Date   

Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Hi, yes ARES 2 is still a bit too low EXT ARES2= 3.2v, 0.5s ARES2=4.5v, 0.2s ARES2=3.2v, 0.1 ARES2=3.2v
So yes it might be that something is wrong with output pin 1.
Question: could just one of the comparator outputs gone bad? If im not wrong inside U781 there should be 4 separate comparator so it seems logical to me that only one could fail without affecting the others, right?


Re: explosion mystery on my 7104

Roy Thistle
 

On Fri, Jun 18, 2021 at 09:22 AM, redarlington wrote:


It's exceptionally
common that those Rifa line filter caps blow here in the States with our
120v lines.
I dunno... if it was "exceptionally common" I would have seen it... or heard about it here... in the colonies... as we have have a nominal 120 V system here too... and I've got those X or Y Rifa caps, in Apple II smps... as well as in HP... and I think Tek too.
It makes a lot of sense to say they are more common to fail in places where the nominal voltage is 230 volts or 240 volts... as many of them were clearly rated for 250V.
AFAIC a lot of it is pure flummery meant to flummox "capacitor replacement kiddies" ... who ape YouTube profiteers.
Not saying it can't happen... if the cracked RIFAs get wet enough... they could cascade short... but I agree with other posters... it's only common on YouTube.
--
Roy Thistle


Hypcon connectors

cmjones01
 

My 7104 is now working well, thanks to advice from this group. Even
the plugins are mostly OK: the 7B15 wouldn't trigger because no +5V
was getting to the trigger board due to a corroded connector. I've
given one 7A29 the epoxy treatment and it works well though needs the
low-frequency gain setting up. The other 7A29 has more serious
attenuator trouble and will have to wait.

Almost all the faults I've experienced have been due to the Hypcon
connectors not making proper contact. I guess that after 40 years
those elastomers are perhaps not as springy as they once were. What
I've found is that removing them and cleaning everything up and
carefully refitting doesn't usually help - I've done it three or four
times in some cases.

It seems that the elastomer part seems to acquire a shape which stops
some pins making contact. My strategy for getting the scope working
well has been to swap around the elastomers between different devices,
finding a combination for each one where all the pins that matter make
contact. To get both horizontal slots working properly I had to borrow
an elastomer from the poorly 7A29 to fit the horizontal channel
switch. The device I borrowed it from only uses four pins, so I'm
hoping that the less-than-perfect elastomer will still allow the 7A29
to work properly.

Apart from misbehaving Hypcons (and the expected scratchy pots and
switches) the only thing I've actually had to adjust was a bit of the
Z-axis calibration in order to get the range of the intensity
controls, especially the readout, right. There are indications from
labels I've found inside that this mainframe may have been sitting
unused since 1994, so it's done pretty well!

Chris


Re: FS: Tek 7K-series Plug-ins, TM503A & 11301A with 2 plug-ins

Eric
 

I might be interested in the 11000 plugins.

On Fri, Jun 18, 2021, 12:00 PM Liam Perkins <hifi@telus.net> wrote:

I need of a new home I have:

2 - 7B80s in good, clean, working condition @ $US35.00ea,
1 - 7B15 in good, clean, working condition @ $US75.00,
1 - TM503A, no handle or cover, otherwise perfect $US100.00,
1 - 11310A with 1 - 11A33 4-channel plug-in & 1 - 11A33
Diff Comparator. $US450 packed up to be UPS-proof.

All prices are w/o shipping and goods ship from Calgary, AB, Canada

Best regards,
Liam






Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Tested again U781, at 0.1s A mode pin1= -8.57v , pin6= 0.6v pin7= -0.27v so it should be ok... I guess
Yes, pin 6 is correct and pin 1 is as should be then.
_ 0.2s pin6 = -3.5v pin7= -0.27v pin1= -8.6v
_ 0.5s pin6= -5.9v pin7= -0.27v pin1= -8.6v
_ EXT pin6= -3.5v pin7= -0.27 pin1= -8.6v
The pin 6 voltages again are correct.
But ... in these three cases pin 1 should be open drain, resulting in the same voltage as ARES2. ARES2 normally is between about zero and +5 V. You might check that the ARES2 voltages certainly are not -8.6 V. Previously you found that ARES2 was somewhat too low, being pulled down by -8.6 V at pin 1, resulting in the next faster time/div display (like .2s displays as .1s).
Albert


Re: explosion mystery on my 7104

redarlington
 

In the Apple II community, we call this RIFA Madness. It's exceptionally
common that those Rifa line filter caps blow here in the States with our
120v lines. We either replace before powering up old equipment, cut em
out, or deal with a cleanup if we ignore them.

-Bob N3XKB

On Thu, Jun 17, 2021 at 10:56 PM Jean-Paul <jonpaul@ix.netcom.com> wrote:

Cracked plastic encapsulant.

Much worse problem on 240 V mains, have yet to see the Rifa X/Y line
filter cap issue on a 120V mains

Jon






FS: Tek 7K-series Plug-ins, TM503A & 11301A with 2 plug-ins

Liam Perkins
 

I need of a new home I have:

2 - 7B80s in good, clean, working condition @ $US35.00ea,
1 - 7B15 in good, clean, working condition @ $US75.00,
1 - TM503A, no handle or cover, otherwise perfect $US100.00,
1 - 11310A with 1 - 11A33 4-channel plug-in & 1 - 11A33
Diff Comparator. $US450 packed up to be UPS-proof.

All prices are w/o shipping and goods ship from Calgary, AB, Canada

Best regards,
Liam


Re: Tektronix 603A Storage Monitor Questions

 

On Fri, Jun 18, 2021 at 05:35 PM, henryfinley wrote:


Can anybody lead me in the right direction?
https://w140.com/tekwiki/wiki/603

Raymond


Re: PG506 repair question.

Michael W. Lynch
 

On Fri, Jun 18, 2021 at 10:37 AM, SCMenasian wrote:


I agree. eBay has proven to be a great resource for me. One has to be very
careful. I avoid everything Chinese or listings which appear to be Chinese. I
have found a number of trustworthy suppliers. They often deal in surplus
manufacturer's inventory. Examine the photos carefully. If they don't show the
actual item(s), be careful. eBay has good buyer protection policies. If you
don't get the item pictured, you can generally get your money back unless the
listing states that the pictured item is one of many and is meant to be
representaive. For example, I recently bought a lot of NOS Motorola MJE2955s
in unopened Motorola sealed packaging for my TM500 series mainframes at a very
reasonable price. Generally, buying in quantity helps with pricing since
shipping one or two can oftern cost as much as the parts. (and not worrying
about running out of inventory for future repairs).
I agree. If one is careful, E-Bay is a treasure trove of "unobtanium". Just be wary of anything Chinese in origin, lots of counterfeit parts from China.

--
Michael Lynch
Dardanelle, AR


Re: Tektronix 603A Storage Monitor Questions

Michael W. Lynch
 

On Fri, Jun 18, 2021 at 10:35 AM, henryfinley wrote:


I have this storage monitor here a buddy gave me. But I can find nothing about
it on the internet. And I mean nothing. He gave it to me along with a Tek 465B
scope, which I have already gotten working. But I think the storage monitor
may be even older than that. No paperwork or information can be found on the
internet. Can anybody lead me in the right direction? Thank you.
There is information at TEKWiki. https://w140.com/tekwiki/wiki/Main_Page Search from there.
--
Michael Lynch
Dardanelle, AR


Re: PG506 repair question.

SCMenasian
 

I agree. eBay has proven to be a great resource for me. One has to be very careful. I avoid everything Chinese or listings which appear to be Chinese. I have found a number of trustworthy suppliers. They often deal in surplus manufacturer's inventory. Examine the photos carefully. If they don't show the actual item(s), be careful. eBay has good buyer protection policies. If you don't get the item pictured, you can generally get your money back unless the listing states that the pictured item is one of many and is meant to be representaive. For example, I recently bought a lot of NOS Motorola MJE2955s in unopened Motorola sealed packaging for my TM500 series mainframes at a very reasonable price. Generally, buying in quantity helps with pricing since shipping one or two can oftern cost as much as the parts. (and not worrying about running out of inventory for future repairs).


Tektronix 603A Storage Monitor Questions

 

I have this storage monitor here a buddy gave me. But I can find nothing about it on the internet. And I mean nothing. He gave it to me along with a Tek 465B scope, which I have already gotten working. But I think the storage monitor may be even older than that. No paperwork or information can be found on the internet. Can anybody lead me in the right direction? Thank you.


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

_ 0.2s pin6 = -3.5v pin7= -0.27v pin1= -8.6v
_ 0.5s pin6= -5.9v pin7= -0.27v pin1= -8.6v
_ EXT pin6= -3.5v pin7= -0.27 pin1= -8.6v


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Ok I found that the timing capacitor can be slightly bent to obtain good visibility on the pins.
Tested again U781, at 0.1s A mode pin1= -8.57v , pin6= 0.6v pin7= -0.27v so it should be ok... I guess


Re: PG506 repair question.

Michael W. Lynch
 

Andy,

Tom is a valuable source of such information. Once I read that he felt that the MPSU06 was a good match, that sealed it for me. Tom has been of similar help to me in the past with repairs. Finding these "odd ball" components is a real problem. I hope that this substitution will help you repair your issue. Looking forward to hearing if this works for you.

--
Michael Lynch
Dardanelle, AR


Re: PG506 repair question.

Andy Warner
 

No, I don't think you are missing anything.

I was not aware of the MPS-U06 as a candidate, I went looking for D40E7,
found none and then used distributor search tools to find candidates.
Initially, I lacked a clear understanding of the critical attributes for
this role, which I learned pretty quickly experimenting with parts with
F(t) of 3MHz or worse.
CEN-U07 seemed the best of a set of poor choices for production parts.

I suspect Tom's suggestion of the MPS-U06 was from experience and
knowledge, rather than from a parametric search.
The chances of me finding that part by myself are thin-to-none.

Thank you for pointing out that the MPS-U06 is still available on the grey
market, I'll probably order some up and swap the parts one more time
(hoping the PCB pads hold up.)

To me that's the benefit of the experience on this mailing list: one person
throws out a compromise solution, someone suggests a much better cross from
experience lamenting that it too is not a production part, someone else
points out the fact that it is not totally unobtainable, end result is a
better solution.

On Fri, Jun 18, 2021 at 8:42 AM Michael W. Lynch via groups.io <mlynch003=
yahoo.com@groups.io> wrote:

On Fri, Jun 18, 2021 at 12:20 AM, Tom Lee wrote:


Yes, transistors with those specs definitely fall into a black hole. The
MPS-U06 would be a very good cross, but it, too, is pretty much
unobtainium
these days.
I know how much everyone here seems to rail against E-Bay; but there are
several lots of these transistors listed on that platform. There are a
couple of lots that appear to be NOS MPSU06 Motorola and the price for 2
pieces is not outrageous. To my mind, better to use the best available
part than to try to find some substitute part that will be marginal at
best. But that is just my opinion. What am I missing?

--
Michael Lynch
Dardanelle, AR





--
Andy


Re: PG506 repair question.

Michael W. Lynch
 

On Fri, Jun 18, 2021 at 12:20 AM, Tom Lee wrote:


Yes, transistors with those specs definitely fall into a black hole. The
MPS-U06 would be a very good cross, but it, too, is pretty much unobtainium
these days.
I know how much everyone here seems to rail against E-Bay; but there are several lots of these transistors listed on that platform. There are a couple of lots that appear to be NOS MPSU06 Motorola and the price for 2 pieces is not outrageous. To my mind, better to use the best available part than to try to find some substitute part that will be marginal at best. But that is just my opinion. What am I missing?

--
Michael Lynch
Dardanelle, AR


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

i do have continuity
between pin 5 of the resistor and pin 6 of U781. I've also tested the voltage
to the said pin at 0,1 sec/div and it resulted to be at -7.9v.
Hi Federico, are you sure that it was the right pin U781/6? At .1 s/div S701A switch 10 should be closed and hence U781/6 should be near zero or positive.
Also previously you found U781/1 to be -8.6 V. If this is still the case, combined with U781/6 at -7.9 V and U781/7 at -0.27 V and correct power at pins 3 and 12, then the comparator is defective.

Albert


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Hi Albert I did a continuity test as you suggested, i do have continuity between pin 5 of the resistor and pin 6 of U781. I've also tested the voltage to the said pin at 0,1 sec/div and it resulted to be at -7.9v.
I'm now quite sure that mechanical stress is part of the problem since when i moved the cable harness i lost some of the A settings that got back working.
I think I'll remove all the sweep assembly in order to check all the solder joints since all the cables were already disconnected and reconnected carefully.
Federco


Re: PG506 repair question.

Tom Lee
 

Yes, transistors with those specs definitely fall into a black hole. The MPS-U06 would be a very good cross, but it, too, is pretty much unobtainium these days. I see that Mouser still sells them but the minimum quantity is 500 pieces (and they quote a very long lead time).

In this circuit, you might be able to get by with a 2N2219 selected for higher than normal breakdown voltage. Both Q745 and Q755 are driven from a fairly low impedance, so the relevant breakdown voltage spec is BVCBO. Finding 2N2219s with >80V BVCBO is not unheard of, so if you aren't happy with the CEN-U07/MPS-U07, you may have other options.

Just a thought.

-- 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 6/17/2021 20:38, Andy Warner wrote:
Final update from me (I hope.)

Looking for modern replacements for the GE D40E7 used in Q745/755 did not
result in a direct modern cross that I could identify from non-exotic
vendors.

= 80V, >= 2A, F(t) > 200MHz, C(ob) ~9pF does not seem to be the sweet spot
for modern BJTs, nor is the TO-202 case, and more importantly pinout.

I found a way to make modern TO-225A packages work physically, but
eventually settled on the CEN-U07 from Central Semi (available from Mouser
& Digikey.)
This is a TO-202 package, so they drop right in and I even get to bend the
tabs over like Tek did originally (pro-tip, support the tab at the package
body with needle nose pliers when bending it, to avoid breaking off parts
of the case.)
The F(t) of the CEN-U07 is only 50MHz, and C(ob) is 30pF, so rise and fall
times are not stellar. At the 1us period, the output does indeed swing the
full amplitude, but the signal is not a great square wave (
https://groups.io/g/TekScopes/photo/265034/3247250)
If anyone has alternate recommendations for a better modern part to use,
that is not made of unobtainium, please let me know, otherwise I recommend
the CEN-U07 as the next best thing, if like me one of your output
transistors is fried (symptom was low max output voltage.)

Additional photos and scope traces are shown in the album:
https://groups.io/g/TekScopes/album?id=265034

Next up - aligning and tuning up the unit.

Thanks again for the help and encouragement, both on and off list. I hope
this might be useful to someone who needs to follow a similar path.

On Tue, Jun 15, 2021 at 10:21 PM Andy Warner <andyw@pobox.com> wrote:

The first round of candidates for Q745/755 in the PG506 high amplitude
output section arrived today.
I have uploaded screenshots using the BD179G parts.

https://groups.io/g/TekScopes/photo/265034/3246294 is 10us period,
amplitude max, terminated into 1MOhm.
https://groups.io/g/TekScopes/photo/265034/3246295 is the same, but
terminated into 50Ohm.

The good news is that the full amplitude output is now restored, I think
Ozan's current-based analysis was right on the money here, and without the
ability to dump the current with both transistors, the full output voltage
swing was not possible.

Note the rise and fall times, which preclude the 1us period being any use
at all - the amplitude of the output signal is limited by the rise and fall
times.
This is clearly shown in
https://groups.io/g/TekScopes/photo/265034/3246296

I think I clearly need to look for faster parts than the BD179G. That has
an F(t) of 3MHz, while the venerable old D40E7 has F(t) of 230MHz.
I think I have one more chance at reworking the Q745/755 pads before I
start lifting traces.

As an aside, the aberration on the falling edge at low frequencies (which I
now accept as a fact of life) goes away when terminated in 50Ohm.

On Tue, Jun 15, 2021 at 11:44 AM Andy Warner <andyw@pobox.com> wrote:

I have another off list confirmation that the falling edge of the high
amplitude waveform, at least on first gen PG506's, routinely has an
aberration as shown in:
https://groups.io/g/TekScopes/photo/265034/3242704
The exact period & amplitude it kicks in at varies between units, but for
the next person that trips over this: it seems like it is just part of
the
design, and the rising edge is the one that matters for this particular
unit's role in life.

On Mon, Jun 14, 2021 at 9:14 PM Andy Warner <andyw@pobox.com> wrote:

Thanks for the additional verification, and advice on diodes.

Given the data points from the group, I plan to ignore the falling edge
artifact, and focus on getting the amplitude correct once I have
replaced D745/755 with modern parts.

On Mon, Jun 14, 2021 at 8:07 PM Tom Norman <jtnorman@fire2wire.com>
wrote:
HI Andy-

I wanted to follow through on my earlier response. My PG is serial
B035037, so similar to Dan's I think. It also shows the same
negative
going edge distortion you show in your posted picture at 100 Hz, and
pretty
well cleans up around 250 Hz. Output voltage into 1 Meg is 64V P-P,
at
maximum amplitude setting, across the frequency range of the
instrument.
I too saw the reference to the rising edge being the "reference"
edge,
so
after repairing the PS issue, I just accepted that they (Tek
designers)
didn't care too much about what was happening to the negative going
edge
at
longer periods. It's good to know that at least two of you are
seeing
a
similar thing. My ignorance is keeping me from understanding why the
designers would have chosen to regulate the entire switching supply
rather
than just locally regulating a fixed -72 rail.

And on the -72 supply diode replacement, I ended up just trying some
1N914
diodes, which seem to have worked well. Also used those to replace
CR80
and CR125, which had taken an absolute beating as a result of the
strange
switching transients that resulted from the "backflow" due to the
slow
rectifier recovery times. 1N4148 seems like it would work too.

Tom






--
Andy





--
Andy





--
Andy





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