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8640B - No Count

 

I've borrowed a 8640B which as far as high level output works well.

The problem is that the counter on both internal and external selection shows all zeros with three decimal points thrown in.

There seems to be a lot of knowledge out there and heaps of discussion but I did not see one on just "0"s without flashing. Has anyone experienced this before?

Dave
 

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Hello Dave,

?

I have the same problem. I found a self-proclaimed expert, but in the end he stopped communicating; his advice got me nowhere. The main thing I learned was that there have been many iterations of the counter, and a counter from one 8640B may not work at all in another, showing just the zeroes and decimal points you and I both get.

?

Please keep me in the loop if you find someone who can fix the counter module.

?

73 de Brian, VK2GCE

?

From: [email protected] [mailto:[email protected]] On Behalf Of Dave Ireland
Sent: Thursday, 10 February 2022 9:20 PM
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 8640B - No Count

?

I've borrowed a 8640B which as far as high level output works well.

The problem is that the counter on both internal and external selection shows all zeros with three decimal points thrown in.

There seems to be a lot of knowledge out there and heaps of discussion but I did not see one on just "0"s without flashing. Has anyone experienced this before?

Dave

 

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I will pull the covers off tomorrow and have a look. I downloaded a rough copy of the service manual.

Is there a way to workout which of the versions the counter is.

The device is not mine but I would love to get it working as I have soft spot for them having used it to tune diplexers in the early 70s and liked them then.

Dave
VK6ZIP



-------- Original message --------
From: Brian <brianclarke01@...>
Date: 10/2/22 19:18 (GMT+08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] 8640B - No Count

Hello Dave,

?

I have the same problem. I found a self-proclaimed expert, but in the end he stopped communicating; his advice got me nowhere. The main thing I learned was that there have been many iterations of the counter, and a counter from one 8640B may not work at all in another, showing just the zeroes and decimal points you and I both get.

?

Please keep me in the loop if you find someone who can fix the counter module.

?

73 de Brian, VK2GCE

?

From: [email protected] [mailto:[email protected]] On Behalf Of Dave Ireland
Sent: Thursday, 10 February 2022 9:20 PM
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 8640B - No Count

?

I've borrowed a 8640B which as far as high level output works well.

The problem is that the counter on both internal and external selection shows all zeros with three decimal points thrown in.

There seems to be a lot of knowledge out there and heaps of discussion but I did not see one on just "0"s without flashing. Has anyone experienced this before?

Dave

 

Hi

You first need the first five characters of the instruments serial number.? There are some 8640B's that were made in Scotland which at first look more like they used parts of a 8640A.? Fifth character of serial number is a U.

George G6HIG
 

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Brian

Hope yours is as easy to fix as my loaner unit.

Traced the internal and external count through the counter chain (was worried the ECL chips had failed but they are all good) up to the counters that drive the display and it was all good.

The time base that triggers the store of the count was not present and traced this back to the other board and though the 5MHz reference was working the time base was deadly quiet. Then I noticed an input into the gate around the reference oscillator that was labelled Int/Ext. There is a input on the back for ext time base option and the toggle switch next to the input was set to external.

Switched to internal, exercised the Int/Ext counter push button and all came good.

I was able to replicate the problem easily. If you power off the machine set the time base input switch on the back panel to external and then turn it on you get the following display every time.

?

Turning it back to internal reactivates the count.

If yours is not the switch in the wrong place but you get the display with the decimal points have a look at the time base reference and check U6B output is 5Mhz out.

Dave



On 10/02/2022 8:12 pm, Dave Ireland wrote:

I will pull the covers off tomorrow and have a look. I downloaded a rough copy of the service manual.

Is there a way to workout which of the versions the counter is.

The device is not mine but I would love to get it working as I have soft spot for them having used it to tune diplexers in the early 70s and liked them then.

Dave
VK6ZIP



-------- Original message --------
From: Brian <brianclarke01@...>
Date: 10/2/22 19:18 (GMT+08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] 8640B - No Count

Hello Dave,

?

I have the same problem. I found a self-proclaimed expert, but in the end he stopped communicating; his advice got me nowhere. The main thing I learned was that there have been many iterations of the counter, and a counter from one 8640B may not work at all in another, showing just the zeroes and decimal points you and I both get.

?

Please keep me in the loop if you find someone who can fix the counter module.

?

73 de Brian, VK2GCE

?

From: [email protected] [mailto:[email protected]] On Behalf Of Dave Ireland
Sent: Thursday, 10 February 2022 9:20 PM
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] 8640B - No Count

?

I've borrowed a 8640B which as far as high level output works well.

The problem is that the counter on both internal and external selection shows all zeros with three decimal points thrown in.

There seems to be a lot of knowledge out there and heaps of discussion but I did not see one on just "0"s without flashing. Has anyone experienced this before?

Dave


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