I have seen this problem before in the vertical direction where a load
resistor in the CRT vertical amplifier was open.

Be sure to check power supply voltages and that the deflection plates
are actually connected. Sometimes the leads loosen and fall off.

Since the trace unrolls when the position control is used indicating
that the sweep signal is not the problem, I would look after that
point on schematic 10. There are lots of DC levels shown on the
schematic which can be checked to narrow down the possibilities.

Some of the voltages are high so be cautious.

Thanks,
Tom

?

?

Looks like the chip can be obtained here:







I did not search further at the other "normal parts vendors" (Sphere, Talon,
etc.)... No particular association with SMC in a monetary way. I am however
a satisfied customer and I do chat with the owner from time to time.



Anyway, not 100% sure he has 155-0021-01 left nor how his price compares to
others out there. Personally I have done enough business with SMC that if he
has it I stop my search and purchase just based on my time being valuable
and results of enough price shopping I am satisfied.



Anyway, hopefully helpful. Sorry for rambling on so.

Rob



From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of chrismh_somenumber
Sent: Thursday, February 28, 2013 8:35 PM
To: TekScopes@...
Subject: [TekScopes] Re: WTB: Readout IC (155-0021-01), or entire readout
board





The readout board part # is 670-1900-XX. Looks like it was used in lots of
scopes, not just those I listed.

Thanks

--- In TekScopes@... <mailto:TekScopes%40yahoogroups.com> ,
"chrismh_somenumber" wrote:

By swapping in the above IC from another scope, I've determined that the

custom IC on my 7844 has died.

Would anyone happen to have one they would part with, or have an entire

working readout board from a 7844/7904A?

Thanks,
Chris

?

?

By swapping in the above IC from another scope, I've determined that the custom IC on my 7844 has died.

Would anyone happen to have one they would part with, or have an entire working readout board from a 7844/7904A?

Thanks,
Chris

Correction: in my early XF unit the charge line is soldered to the board.

Albert

--- The cable has a peltola connector at one end. I have another unit in

---
Albert

Correction: in my early XF unit the charge line is soldered to the board. Probably a peltola jack has been removed there. In my later XH unit the board and the line have SMA connectors.
Albert

--- The cable has a peltola connector at one end. I have another unit in which the cable is soldered to the board.
---
Albert

I think you are being overly concerned about your purchase not working.
These are rugged instruments and not likely to fail. The PV509 manual
is close enough to tell you everything you will need to know about
your purchase. But here is some additional information on the HAPG
that I kept from years ago.



From: "Craig Sawyers" <c.sawyers@>

Date: Tue May 4, 2004 2:25 pm

Subject: Wierd Pulse generator craig_sawyers



Hi Group



Well I took delivery of the strange "High Amplitude Pulse Generator".
This

is a TM500 style plug-in, and I bought it kind of out of curiosity,
since I

had seen nothing like it. It also has no identifying type number at
all -

so it was either a development unit, or an internal use only test
fixture -

hopefully one of the ex-Tek guys on the list will recognize it - I've
put

some pics on the yahoo gallery.



This is the only thing I've seen that uses the strange attenuator that
the

7A29 uses. This has a huge bandwidth - way above 1GHZ, and probably
*way*

above so that it doesn't cramp the 7A29's style. I suspect that the
7A29

has a 1.5GHz bandwidth, so the attenuator is possible approaching 5GHz.



It also has a rigid charge line inside, estimated at around 3m (10') long.

This line isn't secured at all, and is prevented from shorting to the
back

of the PCB with a layer of self-adhesive plastic film - very

Date on the PCB is copyright 1978, and component date codes indicate
late

1982 build.



The unit is basically a pre-trigger pulse generator that uses an
avalanche

transistor to give a fast rising pulse. The pre-trigger can be
adjusted with a front

panel control from 50-125ns early, so that a sampling time base gets
time to

crank itself into action.



Using a 7104/7A29 gives a measured 410ps rise, implying a rise time of
the

pulse gen itself is 240ps (because the 7104/7A29 has a measured rise
time of

330ps).



Preshoot is 2%, and overshoot is un-measurably small, the very
slightest

ripple on the pulse top. One of the cleanest rises I have ever seen.
Front

panel says rise time <=300ps. Pulse length as expected (from the
internal

charge line) is about 30ns and the rep rate is 110kHz. Amplitude can
be

adjusted from 250mV to 25V in switched steps, with a variable control too.



Pretrigger gives a 2.5V pulse 250ns long with a 1.4ns rise.



I'll try it out on a sampler (S4) later and get a better grip on the
pulse

rise and what the pre-trigger does on a 7T11. I always find triggering
a

7T11 from external sources a bit fiddly, not surprising when you read
the

manual in detail and see that each triggering mode has very different

frequency and amplitude characteristics.



This is a comparison between the "Unknown Unit" and a Type 111
pre-trigger

pulse generator:



111

===

Fixed output level of at least 10V, not precise

<500ps rise

Switchable polarity

2ns pulse length without external charge line

Rep rate variable from 10Hz to 100kHz

Pre-trigger 30-250ns early, 300ns duration, <5ns rise, +10V



The unknown one

===============

Switched and variable output level from 250mV to 25V

<300ps rise

Fixed polarity

30ns pulse length without external charge line

Fixed rep rate of 110kHz (probably 100kHz nominal)

Pre-trigger 50-125ns early (measured 30-130ns), 250ns duration, 1.4ns
rise,

+2.5V

From: TekScopes@... [mailto:TekScopes@...] On
Behalf Of iglesia_cristiana_arpas_eternas
Sent: Tuesday, February 26, 2013 3:26 PM



Here the link to this almost new pulsed generator, at first glance is
a transmission line pulser with 300ps ..but no model or number at all.
I just brought it with the hope work right...but a good service manual
will be very appreciated and gratefully.
Link to Pulse Gen.
<
232112
187?autorefresh=true&pt=LH_DefaultDomain_0&hash=item3a7e99ce3b&nma=tru
e&si=w
4%252BkkAkTYIq9sTkPYLC8H98HEpU%253D&orig_cvip=true&rt=nc&_trksid=p2047
675.l2
557>

Regards Gabriel.

_._,___

I think you are being overly concerned about your purchase not working.
These are rugged instruments and not likely to fail. The PV509 manual is
close enough to tell you everything you will need to know about your
purchase. But here is some additional information on the HAPG that I kept
from years ago.



From: "Craig Sawyers" <c.sawyers@>

Date: Tue May 4, 2004 2:25 pm

Subject: Wierd Pulse generator craig_sawyers



Hi Group



Well I took delivery of the strange "High Amplitude Pulse Generator". This

is a TM500 style plug-in, and I bought it kind of out of curiosity, since I

had seen nothing like it. It also has no identifying type number at all -

so it was either a development unit, or an internal use only test fixture -

hopefully one of the ex-Tek guys on the list will recognize it - I've put

some pics on the yahoo gallery.



This is the only thing I've seen that uses the strange attenuator that the

7A29 uses. This has a huge bandwidth - way above 1GHZ, and probably *way*

above so that it doesn't cramp the 7A29's style. I suspect that the 7A29

has a 1.5GHz bandwidth, so the attenuator is possible approaching 5GHz.



It also has a rigid charge line inside, estimated at around 3m (10') long.

This line isn't secured at all, and is prevented from shorting to the back

of the PCB with a layer of self-adhesive plastic film - very prototype-ish.

Date on the PCB is copyright 1978, and component date codes indicate late

1982 build.



The unit is basically a pre-trigger pulse generator that uses an avalanche

transistor to give a fast rising pulse. The pre-trigger can be adjusted with
a front

panel control from 50-125ns early, so that a sampling time base gets time to

crank itself into action.



Using a 7104/7A29 gives a measured 410ps rise, implying a rise time of the

pulse gen itself is 240ps (because the 7104/7A29 has a measured rise time of

330ps).



Preshoot is 2%, and overshoot is un-measurably small, the very slightest

ripple on the pulse top. One of the cleanest rises I have ever seen. Front

panel says rise time <=300ps. Pulse length as expected (from the internal

charge line) is about 30ns and the rep rate is 110kHz. Amplitude can be

adjusted from 250mV to 25V in switched steps, with a variable control too.



Pretrigger gives a 2.5V pulse 250ns long with a 1.4ns rise.



I'll try it out on a sampler (S4) later and get a better grip on the pulse

rise and what the pre-trigger does on a 7T11. I always find triggering a

7T11 from external sources a bit fiddly, not surprising when you read the

manual in detail and see that each triggering mode has very different

frequency and amplitude characteristics.



This is a comparison between the "Unknown Unit" and a Type 111 pre-trigger

pulse generator:



111

===

Fixed output level of at least 10V, not precise

<500ps rise

Switchable polarity

2ns pulse length without external charge line

Rep rate variable from 10Hz to 100kHz

Pre-trigger 30-250ns early, 300ns duration, <5ns rise, +10V



The unknown one

===============

Switched and variable output level from 250mV to 25V

<300ps rise

Fixed polarity

30ns pulse length without external charge line

Fixed rep rate of 110kHz (probably 100kHz nominal)

Pre-trigger 50-125ns early (measured 30-130ns), 250ns duration, 1.4ns rise,

+2.5V

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of iglesia_cristiana_arpas_eternas
Sent: Tuesday, February 26, 2013 3:26 PM



Here the link to this almost new pulsed generator, at first glance is a
transmission line pulser with 300ps ..but no model or number at all.
I just brought it with the hope work right...but a good service manual will
be very appreciated and gratefully.
Link to Pulse Gen.
<
187?autorefresh=true&pt=LH_DefaultDomain_0&hash=item3a7e99ce3b&nma=true&si=w
4%252BkkAkTYIq9sTkPYLC8H98HEpU%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2
557>

Regards Gabriel.

_._,___

?

Howdy folks,

? I have another cleaning question. ?I've got a bunch of type L and type CA (and other) 5-series plug ins and the variable attenuator pots have become "dirty". ?They are intermittent over much of their range, and usually not useful in the "cal" position.

? ?Is there any Tek-net wisdom particular to these pots I should follow in cleaning them? ?What is their failure mechanism?

? I have cleaned these with tuner cleaner or other freon based sprays in the past, and the effect is definitely not permanent as I find I have to clean them aga in (albeit a few years later). ?Is there any benefit to taking them out of the plug-ins, sonicating them in a cleaning bath and re-installing them? ?Anything I should avoid?

? Thanks again for the help.

? Dan