveI have also used HSMS8202 to repair S3A probes and have even made a replacement sampling sampling gate for an S6 sampling head . I can recommend them for the purpose , they have a higher reverse breakdown voltage than the 2825 I think .
regardsBrian

On Wednesday, 9 December 2020, 23:59:22 GMT, Tom Lee <tomlee@ee.stanford.edu> wrote:

Hi Dave,

I’ve used that very combination for 10GHz sampling bridges and it works very well. The rest of the 1S1 would be the performance limiter.

Less-capable diodes would work as well in this case, and would probably be more robust. As you and Jim Ford have noted, the HSMS diodes are now officially obsolete, so the usual distributors no longer stock them. But I see that Dan’s Small Parts and Kits has HSMS-2825 (dual diodes) at 10 for a buck. Hard to beat that. Buy a bunch more stuff to get your shipping dollar’s worth. And as with all of Dan’s deliveries, you’ll also get a large amount of tobacco smoke as a free bonus. Open your package outdoors if you’re sensitive. I’m only partly joking.

— Cheers,
Tom

Sent from my iThing, so please forgive typos and brevity.

On Dec 9, 2020, at 3:31 PM, Dave Wise <david_wise@phoenix.com> wrote:

I replaced my 1S1's four sampling diodes with four HSMS-8202 dual diodes, with each part wired to use the two diodes in series to increase the breakdown voltage and reduce the capacitance.
They are marked Obsolete at the major distributors, but Quest Components appears to have a few, as do MiniKits in Australia. There are about a dozen auctions at eBay.

Today I would use the Macom MA4E2054B1-287T which they list as a direct cross-ref.  They are in stock at DigiKey and Mouser.
Or the Infineon BAT15, BAT17, or BAT62.

HTH,
Dave Wise

These are SOT-23.  I made a little T-shaped "chip carrier" out of bare PCB material that fits in the original clips.
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jim Ford via groups.io <james.ford=cox.net@groups.io>
Sent: Wednesday, December 09, 2020 2:43 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What alternatives?

Although discontinued by Avago/Broadcom, I'm sure.  That's the way it
goes these days.  They discontinued me and a whole lot of others as
well, as some of you are probably tired of hearing me say!

The HSMS-28XX and other former HP Semiconductor devices just don't have
the volume they once had, and the suits at Avago/Broadcom don't like
that, nor do their investors.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 2:31:43 PM
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What
alternatives?

I have not actually fixed one this way, but I would expect an HSMS-28xx Schottky to be a perfect replacement here. These are readily available.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 14:26, "leonard scheepsma" <tubes.leonard@hetnet.nl> wrote:

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard


















Re: Tek 465M saga

Tom Lee
 

Yup. What I was curious about is whether Roy was implying that there were versions of the 465M with circuit differences (he advised getting the right manual for debugging a circuit problem). Obviously, there are cosmetic differences between the mil and industrial versions and, I believe, some differences in the accessories supplied. But I was not (and am still not) aware of any circuit differences.

—Tom

Sent from my iThing, so please forgive typos and brevity.

On Dec 9, 2020, at 3:34 PM, Mlynch001 <mlynch002@gmail.com> wrote:

From Tek Wiki:

“The Tektronix 465M is a 100 MHz dual-channel portable scope, the commercial version of the AN/USM 425 standard military scope.
It is essentially a 100 MHz bandwidth scope in the cabinet of a 455. A large user of the 465Ms was the Federal Aviation Administration.”

The AN/USM425 has a different center model ID faceplate.

The commercial 465M has a center faceplate that looks like that of the 455, simply:

(TEK logo) TEKTRONIX 465M

The “military” version has three lines of text similar to this:
AN/USM-425 (V)1 OSCILLOSCOPE U.S.

TEKTRONIX 466M CONTRACT F41608-76-D-0117

BEAVERTON, OREGON U.S.A. NSN 6625-01-032-6914


So if you have the former front panel, it is not a military version.
--
Michael Lynch
Dardanelle, AR





Re: Tek 465M saga

Mlynch001
 

465M not “466M” typo.


--
Michael Lynch
Dardanelle, AR


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Tom Lee
 

Hi Dave,

I’ve used that very combination for 10GHz sampling bridges and it works very well. The rest of the 1S1 would be the performance limiter.

Less-capable diodes would work as well in this case, and would probably be more robust. As you and Jim Ford have noted, the HSMS diodes are now officially obsolete, so the usual distributors no longer stock them. But I see that Dan’s Small Parts and Kits has HSMS-2825 (dual diodes) at 10 for a buck. Hard to beat that. Buy a bunch more stuff to get your shipping dollar’s worth. And as with all of Dan’s deliveries, you’ll also get a large amount of tobacco smoke as a free bonus. Open your package outdoors if you’re sensitive. I’m only partly joking.

— Cheers,
Tom

Sent from my iThing, so please forgive typos and brevity.

On Dec 9, 2020, at 3:31 PM, Dave Wise <david_wise@phoenix.com> wrote:

I replaced my 1S1's four sampling diodes with four HSMS-8202 dual diodes, with each part wired to use the two diodes in series to increase the breakdown voltage and reduce the capacitance.
They are marked Obsolete at the major distributors, but Quest Components appears to have a few, as do MiniKits in Australia. There are about a dozen auctions at eBay.

Today I would use the Macom MA4E2054B1-287T which they list as a direct cross-ref. They are in stock at DigiKey and Mouser.
Or the Infineon BAT15, BAT17, or BAT62.

HTH,
Dave Wise

These are SOT-23. I made a little T-shaped "chip carrier" out of bare PCB material that fits in the original clips.
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jim Ford via groups.io <james.ford=cox.net@groups.io>
Sent: Wednesday, December 09, 2020 2:43 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What alternatives?

Although discontinued by Avago/Broadcom, I'm sure. That's the way it
goes these days. They discontinued me and a whole lot of others as
well, as some of you are probably tired of hearing me say!

The HSMS-28XX and other former HP Semiconductor devices just don't have
the volume they once had, and the suits at Avago/Broadcom don't like
that, nor do their investors.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 2:31:43 PM
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What
alternatives?

I have not actually fixed one this way, but I would expect an HSMS-28xx Schottky to be a perfect replacement here. These are readily available.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 14:26, "leonard scheepsma" <tubes.leonard@hetnet.nl> wrote:

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard


















Re: Tek 465M saga

Mlynch001
 

From Tek Wiki:

“The Tektronix 465M is a 100 MHz dual-channel portable scope, the commercial version of the AN/USM 425 standard military scope.
It is essentially a 100 MHz bandwidth scope in the cabinet of a 455. A large user of the 465Ms was the Federal Aviation Administration.”

The AN/USM425 has a different center model ID faceplate.

The commercial 465M has a center faceplate that looks like that of the 455, simply:

(TEK logo) TEKTRONIX 465M

The “military” version has three lines of text similar to this:
AN/USM-425 (V)1 OSCILLOSCOPE U.S.

TEKTRONIX 466M CONTRACT F41608-76-D-0117

BEAVERTON, OREGON U.S.A. NSN 6625-01-032-6914


So if you have the former front panel, it is not a military version.
--
Michael Lynch
Dardanelle, AR


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Dave Wise
 

I replaced my 1S1's four sampling diodes with four HSMS-8202 dual diodes, with each part wired to use the two diodes in series to increase the breakdown voltage and reduce the capacitance.
They are marked Obsolete at the major distributors, but Quest Components appears to have a few, as do MiniKits in Australia. There are about a dozen auctions at eBay.

Today I would use the Macom MA4E2054B1-287T which they list as a direct cross-ref. They are in stock at DigiKey and Mouser.
Or the Infineon BAT15, BAT17, or BAT62.

HTH,
Dave Wise

These are SOT-23. I made a little T-shaped "chip carrier" out of bare PCB material that fits in the original clips.
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Jim Ford via groups.io <james.ford=cox.net@groups.io>
Sent: Wednesday, December 09, 2020 2:43 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What alternatives?

Although discontinued by Avago/Broadcom, I'm sure. That's the way it
goes these days. They discontinued me and a whole lot of others as
well, as some of you are probably tired of hearing me say!

The HSMS-28XX and other former HP Semiconductor devices just don't have
the volume they once had, and the suits at Avago/Broadcom don't like
that, nor do their investors.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 2:31:43 PM
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What
alternatives?

I have not actually fixed one this way, but I would expect an HSMS-28xx Schottky to be a perfect replacement here. These are readily available.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 14:26, "leonard scheepsma" <tubes.leonard@hetnet.nl> wrote:

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard








Re: Greetings From a New Member

 

Hi Gordon,
My current project is EHT generation for two TEK 545B's, similar to the 547. TV/Monitor line output transformers are available on ebay, as are 'arc generators' with well isolated secondary windings. Have had good experimental results with the latter, working from 5 to 9 volts, and they are cheap enough to use for the three EHT supplies required.

Unusually in this forum I began work as an entomologist after building my first valve oscilloscope at age 14 (VCR139 cathode ray tube?) then metamorphosed into a science administrator, then psychotherapist, and now spiritual Medium (not charged for). Electronics always came easily to me.

Dark matter to my mind represents higher levels of reality (Cf. harmonic theory) unavailable to existing scientific measurement, given we do not even understand the (four, according to the fully documented Edgar Cayce) different kinds of electricity yet.
Also have a working TEK 475A; very reliable HP 1740A, and expecting a battered TEK 7603 shortly.
Regards


Re: 494AP-How does the Front Panel Amp Cal ie, Blue Shift CAL function work? Mine has a problem

John Gord
 

Bruce,
The vertical character jitter is probably due to poor thermal balance in the vertical amplifier. Driving the trace far away from center for a long time (as with a horizontal line off the top of screen) produces a thermal imbalance in one or more of the differential pairs in the amplifier, and they recover with times on the order of milliseconds. Oscilloscopes often have an adjustment for this, but I don't know if the 494 does.
--John Gord

On Wed, Dec 9, 2020 at 01:52 PM, ebrucehunter wrote:


Bob,
I realize this might not be terribly helpful, but I have encountered a pair of
similarities with my plain 494 that I have been waiting to worsen so that I
might better trace the problem.
When first turned on, the screen characters, but not the other traces, on my
screen exhibit a vertical shake of perhaps 1/16-inch.  This gradually
subsides in less than a minute.  But then when reducing the Frequency Span,
in switching from 500 kHz to 200 kHz, the screen displays "Phaselock Failure
-- 1st LO."
Now by turning the power off and back on again, everything works OK and the
analyzer will phaselock properly down to a resolution bandwidth of 30 Hz.
The voltage test points, near the left-front, show no evidence of jitter.  I
have not changed the power resistors on the deflection board, as recommended
by John Miles, but now have replacements on hand.  It is possible these
resistors in the vertical deflection circuit are arcing internally, but
eventually heat and heal.
Interestingly, if the Peak/Average control is turned all the way CW so that
the horizontal line is off-screen at the top, the screen characters will
jitter vertically.  I assume this is an intentional warning feature that is
digitally generated, and unrelated to the fault.

Bruce, KG6OJI


Re: OT - VTVM’s are awesome

Jim Ford
 

Well, I do have a Simpson 260 analog voltmeter and a Micronta FET input analog meter as well that my wife bought me for Christmas one year back when Radio Shack was still Radio Shack and she didn't know what else to get me. I don't end up using them much, though (could say that for a lot of my stuff - don't tell my wife!). I did show a young man I was tutoring before the Covid outbreak the exponential charging/discharging of a cap through a resistor with one last year. Much easier to get the concept than on a DMM, of which I have several. Bought some Beckman Industrial ones at a swapmeet decades ago, and I have a couple other cheapo ones I check the AC mains voltage with every once in a while.
Next on the list is a HP/Agilent 34401A or two. Sooner or later I'm going to need more than 3 1/2 digits.

I just don't see the point in having a big, bulky vacuum tube scope with low bandwidth on my bench. I'm too young to have worked with a particular model and have a sentimental attachment to it. I guess I can understand that, since I have 5000 series and 7000 series scopes that I'm quite fond of, and an HP 8566 spectrum analyzer and 8350B sweep oscillator like I had at Lockheed several decades ago. Amazing that we can afford that stuff now, when it was several years pay back then!

I can't really relate to all the paint and cosmetic issues that come up, either. Not being retired yet, I don't have a lot of time to worry about such details. It's enough for me to keep stuff working. I figure the plaques with company names of previous owners are badges of honor!

To each his own.

Jim

------ Original Message ------
From: "Stephen" <stephen.nabet@gmail.com>
To: TekScopes@groups.io
Sent: 12/9/2020 2:30:13 PM
Subject: Re: [TekScopes] OT - VTVM’s are awesome

On Wed, Dec 9, 2020 at 10:50 AM, Jim Ford wrote:


Well, tubes (valves, for the Brits in the audience) are for audio and
displays, if you ask me. Maybe in TWTs for moon-bounce. I haven't
found a reason to buy a scope with tubes, other than the CRT, in it yet.
But then, I'm only 55, a mere youngster on this group! ;)

Jim
I’m 54 and I love anything with tubes in it.
If it’s well designed of course, not the cheap Chinese stuff that have tubes glowing just for the looks.

As for VTVM’S or VOM’s for that matter, I use them as much as my DMM’s.
There’s no better or worse. As it has been mentioned, they all have their place.
I personally find needles easier on the eyes. And they can be very accurate if you look closely at the position of the needle, and if your meter has a parallax mirror. Now, if you absolutely need 50000 counts or more of accuracy, that’s not for you...
But honestly, how many times do you really need that level of accuracy or definition. And I mean « need », not « want ». Personally, not many times.

On a side note, like Tektronix scopes of yore, they are just well designed and built to last. The quality is exceptional by nowadays lame standards IMO. These older things are objects of art.





Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Jim Ford
 

Although discontinued by Avago/Broadcom, I'm sure. That's the way it goes these days. They discontinued me and a whole lot of others as well, as some of you are probably tired of hearing me say!

The HSMS-28XX and other former HP Semiconductor devices just don't have the volume they once had, and the suits at Avago/Broadcom don't like that, nor do their investors.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 2:31:43 PM
Subject: Re: [TekScopes] 1S1 sampling bridge GaAs diodes: What alternatives?

I have not actually fixed one this way, but I would expect an HSMS-28xx Schottky to be a perfect replacement here. These are readily available.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 14:26, "leonard scheepsma" <tubes.leonard@hetnet.nl> wrote:

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard








Re: Tek 465M saga

Roy Thistle
 

On Wed, Dec 9, 2020 at 01:08 PM, Tom Lee wrote:


Were there two different versions of the 465M
I don't think so... I've only ever seen the military version; but didn't Tektronix also sell them commercially?... I think I've seen a 465M with an I.B.M. inventory tag on it?... not sure.
The question about the source of the manual the OP was using was more directed towards getting on the same page as the OP.... and a worry about the following:
If there was a commercial version of the 465M, distinct in some way from the military version (speced parts?)... was/were there manual(s) for the commercial version of the 465M... distinct from the manuals the military got?


Re: 1S1 sampling bridge GaAs diodes: What alternatives?

Tom Lee
 

I have not actually fixed one this way, but I would expect an HSMS-28xx Schottky to be a perfect replacement here. These are readily available.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 14:26, "leonard scheepsma" <tubes.leonard@hetnet.nl> wrote:

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard





Re: OT - VTVM’s are awesome

Stephen
 

On Wed, Dec 9, 2020 at 10:50 AM, Jim Ford wrote:


Well, tubes (valves, for the Brits in the audience) are for audio and
displays, if you ask me. Maybe in TWTs for moon-bounce. I haven't
found a reason to buy a scope with tubes, other than the CRT, in it yet.
But then, I'm only 55, a mere youngster on this group! ;)

Jim
I’m 54 and I love anything with tubes in it.
If it’s well designed of course, not the cheap Chinese stuff that have tubes glowing just for the looks.

As for VTVM’S or VOM’s for that matter, I use them as much as my DMM’s.
There’s no better or worse. As it has been mentioned, they all have their place.
I personally find needles easier on the eyes. And they can be very accurate if you look closely at the position of the needle, and if your meter has a parallax mirror. Now, if you absolutely need 50000 counts or more of accuracy, that’s not for you...
But honestly, how many times do you really need that level of accuracy or definition. And I mean « need », not « want ». Personally, not many times.

On a side note, like Tektronix scopes of yore, they are just well designed and built to last. The quality is exceptional by nowadays lame standards IMO. These older things are objects of art.


1S1 sampling bridge GaAs diodes: What alternatives?

leonard scheepsma
 

Dear all, my 1S1 gave up. It looks at least one of my sampling diodes has died. Searching through the related messages I noticed most comments are pretty old, so I hope some new ideas might have been launched on getting alternatives for the original GaAs diodes, just assuming these are completely unobtainable.
Looked at the Agilent/KeySight site, they mention some ultra fast GHz diodes there but these go through a distributor and I suspect ut won't be easy to get 4 of these at reasonable cost (not knowing they would work either)
Any tips, suggestions?

Thanks so much, Leonard


Re: OT - VTVM’s are awesome

Jim Ford
 

LOL about sleeping on top of a pile of 7000 mainframes! Don't give my wife any ideas or I'll be living that!

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 1:49:04 PM
Subject: Re: [TekScopes] OT - VTVM’s are awesome

Absolutely right! The flame wars are entertainingly silly. I resolve the conundrum personally by not limiting the choices to this or that. Why not both? I get a lot of use out of my $4 cheapo DMM, and I don't shed a tear if I break it or lose it. I've got many other meters for other purposes. Of course, sometimes storage space eventually becomes a factor, but a bunch of 7000-series mainframes lashed together with a mattress on top is a pretty decent bed.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 13:39, "tgerbic" <tgerbic@gmail.com> wrote:

I am also a fan of VTVMs. They have their place.

I have seen a lot of discussions, some turning into flame wars, on the net about analog vs. digital test equipment. I learned long ago that there are no perfect test instruments. You need to determine what works when, how you need things displayed and how much accuracy you really need, or makes sense. Though I have multiple midrange bench/handheld Fluke and HP DMMs on the bench, I restored a Heathkit IM-25 and it sits in the middle of the bench. Not actually a VTVM but a solid state version of one. It is accurate enough for many uses and I have lab calibrated instruments if I need higher accuracy.

What is really important, as pointed out below, is the large analog meter. For many measurements a moving needle meter is much easier to read and easier for my eyes to follow than a digital readout. Some meters have bar graphs but not much resolution compared to a large meter. Where VTVMs really shine is when tuning things where you are looking for a peak or null, or when trying to follow signals that vary all over the place. In many cases you don't even need to stare at the meter to get readings (like on a digital meter) but just keep an eye on it in your peripheral vision as you make some preliminary adjustments. A scope can be used in some cases but might be overkill. I also have an analog frequency meter for tuning and following frequency changes. I have spectrum analyzers ranging down to 5hz but an SA might again be overkill or too much setup.

I still have a bunch of Heathkit, RCA and EICO VTVMs and will use one from time to time, mostly on older tube equipment where I might worry about permanently damaging my Fluke meters.

Bottom line is to determine what you want to measure, how much accuracy is needed and how you want/need to see the display. VTVMs still have a niche to fill.

Regards








Re: 494AP-How does the Front Panel Amp Cal ie, Blue Shift CAL function work? Mine has a problem

 

Bob,
I realize this might not be terribly helpful, but I have encountered a pair of similarities with my plain 494 that I have been waiting to worsen so that I might better trace the problem.
When first turned on, the screen characters, but not the other traces, on my screen exhibit a vertical shake of perhaps 1/16-inch.  This gradually subsides in less than a minute.  But then when reducing the Frequency Span, in switching from 500 kHz to 200 kHz, the screen displays "Phaselock Failure -- 1st LO."
Now by turning the power off and back on again, everything works OK and the analyzer will phaselock properly down to a resolution bandwidth of 30 Hz.
The voltage test points, near the left-front, show no evidence of jitter.  I have not changed the power resistors on the deflection board, as recommended by John Miles, but now have replacements on hand.  It is possible these resistors in the vertical deflection circuit are arcing internally, but eventually heat and heal.
Interestingly, if the Peak/Average control is turned all the way CW so that the horizontal line is off-screen at the top, the screen characters will jitter vertically.  I assume this is an intentional warning feature that is digitally generated, and unrelated to the fault.

Bruce, KG6OJI


Re: OT - VTVM’s are awesome

Jim Ford
 

Well, tubes (valves, for the Brits in the audience) are for audio and displays, if you ask me. Maybe in TWTs for moon-bounce. I haven't found a reason to buy a scope with tubes, other than the CRT, in it yet. But then, I'm only 55, a mere youngster on this group! ;)

Jim

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: "TekScopes@groups.io" <TekScopes@groups.io>
Sent: 12/9/2020 1:31:38 PM
Subject: Re: [TekScopes] OT - VTVM’s are awesome

Hi Jim,

Yes, in this case, "better" was the enemy of "best", where "best" was what solved the problem the soonest and with stuff in my junk box. I wouldn't trust the ohmmeter to hold tight tolerances over a wide temperature range (or ever) with this circuit, but it never got too hot or cold in San Diego. Worked well enough to fix TVs and radios. And the VTVM was thankfully hard to kill, even when probing a horizontal output tube's plate voltage. Love them toobz!

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 13:14, "Jim Ford" <james.ford@cox.net> wrote:

No need to overthink it. If it works, go with it. The engineer in me wants to make sure it has some margin, though. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: Tom Lee <tomlee@ee.stanford.edu> Date: 12/9/20 1:05 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] OT - VTVM’s are awesome I didn’t like having a battery in my Heathkit VTVM, either. Having lost countless flashlights and toys to leakage was enough of a lesson. It was in the days before the LM317 (maybe Dobkin was in the process of designing it), so that wasn’t an option. I just put two diodes in series, powered through another rectifier off the filament supply (I think), with a big old ‘lytic across the series diode pair. Not elegant, but as a junior high school student, I was very pleased to have it work. When I revisited the meter after many years in storage, I thought briefly about upgrading it with a more modern implementation. But it still worked well, so I let laziness make the decision.TomSent from my iThing, so please forgive typos and brevity.> On Dec 9, 2020, at 12:47 PM, Jean-Paul <jonpaul@ix.netcom.com> wrote:> > Hi: The Heathkit, Eico, Paco and Knight (Allied) VTVMs all had bannana jacks and probe cables of rubber, that cracked over the years. I recall one meter with the old microphone screw coax perhaps for AC input shield. > > The VT bridge circuit seems to limit meter movement (200 uA?) overload, I never had damage to the movements even with extreme overload. > > IM-28 were the newer series but basically same as the VT-7.> > Hope that someone can please post a link to the Zener or LM317 battery substitue circuit? > > Jon> > > > > > > >







Re: OT - VTVM’s are awesome

Tom Lee
 

Absolutely right! The flame wars are entertainingly silly. I resolve the conundrum personally by not limiting the choices to this or that. Why not both? I get a lot of use out of my $4 cheapo DMM, and I don't shed a tear if I break it or lose it. I've got many other meters for other purposes. Of course, sometimes storage space eventually becomes a factor, but a bunch of 7000-series mainframes lashed together with a mattress on top is a pretty decent bed.

Tom

Sent from my iThing, so please forgive the terseness and typos.

On Dec 9, 2020, at 13:39, "tgerbic" <tgerbic@gmail.com> wrote:

I am also a fan of VTVMs. They have their place.

I have seen a lot of discussions, some turning into flame wars, on the net about analog vs. digital test equipment. I learned long ago that there are no perfect test instruments. You need to determine what works when, how you need things displayed and how much accuracy you really need, or makes sense. Though I have multiple midrange bench/handheld Fluke and HP DMMs on the bench, I restored a Heathkit IM-25 and it sits in the middle of the bench. Not actually a VTVM but a solid state version of one. It is accurate enough for many uses and I have lab calibrated instruments if I need higher accuracy.

What is really important, as pointed out below, is the large analog meter. For many measurements a moving needle meter is much easier to read and easier for my eyes to follow than a digital readout. Some meters have bar graphs but not much resolution compared to a large meter. Where VTVMs really shine is when tuning things where you are looking for a peak or null, or when trying to follow signals that vary all over the place. In many cases you don't even need to stare at the meter to get readings (like on a digital meter) but just keep an eye on it in your peripheral vision as you make some preliminary adjustments. A scope can be used in some cases but might be overkill. I also have an analog frequency meter for tuning and following frequency changes. I have spectrum analyzers ranging down to 5hz but an SA might again be overkill or too much setup.

I still have a bunch of Heathkit, RCA and EICO VTVMs and will use one from time to time, mostly on older tube equipment where I might worry about permanently damaging my Fluke meters.

Bottom line is to determine what you want to measure, how much accuracy is needed and how you want/need to see the display. VTVMs still have a niche to fill.

Regards





Re: OT - VTVM’s are awesome

tgerbic
 

I am also a fan of VTVMs. They have their place.

I have seen a lot of discussions, some turning into flame wars, on the net about analog vs. digital test equipment. I learned long ago that there are no perfect test instruments. You need to determine what works when, how you need things displayed and how much accuracy you really need, or makes sense. Though I have multiple midrange bench/handheld Fluke and HP DMMs on the bench, I restored a Heathkit IM-25 and it sits in the middle of the bench. Not actually a VTVM but a solid state version of one. It is accurate enough for many uses and I have lab calibrated instruments if I need higher accuracy.

What is really important, as pointed out below, is the large analog meter. For many measurements a moving needle meter is much easier to read and easier for my eyes to follow than a digital readout. Some meters have bar graphs but not much resolution compared to a large meter. Where VTVMs really shine is when tuning things where you are looking for a peak or null, or when trying to follow signals that vary all over the place. In many cases you don't even need to stare at the meter to get readings (like on a digital meter) but just keep an eye on it in your peripheral vision as you make some preliminary adjustments. A scope can be used in some cases but might be overkill. I also have an analog frequency meter for tuning and following frequency changes. I have spectrum analyzers ranging down to 5hz but an SA might again be overkill or too much setup.

I still have a bunch of Heathkit, RCA and EICO VTVMs and will use one from time to time, mostly on older tube equipment where I might worry about permanently damaging my Fluke meters.

Bottom line is to determine what you want to measure, how much accuracy is needed and how you want/need to see the display. VTVMs still have a niche to fill.

Regards

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