Date   

Re: Beeswax in Transformers

Chuck Harris <cfharris@...>
 

Hi Barry,

It isn't a coating, but rather an impregnation. The beeswax, or
epoxy is drawn into the spaces between the wires to add additional
insulation, and to keep them from moving.

If you don't add an impregnant, corona effects may eventually break
down the insulation... in my experience, *will*...

-Chuck Harris

n4buq wrote:

I'm curious why transformers (in particular, this transformer) benefit from a coating - beeswax or otherwise. Is it to damp sympathetic vibration at the operating frequency/frequencies?

Thanks,
Barry - N4BUQ






Re: Replacing Variable Vertical Attenuator Shaft

John Bennett
 

Dick,
I don't have advice for 485 access, but I found that 1/8" Nylon 6/6 Round Rod (available in 5' lengths from Amazon at https://www.amazon.com/gp/product/B0070ZEW7K) did the trick for replacing the shaft (in a 2465B). I used 7/16" OD tygon tubing drilled and tapped for set screws as my coupler.
John, AE0AM


Re: 547 HV Transformer: Bill Schell rewind failed

Chuck Harris <cfharris@...>
 

Hi Tom,

Moisture is definitely a factor, but the problem is not
really reversible.

Yes, you can gain an improvement by cooking, or vacuum
drying, a tektronix epoxy transformer, but it will return
to its failed condition in a much shorter time than it did
originally.

My guess is the brownish/red coloration to the epoxy is
because tektronix added a fire retardant to the epoxy...
most everyone did back then, resulting in a lot of failures
over the years. One place you hear quite a lot about it is
in red doorknob style epoxy molded HV capacitors.

Time has showed that the bromine, and other fire retardants,
have failed in a variety of ways everywhere industry used
them.

Fire retardant plywood loses its structural integrity after
about 10 years, causing roofs to collapse. Fire retardant
added to plastic computer and monitor enclosures caused
them to turn brown over time... and let's not forget about
tris added to kid's pajamas!

-Chuck Harris



fiftythreebuick wrote:

Hi Dave-

I'm sorry to hear that you're having trouble with that HV XFMR....

I did a lot of testing and evaluation for Bill Schell over the years and I don't remember him every testing a transformer with any epoxy in it at all. He and I both felt that we oughta get as far away from that as possible. He first wound them without sealing them and I have never had one of those fail. Then when he started treating them with beeswax and a vacuum chamber, it seemed like he had found quite a good process. So far, I have never had one of his fail, of any description.

Just saw your later post and I'm glad that yours is improving! A friend of mine has restored an original xfmr by putting it in a vacuum chamber and keeping it in a deep vacuum for a while. Don't remember how long he left it in there.

I hope yours comes out alright. It really does seem like the moisture is the major factor.

Tom






Beeswax in Transformers

n4buq
 

I'm curious why transformers (in particular, this transformer) benefit from a coating - beeswax or otherwise. Is it to damp sympathetic vibration at the operating frequency/frequencies?

Thanks,
Barry - N4BUQ


Re: Tek 492BP how to save via GPIB to a PC

 

Got the NI installed but I got another error now it said: ibert error no listener. I do have both switches talk only and listen only open in the 492BP. What can I do.


Re: Tektronix 2230 - no readout

Bert Haskins
 

On 3/5/2021 10:45 AM, oneenaht@gmail.com wrote:
Hi Bert,

thanks for reply.
strange coincidence: about a week before I got the 2230, I bought a digital scope (Hanmatek DOS1102,
I have a Hantek DSO5102P and several "pocket" scopes beyond my dozen+ Teks.
same as OWON) during an action at Ama***n, at almost half the normal price. I could not resist that bargain!
My purpose for it is to be able to see fast and slow things like I2C communication.
I use a saleae and/or one of it's ( many many ) clones for things like that.
My workhorse is a 20MHz Hameg HM205 or so, but unsuited for that.

Now for the 2230:
I have removed the GPIB option (+memory) to take a look fot loose connectors hidden behind the mounting plate and under de CRT.
Without this option, the scope looks to be working analog only, do you need to jumper some cables?
Anyhow, I found nothing suspicious.
Also, I tried the Kernel isolation, and looking at the pins of U9112 and U9114.
All looks similar as in the service manual, except for pins 16/17/18/19 of U9114. There is a nice pulsetrain, but not as displayed on figure 6-3.
It looks they are all the same, but no pins are shorted.
A thing I have never came across before: Have you ever experienced bad EPROMS
Not in any of my Tek scopes, but I have certainly improved my bank balance by restoring eproms in failed factory systems.

It's amazing how many things are still running on old vintage micros.

? Ans if so, where could I find hexdumps?
I checked for this in https://w140.com/tekwiki/wiki/2230 and didn't find any, maybe I should fix that.


best greetings, Harry
Where are you located?

I'm in west Michigan near the lake.

 Bert





Re: 547 HV Transformer: Bill Schell rewind failed

Chuck Harris <cfharris@...>
 

Hi Eric,

Beeswax is an easy commodity. I get the highly purified white
variety that candle makers use. Smells like honey, but is
free of bee parts, and pollen granules, that exist otherwise.

It takes very little to impregnate hundreds of coils. I am still
working off of a 10lb block I bought 10 years ago.

Should we change the subject on this post? I don't like seeing
Bill Schell's name associated with failed. He did an amazing
thing for the tektronix community back before most any of us
even knew there was a problem.

-Chuck Harris

Eric wrote:

Chuck,

Are you in need of bees wax? I might be able to get some in bulk. I happen
to know a couple of bee keepers. I would also like to learn more about the
transformer winder when the time is right.

Eric
On Thu, Mar 4, 2021, 7:45 PM Chuck Harris <cfharris@erols.com> wrote:

Hi Bernd,

All indications are that my new machine is going to
do an even better job than the best I could do with
the old manual machine.

As an example, I was able to get 2/3 of the way to a
full wind without using the rosin/alcohol mixture that
I developed to enhance the wire's friction...

Using the rosin/alcohol, I am there already.

And, I will be using beeswax.

I'm glad to hear the prototype is still soldiering
on. Soon, I may be able to get you the winds I promised
oh so long ago...

-Chuck Harris

widgethunter via groups.io wrote:
My memory certainly hasn't improved with age.Not much else seems to
have, either...But, the beeswax thing I'd be willing to put money on - fwiw.
Incidentally, I still have not installed the 2nd wax xfrmr you made for
me, but the 1st prototype continues to perform flawlessly.Bernd



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Thu, Mar 4, 2021 4:05 pm
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

I guess the biggest indicator of a scatter wind would be
the presence of a spool. The universal wind doesn't require
any additional support.

In addition to talking to you, I talked to Deane Kidd, and
Deane talked about Bill using beeswax, like tektronix did in
the earlier transformers.

But, like you, it has been a looong time, and I don't think
our memories are getting any better.

-Chuck Harris

widgethunter via groups.io wrote:
Hi Chuck;Assumed scatter because of the larger size of Schell
rewinds.It has been a looong time, but I think I'd remember if he'd said
anything about epoxy...B



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Wed, Mar 3, 2021 9:57 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound. It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer. The
naked winding is right there for you to see.

-Chuck Harris


















Re: 2235 AN/USM-488 power supply low voltages

 

On Fri, Mar 5, 2021 at 04:31 PM, Raymond Domp Frank wrote:


You may consider noting as exactly as you can the current -7.3V of the -8.6V
supply to be able to see if the voltage changes by slightly adjusting R938 and
carefully readjusting it to the current voltage afterward.

By temporarily re-adjusting R938 you'll likely be able to see if the drive level of the inverter is hard enough. All voltages being off by approximately the same percentage indicates there may be a drive problem, not a load problem.
If the 8.6V can be adjusted up and down, there's probably a reference- or compare-problem (R937/938/939, VR943 and possibly R943, which may have badly drifted).

Raymond


Re: Tek 492BP how to save via GPIB to a PC

 

How can I use an Agilent 82357B as I have drivers for it installed as a GPIB to USB?.


Re: Tektronix 2230 - no readout

oneenaht@...
 

Hi Bert,

thanks for reply.
strange coincidence: about a week before I got the 2230, I bought a digital scope (Hanmatek DOS1102, same as OWON) during an action at Ama***n, at almost half the normal price. I could not resist that bargain!
My purpose for it is to be able to see fast and slow things like I2C communication.
My workhorse is a 20MHz Hameg HM205 or so, but unsuited for that.

Now for the 2230:
I have removed the GPIB option (+memory) to take a look fot loose connectors hidden behind the mounting plate and under de CRT.
Without this option, the scope looks to be working analog only, do you need to jumper some cables?
Anyhow, I found nothing suspicious.
Also, I tried the Kernel isolation, and looking at the pins of U9112 and U9114.
All looks similar as in the service manual, except for pins 16/17/18/19 of U9114. There is a nice pulsetrain, but not as displayed on figure 6-3.
It looks they are all the same, but no pins are shorted.
A thing I have never came across before: Have you ever experienced bad EPROMS? Ans if so, where could I find hexdumps?


best greetings, Harry


Re: 2235 AN/USM-488 power supply low voltages

 

On Fri, Mar 5, 2021 at 02:18 PM, <richardallred@me.com> wrote:


Yup, I knew about that procedure, but was trying to avoid that until I was
sure that was it. It's my understanding once you do that you have to calibrate
the entire scope. Is that correct?

Yes, after adjusting the -8.6V you'll have to calibrate/adjust the 'scope for it to be as accurate as it is capable of.

Be aware that *everything* is connected directly to the mains, until after T948!

Since none of the voltages currently are ok, calibration will be off - if the 'scope works at all. The error is around 15%, which is far too much.

I don't think your problem simply is just a matter of adjusting the -8.6V, *unless* someone misadjusted it or any of the voltage-determining components have drifted. I'd start by checking R937, R938, R939, and the voltage across VR943.

Repeat: Be aware that *everything* is connected directly to the mains, until after T948!

It's a very good idea to fully calibrate/adjust a 'scope which hasn't been calibrated for a long time.

You may consider noting as exactly as you can the current -7.3V of the -8.6V supply to be able to see if the voltage changes by slightly adjusting R938 and carefully readjusting it to the current voltage afterward. The last calibration may have been done with a slightly different voltage than exactly -8.6V and this way, you may be able to restore that. If you find a problem and repair that, the -8.6V hopefully will revert to a voltage close to what it has been adjusted to during the last calibration.

Raymond


Re: 2235 AN/USM-488 power supply low voltages

 

On Fri, Mar 5, 2021 at 03:35 PM, <richardallred@me.com> wrote:


adjusting R 938 has no affect on the -8.6 volt supply

R938 is the -8.6V adjustment pot...

Raymond


Re: Sampling with 7S14

 

Hi Roger,

I tried to tweak those loop gains. They seemed to be in optimal setting.

I am satisfied with the performance now (photos from 28th Feb in the album). I think that the issues with the power supply created the noise in my first try (photo from 26th Feb).
Or there is some intermittent fault still lurking somewhere...

Best Regards,
Jouko


Re: Tek 492BP how to save via GPIB to a PC

 

It is the driver, I cant find the NI-488.2 version 3.0.2 for an GPIB-USB-B device.


Re: 2235 AN/USM-488 power supply low voltages

richardallred@...
 

adjusting R 938 has no affect on the -8.6 volt supply


Re: 2235 AN/USM-488 power supply low voltages

richardallred@...
 

Yup, I knew about that procedure, but was trying to avoid that until I was sure that was it. It's my understanding once you do that you have to calibrate the entire scope. Is that correct? Also will that fix the issue of the trace only displaying on 2/3rds of the screen,

thanks Again

R A


Re: O.T. Digital scopes versus Tek analogue.

cmjones01
 

On Fri, Mar 5, 2021 at 7:56 AM Sean Turner <sdturne@q.com> wrote:
Logic analyzers are headed the same way. I think Keysight is the only company that offers a true benchtop logic analyzer anymore. Tek discontinued the TLA series and directs you to buy a mixed signal scope instead.
There are good reasons for this. There are few applications for
traditional multi-channel logic analyzers these days. The remaining
uses of parallel data buses, such as high-speed DRAM, are extremely
specialized. Everything else uses serial data at hundreds of megabits
or gigabits a second.

As I write, I'm taking a break from debugging a prototype involving a
modern camera chip. It generates data as a 1200Mbit/s serial data
stream. Though I have a logic analyzer which could capture the data,
it would be a pretty poor tool for working with it. Making sense of a
serial data stream is a totally different thing than recording
parallel data bus transactions.

I can honestly say that a 15MHz tube scope (yes, it's my 535A, I'm
working from home) is a more useful tool, at least for the debug I'm
doing right now. Indeed, it's what I've actually been using. I can see
whether data is present or not, whether it contains reasonable-looking
image data, and can see the serial bus moving in and out of its
various power states, and that's enough to help me debug the firmware
that's driving the camera. All of this even though the application
would seem to be far beyond the capabilities of a 1960s instrument.
I'm actually not sure whether a modern cooking-variety 200MHz digital
scope would be any better.

Chris


Re: Tek 492BP how to save via GPIB to a PC

 

Check that the GPOIB-USB-HS is showing up correctly in Device Manger. Mine needed its EEPROM reloading to work.

D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of John Miles
Sent: 05 March 2021 09:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 492BP how to save via GPIB to a PC

Sounds like you either don't have the NI drivers installed, or the board ID is set to something other than GPIB0. What does the menu in GPIB configurator look like? If it doesn't show up as GPIB0 you'll need to select the correct board entry and hit 'Update CONNECT.INI' before you can use the programs with it. (Or you can change the board ID in the NI software, I believe.)

-- john, KE5FX

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Mike
Yepes
Sent: Thursday, March 04, 2021 5:04 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 492BP how to save via GPIB to a PC

I have an 492BP, and a GPIB to USB National Instruments. Can I use the HP
7470A plotter program to save screens?
I tried and I get error borad GPIB0 not found.



Re: 7854 Source Code for version 1.02, 1982 release now on Kurt's TekWiki

 

Aha! Found it in the "Other Info" stuff in the box on the RHS of the main page for the 7854

D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of David C. Partridge
Sent: 05 March 2021 10:20
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7854 Source Code for version 1.02, 1982 release now on Kurt's TekWiki

Where is that please.

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Clark Foley
Sent: 05 March 2021 05:33
To: TekScopes@groups.io
Subject: [TekScopes] 7854 Source Code for version 1.02, 1982 release now on Kurt's TekWiki

Kurt Rosenfeld has posted the entire line printer listing (454 pages) of the 1982 source code version 1.02 for the 7854. It's an early release but it reveals some interesting things.


Re: 7854 Source Code for version 1.02, 1982 release now on Kurt's TekWiki

 

Where is that please.

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Clark Foley
Sent: 05 March 2021 05:33
To: TekScopes@groups.io
Subject: [TekScopes] 7854 Source Code for version 1.02, 1982 release now on Kurt's TekWiki

Kurt Rosenfeld has posted the entire line printer listing (454 pages) of the 1982 source code version 1.02 for the 7854. It's an early release but it reveals some interesting things.

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