Date   
Re: Need Advice on a good used shop scope

John Griessen
 

On 10/07/2017 12:27 PM, pdulaff@... [TekScopes] wrote:
Something like the 465/475 scopes make sense but there are these combo digital/analog scopes that maybe add additional versatility
2230 is good. I use it almost always for the microcontroller pulser work I am doing now.
Capturing one shot events is very helpful for that.

When you say vacuum tube work, and if the "amateur gear" means HAM radios, that can point to a 503 or RM503
differential input scope that takes high volts and RF on the inputs well.

Re: Need Advice on a good used shop scope

Harvey White
 

On 07 Oct 2017 17:27:07 +0000, you wrote:

Hello


I am Paul, WB2NMI. I am looking for recommendations on good affordable used scopes for my home shop. I work on vacuum tube and solid state amateur gear. Something like the 465/475 scopes make sense but there are these combo digital/analog scopes that maybe add additional versatility, but I don't have experience with digital scopes. I would like to buy used and keep the scope affordable and am willing to repair the scope provided parts and documentation are available.
For most work, you need at least two channels, and viewing the trigger
can be a very helpful addition. You could trigger on an input
waveform, then view on channels 1 and 2 the results in a push-pull
stage output. You can view that input waveform with the trigger view.

I have a 468 10 mhz (digital, good for slow stuff) and 100 Mhz
(analog, good for fast stuff) scope. A 465 would do as well, but
without the digital backpack.

Good, rugged, reasonably easy to get parts for (depends on the scope),
and model bandwidths to 300 mhz and above.

I'd recommend mostly analog for what you're doing, and then later
expand into digital if it is warranted.

I use mostly the 7000 series scopes, not so portable, quite versatile.
There are scopes in the 2000 series that can be recommended as well,
but I have no experience with them myself.

Harvey





Let me know your thoughts.


Paul - WB2NMI




Need Advice on a good used shop scope

Paul
 

Hello


I am Paul, WB2NMI. I am looking for recommendations on good affordable used scopes for my home shop. I work on vacuum tube and solid state amateur gear. Something like the 465/475 scopes make sense but there are these combo digital/analog scopes that maybe add additional versatility, but I don't have experience with digital scopes. I would like to buy used and keep the scope affordable and am willing to repair the scope provided parts and documentation are available.


Let me know your thoughts.


Paul - WB2NMI

Re: HV Probe? - Correction

n4buq
 

Did you get your 465M fixed?

Bert
Still working on it. I received a replacement HV module from Walter @Sphere this week and plan to test it and install it today. I should know today whether I have a working scope again.

Thanks for asking,
Barry - N4BUQ

Re: HV Probe?

Harvey White
 

On Sat, 7 Oct 2017 09:49:44 -0400 (EDT), you wrote:

Given my recent/ongoing trials with HV issues in my 465M, I'm considering getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following eBay ad? I've looked for info on it and haven't found much. I don't quite understand how it is connected, etc., nor do I know whether it's decent quality probe. I think Sencore makes/made pretty high quality gear so am assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710

It's a high voltage resistor in a protective housing.

It should have a resistor across the input jacks to the meter.

I have a fluke 80 HV probe. It contains a complete HV divider, with
the resistor across the input about 1.109 megs, forming a 100 to 1 (or
1000 to 1) divider.

This one is designed for a 15 meg input impedance meter. It should
have a parallel resistor which in combination with the meter's
impedance should give you the appropriate division factor. If you use
a DMM with near infinite impedance or the wrong impedance, you could
put a parallel resistance across the meter terminals.

Harvey


Then it will read 1/100th of the applied voltage.




Thanks,
Barry - N4BUQ

Re: HV Probe? - Correction

Bert Haskins
 

On 10/7/2017 9:52 AM, Barry n4buq@... [TekScopes] wrote:

Oops. That's the wrong model number for that link. I was looking at
two different probes and copied the model number from the wrong one.
The probe I'm interested in is the Sencore HP200.

http://www.ebay.com/itm/202071277710

Thanks,
Barry - N4BUQ

Given my recent/ongoing trials with HV issues in my 465M, I'm
considering
getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following
eBay ad?
I've looked for info on it and haven't found much. I don't quite
understand how it is connected, etc., nor do I know whether it's decent
quality probe. I think Sencore makes/made pretty high quality gear so am
assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710

Thanks,
Barry - N4BUQ
Did you get your 465M fixed?

Bert

Re: HV Probe? - Correction

J. L. Trantham
 

Barry,



The HV probes I am familiar with are the Fluke series, 80K-6, 80K-15, and 80K-40. They are designed to work with typical 10 MOhm input impedance DMM’s. The Sencore HP200 is designed to work with 15 MOhm input impedance meters. I’m not familiar with a DMM with that input impedance.



The major difference between them is their Input Resistance. The 80K-6 is 75 MOhm and the other two are 1000 MOhm. The 75 MOhm input resistance will place a substantially larger load on the HV supply than the 1000 MOhm. Depending on the design of your HV supply and it’s designed current capacity, the 1000 MOhm input resistance might be a better choice. It certainly was for me working on the 3500 VDC Ion Pump supply on an HP 5061A.



Hope this helps.



Joe



From: TekScopes@... [mailto:TekScopes@...]
Sent: Saturday, October 07, 2017 8:53 AM
To: TekScopes@...
Subject: [TekScopes] HV Probe? - Correction





Oops. That's the wrong model number for that link. I was looking at two different probes and copied the model number from the wrong one. The probe I'm interested in is the Sencore HP200.

http://www.ebay.com/itm/202071277710

Thanks,
Barry - N4BUQ

Given my recent/ongoing trials with HV issues in my 465M, I'm considering
getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following eBay ad?
I've looked for info on it and haven't found much. I don't quite
understand how it is connected, etc., nor do I know whether it's decent
quality probe. I think Sencore makes/made pretty high quality gear so am
assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710 <http://www.ebay.com/itm/202071277710>

Thanks,
Barry - N4BUQ





[Non-text portions of this message have been removed]

HV Probe? - Correction

n4buq
 

Oops. That's the wrong model number for that link. I was looking at two different probes and copied the model number from the wrong one. The probe I'm interested in is the Sencore HP200.

http://www.ebay.com/itm/202071277710

Thanks,
Barry - N4BUQ

Given my recent/ongoing trials with HV issues in my 465M, I'm considering
getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following eBay ad?
I've looked for info on it and haven't found much. I don't quite
understand how it is connected, etc., nor do I know whether it's decent
quality probe. I think Sencore makes/made pretty high quality gear so am
assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710

Thanks,
Barry - N4BUQ

HV Probe?

n4buq
 

Given my recent/ongoing trials with HV issues in my 465M, I'm considering getting a good HV probe.

Is anyone familiar with the Sencore 39A19 as shown in the following eBay ad? I've looked for info on it and haven't found much. I don't quite understand how it is connected, etc., nor do I know whether it's decent quality probe. I think Sencore makes/made pretty high quality gear so am assuming this would be a good probe.

Anyone know about it?

http://www.ebay.com/itm//202071277710

Thanks,
Barry - N4BUQ

Re: Successful restoration of 564B and 3L5, now looking for 7L5

hpxref
 

Hello Ninad
Ive fixed a few of the 3580A SA series so maybe what i've found common
to all of them may be of use if you ever acquire one.

The older variety used a mechanical frequency read out driven by a motor
and had an operator 'zero frequency' control which you reset at the start of
the sweep to take care of drift, which drifts upwards in frequency from cold.

The later series did away with the mech readout and used a led display driven by a Mostek
LSI part which is now completely unavailable and is prone to failure at this late stage in its life.

However you can hook an external frequency counter up the BNC LO output (1.0 -1.5MHz)
which varies with the manual sweep control and use that at higher accuracy by interpreting the output
for the 50kHz max sweep or whatever. An external FC with a maths facility could make it direct reading
if you wanted

The newer LED RO versions uses a fine frequency control coax with the set frequency knob which is supposed to
go to bottom frequency, but component drifts with time make this less useful than the older method and you will
likely see "wings" near the start of the display where the frequency sweep passes through zero and starts rising
again sometimes near a third of the way across the CRT which is a series objection to using it.
All the 3580's passed through my hands were disposed of because of this problem.
And all components, resistors, caps in this part of the circuitry were still in spec and the problem is likely to be drift
in the varactor section.
To fix this ive taken to adding a zero trim pot connected up so that it offsets the varactor voltage via a resistive adder
There not much room to fit this on the front panel easily so ive added it to the top of the board just behind the front panel
switches,( cant remember the manual card designation now as ive just moved house and the manual is still one of the 45
cardboard cartons in the shed, somewhere )
I drilled a hole in the top cover to access the 10 turn trim pot via a plastic "top hat" tube so the plastic driver used aligns with the pot
adjuster. This has worked out quite well and restores these 3580A' s to usable status again. Ive successfully modified 3 thus far.

Ive also gone through the complete alignment procedure for the IF filters, etc, but surprisingly they didn't need much trimming after
all those years and ive found only one 100kHz vacuum glassed Xtal osc which was out , a tribute to the hp design team.
Not having extender cards ive had to solder in wires to access some if the test points These extenders seems to unobtainable

LONG SWEEP TIMES: Chuck was right about the hour plus sweeps occasionally needed, but Hp recognized this and added an Adaptive
Sweep function, which speeds up the sweep between peaks .
In practice you set the Adaptive knob to raise the base line above the noise level or of any unwanted peaks and the sweep will speed up
till it hits a peak, reverses to the beginning of that peak, then slowly sweeps over only the peak and the speeds up to the next one
It does speed things up quite a bit then

When I uncover the modified manual (or the CD where the circuit drawing is stored) I will post it to anyone who may be interested

Certainly more modern digital S.A.s are better and quicker to use but the 3580A can still be very useful indeed if you cant afford a later one.
I have a 7L5 with the TG (option 25, I think), but always turn to the 3580 for anything up to 50Khz.
Its single digital memory can be used to compare a known response with an unknown and you can quickly restart a sweep before it ends
by pushing the "Clear Write" button , so you can do an adjustment to a filter , see the results and restart the sweep without waiting for
the sweep to go to the end...speeds things up again.
One more comment: Hp made a 3580A with a balanced input (600 Ohm) According to the specs this restricts the range to 25kHz as it
uses transformer coupling. The one I have , though, still works straight to 50kHz despite this with no loss of sensitivity or droop , except a drop
off at around 10Hz. I didn't believe this at first, but several tests all showed the same...virtually the same freq range as the unbalanced models!!
Hp must have put a lot of work and time into this excellent instrument at the time

I doffs me 'at to 'em.

John Byers

Re: Model 317 anyone ?

Vincent Trouilliez
 

Hi Steve,



Great that you managed to fix some "recent" gear with that old 310A ! :-D


As for me, I am not too worried about specs as I didn't buy it for its performance... I obviously have more recent scopes for actual work. Mostly a Tek 2232 and when required, a TDS 544A.


Still, I didn't buy my 317 to have it gather dust, I know myself.. once I will be done refurbishing and fixing it, I just won't resist turning it on and playing with it... this thing is just way too cute to be left alone and turned off ! :-)


Yes DC sensitivity is limited to 100mV but in AC it is 10mV, so for looking at ripple on a power rail for example, could still be plenty good enough. And if the DC level of a signal is of actual interest, I guess one could just (assuming it does not vary) measure it with a DMM, then switch the scope to AC coupling to augment the sensitivity.


The 310 is real cute too, being similar looking but even more compact that then 317 ! Surely I wouldn't mind having one, if I ever come across one in decent nick at a decent price... not holding my breath though ! Finding my 317 in my neck of the woods, was a little miracle, and miracles don't happen this often in ones life...



As for performance improvement of the 317 over the 310.... I guess you must be kidding ?! ;-)
There is a MASSIVE performance improvement in the 317, a 250% increase in BW ! LOL :-)

Even today, such an improvement is not trivial ! A 250MHz Tek is not quite the same price as a 100MHz one...


I didn't expect your comment on the 5100 series, but was most interested ! I mean, I happen to have one, a 5111 rack mount version. Again a nice find, super condition, working, very affordable, real cute, two Quad input plugins, 8 inputs total wow... couldn't believe it, I was impressed, bought it ! And a storage CRT, was intrigued ! And this plug-in system... wanted one of these scopes ! I absolutely love it.
It's only a bit later that I realized that the BW was.... ahem.... what it is !!! 2MHz and the 4 channel plugins are limited to 1MHz ! Still, 1MHz is enough for lots of stuff as I am not at all into high speed digital stuff.
8 channel that's quite something, and with its plugin design I can add cool features to it, at will, I love this concept... I saw there is a dual time base plugin if I am not mistaken, and also a diff amp plugin, that would be useful ! Even, a curve tracer, I see there is one for sale in my neck of the woods in frog land, but the guy doesn't even state a price, he wants top dollar for it so not for me thanks...
I really love this scope and surely will buy more plugins for it in the future :-)


So it was nice reading your comments about it, putting its use cases into perspective...
sensitivity vs BW. The quad channel plugins it came with, just checked, go down to 1mV !

And as you say other plugins achieve even better performance.



Yep, I just love my old Teks :-)

- Steve

465 on Grand Rapids MI CL

Paul Amaranth
 

Anyone need parts?

$20

https://grandrapids.craigslist.org/ele/d/tektronix-465-oscilloscope/6327381583.html

No affiliation, etc.
--
Paul Amaranth, GCIH | Rochester MI, USA
Aurora Group, Inc. | Security, Systems & Software
paul@... | Unix & Windows

Re: Successful restoration of 564B and 3L5, now looking for 7L5

Chuck Harris
 

One thing to note about the 3580A, it is an amazing
spectrum analyzer, but in spite of its digital storage,
and its ability of skipping over signals that are less
than some threshold, they are strictly an old school design.

What do I mean?

Well, they are quick at wide IF/Video filter bandwidths, and
narrow scans, but when you get into the 5Hz filters, they can
take many hours to scan 0 to 50KHz. You have to see this to
really believe it, hours.

The 3580A's ability to skip signals below a certain threshold
is interesting. What it does is sweep fast when the signal
is below the threshold, and when it detects a signal above the
threshold, it backs up, and starts going slow, until the
threshold is again passed, and starts zipping along looking
for the next signal above the threshold.

A more modern low frequency analyzer would use DSP
techniques to perform a Fast or Digital Fourier Transform
on the V-T data and could finish the same job in seconds
to fractions of a second depending on how much horsepower
is in the DSP end... At the cost of less dynamic range.

The 7L5 is similarly old school with digital storage. It
does even less to try to optimize the speed of the scan
than does the 3580A. And it is very hard to work on, where
the 3580A is pretty easy.

Just more information for the files.

-Chuck Harris

Nenad Filipovic ilmuerte@... [TekScopes] wrote:

Hi Steve,

Thanks for the very helpful advice, I mostly use the low freq SA for noise
analysis, so 50kHz upper limit would not be a problem, I will include the
3580A in my search. It even has a quite useful tracking oscillator output,
and appears to go down to approx. 5Hz with really narrow RBW, which is very
handy when analyzing 1/f noise. Some of the questions are how its internal
amplifier fares with its own 1/f noise, and how stable the display is at
these low frequencies and narrow RBWs. But of course we should not expect
miracles from these vintage devices.

I am looking for the 7L5 because I plan to invest also in other handy 7000
series plugins. On paper 7L5 looks quite good, it does not employ such
narrow RBWs as the 3580A but the rest is similar or better at first glance.
7L5 also claims to be very stable due to 1st LO phase lock, not sure how
3580A fares with this. The tracking generator for 7L5 may be an even
greater challenge to find (not sure whether it came attached from the
factory, or you could buy it separately and upgrade your standalone 7L5).

Large dynamic range is not required when dealing with noise analysis (or at
least I have that impression), and noise floor can be improved by using a
LNA (that way even the ancient 3L5 managed to prove quite useful). However
all swept SAs seem to be clumsy when it comes to the low frequency end, but
fortunately that's where FFT based ones should shine, I hope.

Best Regards,
Nenad Filipovic


On Fri, Oct 6, 2017 at 3:35 AM, ditter2@... [TekScopes] <
TekScopes@...> wrote:



Hello Nenad,

If you really NEED a low frequency SA, and can live with an upper
frequency limit of only 50 kHz, you might try to find a used HP 3580A. This
model has digital storage and way better dynamic range and lower noise
floor than the Tek 7L5. I worked in the same design group in TM 500 that
developed the SG505 and AA501/AA5001 audio plug-ins. While we had a couple
of 7L5s in the group. the HP3580A was the workhorse, due to its dynamic
range. It also had true differential input (1Mohm), and a choice of either
start frequency on the left (similar to a VNA) or center frequency in the
center. Since most LF work is looking at Bode plots of frequency response
rather that RF modulation as in communication work, the choice of start
frequency is great. It is self contained, not a plug-in for a scope.

Tek's 5L4 for the 5000 series as similar features, but very few or these
were produced and thus they are quite rare. I have only seen one in over a
decade of searches on e-Bay.

- Steve









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Posted by: Nenad Filipovic <ilmuerte@...>
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Yahoo Groups Links



Re: 2235 power supply noise

Tom Jobe <tomjobe@...>
 

Hi Mike,
On that C906 replacement, grab the leads of the 'snap-in' capacitor
right as they come out of the capacitor with a pointed pair of pliers,
and then do your bending with another pair of pliers so you don't
disturb the connection and seal of the lead where it goes into the
capacitor. It only takes a little tweak of the leads to make it fit into
the PCB.
Your 2235 really needs all of the aluminum electrolytic capacitors
replaced to freshen it up whether it solves your current problem or not.
Put all of your new caps in and see where you stand at that point.
T906 is a very rare failure in 22xx scopes as far as I know, but there
are plenty of them available. For example, there's some on eBay right
now for $15 US and I don't think it matters which dash number T906 part
you get (-00, -01, etc).
http://www.ebay.com/itm/Tektronix-120-1439-00-01-SwitchmodeTransformer-for-22xx-Oscilloscope-/282648416169?hash=item41cf288fa9
Walter at 'Sphere Research' in Canada has some in stock too.
Parts availability should not be a problem for anything you might need
for your 2235.
It seems to me that you either need to take a serious diagnostic
approach to solving the problem you have, or throw some simple parts at
it that you know it needs anyway and just see what happens.
tom jobe...



On 10/6/2017 12:08 AM, Michael Pickwell mikepickwell@...
[TekScopes] wrote:

Good morning, David, Tom, Bert, and anyone else I've forgotten.

Thank you all for your excellent advice.

Bert, that's a good call on the focus resistor string, I had to
replace those last year.

Tom, thanks for the tip about using a snap-in cap for C906!

I have some updates for you. Yesterday I ordered replacements for:

C961, 962, 963, 960, 970 and 968
C954
C940
C956
C942, 943
C925

I also ordered all of the parts necessary to install a small PC
cooling fan as found in the 2236:

CR965
C965
R965

It was only after placing the order for all these parts that I got
around to removing the old capacitors (schoolboy error). I then tested
them all with my little Peak Atlas capacitor tester and they all
tested as healthy!

As a result I'm now worried that the capacitors aren't the problem
after all. Apparently a common fault on the 2235 is an internal short
on the windings of inductor T906.

Replacements for T906 are apparently unobtanium so I may well gave an
irreparable scope now after wasting money on lots of new parts. Doh!

The new parts should be delivered later today and I'm trying to decide
if I should bother fitting them.

I suppose I should at least remove and test the big capacitor C906.

Sent from my Samsung device

-------- Original message --------
From: "Tom Jobe tomjobe@... [TekScopes]" <TekScopes@...>
Date: 06/10/2017 02:34 (GMT+00:00)
To: TekScopes@...
Subject: Re: [TekScopes] 2235 power supply noise

Hi Mike,
I see you have gotten some very good advice on your 2235.
Replace all of the aluminum electrolytic capacitors, there's not that
many of them and they are all worn out.
In general, go up on the voltage rating a bit (but not down!) and get
fresh new 105 degree C caps if possible.
Look at the lead spacing and size of your new caps to make sure they fit
nicely. There is plenty of room on the mainboard so there is no problem
finding new replacements for any of them.
There is nothing special about any of the caps as far as I know and I
have done quite a few 22xx recaps.
C906 is a higher voltage cap, and one of those common 'snap lock' caps
is available and will fit in perfectly with just a slight bend of the
leads.
Some of those caps David told you about are in the back right hand
corner of the mainboard, and a couple of them are mounted under the
metal edge of the frame of the scope.
With good soldering equipment you can reach under the metal edge and get
the old ones out and the new ones in with no problems.
Best of luck with your recap project!
tom jobe...

On 10/5/2017 12:27 PM, David @DWH [TekScopes] wrote:

On Thu, 5 Oct 2017 08:49:50 +0000, you wrote:

If someone familiar with this model could tell me which capacitors
are the most likely culprits I'll get those changed first.

The preregulator's input capacitor C906 and output capacitor C940 are
under the most stress and should be changed first. Usually I would
agree with Nenad about input capacitors but not in this case because
the input capacitor has an unusually low value.

C925, C943, C942, and C944 are not under a lot of stress but are
usually worn out anyway. And that applies to the inverter's output
capacitors as well.

Will I need to do any recalibration after changing caps in the PSU?
No recalibration should be necessary.

If you adjust the -8.6 volt output as described in the manual, then
this will change the CRT's cathode voltage altering the horizontal and
vertical deflection. If the horizontal and vertical deflection are
off by the same amount, then it may be feasible to adjust the -8.6
volt output to bring them into spec as long as the -8.6 volt output is
within the range specified in the service manual.



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Yahoo Groups Links





[Non-text portions of this message have been removed]

Re: 7854 RAM card upgrade only - any interest?

Mark Wendt
 

Thanks Nathan.  Glad to hear you're still working on it.

Mark

On 10/06/2017 08:12 AM, Nathan Johnson jdownj@... [TekScopes] wrote:
And I hit the send button too quick. Right now the prototype APPEARS functional, I haven’t done anything to verify every address etc, but it passes the POST. There is much more to be done in the area of the latches/ejector tabs on the top corners. This does not yet lock in. I’ll try to get my website back up and post the design files and pics this week.
Nathan KK4REY



via Newton Mail [https://cloudmagic.com/k/d/mailapp?ct=pi&cv=9.8.55&pv=11.0.1&source=email_footer_2]
On Fri, Oct 6, 2017 at 7:09, jdownj@... <jdownj@...> wrote:
I’m still here! I didn’t realize I’d missed emails from Cliff or others. My apologies.
I am finally unpacking the lab now, and getting set up again. I am going to post the design files as soon as I can
via Newton Mail [https://cloudmagic.com/k/d/mailapp?ct=pi&cv=9.8.55&pv=11.0.1&source=email_footer_2]
On Fri, Oct 6, 2017 at 7:05, Mark wendt.mark@... [TekScopes] <TekScopes@...> wrote:
I was wondering what progress had been made on these cards. Sorry I
can't help you out but if you do find out any news please let us know.

Thanks,
Mark

On 10/05/2017 11:49 PM, Cliff Carrie cliffcarrie@... [TekScopes]
wrote:
Does anyone have a way to contact Nathan Johnson? He was active on Tekscopes and had developed a replacement low power RAM / ROM card for the 7854. I had quite a few exchanges with him here over this project. It was up to a working prototype when he changed jobs and moved quite a few months ago. I am very interested in getting one of these cards, but Nathan has stopped responding to my off list emails.


Cliff Carrie

Re: 7854 RAM card upgrade only - any interest?

Nathan Johnson
 

And I hit the send button too quick. Right now the prototype APPEARS functional, I haven’t done anything to verify every address etc, but it passes the POST. There is much more to be done in the area of the latches/ejector tabs on the top corners. This does not yet lock in. I’ll try to get my website back up and post the design files and pics this week.
Nathan KK4REY



via Newton Mail [https://cloudmagic.com/k/d/mailapp?ct=pi&cv=9.8.55&pv=11.0.1&source=email_footer_2]

On Fri, Oct 6, 2017 at 7:09, jdownj@... <jdownj@...> wrote:
I’m still here! I didn’t realize I’d missed emails from Cliff or others. My apologies.
I am finally unpacking the lab now, and getting set up again. I am going to post the design files as soon as I can
via Newton Mail [https://cloudmagic.com/k/d/mailapp?ct=pi&cv=9.8.55&pv=11.0.1&source=email_footer_2]
On Fri, Oct 6, 2017 at 7:05, Mark wendt.mark@... [TekScopes] <TekScopes@...> wrote:
I was wondering what progress had been made on these cards. Sorry I
can't help you out but if you do find out any news please let us know.

Thanks,
Mark

On 10/05/2017 11:49 PM, Cliff Carrie cliffcarrie@... [TekScopes]
wrote:
Does anyone have a way to contact Nathan Johnson? He was active on Tekscopes and had developed a replacement low power RAM / ROM card for the 7854. I had quite a few exchanges with him here over this project. It was up to a working prototype when he changed jobs and moved quite a few months ago. I am very interested in getting one of these cards, but Nathan has stopped responding to my off list emails.


Cliff Carrie
________________________________
From: TekScopes@... <TekScopes@...> on behalf of test2cal@... [TekScopes] <TekScopes@...>
Sent: Friday, January 27, 2017 10:04:47 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM card upgrade only - any interest?



Nathan,

I'm the guy who started this thread almost 11 months ago. I really appreciate all the time and effort you have put in. Do you have any estimate of a timeline for a final product? Anything I can do to help?


Cliff Carrie


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Yahoo Groups Links



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Re: 7854 RAM card upgrade only - any interest?

Nathan Johnson
 

I’m still here! I didn’t realize I’d missed emails from Cliff or others. My apologies.
I am finally unpacking the lab now, and getting set up again. I am going to post the design files as soon as I can
via Newton Mail [https://cloudmagic.com/k/d/mailapp?ct=pi&cv=9.8.55&pv=11.0.1&source=email_footer_2]

On Fri, Oct 6, 2017 at 7:05, Mark wendt.mark@... [TekScopes] <TekScopes@...> wrote:
I was wondering what progress had been made on these cards. Sorry I
can't help you out but if you do find out any news please let us know.

Thanks,
Mark

On 10/05/2017 11:49 PM, Cliff Carrie cliffcarrie@... [TekScopes]
wrote:
Does anyone have a way to contact Nathan Johnson? He was active on Tekscopes and had developed a replacement low power RAM / ROM card for the 7854. I had quite a few exchanges with him here over this project. It was up to a working prototype when he changed jobs and moved quite a few months ago. I am very interested in getting one of these cards, but Nathan has stopped responding to my off list emails.


Cliff Carrie
________________________________
From: TekScopes@... <TekScopes@...> on behalf of test2cal@... [TekScopes] <TekScopes@...>
Sent: Friday, January 27, 2017 10:04:47 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM card upgrade only - any interest?



Nathan,

I'm the guy who started this thread almost 11 months ago. I really appreciate all the time and effort you have put in. Do you have any estimate of a timeline for a final product? Anything I can do to help?


Cliff Carrie


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Re: 7854 RAM card upgrade only - any interest?

Mark Wendt
 

I was wondering what progress had been made on these cards.ᅵ Sorry I can't help you out but if you do find out any news please let us know.

Thanks,
Mark

On 10/05/2017 11:49 PM, Cliff Carrie cliffcarrie@... [TekScopes] wrote:
Does anyone have a way to contact Nathan Johnson? He was active on Tekscopes and had developed a replacement low power RAM / ROM card for the 7854. I had quite a few exchanges with him here over this project. It was up to a working prototype when he changed jobs and moved quite a few months ago. I am very interested in getting one of these cards, but Nathan has stopped responding to my off list emails.


Cliff Carrie
________________________________
From: TekScopes@... <TekScopes@...> on behalf of test2cal@... [TekScopes] <TekScopes@...>
Sent: Friday, January 27, 2017 10:04:47 PM
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM card upgrade only - any interest?



Nathan,

I'm the guy who started this thread almost 11 months ago. I really appreciate all the time and effort you have put in. Do you have any estimate of a timeline for a final product? Anything I can do to help?


Cliff Carrie

Re: Successful restoration of 564B and 3L5, now looking for 7L5

Nenad Filipovic
 

Hi Steve,

Thanks for the very helpful advice, I mostly use the low freq SA for noise
analysis, so 50kHz upper limit would not be a problem, I will include the
3580A in my search. It even has a quite useful tracking oscillator output,
and appears to go down to approx. 5Hz with really narrow RBW, which is very
handy when analyzing 1/f noise. Some of the questions are how its internal
amplifier fares with its own 1/f noise, and how stable the display is at
these low frequencies and narrow RBWs. But of course we should not expect
miracles from these vintage devices.

I am looking for the 7L5 because I plan to invest also in other handy 7000
series plugins. On paper 7L5 looks quite good, it does not employ such
narrow RBWs as the 3580A but the rest is similar or better at first glance.
7L5 also claims to be very stable due to 1st LO phase lock, not sure how
3580A fares with this. The tracking generator for 7L5 may be an even
greater challenge to find (not sure whether it came attached from the
factory, or you could buy it separately and upgrade your standalone 7L5).

Large dynamic range is not required when dealing with noise analysis (or at
least I have that impression), and noise floor can be improved by using a
LNA (that way even the ancient 3L5 managed to prove quite useful). However
all swept SAs seem to be clumsy when it comes to the low frequency end, but
fortunately that's where FFT based ones should shine, I hope.

Best Regards,
Nenad Filipovic


On Fri, Oct 6, 2017 at 3:35 AM, ditter2@... [TekScopes] <
TekScopes@...> wrote:



Hello Nenad,

If you really NEED a low frequency SA, and can live with an upper
frequency limit of only 50 kHz, you might try to find a used HP 3580A. This
model has digital storage and way better dynamic range and lower noise
floor than the Tek 7L5. I worked in the same design group in TM 500 that
developed the SG505 and AA501/AA5001 audio plug-ins. While we had a couple
of 7L5s in the group. the HP3580A was the workhorse, due to its dynamic
range. It also had true differential input (1Mohm), and a choice of either
start frequency on the left (similar to a VNA) or center frequency in the
center. Since most LF work is looking at Bode plots of frequency response
rather that RF modulation as in communication work, the choice of start
frequency is great. It is self contained, not a plug-in for a scope.

Tek's 5L4 for the 5000 series as similar features, but very few or these
were produced and thus they are quite rare. I have only seen one in over a
decade of searches on e-Bay.

- Steve

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Re: 2235 power supply noise

Michael Pickwell <mikepickwell@...>
 

I just pulled the big capacitor C906 and it measures 84uF with 1.00 Ohm ESR.





Sent from my Samsung device

-------- Original message --------
From: "Tom Jobe tomjobe@... [TekScopes]" <TekScopes@...>
Date: 06/10/2017 02:34 (GMT+00:00)
To: TekScopes@...
Subject: Re: [TekScopes] 2235 power supply noise

Hi Mike,
I see you have gotten some very good advice on your 2235.
Replace all of the aluminum electrolytic capacitors, there's not that
many of them and they are all worn out.
In general, go up on the voltage rating a bit (but not down!) and get
fresh new 105 degree C caps if possible.
Look at the lead spacing and size of your new caps to make sure they fit
nicely. There is plenty of room on the mainboard so there is no problem
finding new replacements for any of them.
There is nothing special about any of the caps as far as I know and I
have done quite a few 22xx recaps.
C906 is a higher voltage cap, and one of those common 'snap lock' caps
is available and will fit in perfectly with just a slight bend of the leads.
Some of those caps David told you about are in the back right hand
corner of the mainboard, and a couple of them are mounted under the
metal edge of the frame of the scope.
With good soldering equipment you can reach under the metal edge and get
the old ones out and the new ones in with no problems.
Best of luck with your recap project!
tom jobe...





On 10/5/2017 12:27 PM, David @DWH [TekScopes] wrote:

On Thu, 5 Oct 2017 08:49:50 +0000, you wrote:

If someone familiar with this model could tell me which capacitors
are the most likely culprits I'll get those changed first.

The preregulator's input capacitor C906 and output capacitor C940 are
under the most stress and should be changed first. Usually I would
agree with Nenad about input capacitors but not in this case because
the input capacitor has an unusually low value.

C925, C943, C942, and C944 are not under a lot of stress but are
usually worn out anyway. And that applies to the inverter's output
capacitors as well.

Will I need to do any recalibration after changing caps in the PSU?
No recalibration should be necessary.

If you adjust the -8.6 volt output as described in the manual, then
this will change the CRT's cathode voltage altering the horizontal and
vertical deflection. If the horizontal and vertical deflection are
off by the same amount, then it may be feasible to adjust the -8.6
volt output to bring them into spec as long as the -8.6 volt output is
within the range specified in the service manual.







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