Re: Oscilloscope Recommendation

[Ian Finder via cctalk]

+1 for the TDS540.


On Sun, Apr 30, 2017 at 11:54 shad via cctech 
wrote:

> Hello,
> all fine with Rigol or similar oscilloscopes, but there's a very important
> technical specification that often is not considered, which really DOES the
> difference between a cheap oscilloscope and a powerful one: waveforms per
> second.
> Suppose you are searching for a rare glitch, or that you are trying to
> trace an edge of a signal with infinite persistence.
> If the scope is a DSO, it just takes a sampling window,  the memory is full
> and requires data processing and display, in the meantime the signal is not
> analyzed, and you can lose important events.
> A DPO can capture the signal continuously, or at least with very short
> death time, and the display is updated using a large number of triggered
> sampling windows.
> Of course this kind requires a far powerful acquisition circuit.
>
> I really like DPO scopes in place of DSO, for example used Tek TDS540C or
> D, they are quite cheap, no electrolytic caps, and can be optionally
> expended to increase acquisition memory depth.
> Display is small and grey, but you can use a VGA monitor.
>
> My two cents.
>
> Andrea
>
-- 
   Ian Finder
   (206) 395-MIPS
   ian.fin...@gmail.com

Re: Oscilloscope Recommendation

[shadoooo via cctalk]

Hello,
all fine with Rigol or similar oscilloscopes, but there's a very important
technical specification that often is not considered, which really DOES the
difference between a cheap oscilloscope and a powerful one: waveforms per
second.
Suppose you are searching for a rare glitch, or that you are trying to
trace an edge of a signal with infinite persistence.
If the scope is a DSO, it just takes a sampling window,  the memory is full
and requires data processing and display, in the meantime the signal is not
analyzed, and you can lose important events.
A DPO can capture the signal continuously, or at least with very short
death time, and the display is updated using a large number of triggered
sampling windows.
Of course this kind requires a far powerful acquisition circuit.

I really like DPO scopes in place of DSO, for example used Tek TDS540C or
D, they are quite cheap, no electrolytic caps, and can be optionally
expended to increase acquisition memory depth.
Display is small and grey, but you can use a VGA monitor.

My two cents.

Andrea

Re: Something for the P3 you have in your back yard

[Ian S. King via cctalk]

On Sun, Apr 30, 2017 at 10:52 AM, Al Kossow via cctalk <
cctalk@classiccmp.org> wrote:

>
> http://www.ebay.com/itm/Vintage-Military-IBM-Computer-/201911842662
>
> https://fas.org/man/dod-101/sys/ship/weaps/an-uys-1.htm
>
> Does this come under the category of 'home defense'?


-- 
Ian S. King, MSIS, MSCS, Ph.D. Candidate
The Information School 
Dissertation: "Why the Conversation Mattered: Constructing a Sociotechnical
Narrative Through a Design Lens

Archivist, Voices From the Rwanda Tribunal 
Value Sensitive Design Research Lab 

University of Washington

There is an old Vulcan saying: "Only Nixon could go to China."

IBM 4331 Mainframe

[Guy Sotomayor Jr via cctalk]

Just to let folks know that I finally moved the IBM 4331 Mainframe this past 
weekend
from where it was currently stored to my shop.  Pictures are here: 
https://www.flickr.com/gp/150223282@N04/NrX91K 


As can be seen in the pictures, it filled a 26’ box truck that I had rented for 
this purpose.
Right now I just have it placed somewhat in my shop.  Some early tasks will be:
   * I have to verify that I have everything.  Even if I missed some items, 
they won’t be
 scrapped.  I just need to go over what is currently in my shop and verify 
that I didn’t
 leave anything behind.  I’m mostly worried about cables at this point.
  * I have to figure out some way to produce enough “clean” 3-phase power to 
run the
peripherals (the CPU is 220v single phase) as I only have 220v single phase 
coming
into my shop.

Starting to power it up will probably be a while yet.  ;-)

TTFN - Guy

Re: Bulk tape eraser

[jim stephens via cctalk]

On 4/30/2017 6:22 PM, Jerome H. Fine via cctalk wrote:



Looking for recommendations for a bulk tape eraser for SDLT and DLT 
IV tapes. 
Eons ago at Microdata we had a commercial grade bulk eraser which could 
do 2400' reels maybe a bit larger.


I wondered by one day with a new fangled device, a 16k eprom.  while a 
small chat developed by the table where
the eraser was, I casually put the eprom on the eraser, and turned it 
on, just because.


one of my otherwise smart colleagues looked with a concerned look on his 
face and then queried whether that

would work with the eproms.

don't know that he ever lived that one down.

Wish I had it, I'd certainly pass it along.
thanks
jim

Re: Bulk tape eraser

[Chuck Guzis via cctalk]

On 04/30/2017 06:22 PM, Jerome H. Fine via cctalk wrote:
>> Chuck Guzis via cctalk wrote:

> FORTUNATELY, I had an old voice coil fram a speaker available.  It
> must have been a large speaker because the coil was a cylinder about
> 3" in diameter and about 3" long.  The permanent magnet seems to have
> a few pounds of pull on any iron object, so I thought it might be
> useful.  It probably takes about 30 seconds of slowly rotating the
> voice coil over the surface of the TK50 / TK70 tape to sufficiently 
> BULK erase the tape such that the TK70 drive would write on the tape.
>  Since I believe that the TK50 / TK70 tapes are early DLT tapes, this
> method may also be successful, if a bit slow, for a small quantity of
> tapes.

I've entertained the idea of pulling out one of my old microwave oven
transformers, cutting off the "I" sections, so that it's only "E"
laminations, and then removing the high-voltage outer windings (easy
enough to do with a Dremel--some folks re-purpose these boat anchors to
serve as the basis for spot welders and such.

Carefully limiting the current with a large incandescent lamp, that
should give one a whopping AC field that should take the magnetization
out of anything.

But...it feels like too much work for an old man.

--Chuck

Re: Bulk tape eraser

[Jerome H. Fine via cctalk]

>Chuck Guzis via cctalk wrote:


On 04/30/2017 07:38 AM, Mike Loewen via cctalk wrote:
 

Looking for recommendations for a bulk tape eraser for SDLT and DLT 
IV tapes.
   



If it's just a small quantity to be erased, there are many Radio Shack
videotape erasers being offered, some NIB, all for about $20.  I've used
one for years on floppies and tapes.   It's not for erasing piles of
tapes, as there's a thermal overload protector on it, limiting the
amount of time that you can use it.

--Chuck

I don't know if my experience with tapes for the TK50 / TK70 applies, 
but for
what it is worth, here is what was the problem.  When a tape has been 
written

by a TK50 drive, the TK70 drive will no longer be able to write on the tape
until the tape have been BULK erased.  Since I had a number of tapes written
by a TK50 and I wanted to use the tapes for producing backups using a TK70,
I obviously needed to be able to BULK erase those tapes.

FORTUNATELY, I had an old voice coil fram a speaker available.  It must have
been a large speaker because the coil was a cylinder about 3" in 
diameter and about
3" long.  The permanent magnet seems to have a few pounds of pull on any 
iron
object, so I thought it might be useful.  It probably takes about 30 
seconds of slowly
rotating the voice coil over the surface of the TK50 / TK70 tape to 
sufficiently
BULK erase the tape such that the TK70 drive would write on the tape.  
Since I

believe that the TK50 / TK70 tapes are early DLT tapes, this method may also
be successful, if a bit slow, for a small quantity of tapes.

Jerome Fine

os8diskserver help?

[Tom Moss via cctalk]

Hi All,

I'm in the process of building and restoring a PDP-8/e, and now I've got a
second serial card I'd like to give OS/8 a try.
I'm pretty sure I've got the boot loader entered properly, and the address
+ baud rates set correctly on the PDP and PC.

When I start os8diskserver with "./os8disk -1 ../disks/diagpack2.rk05", it
gives the welcome message. When I start the 8/e, It says:
Booting...
Done sending block 0

^ and appears to freeze there. (the 8/e doesn't halt)
I've got a RS-232 tester (blinky light box) hooked up to the port, which
seems to indicate that nothing is being sent after Block 0 has been sent.

Does anyone know what's going on, or what I'm doing wrong?

Regards,
-Tom

mx-80 for free

[Diane Bruce via cctalk]

I found an Epson MX-80 in my pile of junque. I'd rather not ship but
Ottawa, Montreal or Toronto are all possible. Otherwise, out to
recycle.


-- 
- d...@freebsd.org d...@db.net http://www.db.net/~db

Re: Bulk tape eraser

[Al Kossow via cctalk]

On 4/30/17 10:04 AM, Chuck Guzis via cctalk wrote:

> Certainly not DLT IV tapes--I've done the bulk eraser thing with them
> and the result re-recorded just fine.
> 

Sorry, I flipped DLT and LTO in my mind..

Re: Bulk tape eraser

[Zane Healy via cctalk]

On Apr 30, 2017, at 10:04 AM, Chuck Guzis via cctalk  
wrote:
> 
> On 04/30/2017 08:55 AM, Al Kossow via cctalk wrote:
>> You may as well run them through a shredder. All modern tapes have
>> embedded servo tracks.
> 
> Certainly not DLT IV tapes--I've done the bulk eraser thing with them
> and the result re-recorded just fine.
> 
> But then, DLT IV is hardly modern.
> 
> --Chuck

I know you can’t run LTO tapes through one, but if I remember correctly you can 
do at least the original SDLT tapes.  We had a heavy duty degausser in the 
datacenter, up until a couple years ago.  The tape library vendor we were using 
at the time wanted us to degauss tapes prior to reusing them due to all the 
issues we were having.  That meant degaussing 100’s of tapes a week.  Normally 
contractors would do it, but in an emergency, I’d do it at times.  With the 
later tapes, you had to run them through something like 4 different ways, 
otherwise they were still readable (which is why I’m pretty sure we were 
degaussing SDLT tapes).  As I recall, DLT IV tapes only had to go through once.

Zane

Something for the P3 you have in your back yard

[Al Kossow via cctalk]

http://www.ebay.com/itm/Vintage-Military-IBM-Computer-/201911842662

https://fas.org/man/dod-101/sys/ship/weaps/an-uys-1.htm

Re: Bulk tape eraser

[Chuck Guzis via cctalk]

On 04/30/2017 08:55 AM, Al Kossow via cctalk wrote:
> You may as well run them through a shredder. All modern tapes have
> embedded servo tracks.

Certainly not DLT IV tapes--I've done the bulk eraser thing with them
and the result re-recorded just fine.

But then, DLT IV is hardly modern.

--Chuck

Re: Bulk tape eraser

[Chuck Guzis via cctalk]

I'll add that using the little Radio Shack "high power" device well, is
not a simple matter--the trick is to keep the eraser moving  and using
different angles and distances.

If you want a high-power tape *degausser*, be prepared to part with some
real cash--the low end seems to start just north of $1000.   Many even
claim to be able to do hard drives.

--chuck

Re: Bulk tape eraser

[Al Kossow via cctalk]

You may as well run them through a shredder. All modern tapes have embedded 
servo tracks.

On 4/30/17 7:38 AM, Mike Loewen via cctalk wrote:
> 
>Looking for recommendations for a bulk tape eraser for SDLT and DLT IV 
> tapes.
> 
> 
> Mike Loewenmloe...@cpumagic.scol.pa.us
> Old Technologyhttp://q7.neurotica.com/Oldtech/

Re: Bulk tape eraser

[Chuck Guzis via cctalk]

On 04/30/2017 07:38 AM, Mike Loewen via cctalk wrote:
> 
> Looking for recommendations for a bulk tape eraser for SDLT and DLT 
> IV tapes.

If it's just a small quantity to be erased, there are many Radio Shack
videotape erasers being offered, some NIB, all for about $20.  I've used
one for years on floppies and tapes.   It's not for erasing piles of
tapes, as there's a thermal overload protector on it, limiting the
amount of time that you can use it.

--Chuck

Re: Bulk tape eraser

[Alexandre Souza via cctalk]

I'd go to the Athana site, they have some degaussers and a nice write-up
about what can (and can't) be safely degaussed


2017-04-30 11:38 GMT-03:00 Mike Loewen via cctalk :

>
>Looking for recommendations for a bulk tape eraser for SDLT and DLT IV
> tapes.
>
>
> Mike Loewen mloe...@cpumagic.scol.pa.us
> Old Technology  http://q7.neurotica.com/Oldtech/
>

Bulk tape eraser

[Mike Loewen via cctalk]

   Looking for recommendations for a bulk tape eraser for SDLT and DLT IV 
tapes.



Mike Loewen mloe...@cpumagic.scol.pa.us
Old Technology  http://q7.neurotica.com/Oldtech/

Re: Oscilloscope Recommendation

[Michael Thompson via cctalk]

We have lots of dual-trace Hitachi 25MHz analog 'scopes that were donated
by BMI. They are fine for the low speed work that typically do, and don't
have some of the interesting problems that digital 'scopes have. We can get
a deep discount on any of the 'scopes that BMI has:
https://www.bmisurplus.com/products/category/oscilloscopes.

I was looking at some of the mixed-signal 'scopes like the Rigol MSO1104Z.
Having a 'scope and a logic analyzer in the same instrument, with both
'scope and logic analyzer triggering would be very nice.

On Sat, Apr 29, 2017 at 10:07 PM, dwight  wrote:

> If it is your only scope I recommend an analog scope of at least 100 MHz,
> with dual trace and delayed sweep.
>
> If you already have an analog scope, I recommend a logic analyzer instead
> of a digital scope.
>
> If you already have both above, I recommend a digital scope.
>
> Dwight
>
>
> --
> *From:* cctech  on behalf of Michael
> Thompson via cctech 
> *Sent:* Saturday, April 29, 2017 4:15:33 PM
> *To:* allison
> *Cc:* General Discussion: On-Topic Posts
> *Subject:* Re: Oscilloscope Recommendation
>
> Thanks for the recommendation
>
> Sent from my iPhone
>
> > On Apr 29, 2017, at 4:30 PM, allison  wrote:
> >
> >> On 04/29/2017 01:28 PM, Michael Thompson via cctech wrote:
> >> The RICM just received $1,000 to buy a new oscilloscope. I would like a
> >> four channel. and color would also be nice. The bandwidth doesn't need
> to
> >> be high because we usually work on ancient equipment.
> >>
> >> What would you suggest?
> >>
> > I use a RIgol DSO at work to replace a 200mhz Tek with power issues.
> Far better scope.
> > For the money we paid, 4 channels and wide band its very decent.  Being
> able to get
> > screen grabs to a USB stick is a big plus.
> >
> > I personally have a Rigol DS815T spec analyser with tracking generator
> and its a good performer.
> > Not up to the standards of a R FSH6 but about 1/15th the price.
> >
> >
> > Allison
>



-- 
Michael Thompson

Re: Oscilloscope Recommendation

[Michael Thompson via cctalk]

Great idea about looking for a non-profit discount. That might not work for
the Chinese 'scopes, but it could make the US 'scopes prices more
competitive.


On Sat, Apr 29, 2017 at 11:53 PM, Paul Anderson  wrote:

> I've almost always used TEK scopes, and liked them. What ever you choose,
> see if they will cut you a good deal for being a educational or non-profit.
> A lot of companies will, especially on a discontinued model.
>
> On Sat, Apr 29, 2017 at 6:15 PM, Michael Thompson via cctech <
> cct...@classiccmp.org> wrote:
>
>> Thanks for the recommendation
>>
>> Sent from my iPhone
>>
>> > On Apr 29, 2017, at 4:30 PM, allison  wrote:
>> >
>> >> On 04/29/2017 01:28 PM, Michael Thompson via cctech wrote:
>> >> The RICM just received $1,000 to buy a new oscilloscope. I would like a
>> >> four channel. and color would also be nice. The bandwidth doesn't need
>> to
>> >> be high because we usually work on ancient equipment.
>> >>
>> >> What would you suggest?
>> >>
>> > I use a RIgol DSO at work to replace a 200mhz Tek with power issues.
>> Far better scope.
>> > For the money we paid, 4 channels and wide band its very decent.  Being
>> able to get
>> > screen grabs to a USB stick is a big plus.
>> >
>> > I personally have a Rigol DS815T spec analyser with tracking generator
>> and its a good performer.
>> > Not up to the standards of a R FSH6 but about 1/15th the price.
>> >
>> >
>> > Allison
>>
>
>


-- 
Michael Thompson

Re: Reviving VT220?

[Tony Duell via cctalk]

On Sat, Apr 29, 2017 at 7:36 PM, Aaron Jackson via cctalk
 wrote:
>> Since it doesn't smoke, I'm thinking the horizontal sweep
>> transistor may have gone out.  It may have shorted, which
>> then may have burned up the primary winding in the flyback
>> (if left on long enough).  I'd check that transistor for a
>> short, and then you can trace a few traces to identify the
>> primary terminals on the flyback and see if they are an open
>> circuit.
>
> Hmm, not good news. zero ohm between pin one and three of the transistor
> you mentioned. To be fair the board around it looks a little brown, but

Is this with the transistor soldered to the board or removed? If the latter then
the transistor is shorted base-emitter. If the former then you are measuring
the resistance of L200 and the secondary of T201 (horizontal drive transformer)
in seroes which will be essentially zero.

> I assumed this was just because it would have got hot. Could replacing
> this cause damage to the flyback? I seem to have a low resistance on
> what I think is the primary coil.

Most flyback windings have a very low DC resistance. In any case the most
common failure is a short between a couple of turns of such a winding which
will ruin the AC performance of the transformer but have almost no effect
on the resistance. That's why you need to test such a transformer with a
ringing tester, not an ohmmeter.

-tony