Date   

Re: Update (was RE: [TekScopes] TDS510 or TDS460A or 485 scopes as upgrade)

 

On Sun, Feb 21, 2021 at 03:41 PM, Raymond Domp Frank wrote:




On the 4xx scopes never use IPA as it will take the lettering off the
buttons.
...Nor use (anything containing) water! I usually take some butter(!). Works
very well!
Applies to the plastic buttons only...

Raymond


Re: Update (was RE: [TekScopes] TDS510 or TDS460A or 485 scopes as upgrade)

 

On Sun, Feb 21, 2021 at 03:30 PM, <toby@telegraphics.com.au> wrote:


On the 4xx scopes never use IPA as it will take the lettering off the
buttons.
...Nor use (anything containing) water! I usually take some butter(!). Works very well!

Raymond


Re: Update (was RE: [TekScopes] TDS510 or TDS460A or 485 scopes as upgrade)

toby@...
 

On 2021-02-21 8:41 a.m., Giuseppe Marullo wrote:
To avoid any possible mistake I bought the 2465b with frequency and TV trigger option(picked up locally) AND the 485(to be shipped next week)!

There is also a 468 in claimed good shape for like 110 bucks with a probe, thinking I am already become a tekscophile...

Now, I have other questions of course.
- how to clean the front panel? Nothing bad, I could leave as is but wondering if there is any recommendation.
On the 4xx scopes never use IPA as it will take the lettering off the
buttons.



-Which is the weapon of choice in terms of probes with each of these two(2465E and 485)?
- P6138?
- P6053?
- What would you recommend for each and what could be a decent low cost substitute probe (and how/if to deal with the "special" BNC sense for attenuation?

I would also need a probe to measure 900-1100VDC, do you know any cheap/chinese probe you do recommend? I don't plan to use it often it is just to check the anodic voltage of my FT-102s transceivers.

Thanks.

Giuseppe Marullo
IW2JWW - JN45R>






Update (was RE: [TekScopes] TDS510 or TDS460A or 485 scopes as upgrade)

Giuseppe Marullo
 

To avoid any possible mistake I bought the 2465b with frequency and TV trigger option(picked up locally) AND the 485(to be shipped next week)!

There is also a 468 in claimed good shape for like 110 bucks with a probe, thinking I am already become a tekscophile...

Now, I have other questions of course.
- how to clean the front panel? Nothing bad, I could leave as is but wondering if there is any recommendation.

-Which is the weapon of choice in terms of probes with each of these two(2465E and 485)?
- P6138?
- P6053?
- What would you recommend for each and what could be a decent low cost substitute probe (and how/if to deal with the "special" BNC sense for attenuation?

I would also need a probe to measure 900-1100VDC, do you know any cheap/chinese probe you do recommend? I don't plan to use it often it is just to check the anodic voltage of my FT-102s transceivers.

Thanks.

Giuseppe Marullo
IW2JWW - JN45R>


Re: ftgh: 515/515A instruction manual in binder

Leo Potjewijd
 

It's gone now...


Re: P6021 Noise Problem?

 

You confused me there with the probe type in the thread title not matching the content (P6021 - Current Probe, P6201 900MHz FET Probe).

Anyhow - if you are matching the test conditions exactly, then I'd be suspicious of:

C170, C180 (both 1uF, 35V) if the serial number is > B079000 (earlier ones used axial tantalum so less likely to be a problem)

C240 (22uF, 15V), and C350 (if it's an electrolytic, schematic disagrees with parts list).

It's unlikely that C300 (5.6uF, 6V) is a problem - it's in the signal path for the AC amp but it is is misbehaving I'd expect it to impact LF AC.


David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Chappy
Sent: 20 February 2021 21:09
To: TekScopes@groups.io
Subject: [TekScopes] P6021 Noise Problem?

I recently acquired a P6201 active 1X FET probe which appears to have never been used. The inspection tag was still attached, the accessory pack was still sealed, and there was not a single mark on the probe's ground sleeve. All functions of the probe are working but it has a 2mVpp high frequency noise component riding on any signals that I measure.

The manual states a 'Noise Tangental' of 300uV (150uV RMS), a figure well below the noise signal that I am seeing.

I have tried the probe on both my 7403 through a 7A18, and a new Keysight DSOX1102G with the same results. I have tried powering the device with a Tektronix bench power supply, and a home made unit with the same results. Interesting thing is that the noise level riding on the signal is almost non existent when I feed it a supply of +/- 5V. As I increase the supply voltage above this the noise becomes more apparent. Based on this observation I believe that i can rule out noise picked up by the cable between the amplifier and the probe. I have also scoped the power supply rails with negligible abberations on the supply traces on a 2mv/div scale. With the Keysight scope (BW = 70Mhz) a screen capture shows that the lowest component of the noise starts at approx 100MHz.

I am starting to think that there may be components inside either the amp or probe that have degraded over time. Could a degraded or failed electrolytic capacitor contribute to this noise? Or could it be due to a damaged FET or BJT?

If anyone here has one of these I would welcome your input before I go chasing a problem which perhaps is completely normal for this probe. Once again, its physical appearance indicated that it has never (or hardly) been used.

Sincerely,
Steve


Re: Rather than a TM500 module extender....

Tim Phillips
 

From Tim P (UK)
Yes, I discovered this trick when I removed the four screws in the base of
aTM502A, and the entire PSU slid out and landed in my lap !
Someone on this group published a photo of a setup using a small board to
'chock' the plug-in, and a couple of the guide rails to ensure a good
contact with the board connector.
Tim

On Sat, 20 Feb 2021 at 21:36, walter shawlee <walter2@sphere.bc.ca> wrote:

I just want to mention again that all the issues raised with regard to
module extenders are important,
and no matter which route you go, the result is always a bit sub-optimal,
and awkward on the bench

The magic answer is just to take a TM502A apart, removing the blue outer
shell. What's left is a compact dual connector power supply (complete with
power switch + line connector), and total access to the module under test.
This is the simplest, easiest, and most trouble free way to work on a TM500
plug in, and takes up the least possible bench space. I highly recommend
this path over all others. A similar trick is possible with a TM5003 for
the TM5000 modules, but it's certainly bigger.

I should point out that I did not move to this approach until long after I
already had many extenders, and it's only this specific frame that yields
such good results. In any case, it is a magical fix, full of test bench
happiness.

Test plug-ins to validate the frame are still needed, and you may still
want to extend a plug in from a specific frame, so that's the best case for
an extender.

All the best,
walter (walter2 -at- sphere.bc.ca)






Re: TM500 Mainframe Tester construction master thread.

Jared Cabot
 

The mistake with the diode designation was fixed in a later revision of the manual. If you download the latest, it'll have all the problems fixed that are found to date.

As for the knob, mine doesn't line up with the flat either, its just a function of the position of the number markings on the front panel that I copied directly from the Tek design. I would have preferred to use a round shaft switch but only flat was available outside of a custom order, so just ignore the flat and align the knob to the numbering.
I might put a note about that in the manual too (It's these small details that slip my mind when I am writing the manual after building the unit, so keep them coming so I can make the manual as accurate and detailed as possible! :) )

As of now with the addition of information about the knob position, the manual is at Version 1.6


Re: 3T77 tunnel diodes (again)

Tom Lee
 

Very sorry for the multiple posts -- I kept on getting an error message, but apparently the messages got through, despite them.

Yes, it's best not to press onward with VT circuits when tired. Rest up and re-engage in battle tomorrow.

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 20:29, Charles wrote:
That's an amusing anecdote, but did you have to post it three times in a row? :)

Meanwhile, transistor changes didn't help. The staircase never starts (which is what resets the Q135/Q145 latch through R145 Swp Length), and the plate of the Miller tube is sitting at the bottom of the ramp, about 74 volts. There are a lot of carbon comp resistors that may have drifted high in value. Also several switching diodes that could have failed.
I'm tired and don't feel like working around circuits with 300 volt supplies... Will have another crack at it tomorrow!




Re: 3T77 tunnel diodes (again)

 

That's an amusing anecdote, but did you have to post it three times in a row? :)

Meanwhile, transistor changes didn't help. The staircase never starts (which is what resets the Q135/Q145 latch through R145 Swp Length), and the plate of the Miller tube is sitting at the bottom of the ramp, about 74 volts. There are a lot of carbon comp resistors that may have drifted high in value. Also several switching diodes that could have failed.
I'm tired and don't feel like working around circuits with 300 volt supplies... Will have another crack at it tomorrow!


Re: 3T77 tunnel diodes (again)

Tom Lee
 

There's a famous photo of the first IC from Fairchild -- a four-transistor flip-flop, in a round die! One of the contact pads is obviously overetched and barely there, and the chip is full of debris. Some years ago, Gordon Moore was at a conference (ISSCC) and I asked him about the photo. I learned that he was the one who took the photo, and also the one who overetched the pad. He said the only reason the photo was taken was to perform failure analysis. They didn't think that what they were doing was so historic as to merit photographic preservation, so that's the only photo taken of their first real IC. He said he's embarrassed that this photo is now in the Smithsonian's collection, forever enshrining his inattention to etch times.

I then asked him about the debris. He smiled and said, "Well, Noyce was a chain-smoker."

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 19:38, Jim Ford wrote:
Oh, that's funny about cigarette ash getting into IC dice!  Lots more people smoked back then too, and indoors.  Fortunately for us nonsmokers, these days it's basically illegal to smoke indoors in California.  At the beginning of the year in 1990, I was working at the Lockheed Martin Skunk Works, and Lockheed Corp declared there would be no smoking indoors in any Lockheed building.  Very nice, and we all got used to it.  Later that year, in September, I started taking graduate microwave engineering courses at California State University, Northridge (several years before the big earthquake).  I was appalled to see students smoking in the hallways in the engineering building!  Gross!
Hard to imagine such gross (no pun intended) contaminants in ICs these days, with the cleanrooms and bunny suits and all.

Jim Ford


Re: 3T77 tunnel diodes (again)

Tom Lee
 

There's a famous photo of the first IC from Fairchild -- a four-transistor flip-flop, in a round die! One of the contact pads is obviously overetched and barely there, and the chip is full of debris. Some years ago, Gordon Moore was at a conference (ISSCC) and I asked him about the photo. I learned that he was the one who took the photo, and also the one who overetched the pad. He said the only reason the photo was taken was to perform failure analysis. They didn't think that what they were doing was so historic as to merit photographic preservation, so that's the only photo taken of their first real IC. He said he's embarrassed that this photo is now in the Smithsonian's collection, forever enshrining his inattention to etch times.

I then asked him about the debris. He smiled and said, "Well, Noyce was a chain-smoker."

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 19:38, Jim Ford wrote:
Oh, that's funny about cigarette ash getting into IC dice!  Lots more people smoked back then too, and indoors.  Fortunately for us nonsmokers, these days it's basically illegal to smoke indoors in California.  At the beginning of the year in 1990, I was working at the Lockheed Martin Skunk Works, and Lockheed Corp declared there would be no smoking indoors in any Lockheed building.  Very nice, and we all got used to it.  Later that year, in September, I started taking graduate microwave engineering courses at California State University, Northridge (several years before the big earthquake).  I was appalled to see students smoking in the hallways in the engineering building!  Gross!
Hard to imagine such gross (no pun intended) contaminants in ICs these days, with the cleanrooms and bunny suits and all.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: 2/20/2021 6:25:25 PM
Subject: Re: [TekScopes] 3T77 tunnel diodes (again)

In speaking with some of my colleagues whose professional careers extend back to the days when Ge technology was mainstream, it seems that a lot of the drift problems were due to contaminants. There was a prevailing belief that the very heavy doping needed to make TDs implied that you didn't need cleanrooms -- you could make them in dirtyrooms (take a look at early die photos of ICs -- you can see all sorts of crud; apparently, the industry then relied on cigarette ash as a dopant). It really wasn't until CMOS started to become important that the industry was willing to pay for the requisite processing environments. By that time, TDs were in decline, so they probably continued to be processed more or less the old way.

-- Tom

-- Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 18:03, Gary Robert Bosworth wrote:
We used to design tunnel diodes into the trigger circuits of pulse
generators at Datapulse back in 1970. Even back then, we were aware of the
drift in tunnel diode characteriatics with age. Some circuit operational
characteristics would change radically over the years. It was due to the
heavy doping of the semiconductor materials. It is a shame that newly
manufactured tunnel diodes are no longer in production for replacement
purposes.

Gary


On Sat, Feb 20, 2021, 17:53 Charles <charlesmorris800@centurytel.net> wrote:

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904
too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot
faster than the original Ge device. Could always put ferrite beads on the
leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect
as well. It's a DC coupled stage and has a zero-level pot on the base, so
replacing with a Si PNP shouldn't present any problem either.















Re: 3T77 tunnel diodes (again)

Tom Lee
 

There's a famous photo of the first IC from Fairchild -- a four-transistor flip-flop, in a round die! One of the contact pads is obviously overetched and barely there, and the chip is full of debris. Some years ago, Gordon Moore was at a conference (ISSCC) and I asked him about the photo. I learned that he was the one who took the photo, and also the one who overetched the pad. He said the only reason the photo was taken was to perform failure analysis. They didn't think that what they were doing was so historic as to merit photographic preservation, so that's the only photo taken of their first real IC. He said he's embarrassed that this photo is now in the Smithsonian's collection, forever enshrining his inattention to etch times.

I then asked him about the debris. He smiled and said, "Well, Noyce was a chain-smoker."

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 19:38, Jim Ford wrote:
Oh, that's funny about cigarette ash getting into IC dice!  Lots more people smoked back then too, and indoors.  Fortunately for us nonsmokers, these days it's basically illegal to smoke indoors in California.  At the beginning of the year in 1990, I was working at the Lockheed Martin Skunk Works, and Lockheed Corp declared there would be no smoking indoors in any Lockheed building.  Very nice, and we all got used to it.  Later that year, in September, I started taking graduate microwave engineering courses at California State University, Northridge (several years before the big earthquake).  I was appalled to see students smoking in the hallways in the engineering building!  Gross!
Hard to imagine such gross (no pun intended) contaminants in ICs these days, with the cleanrooms and bunny suits and all.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: 2/20/2021 6:25:25 PM
Subject: Re: [TekScopes] 3T77 tunnel diodes (again)

In speaking with some of my colleagues whose professional careers extend back to the days when Ge technology was mainstream, it seems that a lot of the drift problems were due to contaminants. There was a prevailing belief that the very heavy doping needed to make TDs implied that you didn't need cleanrooms -- you could make them in dirtyrooms (take a look at early die photos of ICs -- you can see all sorts of crud; apparently, the industry then relied on cigarette ash as a dopant). It really wasn't until CMOS started to become important that the industry was willing to pay for the requisite processing environments. By that time, TDs were in decline, so they probably continued to be processed more or less the old way.

-- Tom

-- Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 18:03, Gary Robert Bosworth wrote:
We used to design tunnel diodes into the trigger circuits of pulse
generators at Datapulse back in 1970. Even back then, we were aware of the
drift in tunnel diode characteriatics with age. Some circuit operational
characteristics would change radically over the years. It was due to the
heavy doping of the semiconductor materials. It is a shame that newly
manufactured tunnel diodes are no longer in production for replacement
purposes.

Gary


On Sat, Feb 20, 2021, 17:53 Charles <charlesmorris800@centurytel.net> wrote:

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904
too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot
faster than the original Ge device. Could always put ferrite beads on the
leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect
as well. It's a DC coupled stage and has a zero-level pot on the base, so
replacing with a Si PNP shouldn't present any problem either.















Re: 3T77 tunnel diodes (again)

Jim Ford
 

Oh, that's funny about cigarette ash getting into IC dice! Lots more people smoked back then too, and indoors. Fortunately for us nonsmokers, these days it's basically illegal to smoke indoors in California. At the beginning of the year in 1990, I was working at the Lockheed Martin Skunk Works, and Lockheed Corp declared there would be no smoking indoors in any Lockheed building. Very nice, and we all got used to it. Later that year, in September, I started taking graduate microwave engineering courses at California State University, Northridge (several years before the big earthquake). I was appalled to see students smoking in the hallways in the engineering building! Gross!
Hard to imagine such gross (no pun intended) contaminants in ICs these days, with the cleanrooms and bunny suits and all.

Jim Ford

------ Original Message ------
From: "Tom Lee" <tomlee@ee.stanford.edu>
To: TekScopes@groups.io
Sent: 2/20/2021 6:25:25 PM
Subject: Re: [TekScopes] 3T77 tunnel diodes (again)

In speaking with some of my colleagues whose professional careers extend back to the days when Ge technology was mainstream, it seems that a lot of the drift problems were due to contaminants. There was a prevailing belief that the very heavy doping needed to make TDs implied that you didn't need cleanrooms -- you could make them in dirtyrooms (take a look at early die photos of ICs -- you can see all sorts of crud; apparently, the industry then relied on cigarette ash as a dopant). It really wasn't until CMOS started to become important that the industry was willing to pay for the requisite processing environments. By that time, TDs were in decline, so they probably continued to be processed more or less the old way.

-- Tom

-- Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 18:03, Gary Robert Bosworth wrote:
We used to design tunnel diodes into the trigger circuits of pulse
generators at Datapulse back in 1970. Even back then, we were aware of the
drift in tunnel diode characteriatics with age. Some circuit operational
characteristics would change radically over the years. It was due to the
heavy doping of the semiconductor materials. It is a shame that newly
manufactured tunnel diodes are no longer in production for replacement
purposes.

Gary


On Sat, Feb 20, 2021, 17:53 Charles <charlesmorris800@centurytel.net> wrote:

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904
too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot
faster than the original Ge device. Could always put ferrite beads on the
leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect
as well. It's a DC coupled stage and has a zero-level pot on the base, so
replacing with a Si PNP shouldn't present any problem either.












Re: 1L10 crystal needed (Newbie)

Jim Ford
 

AFAIK, all xtal oscillator circuits operate in the microwatt range.
Those more experienced with XOs, feel free to correct me. Say, 5 volts squared divided by say, 100k ohms = 250 microwatts. Voltages are low and impedances are high, so power levels are low. I'd expect an XO to have an output buffer to drive mW into a much lower impedance load.
Good luck!

Jim Ford

------ Original Message ------
From: "Joel B Walker" <joelandjoyce@esinc.net>
To: TekScopes@groups.io
Sent: 2/20/2021 9:06:44 AM
Subject: Re: [TekScopes] 1L10 crystal needed (Newbie)

I posted a picture of the circuit. Perhaps one of you exceptionally intelligent individuals could tell me what the drive level is for this crystal. I tried Lokoselectronics. They are the ones that wouldn't respond to my emails. Bomars website isn't working today. I see that there are SMD crystals available in that frequency range, but they can only be driven with miniscule power levels in the micro watts. This the need to know what the circuit demands of the crystal.





Re: Help replacing a resistor/inductor in SG503

Jim Ford
 

Thanks, Tom, for posting. I'll have to check my two 7A26s. Only channel 2 works on both, and maybe it's one or more of the LR's. Then again, I haven't seen any evidence of smoke, so it's probably something else. One of the 7A26s has the Ch1 knob broken off, so it probably was abused!

Jim Ford

------ Original Message ------
From: "TomC" <tomc@viclink.com>
To: TekScopes@groups.io
Sent: 2/19/2021 4:02:23 PM
Subject: Re: [TekScopes] Help replacing a resistor/inductor in SG503

The 7A26 has 4 such LR components: LR1010, LR1014, LR1020, LR1024. They are 3.2uH wound on 10 ohm carbon comp. resistors. They are on the + and - 15 volt lines and are probably filtering noise going to the A2 board.

They feed 10 uf tantalums which when they go short burn up the LR components and produce a tremendous amount of smoke.

To fix, I took a closeup photo of one that hadn't been damaged and counted turns. There are 47 turns. Found the wire gauge with a micrometer on the wire from one that was destroyed. Then ordered wire and a supply of carbon comp 10 ohm resistors.

Made up a jig to wind the 47 turns on new 10 ohm resistors. Then soldered the ends and painted with dope.

Tom


On 2/18/2021 8:30 AM, Jared Cabot via groups.io wrote:
Hi all,
I recently got myself an SG503 Leveled Sine Wave generator for a good price and I am currently repairing it back to operational condition.

I found a few components in the oscillator section were damaged, from what I guess, is from some ham-fisted poking from someone's previous repair attempt.
Most parts were easy to replace, but I'm a bit stuck on one. LR140 is a 20nH inductor consisting of a couple turns of fine wire around a 1/8w 47ohm carbon composite resistor.
It looks like it has been poked at and one leg was broken off.
Below is linked a page from the schematics with the part highlighted in red.
https://groups.io/g/TekScopes/photo/260912/0/SG503%20Oscillators%20LR140%20Detail.jpg

My question is, How's the best way to recreate this sort of part? I tried winding a few turns on a 1/8 metal film resistor and didn't have much luck, I have a DE-5000 LCR meter and a HP 4276A etc but it's a little difficult to measure such small values reliably.
Should I get a carbon composite resistor from Digikey/Mouser to recreate the part more true to the original design instead of the metal film I used? Or is a plain 20nH axial inductor without the resistor ok to use? Any other ideas or suggestions?

Thanks!








Re: P6021 Noise Problem?

Michael A. Terrell
 

Chappy wrote:
No but I do live next to a military base, and I am about 400ft away from an air traffic control surveillance radar. You may be on to something there. Is it possible that the high frequency FET and transistors are picking this up? It has not been giving me a problem with my lower frequency probes.
It's quite possible. A microwave diode and a foot of wire for an antenna can let you se when the signal is the strongest, on another channel. Years ago, an EE in Orlando mentioned a consistent tick in his stereo that had recently started. I told him to turn his TV n, when the weather report was on a channel that had just installed a weather RADAR to see if it was pointed at his house during the ticks. It was. A Military RADAR runs a lot more power than a TV RADAR, and they can easily overload sensitive circuits in its path.

The main RADAR at Carin Airfield was 2MW pulsed, in the early '70s. I don't know what they use these days. That was a pair of Westinghouse systems, back then.

The shielding in a probe cable was never intended to deal with this. A simple shield along the wall of aluminum foil will block it, if you can use it. Sheets of foam insulation cann be bought with a foil backing, but you can't beat a properly built and maintained RF screened room.


Re: 3T77 tunnel diodes (again)

Tom Lee
 

In speaking with some of my colleagues whose professional careers extend back to the days when Ge technology was mainstream, it seems that a lot of the drift problems were due to contaminants. There was a prevailing belief that the very heavy doping needed to make TDs implied that you didn't need cleanrooms -- you could make them in dirtyrooms (take a look at early die photos of ICs -- you can see all sorts of crud; apparently, the industry then relied on cigarette ash as a dopant). It really wasn't until CMOS started to become important that the industry was willing to pay for the requisite processing environments. By that time, TDs were in decline, so they probably continued to be processed more or less the old way.

-- Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 2/20/2021 18:03, Gary Robert Bosworth wrote:
We used to design tunnel diodes into the trigger circuits of pulse
generators at Datapulse back in 1970. Even back then, we were aware of the
drift in tunnel diode characteriatics with age. Some circuit operational
characteristics would change radically over the years. It was due to the
heavy doping of the semiconductor materials. It is a shame that newly
manufactured tunnel diodes are no longer in production for replacement
purposes.

Gary


On Sat, Feb 20, 2021, 17:53 Charles <charlesmorris800@centurytel.net> wrote:

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904
too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot
faster than the original Ge device. Could always put ferrite beads on the
leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect
as well. It's a DC coupled stage and has a zero-level pot on the base, so
replacing with a Si PNP shouldn't present any problem either.







Re: 3T77 tunnel diodes (again)

Gary Robert Bosworth
 

We used to design tunnel diodes into the trigger circuits of pulse
generators at Datapulse back in 1970. Even back then, we were aware of the
drift in tunnel diode characteriatics with age. Some circuit operational
characteristics would change radically over the years. It was due to the
heavy doping of the semiconductor materials. It is a shame that newly
manufactured tunnel diodes are no longer in production for replacement
purposes.

Gary

On Sat, Feb 20, 2021, 17:53 Charles <charlesmorris800@centurytel.net> wrote:

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904
too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot
faster than the original Ge device. Could always put ferrite beads on the
leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect
as well. It's a DC coupled stage and has a zero-level pot on the base, so
replacing with a Si PNP shouldn't present any problem either.






Re: 3T77 tunnel diodes (again)

 

thanks, I was thinking of that (and possibly swapping Q145 for a 2N3904 too?). Hopefully it won't oscillate since those have a 250 MHz Ft, a lot faster than the original Ge device. Could always put ferrite beads on the leads, I suppose.

Q64 in the Staircase Inverter is also a 2N1516, so a tin whisker suspect as well. It's a DC coupled stage and has a zero-level pot on the base, so replacing with a Si PNP shouldn't present any problem either.

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