开云体育

Hi,

I have a few too many DVM's in the workshop and am thinking about disposing of at least one of them.
Specifically I have a 34401A and 3478A. They appear to have similar features and measure the same values to within a fraction of 1% when tested side by side- although the 3478A does show uncalibrated when first powered up.

So the questions are - what are they worth and which one to keep ?

I'm in the UK so would not want to ship overseas.

I'm tending toward keeping the 34401A as it's newer and doesn't show uncalibrated !

Both are in excellent cosmetic condition.

Regards Tim

I was lucky and got a set of Pozi bits in the local Sears (#26493). Looks
like they are out of them now - they are quoting 13 to 15 days for store
pickup.

Orin.

Or roll your own...



:)

Happy New year, everyone!

--
Anders Gustafsson
Engineer, CNE6, ASE
Pedago, The Aaland Islands (N60 E20)
www.pedago.fi
phone +358 18 12060
mobile +358 40506 7099
fax +358 18 14060

Peter Gottlieb <hpnpilot@...> 2012-12-31 00:13 >>>

Haha, I guess not as it sold really quickly!

John-

If the picture is to be believed, then it appears that 5180-2720 is exactly the right design but about 10% too small.

5180-2720: 3/8 by 5/16

My part: 7/16 by 3/8

I am wondering if HP's photographic technique might be imperfect. Interesting that they use an inch ruler in their picture.

Looking up the whole attenuator on the parts website, this is what I find

5086-7815 exchange with 5086-6815 replaced by 85680-60228

5086-6815: obsolete/unavailable replaced by 85680-60228

85680-60228: obsolete/unavailable replaced by 5062-6643 --> there is actually one for sale on Ebay at $300

5062-6643: aka Replacement Kit 33321RC. obsolete/unavailable --> available on Ebay for $400


The website says that the equipment using 5180-2720 is 33321H, 8495B, 8405H, 8496B, 8672A, E2500B-508.

It does not actually list the 8594A/E that you mention.

Looking up the parts for the 33321H (attenuator assembly), it lists the 5180-2720 40 dB attenuator chip, but says that the 10 dB and 20 dB chips are "agilent trade restricted/ not orderable". Odd. Finding the specs for that attenuator assembly, it appears to be the same size as the 5086-7815.

I think that I will order the 5180-2720 and keep my fingers crossed.

Thanks!

Jim







At 11:22 PM 12/30/2012, you wrote:

Jim,

I think the same basic attenuator hybrids are used in the 8594(A-E) and similar frequency range spectrum analyzers. (Some higher bandwidth analyzers (22GHz) use a pair of 20dB pads to get the 40dB step.) The 40dB hybrid for the 8594E attenuator is Agilent part number 5180-2720, in stock at about $58.00. Go to parts.agilent.com to get a picture of the part (select the "view larger image" after looking up the part in find-by-part and clicking on the part number).
See if it looks like the same physical size.

--John Gord

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@...> wrote:

Vladan and the group -

Wow! That is one fancy piece of miniature mechanical manufacturing. Like a Swiss watch. Beautiful. Crazy. Amazing.

Unfortunately, the 40 dB attenuator is indeed open at one end. And it is nothing like a few simple resistors. It is a beautiful glass contraption about 5 mm by 10 mm with gold and resistive elements plated in a fancy pattern.

Any ideas how I can get a new one?

It is open on the input end. It would appear that someone set the SA for 40dB attenuation and then attached it to some high power source. Apparently, the perpetrator failed to read the manual where it explains (multiple times) that the input limit is 30 dBm AT ALL ATTENUATOR SETTINGS!

Actually, I am kind of surprised that this delicate device can even take 30 dBm. Maybe it really can't....

Thanks!

Jim





At 09:16 PM 12/30/2012, you wrote:

Hi Jim,

Do not unscrew the solenoids on the top, at least not for now. To see what's happening, you will have to open the lower part where the RF action is.

The two SMA connectors have hex-nuts. Remove them. There is thin name plate that you can now remove. It covers the whole area between the SMA connectors. It probably has a few glue spots on its other side, so carefully pry it off without bending the it. Now, you will see a bunch of socket cap screws. When you remove them, you will be able to carefully separate the parts and gain access to the attenuator pads and plungers. The rubber O-rings are on the tiny nylon plungers that are attached to the gold plated spring contacts. I think there are two rings on each plunger, one on the RF side and one on the solenoid side.

Vladan

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@> wrote:

Vladan-

I got the cover off without trouble. By testing I note that when the middle (40 dB) switch is triggered, the output turns off completely. As far as I can determine, the plunger is actuated correctly. Moving it manually also results in the loss of output. The other two switches (10 and 20 dB) work fine.

I suppose that either the switch contacts are failing or the 40 dB resistor is open. Apparently both switches and resistors are inside the two-piece machined steel block. All the RF path seems to be inside. It would appear that I need to get this apart, but I am not sure how to. There are quite a few screws attaching the solenoids to the steel block, but I am not seeing what is holding the steel block together.

This attenuator has a PC board with several chips on it. I have noticed before that HP seems to have adopted the philosophy that if 2 chips are good, then 20 must be better. It is a surprisingly complicated device.

Any advice??

Thanks!

Jim



At 08:45 PM 12/30/2012, you wrote:

Jim,

You will have to pull out the front panel. There are a few flat-head screws along the front frame (top and bottom, maybe even sides - don't remember any more). Once you remove them, the front panel pulls out of the front frame, though it still has a couple of umbilicals attached. From there, you will see how to get the attenuator out.

The most common failure has to do with the tiny rubber O-rings on the plungers. This is all delicate magnifier work. Do not succumb to the "magnetized housing" myth of repair. The attenuator depends on magnets for latching. It's just that when the O-ring fails and either splits or falls off, the mechanism shifts closer to the magnet and the force of magnetic attraction increases. At that point, the solenoid (which has nothing wrong with it) no longer can pull the parts away from the magnet (which also has nothing wrong with it). This is when some people decide that demagnetizing everything will fix things. If you have the patience, study the design, it's interesting. The goal was to use current only when switching a stage is required and then interrupt all current to the coils as soon as the task is accomplished.

You open the attenuator by removing one of the end caps and sliding the U-shaped steel cover off. It comes off relatively easily. Don't try to remove it by prying with screwdrivers.

There are two versions of the attenuators. The older ones are all electro-mechanical, the newer ones have a p.c. board with some ICs on them.

Good luck, they can be fixed, but the work requires some patience and you may have to order no O-rings from Agilent.

Vladan

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@> wrote:

All-

O.k., I have an 8568B with a bad attenuator (40dB and below are dead).

My big question is - how do you get access to the attenuator to take it apart and clean/repair? It seems to be really buried under a maze of stuff...

Thanks!

Jim



At 01:44 PM 12/27/2012, you wrote:

Thanks a lot of this.

I just managed to get a 8568B that attenuator has some problems with the 20dB step.

These instructions encourage me to open the attenuator and clean the pads with isopropyl alcohol. Now it works fine.

I didn't made a testped for it i just cold moved carefully the solenoids and checked with dg8saq vnwa the attenuator pads. I'm not sure is the solenoid stuck or is it actually a contact failure.

The instructions how to disaasemble the attenuator was very accurate and easy to follow.

BR, Jarmo

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

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

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

On Sun, 30 Dec 2012 15:46:26 -0800 (PST), "J. Forster"
<jfor@...> wrote:

The 7854 does take some learning, especially if you want to use the
keyboard functions.

That is sure the case.

BTW, a 7B53A is not the correct PI as a sweep. It is a sweep for something
like a 7603 or other 100 MHz mainframes.

The only problem with the 7B53A or other 100 MHz 7B5x timebases is
that the 7854 vertical delay line at 65ns is too short to show the
leading edge. The same restriction applies to the other 400 MHz and
faster mainframes. I am not sure about the 200 MHz mainframes which
have a 90ns delay line.

One might want to use the 7B53A for its delayed sweep, mixed sweep,
variable holdoff, or external amplifier in capability but in general
like you say, the 7B92A is a better choice.

The 7854 is a 400 MHz mainframe. The proper sweeps for the 7854 are the
7B80 & 7B85 or the 7B92A.

To use the digitizing functions properly, you need the 7B87.

The 7854 only requires the 7B87 for pretrigger and single shot
acquisitions. Full bandwidth equivalent time sampling acquisitions
work fine with any of the other timebases.

Jim,

I think the same basic attenuator hybrids are used in the 8594(A-E) and similar frequency range spectrum analyzers. (Some higher bandwidth analyzers (22GHz) use a pair of 20dB pads to get the 40dB step.) The 40dB hybrid for the 8594E attenuator is Agilent part number 5180-2720, in stock at about $58.00. Go to parts.agilent.com to get a picture of the part (select the "view larger image" after looking up the part in find-by-part and clicking on the part number).
See if it looks like the same physical size.

--John Gord

I know this has come up many times in the past so when I stumbled upon PoziDrive driver bits today in the HomeDepot I thought I would pass on the tip (Pardon the pun please).

There are two driver bit sets, a 29 piece, and a 30 piece, both are three dollars apiece. Between the two there are bits sized from PZ0 to PZ3, with some duplication. I thought that $6 wasn't a bad price to have all these in the tool box.

They are in private labeled assortments sold under the HD brand.

Bob

Vladan and the group -

Wow! That is one fancy piece of miniature mechanical manufacturing. Like a Swiss watch. Beautiful. Crazy. Amazing.

Unfortunately, the 40 dB attenuator is indeed open at one end. And it is nothing like a few simple resistors. It is a beautiful glass contraption about 5 mm by 10 mm with gold and resistive elements plated in a fancy pattern.

Any ideas how I can get a new one?

It is open on the input end. It would appear that someone set the SA for 40dB attenuation and then attached it to some high power source. Apparently, the perpetrator failed to read the manual where it explains (multiple times) that the input limit is 30 dBm AT ALL ATTENUATOR SETTINGS!

Actually, I am kind of surprised that this delicate device can even take 30 dBm. Maybe it really can't....

Thanks!

Jim





At 09:16 PM 12/30/2012, you wrote:

Hi Jim,

Do not unscrew the solenoids on the top, at least not for now. To see what's happening, you will have to open the lower part where the RF action is.

The two SMA connectors have hex-nuts. Remove them. There is thin name plate that you can now remove. It covers the whole area between the SMA connectors. It probably has a few glue spots on its other side, so carefully pry it off without bending the it. Now, you will see a bunch of socket cap screws. When you remove them, you will be able to carefully separate the parts and gain access to the attenuator pads and plungers. The rubber O-rings are on the tiny nylon plungers that are attached to the gold plated spring contacts. I think there are two rings on each plunger, one on the RF side and one on the solenoid side.

Vladan

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@...> wrote:

Vladan-

I got the cover off without trouble. By testing I note that when the middle (40 dB) switch is triggered, the output turns off completely. As far as I can determine, the plunger is actuated correctly. Moving it manually also results in the loss of output. The other two switches (10 and 20 dB) work fine.

I suppose that either the switch contacts are failing or the 40 dB resistor is open. Apparently both switches and resistors are inside the two-piece machined steel block. All the RF path seems to be inside. It would appear that I need to get this apart, but I am not sure how to. There are quite a few screws attaching the solenoids to the steel block, but I am not seeing what is holding the steel block together.

This attenuator has a PC board with several chips on it. I have noticed before that HP seems to have adopted the philosophy that if 2 chips are good, then 20 must be better. It is a surprisingly complicated device.

Any advice??

Thanks!

Jim



At 08:45 PM 12/30/2012, you wrote:

Jim,

You will have to pull out the front panel. There are a few flat-head screws along the front frame (top and bottom, maybe even sides - don't remember any more). Once you remove them, the front panel pulls out of the front frame, though it still has a couple of umbilicals attached. From there, you will see how to get the attenuator out.

The most common failure has to do with the tiny rubber O-rings on the plungers. This is all delicate magnifier work. Do not succumb to the "magnetized housing" myth of repair. The attenuator depends on magnets for latching. It's just that when the O-ring fails and either splits or falls off, the mechanism shifts closer to the magnet and the force of magnetic attraction increases. At that point, the solenoid (which has nothing wrong with it) no longer can pull the parts away from the magnet (which also has nothing wrong with it). This is when some people decide that demagnetizing everything will fix things. If you have the patience, study the design, it's interesting. The goal was to use current only when switching a stage is required and then interrupt all current to the coils as soon as the task is accomplished.

You open the attenuator by removing one of the end caps and sliding the U-shaped steel cover off. It comes off relatively easily. Don't try to remove it by prying with screwdrivers.

There are two versions of the attenuators. The older ones are all electro-mechanical, the newer ones have a p.c. board with some ICs on them.

Good luck, they can be fixed, but the work requires some patience and you may have to order no O-rings from Agilent.

Vladan

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@> wrote:

All-

O.k., I have an 8568B with a bad attenuator (40dB and below are dead).

My big question is - how do you get access to the attenuator to take it apart and clean/repair? It seems to be really buried under a maze of stuff...

Thanks!

Jim



At 01:44 PM 12/27/2012, you wrote:

Thanks a lot of this.

I just managed to get a 8568B that attenuator has some problems with the 20dB step.

These instructions encourage me to open the attenuator and clean the pads with isopropyl alcohol. Now it works fine.

I didn't made a testped for it i just cold moved carefully the solenoids and checked with dg8saq vnwa the attenuator pads. I'm not sure is the solenoid stuck or is it actually a contact failure.

The instructions how to disaasemble the attenuator was very accurate and easy to follow.

BR, Jarmo

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

Hi,
I am looking for a schematic, or service manual with schematic, for the
HP8648B.
My set is faulty with these error codes :

Opt 1E6. 100khz-2000Mhz. .

Faults are :
516 Config 2 restore failure
620 Comms failure -A6, A3, A7. Sometimes only A3 appears.
That is 620 Comms - A3.

After a while, display goes to normal mode. Freq, amplitude and amodulation
could be changed but no output.
Register could be accessed. And another error appears - could not write to
non volatile ram.

Note that a screw was found loose inside, so it could have shorted some
Ics.
Voltages were measured:
+5.22, +14.87, -14.87, +37.88. Wonder if 5.22 is too high?

Anyway to get a schematic, maybe some interfacing bus ICs are bad?
cslim

On Sun, 30 Dec 2012 20:10:34 -0800 (PST), "J. Forster"
<jfor@...> wrote:

On Sun, 30 Dec 2012 14:40:09 -0800 (PST), you wrote:

Yes.

The Tek DPO, based on the 7704 (or possibly the 7704A) was the first
AFAIK.

That would be the Tektronix 7D20 (as a combined timebase/dual channel
scope) which was intended to run at least in the 760x series.

No. The DPO uses an LSI-11 as a 'puter. I have one.

The 7D20 is much later. The DPO separated thye PI and display sections of
the scope with a digitizer unit, maybe the d7001.

10 MHz bandwidth for the 468, and about 70 Mhz bandwidth for the 7D20
(IIRC).

Are you sure about the 70 MHz on the 7D20. I doubt that it was that good
one shot.

The specifications say 70 MHz bandwidth and simultaneous sampling of
40 MS/sec on each channel. I have heard that the bandwidth could be
significantly higher on some units.

Hi Jim,

Do not unscrew the solenoids on the top, at least not for now. To see what's happening, you will have to open the lower part where the RF action is.

The two SMA connectors have hex-nuts. Remove them. There is thin name plate that you can now remove. It covers the whole area between the SMA connectors. It probably has a few glue spots on its other side, so carefully pry it off without bending the it. Now, you will see a bunch of socket cap screws. When you remove them, you will be able to carefully separate the parts and gain access to the attenuator pads and plungers. The rubber O-rings are on the tiny nylon plungers that are attached to the gold plated spring contacts. I think there are two rings on each plunger, one on the RF side and one on the solenoid side.

Vladan

On Sun, 30 Dec 2012 14:40:09 -0800 (PST), you wrote:

Yes.

The Tek DPO, based on the 7704 (or possibly the 7704A) was the first
AFAIK.

That would be the Tektronix 7D20 (as a combined timebase/dual channel
scope) which was intended to run at least in the 760x series.

No. The DPO uses an LSI-11 as a 'puter. I have one.

The 7D20 is much later. The DPO separated thye PI and display sections of
the scope with a digitizer unit, maybe the d7001.

10 MHz bandwidth for the 468, and about 70 Mhz bandwidth for the 7D20
(IIRC).

Are you sure about the 70 MHz on the 7D20. I doubt that it was that good
one shot.

There were also some Transient Data Digitizers that used specialized
double ended CRTs, I think.

That would be the 7912, IIRC, which used the 7B16P and 7B90P
programmable plugins as a minimum. Never had one, but it looks like
an interesting possibility to have.

There were actually several different ones.

-John

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

Harvey

Vladan-

I got the cover off without trouble. By testing I note that when the middle (40 dB) switch is triggered, the output turns off completely. As far as I can determine, the plunger is actuated correctly. Moving it manually also results in the loss of output. The other two switches (10 and 20 dB) work fine.

I suppose that either the switch contacts are failing or the 40 dB resistor is open. Apparently both switches and resistors are inside the two-piece machined steel block. All the RF path seems to be inside. It would appear that I need to get this apart, but I am not sure how to. There are quite a few screws attaching the solenoids to the steel block, but I am not seeing what is holding the steel block together.

This attenuator has a PC board with several chips on it. I have noticed before that HP seems to have adopted the philosophy that if 2 chips are good, then 20 must be better. It is a surprisingly complicated device.

Any advice??

Thanks!

Jim



At 08:45 PM 12/30/2012, you wrote:

Jim,

You will have to pull out the front panel. There are a few flat-head screws along the front frame (top and bottom, maybe even sides - don't remember any more). Once you remove them, the front panel pulls out of the front frame, though it still has a couple of umbilicals attached. From there, you will see how to get the attenuator out.

The most common failure has to do with the tiny rubber O-rings on the plungers. This is all delicate magnifier work. Do not succumb to the "magnetized housing" myth of repair. The attenuator depends on magnets for latching. It's just that when the O-ring fails and either splits or falls off, the mechanism shifts closer to the magnet and the force of magnetic attraction increases. At that point, the solenoid (which has nothing wrong with it) no longer can pull the parts away from the magnet (which also has nothing wrong with it). This is when some people decide that demagnetizing everything will fix things. If you have the patience, study the design, it's interesting. The goal was to use current only when switching a stage is required and then interrupt all current to the coils as soon as the task is accomplished.

You open the attenuator by removing one of the end caps and sliding the U-shaped steel cover off. It comes off relatively easily. Don't try to remove it by prying with screwdrivers.

There are two versions of the attenuators. The older ones are all electro-mechanical, the newer ones have a p.c. board with some ICs on them.

Good luck, they can be fixed, but the work requires some patience and you may have to order no O-rings from Agilent.

Vladan

--- In <mailto:hp_agilent_equipment%40yahoogroups.com>hp_agilent_equipment@..., Jim Schatzman <james.schatzman@...> wrote:

All-

O.k., I have an 8568B with a bad attenuator (40dB and below are dead).

My big question is - how do you get access to the attenuator to take it apart and clean/repair? It seems to be really buried under a maze of stuff...

Thanks!

Jim



At 01:44 PM 12/27/2012, you wrote:

Thanks a lot of this.

I just managed to get a 8568B that attenuator has some problems with the 20dB step.

These instructions encourage me to open the attenuator and clean the pads with isopropyl alcohol. Now it works fine.

I didn't made a testped for it i just cold moved carefully the solenoids and checked with dg8saq vnwa the attenuator pads. I'm not sure is the solenoid stuck or is it actually a contact failure.

The instructions how to disaasemble the attenuator was very accurate and easy to follow.

BR, Jarmo

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

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

Jim,

You will have to pull out the front panel. There are a few flat-head screws along the front frame (top and bottom, maybe even sides - don't remember any more). Once you remove them, the front panel pulls out of the front frame, though it still has a couple of umbilicals attached. From there, you will see how to get the attenuator out.

The most common failure has to do with the tiny rubber O-rings on the plungers. This is all delicate magnifier work. Do not succumb to the "magnetized housing" myth of repair. The attenuator depends on magnets for latching. It's just that when the O-ring fails and either splits or falls off, the mechanism shifts closer to the magnet and the force of magnetic attraction increases. At that point, the solenoid (which has nothing wrong with it) no longer can pull the parts away from the magnet (which also has nothing wrong with it). This is when some people decide that demagnetizing everything will fix things. If you have the patience, study the design, it's interesting. The goal was to use current only when switching a stage is required and then interrupt all current to the coils as soon as the task is accomplished.

You open the attenuator by removing one of the end caps and sliding the U-shaped steel cover off. It comes off relatively easily. Don't try to remove it by prying with screwdrivers.

There are two versions of the attenuators. The older ones are all electro-mechanical, the newer ones have a p.c. board with some ICs on them.

Good luck, they can be fixed, but the work requires some patience and you may have to order no O-rings from Agilent.

Vladan

All-

When all else fails, read the manual! The 8568B service manual says to remove the front panel. That is easy and the attenuator is then right in front of you. I was trying to get at it from the interior....

Jim



At 01:44 PM 12/27/2012, you wrote:

Thanks a lot of this.

I just managed to get a 8568B that attenuator has some problems with the 20dB step.

These instructions encourage me to open the attenuator and clean the pads with isopropyl alcohol. Now it works fine.

I didn't made a testped for it i just cold moved carefully the solenoids and checked with dg8saq vnwa the attenuator pads. I'm not sure is the solenoid stuck or is it actually a contact failure.

The instructions how to disaasemble the attenuator was very accurate and easy to follow.

BR, Jarmo

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

Hi Christian,

There is very little information available about the firmware revisions for the 8970B. Certainly, if you have a standard unit (1600 MHz high end), you will not want any version of the firmware that was made for the H1800 or 020 options. I am pretty sure the roms for the units with extended range had different part numbers.

I have recently looked at the manual change pages for the 8970B and I didn't see any obvious signs that the hardware changed so much as to require new firmware. But ... I don't know that for a fact. If you are concerned about firmware compatibility, your odds of success are higher if you choose a firmware version that is close to your meter's vintage than a very late date code. If I were in your situation, I would get a pair of spare roms and try the newer firmware to see what happens. Just don't erase the originals and you can always go back.

I think the text file that is included with the 8005 roms gives the full serial no. of the donor instrument. Compare the last four digits of that unit's SN with yours and you will know how far apart they were.

Vladan

I have a Phillips PM3375 out in the workshop, and I'm using an HP54601A in the radio shack to monitor transmitter RF; with accurate directional couplers, I can calibrate watt meters. Not far away, on a very heavy-duty turntable, sits a 141T with 8552B and 8554B plugins. I don't actually use that very much, mainly to check harmonics.

I was using a Leader 15 MHz analog scope with a cracked graticule (now at our radio club) which served almost as well,at least letting me know if the sound card output has reset itself to 100 percent again, but the digitizer lets me capture peaks and know what I have.

The 141T has an analog storage CRT, writing to a charged grid then flooding the CRT with electrons. It's finicky, and the display is perishable, so my "digital" storage is a digital camera on a tripod.
Couldn't afford Polaroid film now even if I had the camera.


Cortland
KA5S

On Sun, 30 Dec 2012 21:34:36 -0500, Harvey White
<madyn@...> wrote:

On Sun, 30 Dec 2012 19:57:46 -0600, you wrote:

On Sun, 30 Dec 2012 20:03:41 -0500, Harvey White
<madyn@...> wrote:

On Sun, 30 Dec 2012 14:40:09 -0800 (PST), you wrote:

Yes.

The Tek DPO, based on the 7704 (or possibly the 7704A) was the first AFAIK.

That would be the Tektronix 7D20 (as a combined timebase/dual channel
scope) which was intended to run at least in the 760x series.

I think he means the Tektronix P7001 which attaches to a 7704A between
the display and mainframe:

That's a new one on me.

The P7001 is not as common as the 7854 which is the same basic design.
I have seen one or two in the past couple of years for sale but would
prefer the 7854 if only because it is relatively common.

Then there was the magnificent 7854. IMO, this is the BEST lab 'scope
ever made. It is still my 'scope of choice.

and I'd like to have one, but that's still out there, somewhere.....

The downfall of both of these units was the relatively slow A/D by modern
standards.

10 MHz bandwidth for the 468, and about 70 Mhz bandwidth for the 7D20
(IIRC).

The 7D20 uses a CCD based sampler like the 2430 series of DSOs.

Yep, and they do mention that the CCD has absolutely no static
immunity.

Those CCD sampling DSOs occupy a weird place in history. Since
Tektronix had access to 100 MS/sec 8 bit ADCs like those used in the
2232, I am not sure why they used them for as long as they did. My
guess is that the CCDs were easier to interleave then the digital side
of the fast ADCs. The 2232 is limited to 50 MS/sec in chop mode
because of that.

All-

O.k., I have an 8568B with a bad attenuator (40dB and below are dead).

My big question is - how do you get access to the attenuator to take it apart and clean/repair? It seems to be really buried under a maze of stuff...

Thanks!

Jim