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Hi all

I have a faulty/dead HP 8648B. I purchased this generator in a none working state, which is normally not a problem for me as I have been repairing such equipment for well over fifty five years.

I was original told that the problem first manifested itself when the Lithium backup battery was changed, now when the unit is powered on all I get is the top row of the liquid crystal display producing a complete line of squares.

I have obtained from the Keysight web site the only information/manual that there appears to be available for the 8648B.

I have checked the power supply voltages, they are correct, I have also checked the voltages given on the power supply distribution drawing. Most are correct with the exception of pin 15 of the display connector J22, which should be +5v but is 4.35v. Also the voltages on the Amplitude RPG are not correct.

A quick look at the +5v supply with a scope would indicate that there was at least some activity on the mother/processor board.

Has anyone any experience with repairing 8648B's or actual component level circuit diagrams for it.

Worryingly the available information that I have appears to indicate that the available? diagnostics are GPIB based and will not run on any operating sysem latter the Windows95.

I may be forced to break this 8648B for spares, but, it is not in my nature to do so.

I hope that you do not mind me asking this off topic question, I ask it because the same individuals that have a component level knowledge of an 8648B may well know about a Time Electronics 9822 Multifunction AC/DC Calibrator.

Some time ago I acquired one of these at an amateur radio rally, at first it partially worked with the led's and displays coming to life, now if the unit is powered up all that happens is that some relays click. I would appear that there is now a fault on one of the +5v power supply's, I say one as there appears to be more than one. Is anyone able to help or have access to a manual/circuit drawings for it.

Kind regards

George G6HIG

Hi Don

Thank you for replying to me, it is much appreciated.

First I have never seen an extension card that would work with this generator, the three plug in modules use a 9 pin D for the power and two edge connectors either side of the 9 pin D as in the HP8920A test set.

I did search for a manual and found one on the keysight web site, it is almost useless as it gives no circuit diagrams and assumes that to only repair possible is a module change.

Unfortunately, this group does not allow attachments with the result that your clip of the manual has been removed. Also it may be that your email has been clipped down.

Could you be so kind as to point me to where you found a manual that provides circuit information.

Basically I came to the same conclusion as yourself in as much as the fault is around the uP. The power distribution drawing indicates that there should be two +5v supplies to the display, there is only one and the voltages around the RPG's are not correct, I am not at my workshop with the drawing at present as a result I am somewhat hampered in providing exact detail.

My fear is that in attempting to replace the Lithium battery the previous owner has do damage to the uP or the circuitry around it.

Your email finishes with the words "will cease to attempt operations." is this what you intended to do?

I really appreciate your help
73

George G6HIG



________________________________________
From: hp_agilent_equipment@... <hp_agilent_equipment@...> on behalf of dondoughty@... [hp_agilent_equipment] <hp_agilent_equipment@...>
Sent: 29 April 2017 17:52
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP 8648B and an off topic request.

George G6HIG,

Looks like a useful instrument,
I found several manuals searching "agilent 8648b manual."

Also, try looking at the uP and the memory circuits supported by the backup battery.

An extension card would be useful, some of the old HP Instruments had one stored in the card cage.

Are the keyboard and display being scanned by the uP?

The best place to check is the keyboard,
here is a clip from the manual, page 5a-5 (203):

"The front panel contains two RPGs (rotary pulse generators), the keyboard, and the
display.
The two RPGs, one for frequency and one for amplitude, are connected directly to the
controller on the A3 board. Each RPG receives power and ground from the controller. Each
RPG returns two out-of-phase pulsed lines when the knob is turned.
The keyboard is a matrix of keys as shown in Table 5-1. on page 5-6. The keyboard is
scanned by the controller. Scanning pulses are sent alternately to the keyboard rows and
are read back on the columns when a key is pressed. The controller determines which key
was pressed based on the row that was pulsed and the column that the signal was
returned on. The column lines are pulled-up through resistors and are pulsed low when a
key is pressed. The row output latches are open-collector, therefore, pulses can not be seen
until the circuit is completed by pressing a key. The keyboard connects directly to the
controller at A3J3.
The display is driven by the controller through data latches on the A3 assembly. The
display control lines are eight bi-directional data lines, an enable clock line, a read/write
line, and a data/instruction line. The other lines going to the display are the display +5 V
and ground. The enable clock line is high during every data interchange. The read/write
line is high for a read operation and low for a write operation. The data/instruction line is
high for a data operation and low for an instruction operation. The data/instruction line is
used only during write operations. Data refers to the character data while instruction
refers to commands, such as return or space. When interchanging data, the controller
polls the display for acknowledgment.
This means that if the display is disconnected the controller will cease to attempt operations."

Hi

Thank you for your reply, I still do have WinXP sp3 machines, however, the 82357B adapter is not easily available in the UK. The only ones listed on a famous action site are from China and vary in price from about $100 To almost $1000 and are they totally working clones?

I am pleased to know that it is possible to use WinXP.

73

George G6HIG


________________________________________
From: hp_agilent_equipment@... <hp_agilent_equipment@...> on behalf of Colby Burkett burkettc@... [hp_agilent_equipment] <hp_agilent_equipment@...>
Sent: 29 April 2017 18:36
To: hp_agilent_equipment@...
Subject: Re: [hp_agilent_equipment] Re: HP 8648B and an off topic request.

I've successfully run the 8648 calibration and motherboard utilities on WinXP SP3 w/Agilent IO v16.x and 82357B USB GPIB adapter. No special hacks needed other than it only worked on a physical machine and not a VM. Though I didn't try the mobo util in a VM, just know that the Cal util failed to actually calibrate when run from a VM. Initial results were promising in a VM, but couldn't get all the completed.

On Apr 29, 2017 10:52 AM, "dondoughty@...<mailto:dondoughty@...> [hp_agilent_equipment]" <hp_agilent_equipment@...<mailto:hp_agilent_equipment@...>> wrote:



George G6HIG,

Looks like a useful instrument,
I found several manuals searching "agilent 8648b manual."

Also, try looking at the uP and the memory circuits supported by the backup battery.

An extension card would be useful, some of the old HP Instruments had one stored in the card cage.

Are the keyboard and display being scanned by the uP?

The best place to check is the keyboard,
here is a clip from the manual, page 5a-5 (203):

"The front panel contains two RPGs (rotary pulse generators), the keyboard, and the
display.
The two RPGs, one for frequency and one for amplitude, are connected directly to the
controller on the A3 board. Each RPG receives power and ground from the controller. Each
RPG returns two out-of-phase pulsed lines when the knob is turned.
The keyboard is a matrix of keys as shown in Table 5-1. on page 5-6. The keyboard is
scanned by the controller. Scanning pulses are sent alternately to the keyboard rows and
are read back on the columns when a key is pressed. The controller determines which key
was pressed based on the row that was pulsed and the column that the signal was
returned on. The column lines are pulled-up through resistors and are pulsed low when a
key is pressed. The row output latches are open-collector, therefore, pulses can not be seen
until the circuit is completed by pressing a key. The keyboard connects directly to the
controller at A3J3.
The display is driven by the controller through data latches on the A3 assembly. The
display control lines are eight bi-directional data lines, an enable clock line, a read/write
line, and a data/instruction line. The other lines going to the display are the display +5 V
and ground. The enable clock line is high during every data interchange. The read/write
line is high for a read operation and low for a write operation. The data/instruction line is
high for a data operation and low for an instruction operation. The data/instruction line is
used only during write operations. Data refers to the character data while instruction
refers to commands, such as return or space. When interchanging data, the controller
polls the display for acknowledgment.
This means that if the display is disconnected the controller will cease to attempt operations."

Hi Don

I now understand your email, having looked at the available HP manual, I will probe around the display connector and the RPG connector.

However I suspect that without component level information I will be unable to get very far. Every search comes back to the same document, HP part number 08648-90048 which as you are aware has no component level information.

Many thanks for your efforts

George G6HIG


________________________________________
From: hp_agilent_equipment@... <hp_agilent_equipment@...> on behalf of dondoughty@... [hp_agilent_equipment] <hp_agilent_equipment@...>
Sent: 29 April 2017 17:52
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP 8648B and an off topic request.

George G6HIG,

Looks like a useful instrument,
I found several manuals searching "agilent 8648b manual."

Also, try looking at the uP and the memory circuits supported by the backup battery.

An extension card would be useful, some of the old HP Instruments had one stored in the card cage.

Are the keyboard and display being scanned by the uP?

The best place to check is the keyboard,
here is a clip from the manual, page 5a-5 (203):

"The front panel contains two RPGs (rotary pulse generators), the keyboard, and the
display.
The two RPGs, one for frequency and one for amplitude, are connected directly to the
controller on the A3 board. Each RPG receives power and ground from the controller. Each
RPG returns two out-of-phase pulsed lines when the knob is turned.
The keyboard is a matrix of keys as shown in Table 5-1. on page 5-6. The keyboard is
scanned by the controller. Scanning pulses are sent alternately to the keyboard rows and
are read back on the columns when a key is pressed. The controller determines which key
was pressed based on the row that was pulsed and the column that the signal was
returned on. The column lines are pulled-up through resistors and are pulsed low when a
key is pressed. The row output latches are open-collector, therefore, pulses can not be seen
until the circuit is completed by pressing a key. The keyboard connects directly to the
controller at A3J3.
The display is driven by the controller through data latches on the A3 assembly. The
display control lines are eight bi-directional data lines, an enable clock line, a read/write
line, and a data/instruction line. The other lines going to the display are the display +5 V
and ground. The enable clock line is high during every data interchange. The read/write
line is high for a read operation and low for a write operation. The data/instruction line is
high for a data operation and low for an instruction operation. The data/instruction line is
used only during write operations. Data refers to the character data while instruction
refers to commands, such as return or space. When interchanging data, the controller
polls the display for acknowledgment.
This means that if the display is disconnected the controller will cease to attempt operations."

George,

Hi John

Thank you for your suggestion, however, the fault in the 8648B is not in the RF portion but in the uP display/control circuitry which is totally different between the 8920A and the 8648B.

I appreciate your input.

73

George G6HIG


________________________________________
From: hp_agilent_equipment@... <hp_agilent_equipment@...> on behalf of johngord@... [hp_agilent_equipment] <hp_agilent_equipment@...>
Sent: 29 April 2017 22:43
To: hp_agilent_equipment@...
Subject: Re: [hp_agilent_equipment] Re: HP 8648B and an off topic request.

George,

Some of the boards in the 8648 are very similar to those in the 8920. The Component Level Information Packet Manual Part Number: 08920-90107, has schematics. It is (or was) on Keysight.com.
--John Gord


---In hp_agilent_equipment@..., <g_einst@...> wrote :

Hi Don

I now understand your email, having looked at the available HP manual, I will probe around the display connector and the RPG connector.

However I suspect that without component level information I will be unable to get very far. Every search comes back to the same document, HP part number 08648-90048 which as you are aware has no component level information.

Many thanks for your efforts

George G6HIG

Hi George,

I hava a 8648B with the same symptoms, did you succeed in fixing it ?

?

Thanks

搁é尘颈