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Hi Michael,

I'm afraid you are right. There are scammers everywhere. When I see words
like "I don't know how to use it", I assume its broken and bid accordingly.
I sell a LOT of stuff on eBay, some of it I can't test and sell as is.
Sometimes all I can do is plug it in and look for smoke and report that it
did not smoke, if that is all I know about it . . . In the case of a recent
CB radio I sold, I didn't even power it up . . . and said so. I did say that
I had no reason to believe it did not work and that it came from an estate
sale. I saw no obviously smoked or burned parts and described any physical
damage and took several pictures. After that, it is buyer beware . . . I
also priced it cheap . . . $4.

In another case, I was selling an HP-01 1975 vintage digital calculator
watch. This one worked great and had an extra watch band, the book, original
box, etc. It went for $2300 . . . ! ! Before I put it up for sale, I
looked at previous HP-01 auctions and noted one that eventually sold for
about $400. The seller claimed he did not know if it worked or not and said
the battery was dead so he could not test it . . . I investigated further
and found that that very seller had just a few weeks before that purchased a
known dead HP-01 for about $200. I further found out that he had purchased a
couple of known working HP-01's for about $1200-$1500. I can't believe he
could not install a battery and see if it worked or not . . . he had
batteries in the other two HP-01's and they are available where ever watch
batteries are sold . . . He certainly knew how much a "good" HP-01 was worth
. . . My opinion: he was fraudulant in his presentation and knew EXACTLY
what he was doing . . . The buyer was Japanese . . . with little or no
recourse . . . I notified eBay of my observations and never heard a word
about it from anyone . . . including eBay.

Buyer beware . . .

Stan
w7ni@...

More comments below . . .

Michael Dunn wrote:

Is anyone else suspicious of some of the auctions on eBay. In one
auction, the seller says he doesn't know how to use it, so therefore
can't guarantee it (a 5L14 analyzer), yet has pictures of it in full
operation. Another of his auctions for a storage mainframe - he says
he doesn't know how to use the storage... Gimme a break.

In the case of the 5L14N, it is one of the hardest instruments to use that I
have ever encountered . . . and I used to sell them as a Tektronix Sales
Engineer from 1979-1989, specializing in Tek Spectrum Analyzers . . .

I expect some people might do this to cover up a non-working
function, instead of just coming out and saying (e.g.) "Storage
doesn't work"!

Comments?

p.s., Are 5000 and 7000 plug ins compatible?

NO.

For example, my 7S14
has a sticker on it that says 5S14 too.

I wonder what that is all about . . . ?? Just a quick look will tell you
that a 5000 Series plugin will not fit a 7000 series mainframe and vice-versa
and they are not electrically compatible, either.

Stan
w7ni@...

mtmpsmp@... wrote:

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:

mtmpsmp@y... wrote:

I have a 454 that has no vertical deflection on ch1 or ch2, using
another scope I am able to trace signal from the preamps to the
deflection plates. The sweep appears to be in good shape and the
trace is centered on crt. ( position controls have no effect on
trace) What I don't understand is that I have a voltage imbalance

on

vertical plates and the trace is still centered!

Boy! I don't understand that either. I have to wonder if the

voltage

unbalance is actually getting to the deflection plates inside the

CRT.

Perhaps there is a broken connection INSIDE the CRT. If the

unbalance is

actually on the CRT plates, I don't see how the trace can be

centered

vertically . . .

Stan
w7ni@e...
.....................................................................

......................................................................
Stan,
Upon further investigation I have found that when the scope is
turned on the collector voltage is the same (74.6 volts) on each
output device. The voltage will stay in that condition ( flat
centered trace) until I start making voltage measurements with my
voltmeter ( high impedance digital) then the top connecter drops to
56.8 -62.0 volts and the bottom to 32.5 -29.8 volts, the voltage of
course being determined by position control. The trace is at this
point off screen in all modes ( chop, add ect) I can seem only to
bring this condition on by taking voltage measurement on either vert
plate.
Do you think maybe a bad output transistor? thanks for your help.
Mike

Maybe, Mike. Looking at my 454 manual, I see that the collector voltage on
both Q394 and Q494 should be about 41-42 volts measured with a voltmeter.
Also, I don't think the voltmeter should "load" the circuit such that the
voltage changes very much because of attaching the voltmeter. There are TWO
sets of vertical deflection plate pins. Are you sure all FOUR pins are
connected?

A good troubleshooting method for balanced circuits like vertical amplifiers
is to short together like points such as the upper and lower CRT deflection
plates in order to force them to be at the same voltage. This should force
the trace to be centered vertcially and should not damage the circuitry. If
the trace is centered with the CRT vertical deflection plates shorted
together (this is also the same as shorting the collectors of the vertical
output stage transistors together), it is a very good indication that the CRT
itself is good.

Next, you can remove the short and move it to the emitters of Q394 and Q494.
If the trace is once again centered vertically, most likely Q394 and Q494 are
good. Next, move the short to the base of Q374 and the base of Q474. If the
trace is once again centered, most likely Q374 and Q474 are good. You can
work your way a stage at a time through the vertical amplifier this way until
you do not get a centered trace. Now you are very close to the problem and
it is time to check for shorted or open transistors in this immediate area.
Be careful not to brush ground with the loose end of the short wire while the
instrument is powered up and the other end is connected because you will have
a LOT of destroyed transistors if you do that . . . Also, be sure BOTH ends
of the short wire are disconnected before connecting one end to another part
of the circuit . . .

Let me know how this works for you.

Stan
w7ni@...

Is anyone else suspicious of some of the auctions on eBay. In one auction, the seller says he doesn't know how to use it, so therefore can't guarantee it (a 5L14 analyzer), yet has pictures of it in full operation. Another of his auctions for a storage mainframe - he says he doesn't know how to use the storage... Gimme a break.

I expect some people might do this to cover up a non-working function, instead of just coming out and saying (e.g.) "Storage doesn't work"!

Comments?

p.s., Are 5000 and 7000 plug ins compatible? For example, my 7S14 has a sticker on it that says 5S14 too.

-----------------------------------------------------------------
Michael Dunn | Surround Sound Decoder & Stereo Enhancer
Cantares | Self-Amplified Speakers, Test Equipment
74 George St. | Ambisonic Surround Sound CDs and Recording
Waterloo, Ont. | (519) 744-9395 (fax: 744-7129)
N2J 1K7 | mdunn@...
Canada |
-----------------------------------------------------------------

Hi all, :)

Not exactly a TekSCOPE, and not catastrophic, but I have a DM501A with a
VERY bright LED display. A glance at the cct diagram does not suggest (to
me) the possibility of adding a simple series resistor for the common side
of the LED display. Anyone know enough about the unit to suggest a fix?

Thanks and regards,
:)
Michael Dunn
(the other one)
<g>

--- In TekScopes@y..., Stan or Patricia Griffiths <w7ni@e...> wrote:

mtmpsmp@y... wrote:

I have a 454 that has no vertical deflection on ch1 or ch2, using
another scope I am able to trace signal from the preamps to the
deflection plates. The sweep appears to be in good shape and the
trace is centered on crt. ( position controls have no effect on
trace) What I don't understand is that I have a voltage imbalance

on

vertical plates and the trace is still centered!

Boy! I don't understand that either. I have to wonder if the

voltage

unbalance is actually getting to the deflection plates inside the

CRT.

Perhaps there is a broken connection INSIDE the CRT. If the

unbalance is

actually on the CRT plates, I don't see how the trace can be

centered

vertically . . .

Stan
w7ni@e...
.....................................................................

......................................................................
Stan,
Upon further investigation I have found that when the scope is
turned on the collector voltage is the same (74.6 volts) on each
output device. The voltage will stay in that condition ( flat
centered trace) until I start making voltage measurements with my
voltmeter ( high impedance digital) then the top connecter drops to
56.8 -62.0 volts and the bottom to 32.5 -29.8 volts, the voltage of
course being determined by position control. The trace is at this
point off screen in all modes ( chop, add ect) I can seem only to
bring this condition on by taking voltage measurement on either vert
plate.
Do you think maybe a bad output transistor? thanks for your help.
Mike

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STunwall@... wrote:

mtmpsmp@... wrote:

I have a 454 that has no vertical deflection on ch1 or ch2, using
another scope I am able to trace signal from the preamps to the
deflection plates. The sweep appears to be in good shape and the
trace is centered on crt. ( position controls have no effect on
trace) What I don't understand is that I have a voltage imbalance on
vertical plates and the trace is still centered!

Boy! I don't understand that either. I have to wonder if the voltage
unbalance is actually getting to the deflection plates inside the CRT.
Perhaps there is a broken connection INSIDE the CRT. If the unbalance is
actually on the CRT plates, I don't see how the trace can be centered
vertically . . .

Stan
w7ni@...

To unsubscribe from this group, send an email to:
TekScopes-unsubscribe@...



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I have a 454 that has no vertical deflection on ch1 or ch2, using
another scope I am able to trace signal from the preamps to the
deflection plates. The sweep appears to be in good shape and the
trace is centered on crt. ( position controls have no effect on
trace) What I don't understand is that I have a voltage imbalance on
vertical plates and the trace is still centered!

--- Im TekScopes@e..., msfix56@y... schrieb:

Hello All,

It was suggested that perhaps the nuvistors in the B channel were

the

cause of the drift. This does seem to be the case. In an attempt to
prove that case I swapped the tubes out and the drift changed
channels. I have tested the nuvistors in the scope and several of
them test weak including the front end of the channel B preamp

which

if you watch the tube test meter drifts up from about 3000 uMhos to
about 7600 uMhos before dropping off sporadically.

Have you tried to clean the connector pins of the Nuv?
Maybe the heater has a bad contact that could make unstable and
weak conditions.

The other tubes in
the scope vary from 10000 uMhos to 11500 uMhos. My question is that

The 8393 is exactly equal to a 7586 exept the heater voltage (13.5V)


Jorgen
dj0ud

An update.
I spent two hours in dismounting the vboard and un removing the pots
from it. What a nightmare! If any other people is about to start an
adventure like this, please be sure to have a perfect and efficient
unsoldering machine. I spent a lot of time trying to get rid of the
tin that was keeping the pots on the board. My solder sucking tool
was insufficient. I used a thin plaited wire to get the tin out of
the PCB holes by capillarity.
The pots are now in my hands and I am going to work on them the next
weekend (hopefully).
until next time
ciao

--- In TekScopes@y..., "Emanuele Girlando" <emanuele_girlando@y...>
wrote:

I confirm: "the pots are Allen Bradly, and have a double section";
one section seems unused (not connected).
I confirm: they are "the ones which you can nicely open with four
screws".
So your tips are very very useful.
For the sake of completeness and want to say that I have already
tryed to turn them back and forth a lot of times but with almost no
result.
Furtheremore it is impossible to squirt any form of conctact

cleaner

without opening them.
Thank you very much for your contribution, I'll keep the list

updated

on my activity.
ciao



--- In TekScopes@y..., pe1fbo@h... wrote:

--- In TekScopes@y..., Emanuele Girlando <emanuele_girlando@y...>
wrote:

Vertical position pots on my tek475 are so noisy to make my

scope

almost unusable.
Any suggestion on refurbishing those pots?
They are two sections pots, can I try to use the unused section?
Any source for them?
Thank a lot !
ciao

=====

Emanuele Girlando (IW1DHI)




__________________________________________________
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Hi Emanuele,

Those pots are probable Allen Bradly, and and have a double

section.

There are two type of AB pots, The plastic sealed ones, and the

ones

which you can nicely open with four screws. To clean the pot, you
have to take it apart (first remove them carefully from the

Vertical

amp board). Once you have opened them you need to cut the plastic
seal inside the black plasic section to get to the brown whiper
section.

If you have everything apart, remove all the old grease and clean

all

sections with alcohol. Mind you that the whiper has a tiny carbon
pallet, which comes loose very easy.

Once this is done you need to re-apply new grease. I use for this
purpose lithium based grease from Dow Corning, Molycote DX. Other
types of grease I cannot recomend to use. This is probably the

same

stuff that Bourns uses.

After this, everything has to be assembled again.

There is one small remark on this whole procedure, that is, if

the

carbon conductive film is worn out, the result will probably
disapoint you.

I have personally used this procedure on a lot of AB pots. They

are

the ones usuly having problems due to the aging of the grease.

And

can be restored most of the time with a good result.


- Fred de Vries

--- In TekScopes@y..., "Emanuele Girlando" <emanuele_girlando@y...>
wrote:

Referring to my other post "tek 475 vertical position pots", I am

now

required to dismount those pots. To do it (the one for channel 2 in
particular), I have to remove the vertical amplifiers board.
What I am afraid of is that it seems I have to desolder two

resistors

having one lead on the borad and one on the VOLTS/DIV rotary

switches.

Can I do it safely? Anything to be aware of?
Furtheremore, how can I safely dismount the BW/TRIG VIEW command
shaft from the switch it is linked to? Is it sufficient to unscrew
the tiny screws?
Thank a lot
ciao

Hi Emanuele,

You can safely desolder the two resistors. They are connected to the
input FET. Just make sure that your solderingiron ground is on the
same potential as the scope, otherwise you could damage the input FET
(2N5911 discontinued by VISAY). The BW trig view screw (I think allen-
key 1/16") is best taken loos at the switch.

On most 475s there is also a strap from the main board to the
vertical board which can easy be overlooked. It is close to the HV
section. You have to unsolder it as well. The same with the Delay
line which is normaly soldered to the vertial amp board.

Good luck.

Fred de Vries

Referring to my other post "tek 475 vertical position pots", I am now
required to dismount those pots. To do it (the one for channel 2 in
particular), I have to remove the vertical amplifiers board.
What I am afraid of is that it seems I have to desolder two resistors
having one lead on the borad and one on the VOLTS/DIV rotary switches.
Can I do it safely? Anything to be aware of?
Furtheremore, how can I safely dismount the BW/TRIG VIEW command
shaft from the switch it is linked to? Is it sufficient to unscrew
the tiny screws?
Thank a lot
ciao

I confirm: "the pots are Allen Bradly, and have a double section";
one section seems unused (not connected).
I confirm: they are "the ones which you can nicely open with four
screws".
So your tips are very very useful.
For the sake of completeness and want to say that I have already
tryed to turn them back and forth a lot of times but with almost no
result.
Furtheremore it is impossible to squirt any form of conctact cleaner
without opening them.
Thank you very much for your contribution, I'll keep the list updated
on my activity.
ciao



--- In TekScopes@y..., pe1fbo@h... wrote:

--- In TekScopes@y..., Emanuele Girlando <emanuele_girlando@y...>
wrote:

Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?
They are two sections pots, can I try to use the unused section?
Any source for them?
Thank a lot !
ciao

=====

Emanuele Girlando (IW1DHI)




__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.

Hi Emanuele,

Those pots are probable Allen Bradly, and and have a double

section.

There are two type of AB pots, The plastic sealed ones, and the

ones

which you can nicely open with four screws. To clean the pot, you
have to take it apart (first remove them carefully from the

Vertical

amp board). Once you have opened them you need to cut the plastic
seal inside the black plasic section to get to the brown whiper
section.

If you have everything apart, remove all the old grease and clean

all

sections with alcohol. Mind you that the whiper has a tiny carbon
pallet, which comes loose very easy.

Once this is done you need to re-apply new grease. I use for this
purpose lithium based grease from Dow Corning, Molycote DX. Other
types of grease I cannot recomend to use. This is probably the same
stuff that Bourns uses.

After this, everything has to be assembled again.

There is one small remark on this whole procedure, that is, if the
carbon conductive film is worn out, the result will probably
disapoint you.

I have personally used this procedure on a lot of AB pots. They are
the ones usuly having problems due to the aging of the grease. And
can be restored most of the time with a good result.


- Fred de Vries

--- In TekScopes@y..., Emanuele Girlando <emanuele_girlando@y...>
wrote:

Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?
They are two sections pots, can I try to use the unused section?
Any source for them?
Thank a lot !
ciao

=====

Emanuele Girlando (IW1DHI)




__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.

Hi Emanuele,

Those pots are probable Allen Bradly, and and have a double section.
There are two type of AB pots, The plastic sealed ones, and the ones
which you can nicely open with four screws. To clean the pot, you
have to take it apart (first remove them carefully from the Vertical
amp board). Once you have opened them you need to cut the plastic
seal inside the black plasic section to get to the brown whiper
section.

If you have everything apart, remove all the old grease and clean all
sections with alcohol. Mind you that the whiper has a tiny carbon
pallet, which comes loose very easy.

Once this is done you need to re-apply new grease. I use for this
purpose lithium based grease from Dow Corning, Molycote DX. Other
types of grease I cannot recomend to use. This is probably the same
stuff that Bourns uses.

After this, everything has to be assembled again.

There is one small remark on this whole procedure, that is, if the
carbon conductive film is worn out, the result will probably
disapoint you.

I have personally used this procedure on a lot of AB pots. They are
the ones usuly having problems due to the aging of the grease. And
can be restored most of the time with a good result.


- Fred de Vries

At 3:56 PM -0800 2001/3/24, Emanuele Girlando wrote:

Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?

Surely any owner of "classic" equipment should have a can of good contact cleaner always at hand!!! :-) Perhaps even WD40 would work??? If the pot is just supplying a DC voltage, I guess you could always hang a big capacitor on the wiper!? Have you tried simply rotating the pot back and forth a few dozen times? This often helps, at least a bit.

-----------------------------------------------------------------
Michael Dunn | Surround Sound Decoder & Stereo Enhancer
Cantares | Self-Amplified Speakers, Test Equipment
74 George St. | Ambisonic Surround Sound CDs and Recording
Waterloo, Ont. | (519) 744-9395 (fax: 744-7129)
N2J 1K7 | mdunn@...
Canada |
-----------------------------------------------------------------

Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?
They are two sections pots, can I try to use the unused section?
Any source for them?
Thank a lot !
ciao

=====

Emanuele Girlando (IW1DHI)




__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.

Michael,

I visited the site for you but unfortunately the 564 is not on that site
(also the one I was looking for the type 468 was not there)
Several others were.

kind regards,
Andre Roest

Michael,

I could download all the pdf files in holland.
Perhaps I can help you by sending you what is put there.
Can you give me a number you are looking for.

Kind regards,
Andre Roest

replacing the GaAs diodes with Schottkys sounds extremly
interesting. Could you write which type of Schottky diodes you
used? I think a lot of (potential) sampling plugin repairers
would appreciate this information, at least I would.

Thanks a lot,
Laurent Lamesch

Giving you part numbers would not be too useful, since the 1S1
still has the offset problems I mentioned.

maybe due to a unmatched set?


I got a couple of

different types through Digikey. If you want to experiment, I

expect

it's best to look for low-capacitance parts, say, 1-2pF. I'll get
back to the 1S1 when I have time. It *is* a weird circuit, and
difficult to troubleshoot, even with the manual!

I have tried a hp HSMS28xx (I don't remember the number but i can
have
a look, its a bridge-connected 4-diodes in one SMD housing) and a
(matched set) hp 5082-2815 in a a 3S76 a time ago,
as i mentioned in the tektronix-forum(@reprise.com) last year.
The balance and offset is ok, i have not checked the risetime and
aberations, because it was only a test. (My original sampling diodes
are OK)
I have tried those diodes because i have studied some service manuals
from samplingbridges in (vector-) voltmeters by hp. The HSMS28xx was
used up to 2 GHz in a hp VV-plug in, the 5082-2815 was used to 1 GHz
in 8405 VV and 3406 Sampling Voltmeter.

Jorgen
dj0ud

Hi Nick,

There is a list of vendors of Tek manuals at our web site. Try this URL:



If none of those guys can help, there is always eBay . . .

Stan
w7ni@...

nick weyland wrote: