Date   

Re: Beware of old AntiStatic foam

Eric-K0ELB
 

This is well known in the gun community, people buy those nice hard shell plastic gun cases with the foam inside and leave their guns in there for years, and corrosion always results.

They found out that the real problem is the type of foam. Open celled foam will absorb moisture and thus corrode anything that's stored in it for a length of time. Even if it's covered in oil like a firearm usually is. The more humid the area you live in the worse it is, obviously. The trick is to never leave anything you want to use again in foam.

For storing things like IC's, I would use something like a small hard plastic case and no foam at all. And check them at least once a year.


Re: FG502 doesn't start at some specific settings

Ozan
 

I don't have this equipment but here is my feedback in addition to Mark's suggestions:

Digging around I found that the triangular generator stays in a state where is
happy (I can provide all voltages in significant points of the schematic)
Are +17V, "+17V (DCPL 1)", -17V, "-17V (DCPL 1)" on sheet <1> stable when cold (not working)?

In the happy non-working state what are the voltages (partial list is OK if you don't have them all):
1) at the gate of Q200, and collector of Q292.
2) bases of Q230A and Q230B
3) bases of Q290 and Q292
4) emitters of Q140 and Q175

In case gate circuit is acting funny: Voltage at collectors of Q325 and Q315

until it decides to start working. I'm attaching two pictures of a normal
start and the delayed one. In the second one (4018-1) note the Ch4 (blue)
baseline is at the top of the display screen.
What are the test points for the different traces?

Ozan


Re: 7D15 internal trigger not working

Steve Nossen
 

Dan and Mark,

Thanks for the tips. I had the covers off a few times and removed the -5 V board. Never noticed the socket pins allowing perpendicular mounting.

Measured the transistors and Q213 measures 30 ohms from C to E and E to C on my SImpson 260. Much higher on a DVM but the same in both directions. Seems leaky to me. Q203 measured more like a diode, conducts in one direction. I'll add some transistors to my next order. The 1 uF caps both measure 1 uF and D of .02 at 1KHz, about 3.3 ohms. The 2.2 uF caps measure 2.3 uF and D of .1, about 7.2 ohms. I'll start with a transistor swap.

Steve


Re: PS 5010 troubleshooting (no negative, erratical display)

ditter2
 

Hello Martin,

The main voltage reference used in the PS5004 is a National Semiconductor LM399. These references are thermally stabilized, and after about 6 months of aging through normal use, have a stability which rivals standard cell primary voltage references. However, the IC process did not support laser trimming, so the only downside to these otherwise great parts is they have about a 5 % initial voltage tolerance – a challenged to adjust to the precision required for an instrument with target accuracy of 0.01%. This is way beyond the acceptable adjust resolution of a 20 turn trimmer pot. I ended up with a bank of binary weighted resistors in the leg of a voltage divider to pre-select the voltage to be in range that can be adjusted by the 20 turn trimmers. Initially these were to be controlled with a DIP switch, but this would require the user to correctly enter the 4 bit binary code for each “try and miss” step during calibration. I found the cam operated DIP switch we ended up using, which simplifies this step by doing the proper binary coding for each increment/decrement.

As the manual reads, you would only need to perform this step when replacing the reference IC, as any aging drift should be adjustable with the range of the 20 turn trimmer. To set this coarse pre-selector switch, you need to adjust the span trimmers to the center of their range, which is a lot of turns for a 20 turn pot. The trimmers don’t have positive stops at the end, they just keep turning and a small “click” is felt in your screwdriver when you get to the end. So centering a 20 turn trimmer first requires turning to the end more than 20 turns (to assure you are at the end, then backing up 10 turns. This is why you see these span trimmers being adjusted so many times in the Cal procedure.

Second question:
If this is quoted directly from the manual (I don’t have access to my copy right now), it looks like there is a missing word that would help.
“Connect the PS 5004 OUTPUT to the digital voltmeter input using a BNC cable and a pair of BNC-to-banana plug adapters. The shield side of the BNC is connected to the PS 5004 OUTPUT terminal, and the voltmeter Low input.”
Should read:
Connect the PS 5004 OUTPUT to the digital voltmeter input using a BNC cable and a pair of BNC-to-banana plug adapters. The shield side of the BNC is connected to the PS 5004 - OUTPUT terminal, and the voltmeter Low input.” (add a minus sign between “PS4004” and “OUTPUT” - these should be Bold type face to indicated these are the connection point names)

A challenge in manual writing is that everyone, the engineers, technicians, and even manual writers themselves, are “too close” to the equipment we are writing about, and procedures are the same as we have all used over and over. So it is easy to assume the reader already knows something that we all know – but only because we are “insiders”. What this step is trying to say is to use a shielded BNC cable to measure these precision DC voltages, and make sure the shield is connected to the PS5004 negative output terminal, and the DMM low / guard terminal. It is important to drive the DMM Guard input and not leave it floating.

Third question: These are 20 turn trimmers, so needing to two resolutions is possible, especially if the instrument is being calibrated the first time after many years of storage. I think the need for the coarse adjustment is described above – it is necessary to get the range covered by the 20 turn span trimmers close enough to account for a 5% initial tolerance in the initial voltage reverence.
On this topic – if you are calibrating a PS5004 or any high precision instrument (Fluke DMM etc.) that has been not used for a decade or more, you should probably first power it up and let it run for a week or more. Large drifts from aging may be moisture absorption in components and circuit boards.

Final question – there is interaction between the span and zero adjustments. This results because Zero volts output is not actually zero. Studying the schematic, see the output has an active load on it that can sink small currents below 0 V. So the supply can be adjusted to negative output. In fact, the original design would allow precision adjustment of the output to minus 100 mV, but the supply can only sink a few mA in the negative direction, as it is not q four quadrant supply (only single pass transistor). The application would be measuring input offset in DC amplifiers, etc. I thought it would be quite useful, We did some customer trials with an engineering prototype, and the users found the feature to be confusing because of the current limitation when the output went negative. So we pulled it out. This feature is implemented only in the firmware – no hardware changes were made. Thus the supply actually has some output voltage when adjusted to Zero, which is removed by other offsets in the circuit. Thus the gain action of the coarse and fine span trimmers will move the zero output setting, which requires an iterative adjustment procedure.

Steve


Re: 7A16A high frequency compensation.

unclebanjoman
 

Hi Albert,

to check my PG506 I used 3S1/3T77A pair, connected with a 20 cm GR874 airline. Measured a risetime of 750 ps and aberrations as per service manual. So I did prefer touch nothing. :-)

R436 is the one pointed by the green arrow in my photo and it's O.K.
The unknown R is the one pointed to by the red arrow. See https://groups.io/g/TekScopes/photo/262075/3

Max


Re: Beware of old AntiStatic foam

Renée
 

unfortunately I too have had the same experience. foam-lost a bunch of microprocessors and assorted items that I thought were in safe place....
and regarding Duracell---lost a couple pieces of test equip..now this was a long time ago-their answer was "send it in we will fixit"...well I did that with one item and then they said not repairable and it is too old to replace...we disposed of it for you and sent me a cheque for cost of shipping and a coupon for more batteries. furious was not the word i would use......Duracell is !@#$%* no more around here...somewhere we (as a consumer of things) want stuff cheap and well we received cheap.
with regard to duracell...IMHO there is no excuse! more of us need to vote with our wallets....

as a friend of mine eons ago said....."If you buy quality, then long after the price is forgotten the quality remains"
and that is why many of us are here.
Renée

On 3/21/21 9:18 AM, Ken, WA2LBI wrote:
That old foam is awful stuff. I’ve had headphone head bands and ear pads
crumble to dust. I’ve also lost ICs that were pressed into the foam.
Foam-lined storage cases have damaged or destroyed stored items. Old
microphone inserts become dust. There are many other examples...

A few years ago, after many leaking batteries - some still new in the
package, I removed every Duracell battery from every device I own. I’ve
lost a number of flashlights, kid’s toys, remote controls, etc. The worst
is the damage done to my electronic test gear. I switched to Energizer and,
since then, have not had a single device device damaged by battery leakage.

The other item to check is the stick on feet used on so much equipment. As
we know, they turn to a slimy, sticky mess that also gets on the adjacent
surface and is difficult to remove. At the very least, over time, they
“migrate” from their original position and leave a slimy trail.

<rant off>

Ken
WA2LBI


On Sun, Mar 21, 2021 at 12:01 Harvey White <madyn@dragonworks.info> wrote:

As I've mentioned previously, the latest run of Duracell (guaranteed not
to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the
damaged item if you call them. Their warranty is "repair or replace",
but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static
foam corrode and crumble, etc...

Harvey


On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed
to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and
a multimeter that way, so now cells get removed from rarely used items
and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog. This is exactly the
kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<
https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen
--
Ken
WA2LBI

Sent from one of my mobile devices




Re: Beware of old AntiStatic foam

snapdiode
 

Yes I've gotten a dozen or so Commodore computer chips damaged that way, I just scraped off the residue with tweezers and hope that there isn't too much chemical residue left for damage to continue.


Re: FG502 doesn't start at some specific settings

Mark Vincent
 

Since you say it needs to be warm to work, it suggests the electrolytics are bad. The schematic parts says they are electrolytic, not tantalum. Tantalums can go bad also. If you have or get access to an ESR meter, that will tell you about the condition of the electrolytics. The 1mfd ones can be replaced with film of 50V or 63V type. Film types do not suffer ESR change with temperature and the ESR is lower. The 10mfd ones could be replaced with tantalum rated at 35V or electrolytics at 35V or 50V. The 22mfd that are the output filters from the series pass transistors can be the same value or higher, e.g. 47mfd. The mail filters of 750mfd could be 1000mfd 50V (Nichicon UHE as an example). Leave the timing caps alone. They are precision types. For the electrolytics, Nichicon ULD types are the best for ESR and life I have found. The films can be Kemet, Arcotronics, Wima, etc.. If you want to really confirm that temperature is the problem on start up, spray the capacitors with component cooler when warm. If it stops working, that confirms that one is bad. Since all of the electrolytics are the same age, it is better to replace all of them. Use high temperature, low ESR and long life types for the electrolytics.

It is also possible a transistor/IC is bad when cold. The cooler will confirm that. Spray enough to cool. Maybe 1/2 second.

If other plug-ins in the TM500 frame have problems when cold, that means they and/or the capacitors in the mainframe need replacing. If it is only this plug-in, then work on this one. I hope this helps.

Mark


Re: Beware of old AntiStatic foam

greenboxmaven
 

Tales abound about polyurethane sheet and foam.  There is no doubt it decomposes, almost overnight, into a vile mess.  One explanation I have seen is based on industrial disagreement. Supposedly, the original formulations of polyurethane were quite stable. When other companies began to make it, the formula was not correct. Various legal issues supposedly prevented the correct formula from being used, and the results are seen everywhere today. One very costly failure occured with pipe organs. The valving mechanisms have used leather for centuries, but it is perishable. In the early 1970s, a quantity of original formula polyurethane was obtained and put into use by the organ industry. It worked very well, and is still working well today. Once that supply was consumed, new production did not use the complete or correct formula, and the results were a multi million dollar disaster. A similar disaster occured with recording tape made in the early 1970s. Fortunately, the tapes can often be made to play well enough to transfer their recordings by baking them for several hours at the correct temperature.

   Bruce Gentry, KA2IVY

On 3/21/21 12:00, Harvey White wrote:
As I've mentioned previously, the latest run of Duracell (guaranteed not to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the damaged item if you call them.  Their warranty is "repair or replace", but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static foam corrode and crumble, etc...

Harvey


On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and a multimeter that way, so now cells get removed from rarely used items and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog.  This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen










Re: Beware of old AntiStatic foam

Ken, WA2LBI
 

That old foam is awful stuff. I’ve had headphone head bands and ear pads
crumble to dust. I’ve also lost ICs that were pressed into the foam.
Foam-lined storage cases have damaged or destroyed stored items. Old
microphone inserts become dust. There are many other examples...

A few years ago, after many leaking batteries - some still new in the
package, I removed every Duracell battery from every device I own. I’ve
lost a number of flashlights, kid’s toys, remote controls, etc. The worst
is the damage done to my electronic test gear. I switched to Energizer and,
since then, have not had a single device device damaged by battery leakage.

The other item to check is the stick on feet used on so much equipment. As
we know, they turn to a slimy, sticky mess that also gets on the adjacent
surface and is difficult to remove. At the very least, over time, they
“migrate” from their original position and leave a slimy trail.

<rant off>

Ken
WA2LBI


On Sun, Mar 21, 2021 at 12:01 Harvey White <madyn@dragonworks.info> wrote:

As I've mentioned previously, the latest run of Duracell (guaranteed not
to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the
damaged item if you call them. Their warranty is "repair or replace",
but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static
foam corrode and crumble, etc...

Harvey


On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed
to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and
a multimeter that way, so now cells get removed from rarely used items
and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog. This is exactly the
kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<
https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen
--
Ken
WA2LBI

Sent from one of my mobile devices


Re: Beware of old AntiStatic foam

Harvey White
 

As I've mentioned previously, the latest run of Duracell (guaranteed not to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the damaged item if you call them.  Their warranty is "repair or replace", but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static foam corrode and crumble, etc...

Harvey

On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and a multimeter that way, so now cells get removed from rarely used items and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog.  This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen







Re: More fun with avalanche pulsers

 

Thanks for the tip!
It turns out that paint color is not useful as a guide to the material's specs though. I had expected a color-coding standard but there does not seem to be one. I have found some tables validating my assumption that yellow is low permeability and green is high, although not to be relied on.

Anyhow, I found that using a 33 ohm emitter load instead of 50 for the avalanche transistor (adding another 100 ohm in parallel) minimized the reflection and other distortion of the falling edge, although at the cost of some amplitude. 8 volts is still more than enough into 50 ohms.

Now to figure out the smallest Minibox I can cram it all into. I can't believe how expensive they have become! Price of aluminum, or price of labor? I think I may use a 10-turn pot to adjust the avalanche bias supply rather than an internal trimmer.


Photo Notifications #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

The following photos have been updated in the FG502 doesn't start at some specific settings album of the TekScopes@groups.io group.

By: durechenew@...


The following photos have been updated in the FG502 doesn't start at some specific settings album of the TekScopes@groups.io group.

By: durechenew@...


FG502 doesn't start at some specific settings

durechenew@...
 

The following post was initially in tek500 group; it seems that group is not as active as this one and I thought it may help if it's posted here (I see other posts for 500):

Have an FG502 for while; repaired some issues (if someone interested, I can provide details). For the specific item I have the issue is it doesn't start right away (triangular form generator) on rages 10^2, 10^3, 10^4 with the dial set at 7 and above (to 11); that happens when device is cold. It starts after 40 to 90 seconds (I believe it's about how cold it is). If worm, starts normal. In all other settings starts normal.
Digging around I found that the triangular generator stays in a state where is happy (I can provide all voltages in significant points of the schematic) until it decides to start working. I'm attaching two pictures of a normal start and the delayed one. In the second one (4018-1) note the Ch4 (blue) baseline is at the top of the display screen.
Question: has someone encountered this behavior (and a solution; or suggestions)?

P.S. it may be that the issue is larger (doesn't start rightaway above 10^2 in any condition when very cold); hope someone can suggest something, as I exhausted all (first) thoughts about how to deal with it. Two pictures in album with same name.


Added album FG502 doesn&#39;t start at some specific settings #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

durechenew@... added the album FG502 doesn't start at some specific settings


Re: Beware of old AntiStatic foam

David Slipper
 

Nasty!!  I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and a multimeter that way, so now cells get removed from rarely used items and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave

On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog. This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen



Re: OT: MC12080 prescaler chip weirdness

Alex
 

Perhaps this item might be of use, or at least a good guide as there is a schematic posted as well. No relation to listing.

https://www.ebay.com/itm/153648250450


Beware of old AntiStatic foam

-
 

Well, this thread just showed up on EEVBlog. This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen


Re: PS 5010 troubleshooting (no negative, erratical display)

 

Hi Steve,

interesting... I like this supply and use it quite often. You can even use it to drive and control a transistor's base!

When I first used these PS5004 I thought the display was digitally controlled, but since it was able to show a negative voltage or a bit above 20V I began to doubt. And indeed.

For the alignment I was referring to the fact that alignment of the same 3 pots (zero, fine and coarse) is done several times in different chapters.

FIRST: §2 "Full Scale (R2043) and Fine Span (R2044) Presets"
This comes right after §1 coarse reference adjust (the switch).
A note says this should only be done when the reference IC has been changed. It consists of aligning the pots for a voltage of 6,550 volts.

SECOND: §4 "Zero Output Adjust (R3062)"
There is an instruction of how to connect the PS5004 to the voltmeter that I did not really understand. It says
"Connect the PS 5004 OUTPUT to the digital voltmeter input using a bnc cable and a pair of bnc-to-banana plug adapters. The shield side of the bnc is connected to the PS 5004 OUTPUT terminal, and the voltmeter Low input. The voltmeter guard is driven by the Low input. Connect the patch cable from the PS 5004 OUTPUT terminal to the ground post connector."
Anyone else who finds that substandard in terms of clarity? It looks like a cut&paste mess to me, but did Tektronix already have text processing these days?

THIRD: §§5&6: "Full Scale Adjust (R2043) & Fine Span Adjust (R2044)"
This time you align the same pots as in §2 with reference to the real output (in CAL mode). The pots had to be turned quite a bit (plusminus 2 revolutions) to get the right voltage here. But that means that the preset alginment in §2 was useles... No?

FOURTH: §7 "Full Scale (R2043), Fine Span (R2044), and Zero Output (R3062) Final Adjusts"

This time all three pots are re-aligned with reference to the real output, with the unit in normal RUN mode (not CAL mode). Again, I wonder what the alignments in §§2, 4, 5 & 6 were good for. I could have started the whole alignment right here, skipping the previous steps, couldn't I?
Perhaps not because these alignments interact somewhat, so you would have to repeat the steps in §7 several times if the previous steps haven't been done.

The next steps are for alignment of the DMM and current output. I always end up with a quite precise power supply, the DMM usually shows -0,0001 when at minimum. But thats well within specs...

cheers
Martin


Re: chinese witches hats for old probes help

Stephen
 

While I was looking for hook tips for a pair of P6105, I’d read a few reports on these Chinese probe tips. Some sais they worked fine and are good, while some stated the exact opposite... They said they were very fragile and broke easily.
Please let us know what you think when you get them.

Cheers

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