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Hi all,
I have this 8640b that got used, it shows voltage on the meter but does not have RF out. the frequency display works and tracks but the output does not trigger my 5328a counter.?
Were should I start first to troubleshoot ? im perplexed that can see voltage with no output.
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On 2/27/21 9:51 PM, Eliud Caraballo wrote: I have this 8640b that got used, it shows voltage on the meter but does not have RF out. the frequency display works and tracks but the output does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that can see voltage with no output. If I remember the 8640B's topology correctly, the detector that drives the level meter circuit is after the RF amplifier, but before the attenuator. The attenuator could have a problem (either fried by reverse power input, or contact problems), or the cable from the attenuator to the output bulkhead connector could have failed. Do you have some way of measuring approximate RF power, like an RF power meter, or a coaxial crystal detector? -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Thanks Dave, ?got rf power meter and a hp 410b vtvm. no coaxial crystal detector though.?
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On 2/27/21 10:40 PM, Eliud wrote: Thanks Dave, ?got rf power meter and a hp 410b vtvm. no coaxial crystal detector though. What sort of RF power meter do you have? -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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It is probably that the output level setting is done prior to the final output stages. Most likely the coarse step attenuator is causing the fault (perhaps a faulty step pad) or maybe a damaged hardline between the wide band amplifier - attenuator - output connector.
The meter pickup will be ahead of this, hence it shows a reading... A good visual inspection is suggested as a first step, then carefully disconnect the attenuator input and measure the signal where it leaves the rf box. A signal (or lack of) here will tell you where to look next.
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On 28 Feb 2021, at 02:51, Eliud Caraballo < carabe01@...> wrote: Hi all,
I have this 8640b that got used, it shows voltage on the meter but does not have RF out. the frequency display works and tracks but the output does not trigger my 5328a counter.?
Were should I start first to troubleshoot ? im perplexed that can see voltage with no output.
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your average ham radio wattmeter, an sw2000?
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? ?Eliud,
The lowest range on the sw2000 is 200 watts. At full output a good 8640B puts out +19 dbm, about 80 milliwatts. I don¡¯t think that¡¯s enough RF to even tickle the needle on the sw2000 meter. You need a wattmeter and sensor designed to measure test equipment levels, not amateur radio transmitter levels. Or an ac voltmeter like the 410 series, rated for the frequency range and RF levels of interest, with the appropriate ¡°T¡° connector and 50 ohm termination.?
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On Feb 28, 2021, at 5:55 AM, Eliud <carabe01@...> wrote:
?your average ham radio wattmeter, an sw2000?
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Hi Dave, I don't know how familiar you are with the 8640B. Is the RF output switch set to on?? In on the front panel right above the main output on the generator. Look there first. If you're not familiar with the gear, it's easily missed. On 27 Feb 2021 at 22:00, Dave McGuire wrote: On 2/27/21 9:51 PM, Eliud Caraballo wrote:
I have this 8640b that got used, it shows voltage on the meter but does
not have RF out. the frequency display works and tracks but the output
does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that can see
voltage with no output. If I remember the 8640B's topology correctly, the detector that
drives the level meter circuit is after the RF amplifier, but
before
the attenuator. The attenuator could have a problem (either fried
by
reverse power input, or contact problems), or the cable from the
attenuator to the output bulkhead connector could have failed.
Do you have some way of measuring approximate RF power, like an
RF
power meter, or a coaxial crystal detector?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV kim.herron@... 1-616-677-3706
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Eliud is the guy with the 8640B problem, not me.
I'm pretty familiar with them; I've had three and have used them a lot, and repaired them a few times.
Though, it has been years since I've powered one up...If memory serves, the output level meter does not indicate power when the RF output switch is set to off.
-Dave
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On 2/28/21 8:43 AM, kim.herron@... wrote: I don't know how familiar you are with the 8640B. Is the
RF output switch set to on?? In on the front panel right
above the main output on the generator. Look there first.
If you're not familiar with the gear, it's easily missed.
On 27 Feb 2021 at 22:00, Dave McGuire wrote:
On 2/27/21 9:51 PM, Eliud Caraballo wrote:
I have this 8640b that got used, it shows voltage on the meter but does
not have RF out. the frequency display works and tracks but the output
does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that can see
voltage with no output. If I remember the 8640B's topology correctly, the detector that
drives the level meter circuit is after the RF amplifier, but
before
the attenuator. The attenuator could have a problem (either fried
by
reverse power input, or contact problems), or the cable from the
attenuator to the output bulkhead connector could have failed.
Do you have some way of measuring approximate RF power, like an
RF
power meter, or a coaxial crystal detector?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV
kim.herron@...
1-616-677-3706
--
Dave McGuire, AK4HZ
New Kensington, PA
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On 2/28/21 6:55 AM, Eliud wrote: your average ham radio wattmeter, an sw2000 Ok...What Steve said about this is absolutely right. For future reference, there's a subtle distinction between, and terminological problems surrounding, RF power meters and "wattmeters". They both do essentially the same thing, but wattmeters (your SW-2000, the famous Bird model 43, etc) are intended for rather gross measurements of fairly high RF power, like the output from a transmitter or a power amplifier. These would typically be classified as "transmitter site" or "ham shack" instruments. In contrast, what we generally talk about in places like this as an "RF power meter" is an extremely sensitive device, typically calibrated in dBm, or dB referenced to 1 milliwatt. These would typically be characterized as "laboratory" or "test bench" instruments. An even bigger difference between the two is, unfortunately for your case, the number of digits in the price tag. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Sorry Dave!! Got confused before the third cup of coffee!! On 28 Feb 2021 at 12:19, Dave McGuire wrote:
Eliud is the guy with the 8640B problem, not me.
I'm pretty familiar with them; I've had three and have used them
a
lot, and repaired them a few times.
Though, it has been years since I've powered one up...If memory
serves, the output level meter does not indicate power when the RF
output switch is set to off.
-Dave
On 2/28/21 8:43 AM, kim.herron@... wrote:
I don't know how familiar you are with the 8640B. Is the
RF output switch set to on?? In on the front panel right
above the main output on the generator. Look there first.
If you're not familiar with the gear, it's easily missed.
On 27 Feb 2021 at 22:00, Dave McGuire wrote:
On 2/27/21 9:51 PM, Eliud Caraballo wrote:
I have this 8640b that got used, it shows voltage on the meter but
does
not have RF out. the frequency display works and tracks but
the
output
does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that
can
see
voltage with no output. If I remember the 8640B's topology correctly, the detector
that
drives the level meter circuit is after the RF amplifier, but
before
the attenuator. The attenuator could have a problem (either
fried
by
reverse power input, or contact problems), or the cable from
the
attenuator to the output bulkhead connector could have failed.
Do you have some way of measuring approximate RF power, like
an
RF
power meter, or a coaxial crystal detector?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV
kim.herron@...
1-616-677-3706
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV kim.herron@... 1-616-677-3706
|
No worries, I just wanted to straighten that out.
-Dave
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On 2/28/21 12:39 PM, kim.herron@... wrote: Sorry Dave!!
Got confused before the third cup of coffee!!
On 28 Feb 2021 at 12:19, Dave McGuire wrote:
Eliud is the guy with the 8640B problem, not me.
I'm pretty familiar with them; I've had three and have used them
a
lot, and repaired them a few times.
Though, it has been years since I've powered one up...If memory
serves, the output level meter does not indicate power when the RF
output switch is set to off.
-Dave
On 2/28/21 8:43 AM, kim.herron@... wrote:
I don't know how familiar you are with the 8640B. Is the
RF output switch set to on?? In on the front panel right
above the main output on the generator. Look there first.
If you're not familiar with the gear, it's easily missed.
On 27 Feb 2021 at 22:00, Dave McGuire wrote:
On 2/27/21 9:51 PM, Eliud Caraballo wrote:
I have this 8640b that got used, it shows voltage on the meter but
does
not have RF out. the frequency display works and tracks but
the
output
does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that
can
see
voltage with no output. If I remember the 8640B's topology correctly, the detector
that
drives the level meter circuit is after the RF amplifier, but
before
the attenuator. The attenuator could have a problem (either
fried
by
reverse power input, or contact problems), or the cable from
the
attenuator to the output bulkhead connector could have failed.
Do you have some way of measuring approximate RF power, like
an
RF
power meter, or a coaxial crystal detector?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV
kim.herron@...
1-616-677-3706
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV
kim.herron@...
1-616-677-3706
--
Dave McGuire, AK4HZ
New Kensington, PA
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If I'm not mistaken, if the switch is not on, the meter doesn't work either.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "kim herron" <kim.herron@...>
To: [email protected]
Sent: Sunday, February 28, 2021 7:43:52 AM
Subject: Re: [HP-Agilent-Keysight-equipment] HP8640B no rf out
Hi Dave,
I don't know how familiar you are with the 8640B. Is the
RF output switch set to on?? In on the front panel right
above the main output on the generator. Look there first.
If you're not familiar with the gear, it's easily missed.
On 27 Feb 2021 at 22:00, Dave McGuire wrote:
On 2/27/21 9:51 PM, Eliud Caraballo wrote:
I have this 8640b that got used, it shows voltage on the meter but does
not have RF out. the frequency display works and tracks but the output
does not trigger my 5328a counter.
Were should I start first to troubleshoot ? im perplexed that can see
voltage with no output. If I remember the 8640B's topology correctly, the detector that
drives the level meter circuit is after the RF amplifier, but
before
the attenuator. The attenuator could have a problem (either fried
by
reverse power input, or contact problems), or the cable from the
attenuator to the output bulkhead connector could have failed.
Do you have some way of measuring approximate RF power, like an
RF
power meter, or a coaxial crystal detector?
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
Kim Herron W8ZV
kim.herron@...
1-616-677-3706
|
Thanks Steve- will try with the 410 if that dosnt work well then can get a used bontoon or other meter as It seems ill come handy.
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Bonjour Eliud: 8640B has an HP custom hybrid output RF amp that is easily fried by any applied RF.
If the gen was used in broadcast, or a lab with high power RF, it could be blown.
Highly suggest to get the op and the (enormous and fine) service manual PDFs at BAMA
The block and troubleshoot flow charts should reveal the culprit.
Finally there is an RF amp protection option, with a relay. Check the rear panel SN label for the options if any.
These are fine cavity oscillator generators and there is no modern replacement with as low a phase noise.
Enjoy,
Jon
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And, generally, the sensitivity to irreparable damage due to abuse also increases (kwadratically or so?) with price.
Another special case of Murphy's Law
Wilko
PA1WBU
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Corollary: An object's durability is inversely proportional to its cost.
Thanks,
Barry - N4BUQ
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----- Original Message ----- From: "Wilko Bulte" <wkb@...>
To: [email protected]
Sent: Sunday, February 28, 2021 2:43:50 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP8640B no rf out
And, generally, the sensitivity to irreparable damage due to abuse also
increases (kwadratically or so?) with price.
Another special case of Murphy's Law
Wilko
PA1WBU
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Thanks Jon,
previous owner gave me a nice original copy of the service manual and it has all the diagrams. Ill give it some time TLC and will report back.?
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It has options 1 and 2 but not 3 which may have helped. Posible it did suffer from accidentally TX from a transmitter- ive heard its quite common. Former owner said it was working ok until one day it stopped.?
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I transmitted into my 8657B and the protection circuitry activated.? After a reset, the output of the generator was down 20 dB from normal.? The problem was in the switches, two ICs, that switched the frequency doubler in and out.? After replacing those all was well again.
Bob
On Sunday, February 28, 2021, 01:16:40 PM PST, Eliud <carabe01@...> wrote:
It has options 1 and 2 but not 3 which may have helped. Posible it did suffer from accidentally TX from a transmitter- ive heard its quite common. Former owner said it was working ok until one day it stopped.?
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Dave McGuire
Froggie the Gremlin