Date   

Re: 7104: Self-blurring focus

Rex W. Athey <mister_twister@...>
 

I've been starting to notice a problem with most carbon resistors in general that they are way off in value. I discovered this when a couple years ago I went through some of my parts inventory and found values to be way out of tolerance. Best example I remember was 47K, probably because I had some many of them. Now when ever I get replacement resistors, I avoid carbon resistors as much as I can for this reason. Have not had any problems replacing resistors in any piece of equipment since. There are some exceptions, but I now try to avoid the aggrevation of carbons all together. I'm mostly talking old carbon resistors in inventory.

Now I'll probably start a bad resistor thread to go with the bad electrolytics / paper caps threads. Been weeding out some of them too.

Rex


GR, not Tek!

Craig Sawyers <c.sawyers@...>
 

Hi all

Anyone interested in the history of GR, I found a downloadable 1916
catalogue here
http://www.teradyne.com/corp/grhs/pdf/catalog-bulletins/Catalog_A_1916.pdf .
In fact this is just a section in the General Radio Historical Society on
http://www.teradyne.com/corp/grhs/ - it seems to have lots of fascinating
stuff there if you like the early history of electronics.

Enjoy!

Craig


Re: 7104: Self-blurring focus

John Miles <jmiles@...>
 

Usually aged resistors in the focus voltage divider are responsible for this
symptom. They may be potted in a hybrid, in which case you'll have to break
some traces and rebuild the divider on an outboard basis.

I am slowly learning to view all carbon-composition resistors above 100K
ohms with the same suspicion that people reserve for old paper capacitors.

-- john KE5FX

-----Original Message-----
From: Bruce Lane [mailto:kyrrin@bluefeathertech.com]
Sent: Thursday, January 15, 2004 3:47 PM
To: tekscopes@yahoogroups.com
Subject: [TekScopes] 7104: Self-blurring focus


Well... I think I may have a couple of leaky caps or something.

Having cycled the pots a whole bunch on my newly-acquired
7104, I find that they're doing well enough. However, it looks
like there may be an issue in the focus section.

What will happen is that the trace will be razor-sharp and
hair-fine one moment, and then it'll start blurring. This affects
the entire screen (readout included). The interesting thing is
that the focus will blur up to its (apparent) maximum degree of
'defocused,' and then it'll snap back to razor-sharp and clear.
It'll do this three or four times, and then stay sharp or blurred
at any given moment. After the 'scope's been on for an hour or
so, this behavior disappears.

Has anyone seen this symptom before? I suspect
thermal-intermittent caps in the high-voltage area, but I don't
yet have a service manual for the unit. Pointers appreciated.

Thanks much.


-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been
equipped with surreal ports?"




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7104: Self-blurring focus

Bruce Lane
 

Well... I think I may have a couple of leaky caps or something.

Having cycled the pots a whole bunch on my newly-acquired 7104, I find that they're doing well enough. However, it looks like there may be an issue in the focus section.

What will happen is that the trace will be razor-sharp and hair-fine one moment, and then it'll start blurring. This affects the entire screen (readout included). The interesting thing is that the focus will blur up to its (apparent) maximum degree of 'defocused,' and then it'll snap back to razor-sharp and clear. It'll do this three or four times, and then stay sharp or blurred at any given moment. After the 'scope's been on for an hour or so, this behavior disappears.

Has anyone seen this symptom before? I suspect thermal-intermittent caps in the high-voltage area, but I don't yet have a service manual for the unit. Pointers appreciated.

Thanks much.


-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"


Any way to clean...?

Bruce Lane
 

Does anyone know of a way to clean the (apparently sealed) pots on the front panel of a 7000 series?

My 7104 works great, but the intensity and focus pots are noisy as sin. Is it just a case of working them back and forth until they clear up or what?

Thanks much.


-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"


3A10 manual/scan

Tim Phillips <t.phillips@...>
 

Hi, all;
many thanks to all the people who kindly sent me info about
the 3A10. My problem with BAMA download was caused by me using
a really ancient version of Acrobat.
kindest regards
Tim.
p.s. I would really like a 3A10 ! c'mon ebay etc. ;-)


7503 repair

lloydepowell <lloydepowell@...>
 

Does anybody have a Tek 7503 mainframe repair manual? Does anyone
know how close it is to a 7603?


Re: Hah! SCORE!!

Miroslav Pokorni
 

Any advice or 'gotchas' regarding this model would be appreciated. I already
know to treat it delicately because of the microchannel plate CRT -- how
'delicately' does that mean?


The microchannel plate is not as delicate as it is frequently described.
Sure, you can not have a bright trace seating in a spot all day long or plug
setting data on bright, without getting some burns, but even then it looks
more like phosphor that burned, not MCP.

I had a 2467 as my working scope for more then ten years and never got any
burns on it's screen. It is true, I watched it, but that was within reason,
trace was turned as bright as needed to see rant pulses, but it was not
abused. When test department wanted that scope, I always read them riot act
about unnecessary brightness, because they always kept their scopes very
bright.

Regards

Miroslav Pokorni


Hah! SCORE!!

Bruce Lane
 

Dang it... I know I'm going to hate myself when the credit card bill shows up, but...

Perusing Boeing Surplus today, I found several 2465's (original model) in clean condition priced at $350 each. Bit high for me, especially since I'm aware of their vertical IC issues, so I didn't get any of them.

HOWEVER -- There was also a 7104 mainframe in extremely clean condition sitting there. The thing looked like it had spent most of its life in a lab or holding area (very possible, given what I know of Boeing's test equipment program).

They only wanted $225 for it, and that's lower than I've seen ANY 7104 frame going for anywhere, so I grabbed it. Haven't had a chance to power it yet, but the last cal dates are '99 and 2001, so it can't be too far gone.

My next task is to locate appropriate main and delaying timebases for it (7B15 and 7B10, if I'm not mistaken). I'll probably do that when I hit the Bay Area later this year for my annual scrounging trip. I've already got some 7A19's and 29's, so I'm good for high-frequency vertical plug-ins.

Any advice or 'gotchas' regarding this model would be appreciated. I already know to treat it delicately because of the microchannel plate CRT -- how 'delicately' does that mean?

Thanks much.


-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"


Re: Single-sweep mod for 531/541

Stan & Patricia Griffiths <w7ni@...>
 

Hi Tim,

I think there was a Tek Mod Kit to add single sweep to a 531 or 541. A copy
of the Mod Kit instructions is probably in the Tek Microfiche if you can get
ahold of that somewhere . . . You could probably fabricate your own kit
from the instructions.

Stan
w7ni@easystreet.com

----- Original Message -----
From: "Tim Phillips" <t.phillips@ucl.ac.uk>
To: <tekscopes@yahoogroups.com>
Sent: Monday, January 12, 2004 8:45 AM
Subject: [TekScopes] Single-sweep mod for 531/541


Hi, all;
I have a 531A (with it's service manual), and
I recently saw on ebay what looked like a 531 with a
single-sweep feature added; (switch on front panel.)
Is this easy to implement? The photo I saw looked like
a genuine Tek mod, with a small photo-etched plate for the
switch.
kindest regards
Tim.





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Re: What's the best manual?

Stan & Patricia Griffiths <w7ni@...>
 

Tektronix put a LOT of data on microfiche in many different databases. Each
different database offers answers to different questions. It is not
reasonable to conclude that you must have ALL the data and all the databases
to get any useful information from any of it. Also, SOME of the info in
those databases has never been released by Tek for publication, unlike
obsolete manuals. Here are some example sources of data and the kind of
questions these sources will answer.

Instrument Microfiche:

This is what people normally refer to as "Tek Microfiche" but Tek had lots
of different databases on microfiche besides these. The instrument
microfiche consists of 3 parts, one part of which has always, and still is,
"Tek Company Confidential". The most common part of this database is the
complete instrument manual which may actually be several volumes for some
instruments. By now, you know that all manuals are not identical for the
same product. As the instrument progressed through life, so did the manual
and changes were introduced throughout its life in both instrument and
manual. Tek generally tried very hard to make "composite manuals" that
covered the current state of the instrument (whatever that was) and all
earlier instruments, too. Sometimes this was not possible if a rather
drastic change was made in the instrument and another whole version of that
manual had to be printed for instruments "above serial number XXX" in which
case two manuals would be required to have the complete story on all serial
numbers of that instrument. Of course, the last manual printed is the best
and most complete one and should cover all serial numbers. This is the
manual that appears in the microfiche at the time the instrument is
discontinued.

The second part of the instrument microfiche is the instrument "Modification
Summary". This part describes, in detail, each change that was made to the
instrument, why it was made, usually the date, the serial numbers which it
applies to, and how you can install it in an earlier instrument (sometimes
not possible). By examining the Mod Summary, you can estimate the total
number of instruments manufactured and the approximate time for any
particular serial number, just by comparing the modifcation date and the
serial numbers it applies to. The Mod Summary grew with the instrument,
too, just like the manual and the last Mod Summary published for a
particular instrument has the best and most complete data. It has been
argued that the modification data is in the latest manuals but this is not
really true. Yes, the manual shows changes of certain parts to new values
at specific serial numbers, but it does not tell you WHY these changes were
made or how many parts and what OTHER wiring changes need to be made to
install the ENTIRE modification. Partial installation of a modification can
be worse than not putting it in at all . . . This database can tell me
exactly which modifications I can install in my 7A24 s/n B116058, for
example, and WHY I should install them.

The third part of this instrument microfiche database was called "Sales and
Service" and still is considered "Tek Company Confidential". The
confidentality is not usually because it contains any "secrets" but rather
because the data in it was intended for use by Tek employees only and not
carefully screened nor written for publication to the world. It may contain
notes for sales engineers on how to best demonstrate the insturment in order
to win over the competition, for example. It may contain the original
design goals for the product and the final product MAY not have met them all
. . . It may contain snipets of service information not falling into the
category of a modification, like certain unreliable batch numbers for
failing components . . . All useful info but not necessarily what Tek would
want published to the world, hence, this part was classified "Tek Company
Confidential".

Most of the Tek Instrument Microfiche was used by Tek themselves with
complete libraries of it in each of the 35 or so Service Centers in the U.S.
and a bunch more overseas. Some sets of parts 1 and 2 (not part 3) were
sold to customers. Tek's sets included parts 1, 2, and 3 and were updated
weekly from Beaverton. Customers had the option to buy an update
subscription service. Customers could also buy partial sets such as "7000
K", "TM500", or "530/540 Series". As the sets of microfiche were updated,
sheets of microfiche containing approximately 60 images were replaced but
sometimes only one or two sheets of an instrument set containing 6 or 7
sheets total. Many times the old fiche were saved and these are sometimes
available on the market. Usually, you cannot find the entire set for any
particular instrument but partial data is usually better than none.

It has been suggested that digitizing these microfiche images provides no
advantage over using the microfiche sheets themselves in a microfiche
reader. I beg to differ with this opinion. While I have access to many
original Tek microfiche sheets, most of you do not. I can digitize mine and
make them available to you as PDF files. Another possibilty would be to
turn the images into hardcopies and make those available to you. While
making a PDF file takes more time and labor intitally, making additional
copies is MUCH easier than dealing with paper copies. Besides, if you
really want paper copies, you can print them yourself from the PDF file. It
has also been suggeted that unless you have the entire library, none of it
is useful. This is like saying you have to have ALL Tek Manuals before ANY
of them are useful!

Numerical Parts Record (NPR)

This Tek Company Confidential microfice database was intended primarily as a
parts pricing document for use by Tek's Field Sales Offices. It contains
much more than prices, however. If the part number was obsolete, for
example, it told you what the replacement part number was, and what
insturment types and serial numbers used it. It also told you if this part
was manufactured inside of Tek or purchased outside and who the primary
supplier was, complete with mailing address. There were about 75 sheets of
microfiche to this database with maybe 100 images per sheet and lots of
individual part numbers in each image. With this database, I can look up
Part Number 120-0612-01 see where it was made and who made it, as well as
find out which instruments and serial numbers used it.

Tektronix Catalogs

Tektronix made lots of different catalogs. We are all familiar with the big
ones done each year containing all the current products for sale. You can
get a LOT of really valuable data from those which is why they sell for as
much as $30 or more on eBay. It can tell you information such as which
probes Tek recommended for a particular scope model, what plugins are
compatible with which mainframes, what accessories were included, how much
the instrument cost when new, major specifications if the products in the
catalog, what years particular products were offered by Tek, etc. etc.
Since many of these original old catalogs are getting impossible to find, I
have digitized both the 1970 and 1975 Tek catalogs (with specific legal
permission from Tek) and offer them for sale on CD. Thes two catalogs give
you most everything you want to know about 7K scopes and TM500 instruments.
I plan to digitize more Tek Catalogs in the near future.

You may NOT know that Tek also made catalogs specific to TV and computer
products. You may also not know that Tek made a "Calibaration and Test
Fixtures Catalog" that lists things like the 067 fixtures and Input
Normalizers. With regard to 067-0542-99, do not expect to find ANY
published information on it because all 067 fixtures that ended in "-99"
were never offered for sale to customers and no official manuals were ever
printed. These were "in-house" test fixtures for use on the production line
and very few of them ever made it to the field. Information about these
fixtures was intentionally supressed to reduce the demand for support on
them from the field . . . since you can't find much on this product, I guess
Tek was successful . . .

CRT by Instrument List

Tek had such a microfiche list made in about 1990 that covered all
instruments that used CRT's up to that time. I extracted the data, line by
line, from a copy of the microfiche images I have in my possession and put
it in a database that is on the www.reprise.com web site. This was very
time-consuming work but also very valuable data to have.

Tektronix Transistor Part Numbers to Generic Part Numbers Cross Reference

I also extracted this data, line by line, and we have published it on
www.reprise.com. I would like to do it for diodes and IC's but, so far,
time just does not permit me to do it. The source of this data is not from
microfiche. Rather, Tek published a whole series of Company Confidential
reference books for use by Tek design engineers to help them select parts
for use in new designs. The entire set of reference books makes a stack
about a foot high and covers tens of thousands of electrical and mechanical
components.

Did you ever want to know exactly WHAT parameters checked and matched tubes,
transistors, and diodes were matched or checked for? The data exists but
not published at this time. So, there are LOTS of databases on Tek stuff
and each one answers some questions. I happen to think that even just a
small part of this data can be helpful and more can be more helpful. As I
get time, I will attempt to make more of it available on www.reprise.com.

Stan
w7ni@easystreet.com

PS One thing that slows down this whole process is the tons of individual
requests I receive for specific pieces of data. Each one of these is a
valid request but the volume of questions precludes me from working on
publishing more databases for all to use. This is the well known "kill
aligators or drain the swamp" enigma . . .

----- Original Message -----
From: "maddisassembler" <320041677522-0001@t-online.de>
To: <TekScopes@yahoogroups.com>
Sent: Monday, January 12, 2004 1:39 AM
Subject: [TekScopes] Re: What's the best manual?


January 12th, 2004


Albert and all others who care for this issue,

even if one has a complete collection of
microfiche (which would be well above 10,000
microfiche I estimate) he would have to spend
appr. USD 2,000 (0.20 times 10,000) just to
have them digitized.

All this is worthless (or at least the same level
as putting microfiche into a reader) if this whole
action cannot give immediate answers to questions
like (just examples):
What is a 067-0542-99 good for? Where was part
120-0612-01 used and what was the serial number
range? Under which modification falls my 7A24
serial B116058?
etc etc etc

From my point of view such answers can only be
found in reasonable time if the contents of all
microfiche are linked into some kind of data base
or retrieval system.

To build up such a system it would need a big
effort of labour - too much for single a person
with only 24 hours a day to spend on this...

Comments welcome.

Best regards
-Roland



--- In TekScopes@yahoogroups.com, "Albert LaFrance" <lafrance@a...>
wrote:
Another option which might be worth considering is to have the
microfiche
scanned onto a CD-ROM. I looked into this a while ago for some
Bell System
Practice manuals, and several service companies estimated prices of
15-35
cents per image, depending on quantity, fiche quality, need for
post-scanning image cleanup, etc.

Albert

----- Original Message -----
From: "Stan & Patricia Griffiths" <w7ni@e...>
To: "maddisassembler" <320041677522-0001@t...>
Cc: "TekScopes" <TekScopes@yahoogroups.com>
Sent: Monday, November 03, 2003 4:43 PM
Subject: [TekScopes] What's the best manual?


<SNIP>
Our local library has microfiche readers that can read either
fiche sheets
or 35mm filmed images and convert any image to hard copy on
excellent copy
paper similar to what you use in your own laserjet printer. It
costs 10
cents per image to do prints and I sometimes use that service.
<SNIP>




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3A10 plug-in unit

Tim Phillips <t.phillips@...>
 

Hi, all;
Anyone ever seen a 3A10 'transducer plug-in'?
(presumably fits in a 560-series 'scope)
BAMA seems to have a manual, which I can't get
to download. Anyone have a catalog page scan of this thing?
many thanks
Tim.


Re: New electrolyitc capacitors vs old ones

Howard Matthews
 

Not to disparage your advice, Bill, which is excellent for restoring
old vacuum tube radios. But... a 454 scope has about 38
electrolytics and a dozen paper caps. Replacing 40 caps "on general
principle" requires an awful lot of dedication. ;-)

I guess we need a more sophisticated way to anticipate future
problems in these old scopes.

-Howard

--- In TekScopes@yahoogroups.com, Bill Smith <ko4nrbs@y...> wrote:
The capacitors manufactured today are much better than
the ones manufactured 10, 20 or 30 years ago. The
technological advances made in the materials used to
manufacture the capacitors provide you with an
excellent product. In addition they are usually much
smaller while having the same or higher voltage and
capacity ratings.

Within reason I always replace the electrolyitcs in
any old gear I buy. Especially in the power supply.
This is a good web site that explains the process:
http://antiqueradio.org/recap.htm

Thanks,
Bill Smith KO4NR

=====
Bill Smith KO4NR

__________________________________
Do you Yahoo!?
Yahoo! Hotjobs: Enter the "Signing Bonus" Sweepstakes
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Need Tek IC 155-0050-01

Robert Morein <morepub@...>
 

This is just my non periodic asking if anyone has a Tek vertical amp chip for a 434, 155-0050-01.

The chip is socketed, an easy pull if you have a junked 434.

Amazingly, I've purchased two bad replacements already, but swapping the one from the other channel makes the scope work.


two 475 and one 475A scopes

ko4nrbs <ko4nrbs@...>
 

I found a guy in Chicago, Chris, that had a bunch of Tektronix scopes
for sale. His phone number is 903-732-3892. I bought two 453 scopes
from him Sunday for $50.00 each plus a 2 1/2 hour round trip drive to
get them. He told me over the phone that they were in good conditon,
complete and that they worked. I was surprised to find that both of
them were very clean, had two probes each, both had the hard covers
that goes over the front, and that they both worked as he said they
did. I have had them on for several hours since I got them and they
have had no problems.

He now has one 475A and two 475 scopes for sale. I have not seen
them so I can not comment on their condition. All I can say is that
he was honest with me. If you are near Chicago it may pay to look at
them.

I have no interest in this other than passing along what I found
out. I don't know Chris having only met up with him to get the
scopes.
Thanks,
Bill


Re: Uncal light on 453

Robert Morein <morepub@...>
 

If it's like other scopes, an uncal light is associated with a red vernier knob that isn't parked in the fully clockwise position, with a positive click.

----- Original Message -----
From: ko4nrbs
To: TekScopes@yahoogroups.com
Sent: Tuesday, January 13, 2004 8:40 AM
Subject: [TekScopes] Uncal light on 453


My 453's Uncal light is on. I saw something about this on a post but
can't find it now. I couldn't find any mention of it in the
operating manual. What does it mean and how do I get it to go out?
Thanks,
Bill Smith KO4NR



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New electrolyitc capacitors vs old ones

Bill Smith <ko4nrbs@...>
 

The capacitors manufactured today are much better than
the ones manufactured 10, 20 or 30 years ago. The
technological advances made in the materials used to
manufacture the capacitors provide you with an
excellent product. In addition they are usually much
smaller while having the same or higher voltage and
capacity ratings.

Within reason I always replace the electrolyitcs in
any old gear I buy. Especially in the power supply.
This is a good web site that explains the process:
http://antiqueradio.org/recap.htm

Thanks,
Bill Smith KO4NR

=====
Bill Smith KO4NR

__________________________________
Do you Yahoo!?
Yahoo! Hotjobs: Enter the "Signing Bonus" Sweepstakes
http://hotjobs.sweepstakes.yahoo.com/signingbonus


Uncal light on 453

ko4nrbs <ko4nrbs@...>
 

My 453's Uncal light is on. I saw something about this on a post but
can't find it now. I couldn't find any mention of it in the
operating manual. What does it mean and how do I get it to go out?
Thanks,
Bill Smith KO4NR


Re: Those old capacitor

Larry Coleman <bioengaust@...>
 

I have been sitting on the side line reading and enjoying the
postings on old electro's and your attemps to restore them.

I cound'nt resist any longer but I am not sure what you are trying to
do,From experiance I have developed a restoration proceedure when it
comes to restoring a vintage electronic device.
Step 1 replace all electro's where possible then look for obvious
faults.
Step 2 disconect the power suply and check voltages.
Step 3 connect supply with suitable resister and measure current draw
with low amp quick blow fuse.

As evil as the four steps are you can save a lot of heart ache.

Having worked for allied capacitors for a short time I know that
those electro's have a shelf life as the electrolite dries out and
the component becomes unreliable and possibly dangerous. As a person
who has lived through many explosions without shrapnal wounds watch
your eyes chaps,wear safety glasses if your face is close to the
component when powering up.
If you think you can rejuvinate them with any sort of reliability I
doubt if you will have any success,but if you are trying to make them
you are on the right track.
If you replace them with tantalums compare the performance data first.
Remember if a capacitor go's short circuit it can damage other
components worth more than a capacitor.
When the smoke gets out its very hard to put it back in, and IT can
come out with a big bang.

Anyway carry on you are developing some very interesting information
and I will see if I can find some data for you.

Good luck
Larry Coleman
Australia


Re: Dang'd old electrolytics again?

Robert Morein <morepub@...>
 

I had a 7904A that would not start up with a full load of plugins.
I removed the plugins, started up the scope, ran it for a couple hours.
I replaced the plugins, started it up, and ran it overnight.
No problems since.

It suggests to me that there was a cap seriously leaking in the power supply, that it managed to heal itself, by blowing off whiskers or reforming, and that it was, incredibly, a "good repair."

This doesn't happen often :).

----- Original Message -----
From: Howard Matthews
To: TekScopes@yahoogroups.com
Sent: Monday, January 12, 2004 9:30 PM
Subject: [TekScopes] Dang'd old electrolytics again?


Risking turning this group from a Tek scopes group to an
electrolytic capacitor group, I have questions.

I bought a "fixer" 454. Initial review showed chan 1 working okay,
but chan 2 not. After it sat a few months in my "shop", I started
working on it. First I checked and set all the voltage supplies.
They were all within spec, and now right on. However, now both chan
1 and chan 2 were visible ONLY using the beam finder. They were
both offscreen high.

So, I started tracing the voltage levels and signals in the chan 1
preamp first. A number of DC levels were off enough to throw the
trace off screen. And there was disturbing noise on top of the
signal. But before I could pin-point the source of the problem(s),
chan 1 starts working! It drifts around a bit, but the bias and
noise problems are gone.

Turning to chan 2 - guess what. After a few hours of trying to get
consistent readings and find the source of the problem, BINGO - chan
2 is working.

I left the scope powered off over night. The next day, both
channels are still working and now quite stable. No noise, no drift
after warmup.

The power supplies had and have NO problems. There are a number of
small bypass electrolytics in the preamp circuits which I did not
get around to checking.

Questions:
1. Is it likely that some electrolytics were "reformed" while I was
looking for the problem.

2. If so, is it likely the electrolytics will fail again soon, if
not used frequently? Might they have poor ESR, or high leakage now?

3. Should I pull the little electrolytics in the preamp and
check/replace them? I'm thinking modern tantalums might be good
replacements.

Anyone have similar experiences? Opinions? Advice?

TNX
-Howard





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