Date   

Re: Cheap cables from China

 

I'm learning a lot about cables ;)

The cable jackets do say "RG-58/U" but, as mentioned, the offshore factory will print whatever you want. There have been documented cases where they lightly sand the top of whatever batch of IC's they have on hand (or even empty packages), and print the "correct" marking for the chips the customer ordered! They will go to the trouble of putting fake undersized die in TO-3 transistor cases, so they pass a superficial test but fail in use... Lots of stories here: https://hackaday.com/2018/01/15/is-that-part-a-counterfeit-here-are-a-few-pointers/
There used to be a great web page that had pictures of all the phony semiconductors but it seems to be offline.

Anyway. For comparing cables I would use the GR ones as my standard, thus compensating for any leakage from the transmitter and dummy load (unless, of course, said leakage swamps the hopefully small amounts from the cable under test). I also can generate about 20 watts at 148 MHz, which would be easier to detect than 30 MHz leakage...


Re: CRT anode discharge

Dave Peterson
 

Being a former technician getting bit is something I've experienced, but never anything more than line voltage. Military 400Hz power has a definitely different flavor than civilian 60Hz. I don't like being bit at all. So far no scars.

I suspect it just as likely that being bit by 40KV (or whatever it decays to in 5 minutes) can cause cardiac arrest out of shear fright. This is not the first CRT I've pulled, but the first time I've ever experienced such an arc. Still feel some lingering adrenaline metabolizing. Who needs a fourth cup of coffee on a Sunday?

Yeah, I put it back in the sheath while my shakes settled down. Found it still snapped when removed again. Left it wedged to the chassis for several minutes.

This is a pre SN250K 465. Could that have anything to do with it retaining charge more than the other post SN250K 465s I've pulled?

I went ahead and posted this as a cautionary tale for any new arrivals. Too bad we can't have sticky posts at the top of the list. HV safety is always a good thing. Complacency is sometimes corrected - harshly.

Stay safe folks!
Dave

On Sunday, March 14, 2021, 01:55:06 PM PDT, Tom Lee <tomlee@ee.stanford.edu> wrote:

Being the discharge path for a scope CRT is certainly unpleasant, but
not particularly dangerous if the unit isn't powered up (and if you're
in reasonably good health). Sure wakes you up, though, doesn't it?

If you do discharge the HV with a shorting tool, be aware that you'll
need to keep the shorting tool in place a good deal longer than you'd
think. If you remove the tool soon after hearing or seeing the
discharge, you'll be unpleasantly surprised to find that the voltage
soon climbs back up to some non-negligible percentage of the original
value. A "discharged" HV cap (including ones that may be integral with
the CRT) can still bite you.

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 3/14/2021 13:40, Dave Peterson via groups.io wrote:
Thank you for saving my life!

Or at least a painful reminder.

Just experienced my first healthy CRT anode discharge arc. Thanks to advice I've read here I: grounded the chassis, kept one hand behind my back, used a pair of  insulated pliers to gently twist and pull the anode connection out, and before I could even consciously try, ZAP! To ground. Big 'ol blue nasty looking arc. But not even a mark on the chassis.

I'll have to see if my Fitbit registers a sudden spike in heart rate! :P

Been getting "comfortable" working around the HV stuff, but this is a good reminder to keep my guard up. That was a nasty looking arc. Spark seems too mild a word. But I'm fine. Scope appears fine.

Credit to those here who've espoused save HV practices.
Dave





Re: CRT anode discharge

Tom Lee
 

Being the discharge path for a scope CRT is certainly unpleasant, but not particularly dangerous if the unit isn't powered up (and if you're in reasonably good health). Sure wakes you up, though, doesn't it?

If you do discharge the HV with a shorting tool, be aware that you'll need to keep the shorting tool in place a good deal longer than you'd think. If you remove the tool soon after hearing or seeing the discharge, you'll be unpleasantly surprised to find that the voltage soon climbs back up to some non-negligible percentage of the original value. A "discharged" HV cap (including ones that may be integral with the CRT) can still bite you.

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 3/14/2021 13:40, Dave Peterson via groups.io wrote:
Thank you for saving my life!

Or at least a painful reminder.

Just experienced my first healthy CRT anode discharge arc. Thanks to advice I've read here I: grounded the chassis, kept one hand behind my back, used a pair of insulated pliers to gently twist and pull the anode connection out, and before I could even consciously try, ZAP! To ground. Big 'ol blue nasty looking arc. But not even a mark on the chassis.

I'll have to see if my Fitbit registers a sudden spike in heart rate! :P

Been getting "comfortable" working around the HV stuff, but this is a good reminder to keep my guard up. That was a nasty looking arc. Spark seems too mild a word. But I'm fine. Scope appears fine.

Credit to those here who've espoused save HV practices.
Dave




CRT anode discharge

Dave Peterson
 

Thank you for saving my life!

Or at least a painful reminder.

Just experienced my first healthy CRT anode discharge arc. Thanks to advice I've read here I: grounded the chassis, kept one hand behind my back, used a pair of insulated pliers to gently twist and pull the anode connection out, and before I could even consciously try, ZAP! To ground. Big 'ol blue nasty looking arc. But not even a mark on the chassis.

I'll have to see if my Fitbit registers a sudden spike in heart rate! :P

Been getting "comfortable" working around the HV stuff, but this is a good reminder to keep my guard up. That was a nasty looking arc. Spark seems too mild a word. But I'm fine. Scope appears fine.

Credit to those here who've espoused save HV practices.
Dave


Re: 475B intermittent horizontal

Ondrej Pavelka
 

Hi Raymond,

I have their complete set of chemicals and I am very familiar with damage
unwashed contact sprays can do.
WL is good but all 3 requires really good ventilation it stinks and gives
headache pretty much instantly.

On Sun, 14 Mar 2021, 00:57 Raymond Domp Frank, <hewpatek@gmail.com> wrote:

On Sun, Mar 14, 2021 at 12:49 AM, Raymond Domp Frank wrote:


Yes, I remember having seen CRC on the cans for a few years now. Have a
look
at kontaktchemie.com under the "About" heading.
Just remembered that Kontakt WL is their preferred rinsing fluid. I use
IPA instead, in larger containers.
Raymond






Re: Modifying W Plugin to use 6DJ8 Tubes

Dave Wise
 

6DJ8 CONVERSION SUCCESS

CAUTION: I prefer a constant-current supply, even though you can't
interchange 6DJ8/7DJ8/PCC88/E88CC/6922 due to heater current.
They all have to be the same and the regulator set for that type.
You can also do a constant-voltage supply, but a Nuvistor Type W
will see more drift with mains voltage. (FET Type W doesn't care
either way.)

1) Change R290 from 150 ohm to 250 ohm.
2) Add isolated current source across V124-V214-V114.
It's just an LM317 with a resistor between OUT and ADJUST,
and take output from ADJUST. Two 15 ohm 1/4W resistors in
parallel gives 170mA, close enough. This gives the 6DJ8's
350mA so they drop about 18V.
3) Annotate new tube types.

You have to handle 100V backfeed if a tube burns out. Just put
a diode in series.

I've tried a few sets of 6DJ8, and everything makes 26-27MHz
vs 27-28MHz on the 8416's. I thought they were identical.
FWIW, Sylvania made a single datasheet for 6DJ8/7DJ8/12DJ8.

OTHER 6V TUBES

6BQ7 and 6BS8 fail with Q154 starved.
6ES8 gives Q154 2-3V but only makes 17MHz, same as 12AU7. What's up with that?
Looks like 6DJ8 is *the* way to meet spec.

TRANSFORMER POWER SUPPLY FOR 6DJ8's

6V-24V WORKS

I fitted S/N 7465 with 120-0252-00, which is used in Type 3T77 and 3T77A.
I have several. The best position is the rear bulkhead upper right
corner with the long axis of the core vertical. I can't see any hum
at 1mV and line triggering. I put the rectifier/filter/regulator
high on the rear bulkhead to the left of the transformer, securing
the rectifier and cap with hot glue to facilitate short leads. I
strung the diode between the cap and the LM317 to avoid a tie point.
With 200uF/50V (two 100's in parallel), I see 4V peak to peak ripple
at IN, with the trough 8V above OUT. It's a symmetrical triangle wave.

OTHER TRANSFORMERS

TEK

Maybe can use 120-0481-00, used in Type 1A4. It has a 20V winding
that puts out 135mA, should be okay at 180mA since the other
winding won't be used.

OTHER

Nobody sells a 6V-24V transformer AFAIK.

Maybe a 110V-36V transformer on pins 13-14 with
primary and secondary reversed, rectifier, filter, and LM317.
We need at least a 20VA rating to stay within spec for copper loss.
That means a big transformer and hum shielding.
Specify 110V|110V primary and 15+15 secondary.
Convenient available space in the plugin is 65x50x50mm.
Here are YHDC 20VA transformers.

PE5424E-M is PCB mount, 57x48x44mm. Not a toroid.
The following don't fit:
PE5424K-M PCB mount plus holes, 75x49x44mm.
LKB5424-L bolt-down with wire leads, 75x43x50mm.
PU3917B low-profile bolt-down, 68x55x33mm.
PTC25 25VA PCB with hole toroid 60x60x38mm.


Photo IMG_0890.jpeg updated #photo-notice

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

The following photos have been updated in the Type W Plugin 8416-to-6DJ8 Conversion album of the TekScopes@groups.io group.

By: Dave Wise <david_wise@...>


Photo IMG_0891.jpeg updated #photo-notice

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

The following photos have been updated in the Type W Plugin 8416-to-6DJ8 Conversion album of the TekScopes@groups.io group.

By: Dave Wise <david_wise@...>


11 photos uploaded #photo-notice

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

The following photos have been uploaded to the Type W Plugin 8416-to-6DJ8 Conversion album of the TekScopes@groups.io group.

By: Dave Wise <david_wise@...>


Re: 308 Data Analyzer

Mlynch001
 

On Sun, Mar 14, 2021 at 12:51 PM, stevenhorii wrote:


I know that HP (sorry!) uses signature analysis for troubleshooting some of
their computing counters. Does Tek specify signature analysis for
troubleshooting of their scopes with digital processing and control?
Steve,

Yes, the 308 is used extensively for signature analysis on the 468. It is part of the “recommended” test equipment in the Service Manual. I just used mine to repair a broken 468. Still a useful tool.

--
Michael Lynch
Dardanelle, AR


Photo Notifications #photo-notice

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

Dave Wise <david_wise@...> added the album Type W Plugin 8416-to-6DJ8 Conversion: Using 120-0252-00 transformer from 3T77/3T77A for auxiliary heater power


The following photos have been uploaded to the Type W Plugin 8416-to-6DJ8 Conversion album of the TekScopes@groups.io group.

By: Dave Wise <david_wise@...>


Re: Repairing broken pots

 

On 14. Mar 2021, at 06:40, Martin <musaeum@arcor.de> wrote:
...so what I have here is not "Bourns" but "Allen/Bradley"...
I'm wrong, it is a Bourns pot. Found it out after a thorough research (= reading the back of the pot).

Looking after more information about these pots I came across Bourn's Potentiometer Handbook.
Interesting, many nice pictures, came close to what I was looking for - but only close

https://www.bourns.com/docs/technical-documents/technical-library/corporate/OnlinePotentiometerHandbook.pdf?sfvrsn=182b1126_4

cheers
Martin


Re: Cheap cables from China

SCMenasian
 

Not all RG58s are the same. Depending upon whether a cable is RG58, RG58/U, RG58A, RG58B, RG58C, etc. the impedance can vary from 50 ohms to 53.5 ohms without even taking into account differences between various manufacturers and each manufacturer's process control. RG223 might be a better choice, particularly for high frequency applications. It's double shielded and microwave power loss is lower. IIRC, the impedance is more dependably closer to 50 ohms.


Re: 308 Data Analyzer

Harvey White
 

I don't know about the scopes, but the TM500 (some) and the TM5000 series modules generally have a signature analysis section.  IIRC, so do some pieces of HP equipment of the time.

Harvey

On 3/14/2021 1:51 PM, stevenhorii wrote:
I know that HP (sorry!) uses signature analysis for troubleshooting some of
their computing counters. Does Tek specify signature analysis for
troubleshooting of their scopes with digital processing and control?

Steve Horii

On Sun, Mar 14, 2021 at 12:44 Dick <w1ksz@outlook.com> wrote:

In my 5 year purge of deep storage I came across a Model 308
Data Analyzer. It seems to have all the cables and manual and
does turn on.

Is this of any use in todays world or should I just recycle it ?

Thanks, Dick, W1KSZ








Re: Cheap cables from China

Greg Muir
 

I think I may have mentioned this before.

When attending a seminar at NIST (then NBS) I learned quite a bit about coaxial cables and their connectors. With regards to cables carrying the MIL RG numbering system not all manufacturers cables are the same. For a true RG cable meeting the original military specifications for shield coverage, dielectric, size and even impedance the designation will specifically state “RG-xx” or “Mil-C-17 RG-xx”. Those cables that contain the designation “RG-xx” followed by “Type” are cables that look like the military styles but do not necessarily meet the published specifications.

As for Chinese cables, well, you are on your own. They don’t seem to follow the rules of the game when it comes to labeling things.

Greg


Re: Modifying W Plugin to use 6DJ8 Tubes

Dave Wise
 

Correction to previous post number 179890. With 12AU7 I see 17MHz not 22MHz. I was counting graticule minor divisions wrong.


Re: Cheap cables from China

Mark Goldberg
 

I've tended to use double or triple shielded cable or hardline for
interconnects. I happened on some really good ones. I suppose you
could transmit into a dummy load and see what leaks out the cable, but
it depends on the leakage in the dummy load and transmitter also. I've
definitely seen differences in cable leakage but have not taken
qualitative measurements.

Regards,

Mark

On Sun, Mar 14, 2021 at 8:07 AM Charles <charlesmorris800@centurytel.net> wrote:

Thanks for the info. I'd forgotten about the shield coverage! Can anyone help me devise a simple test that doesn't require switching 200 amps? :) I can generate 500 watts or more of RF at 50 ohms with my ham gear, but only up to 30 MHz.

These cables actually do look reasonably well made, but of course I would not expect them to hold up to daily continuous use like Tek or GR cables. For 99 cents each, they'll probably be fine for occasional tinkering.





Re: 308 Data Analyzer

stevenhorii
 

I know that HP (sorry!) uses signature analysis for troubleshooting some of
their computing counters. Does Tek specify signature analysis for
troubleshooting of their scopes with digital processing and control?

Steve Horii

On Sun, Mar 14, 2021 at 12:44 Dick <w1ksz@outlook.com> wrote:

In my 5 year purge of deep storage I came across a Model 308
Data Analyzer. It seems to have all the cables and manual and
does turn on.

Is this of any use in todays world or should I just recycle it ?

Thanks, Dick, W1KSZ






Re: 308 Data Analyzer

Dick
 

OK, you talked me into keeping it. Back on the shelf it goes.

Thanks for replying,

Dick, W1KSZ
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Paul Amaranth <paul@auroragrp.com>
Sent: Sunday, March 14, 2021 9:58 AM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] 308 Data Analyzer

Do NOT recycle it!

It's a useful 8 bit logic analyzer along with a signature analyzer.

With all the cables you should be able to get $75-100 for it, give
or take.

Signature analyzers have been going up in price in the last
couple years.

Somebody's going to want it.

Paul

On Sun, Mar 14, 2021 at 04:44:19PM +0000, Dick wrote:
In my 5 year purge of deep storage I came across a Model 308
Data Analyzer. It seems to have all the cables and manual and
does turn on.

Is this of any use in todays world or should I just recycle it ?

Thanks, Dick, W1KSZ







!DSPAM:604e3d77221071127818502!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: 308 Data Analyzer

Paul Amaranth
 

Do NOT recycle it!

It's a useful 8 bit logic analyzer along with a signature analyzer.

With all the cables you should be able to get $75-100 for it, give
or take.

Signature analyzers have been going up in price in the last
couple years.

Somebody's going to want it.

Paul

On Sun, Mar 14, 2021 at 04:44:19PM +0000, Dick wrote:
In my 5 year purge of deep storage I came across a Model 308
Data Analyzer. It seems to have all the cables and manual and
does turn on.

Is this of any use in todays world or should I just recycle it ?

Thanks, Dick, W1KSZ







!DSPAM:604e3d77221071127818502!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows

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