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Greetings;

I am trying to understand the failure mode of one of these in a 3A6.
Both cathode tabs are melted and the 47^ screen resistor is smoked.
With great trepidation, I replaced the defective tube after checking
the asssociated 6DJ8s, xistors, and diodes. The replacement held and
the screen resistor stayed cool. However, there is a DC imbalance on
both traces that the controls won't comp. I suspected possible
filament-cathode leakage in the otherwise fresh looking dead tube. No
way to check for that now. I definitely don't want to risk a
presently good 8233/E55L. Any ideas on the probable failure mode?
Thanx in advance; Steve

P.S., Hi Stan, nice to find you again. Great Resource!

At 01:11 AM 5/31/2001 +0000, morriso2002@... wrote:

--- In TekScopes@y..., "Phil (VA3UX)" <phil@v...> wrote:

Finding a non-blank plug-in for a 555 is tough enough,

The 555 will take quite a wide range of vertical plugins including the
53/54 series, the letter series and the 1- series. With some of them
(such as the 1A4) you have to be careful that the timebase plugins
have been appropriately modified to remove DC bias from one of the
pins which could otherwise damage the plugin (I have details if anyone
needs them).

Sorry Morris. It was the 21A/22A timebase plug-ins I was referring to in my comment, rather than the vertical plug-ins.

Timebase plugins however are not so easy to find - in fact if anyone
has a spare 21A/22A combo for disposal I would be happy to give them a
good home here in Melbourne Australia :-)

I *might* be coming into some of these shortly. If I do I'll let you know.

Phil

Morris



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--- In TekScopes@y..., "Phil (VA3UX)" <phil@v...> wrote:

Finding a non-blank plug-in for a 555 is tough enough,

The 555 will take quite a wide range of vertical plugins including the
53/54 series, the letter series and the 1- series. With some of them
(such as the 1A4) you have to be careful that the timebase plugins
have been appropriately modified to remove DC bias from one of the
pins which could otherwise damage the plugin (I have details if anyone
needs them).

Timebase plugins however are not so easy to find - in fact if anyone
has a spare 21A/22A combo for disposal I would be happy to give them a
good home here in Melbourne Australia :-)

Morris

At 11:12 AM 5/30/2001 +1000, Andrew Campbell wrote:

Hi All,

Could anyone tell me where I could find a "blank" vertical plug-in module
for a Tek 555 series scope?

Apparently there was a kit available at one time.

Finding a non-blank plug-in for a 555 is tough enough, let alone a blank one. I've never seen one Andrew but I'll keep my eyes open during flea market hunts. Stan G. and Deane Kidd are the only other potential sources I can think of at the moment.

Phil

Regards,

Andrew





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Hi All,

Does anyone know of a company or business that may be able to supply boards
for the Tektronix TDS model oscilloscope. They could be boards that have
been pulled from non-repairable instruments.

Tektronix has recently removed from their "Long Term Support Program" a
variety of early model TDS oscilloscopes.

In particular I am interested in obtaining TDS540 Acquisition Boards and
TDS540 Processor Boards. I have recently tried Verizon (GTE) and they won't
part with boards, they want me to send in the instrument for them to survey.

Not a good option from Sydney, Australia.

Best Regards,

Andrew

--- In TekScopes@y..., "Andrew Campbell" <service@c...> wrote:

Could anyone tell me where I could find a "blank" vertical plug-in

module

for a Tek 555 series scope?

Apparently there was a kit available at one time.

I would be surprised if a kit is still around. When I wanted to build
a custom plugin I butchered an old type 80. The dimensions are the
same and the plug just has to be reversed. I'm sure there are plenty
of junker plugins around at hamfests etc.

morris

Hi All,

Could anyone tell me where I could find a "blank" vertical plug-in module
for a Tek 555 series scope?

Apparently there was a kit available at one time.

Regards,

Andrew

need help on repairing the time sweep for tek 321a-everything else
works.

thanks,
sid

does anyone know how i can get a hold a tek 2221 tek
service manual.

thanks,
sid

The 1L20 manual is available for rental from W.J. Ford:

Hi Andrew,

You are right about the 1L20 being used in the 555. It can also be used in any
other 530/540/550 mainframe.

There are a lot of places to look for manuals if your request here does not
turn one up for you. You might try eBay. Another possibility is to take a
look at the list of manual suppliers on my web page at:



Stan
w7ni@...

Andrew Campbell wrote:

Thank you Dean. As soon as my manual arrives I will
look into this. I thought the fan was maybe a 12vdc
fan.

Richg




--- dhuster@... wrote:

Rich, the 465, 465B, 475, 475A, 464, 466 and 468 had
identical fan
modules. And by the way, this has nothing to do
with bearing noise,
but if you have a fan that has a dead spot and won't
always start up
and you don't know whether to blame the motor or the
driver chip,
just put the motor on the dead spot and then pull
the driver chip and
reinstall it "backwards". It has a symmetrical
pinout, and if one of
the transistors in the driver chip is bad, you'll
have moved it to a
different spot in the switching sequence, the motor
will no longer be
on a dead spot with the reversed chip and will
probably start up when
power is applied. If the dead spot is still in the
same place, then
you can blame the motor.

And Rich, the 475 has had several reliability mods
over it's life,
and if you have a lower serial number, it may need
some of them.
The -8v P/S should have a new rectifier that's much
larger than the
others (i.e., it's NOT a 152-0488-00) and will be
laying down rather
than standing up in order to clear the case.

There's also a bluish 1% resistor (with the scope
upside-down as you
look on the main board with the front panel facing
you, it's along
the left edge maybe 2 or 3 inches from the front)
that overheats,
turns brownish and changes value, goofing up the
timebases. If
there's a black resistor in that spot, the mod has
already been
made. Otherwise, it needs replaced with a
higher-power resistor.

And the one mod that may concern you most is down
near the hole where
the horizontal deflection plate leads go down to the
jug. An
unmodified scope has a silver-colored, axial-lead,
tantalum, 1000?F
capacitor just to the front of the hole. If it's
there, get rid of
it, for it's underrated in voltage and will cause a
jittering
problem. A modified scope usually has a
physically-larger, black
aluminum electrolytic with a higher voltage rating
installed in it's
place.

Dean

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Hi,

I am looking for a manual for a Tektronix 1L20 Spectrum Analyzer plug-in. I
believe it is used with the 555 Scope?

Regards,

Andrew

Rich, the 465, 465B, 475, 475A, 464, 466 and 468 had identical fan
modules. And by the way, this has nothing to do with bearing noise,
but if you have a fan that has a dead spot and won't always start up
and you don't know whether to blame the motor or the driver chip,
just put the motor on the dead spot and then pull the driver chip and
reinstall it "backwards". It has a symmetrical pinout, and if one of
the transistors in the driver chip is bad, you'll have moved it to a
different spot in the switching sequence, the motor will no longer be
on a dead spot with the reversed chip and will probably start up when
power is applied. If the dead spot is still in the same place, then
you can blame the motor.

And Rich, the 475 has had several reliability mods over it's life,
and if you have a lower serial number, it may need some of them.
The -8v P/S should have a new rectifier that's much larger than the
others (i.e., it's NOT a 152-0488-00) and will be laying down rather
than standing up in order to clear the case.

There's also a bluish 1% resistor (with the scope upside-down as you
look on the main board with the front panel facing you, it's along
the left edge maybe 2 or 3 inches from the front) that overheats,
turns brownish and changes value, goofing up the timebases. If
there's a black resistor in that spot, the mod has already been
made. Otherwise, it needs replaced with a higher-power resistor.

And the one mod that may concern you most is down near the hole where
the horizontal deflection plate leads go down to the jug. An
unmodified scope has a silver-colored, axial-lead, tantalum, 1000?F
capacitor just to the front of the hole. If it's there, get rid of
it, for it's underrated in voltage and will cause a jittering
problem. A modified scope usually has a physically-larger, black
aluminum electrolytic with a higher voltage rating installed in it's
place.

Dean

I recently picked up a 475 that has intermittent horizontal jitter and
a noisy fan. Does anyone have any ideas about the jitter? The fan
looks like it could be a challenge to replace. I am shopping around
for a manual and I have had the case open to clean around the hv area,
though it was very clean inside. Thank you.

Richg

Hey, its perfectly OK to disagree with me, but in this case, you are also
disagreeing with Tektronix since it is in the Tek microfiche where I read
about the power supply problem. Yes, I suspect Tek probably assumes power
hungry plugins will be used along with the 7A16P. There probably will be no
overload with only two plugins installed in a 4 hole mainframe, for example.

I did not know about the front panel lockout since I have never tried to power
up my 7A16P in a 7K mainframe. Interesting . . .

Stan
w7ni@...

dd@... wrote:

--- In TekScopes@y..., dd@a... wrote:

(Still.. it's fun to see the readout say, "500 pSec" on the -92s -
and realize it's even true within 3-5% !!

Most of them will give a solid trigger on a 1GHz signal - a tribute

to the

power of tunnel diodes.

... but the 7B92A SN B070000&up has no tunnel diodes anymore.


Jorgen
dj0ud

Hi,
Would the person that responded back to my message
concerning the communication options for the TEK 2230
please respond again. I can't seem to find your
message.
Thank you,
Vince

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I hate to disagree with Stan, but my experience with 7A16Ps is that if you
install them in a non-programmable mainframe, they power up OK, but the
front panel is locked out. From looking at the schematic, it appears
possible to force them to local mode, but I haven't tried that yet.

I didn't see any way to reduce the +5V loading, but in my experience, that
is not an issue. (Maybe if you put 2 of them in one mainframe along with
some other +5V hungry plugins?)

BTW, the 7A16P is used with the 7612D as well as the 7912s.

Thanks all, for your replies to my question...

Kind regards,
:)
Michael