Re: 8558B centre frequency wildly unstable above 1250MHz
Found that a new Bourns 10 turn pot is rather expensive so took the risk of injecting a little jungle juice into it. Now the 8558B is back to normal. I love simple faults.
Dick G4BBH
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--- In hp_agilent_equipment@..., "tcxo" <tcxoe@...> wrote:
Noisy / Intermittent / Bad tuning potentiometer?
-Greg
----- Original Message -----
From: ferrymanr
To: hp_agilent_equipment@...
Sent: Sunday, August 28, 2011 4:26 PM
Subject: [hp_agilent_equipment] 8558B centre frequency wildly unstable above 1250MHz
I have an 8558B which becomes totally unstable if the centre frequency is set above about 1250MHz at any span setting. If the span is sufficiently wide it is clear that the SA it is covering perfectly up to about 1550MHz or 1600MHz with some loss of sensitivitity at the top end. When the centre frequency is set above about 1250MHz the frequency display becomes random from blank up to some random number. This indicates to me that the control voltage is unstable above that frequency setting. The display looks like it is jumping all over the spectrum (have I discovered 'spread spectrum').
Any suggestions as to a likely cause or common problem before I delve into the murky depths.
Thanks
Dick G4BBH
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Re: 8558B centre frequency wildly unstable above 1250MHz
Bang on Greg. Slid the plug-in forward and measured the pot as it is very easy to access. Looks as if I will have to locate another. It looks like a standard Bourns 10 turn job but will consult the manual.
Dick G4BBH
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--- In hp_agilent_equipment@..., "tcxo" <tcxoe@...> wrote:
Noisy / Intermittent / Bad tuning potentiometer?
-Greg
----- Original Message -----
From: ferrymanr
To: hp_agilent_equipment@...
Sent: Sunday, August 28, 2011 4:26 PM
Subject: [hp_agilent_equipment] 8558B centre frequency wildly unstable above 1250MHz
I have an 8558B which becomes totally unstable if the centre frequency is set above about 1250MHz at any span setting. If the span is sufficiently wide it is clear that the SA it is covering perfectly up to about 1550MHz or 1600MHz with some loss of sensitivitity at the top end. When the centre frequency is set above about 1250MHz the frequency display becomes random from blank up to some random number. This indicates to me that the control voltage is unstable above that frequency setting. The display looks like it is jumping all over the spectrum (have I discovered 'spread spectrum').
Any suggestions as to a likely cause or common problem before I delve into the murky depths.
Thanks
Dick G4BBH
[Non-text portions of this message have been removed]
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Re: 8558B centre frequency wildly unstable above 1250MHz
Noisy / Intermittent / Bad tuning potentiometer?
-Greg
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----- Original Message -----
From: ferrymanr
To: hp_agilent_equipment@...
Sent: Sunday, August 28, 2011 4:26 PM
Subject: [hp_agilent_equipment] 8558B centre frequency wildly unstable above 1250MHz
I have an 8558B which becomes totally unstable if the centre frequency is set above about 1250MHz at any span setting. If the span is sufficiently wide it is clear that the SA it is covering perfectly up to about 1550MHz or 1600MHz with some loss of sensitivitity at the top end. When the centre frequency is set above about 1250MHz the frequency display becomes random from blank up to some random number. This indicates to me that the control voltage is unstable above that frequency setting. The display looks like it is jumping all over the spectrum (have I discovered 'spread spectrum').
Any suggestions as to a likely cause or common problem before I delve into the murky depths.
Thanks
Dick G4BBH
|
8558B centre frequency wildly unstable above 1250MHz
I have an 8558B which becomes totally unstable if the centre frequency is set above about 1250MHz at any span setting. If the span is sufficiently wide it is clear that the SA it is covering perfectly up to about 1550MHz or 1600MHz with some loss of sensitivitity at the top end. When the centre frequency is set above about 1250MHz the frequency display becomes random from blank up to some random number. This indicates to me that the control voltage is unstable above that frequency setting. The display looks like it is jumping all over the spectrum (have I discovered 'spread spectrum').
Any suggestions as to a likely cause or common problem before I delve into the murky depths.
Thanks
Dick G4BBH
|
Re: Want to buy: HP 3325A attenuator board
Hi Dickson,
Yes, my attenuator board has the Rev C part number as you surmised below. However the exposed circuit traces appear to be gold plated.
The serial number of my unit starts with 1748A13xxx, so I think that it was produced fairly early in that product's lifecycle.
Patrick Wong AK6C
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--- In hp_agilent_equipment@..., "Dickson" <dicksonfuhk@...> wrote:
I think Patrick's attenuator board is the newer "03325-66523 Rev C" which used the relay made by Aromat (Japan). I think Aromat is being merged with the Japanese giant Panasonic.
It seems to me "Rev C" is a cost down version because it is not longer having the gold plated PCB.
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Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
You might try Tanner Electronics in Dallas. Jimmy Tanner used to carry many of the old logic families, and he might still have some around. I think he still has a website, but you will have to phone or email for part info.
Dave
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On 8/28/2011 2:42 PM, mrcschrdrs wrote: According to the 436 manual, 1820-1361 is a Fairchild 9374DC.
From the schematic it looks like some BCD to 7 segment decoder. Quite a different beast then the 75491 which seems to be just 4 drivers.
Now where to get one - salvage one from an other 436?
Marc.
--- In hp_agilent_equipment@..., francesco messineo<francesco.messineo@...> wrote:
Hello,
On 8/28/11, m_elec_guy<mm777888@...> wrote:
Hi Group, I've got a HP436A with a defective LED display decoder IC
(A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine.
I can't seem to find a replacement or substitute. Does anyone know where
one can get a replacement? From the cross reference I have, it's reported as equivalent to
SN75491 display driver.
Best regards
Frank
------------------------------------
Yahoo! Groups Links
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Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
On 8/28/11, mrcschrdrs <mrcschrdrs@...> wrote:
According to the 436 manual, 1820-1361 is a Fairchild 9374DC.
From the schematic it looks like some BCD to 7 segment decoder.
ops, then the cross reference floating around on the internet isn't at all accurate. You can try the NTE8374 equivalent or try to adapt a CD4511 (which is BCD latch/decoder/driver, you'd need to make an adapter board I think). Best regards Frank
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Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
And again ... they are available "over there" !!
73, Dick, W1KSZ
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-----Original Message----- From: mrcschrdrs <mrcschrdrs@...>
Sent: Aug 28, 2011 12:42 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
According to the 436 manual, 1820-1361 is a Fairchild 9374DC.
From the schematic it looks like some BCD to 7 segment decoder.
Quite a different beast then the 75491 which seems to be just 4 drivers.
Now where to get one - salvage one from an other 436?
Marc.
--- In hp_agilent_equipment@..., francesco messineo <francesco.messineo@...> wrote:
Hello,
On 8/28/11, m_elec_guy <mm777888@...> wrote:
Hi Group, I've got a HP436A with a defective LED display decoder IC
(A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine.
I can't seem to find a replacement or substitute. Does anyone know where
one can get a replacement? From the cross reference I have, it's reported as equivalent to
SN75491 display driver.
Best regards
Frank
------------------------------------
Yahoo! Groups Links
|
Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
According to the 436 manual, 1820-1361 is a Fairchild 9374DC.
From the schematic it looks like some BCD to 7 segment decoder.
Quite a different beast then the 75491 which seems to be just 4 drivers.
Now where to get one - salvage one from an other 436?
Marc.
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Show quoted text
--- In hp_agilent_equipment@..., francesco messineo <francesco.messineo@...> wrote:
Hello,
On 8/28/11, m_elec_guy <mm777888@...> wrote:
Hi Group, I've got a HP436A with a defective LED display decoder IC
(A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine.
I can't seem to find a replacement or substitute. Does anyone know where
one can get a replacement? From the cross reference I have, it's reported as equivalent to
SN75491 display driver.
Best regards
Frank
|
Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
There are two listings for the SN75491 over on the "evil empire".
73, Dick, W1KSZ
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-----Original Message----- From: francesco messineo <francesco.messineo@...>
Sent: Aug 28, 2011 11:54 AM
To: hp_agilent_equipment@...
Subject: Re: [hp_agilent_equipment] HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
Hello,
On 8/28/11, m_elec_guy <mm777888@...> wrote:
Hi Group, I've got a HP436A with a defective LED display decoder IC
(A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine.
I can't seem to find a replacement or substitute. Does anyone know where
one can get a replacement? From the cross reference I have, it's reported as equivalent to
SN75491 display driver.
Best regards
Frank
------------------------------------
Yahoo! Groups Links
|
Re: HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
Hello, On 8/28/11, m_elec_guy <mm777888@...> wrote: Hi Group, I've got a HP436A with a defective LED display decoder IC
(A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine.
I can't seem to find a replacement or substitute. Does anyone know where
one can get a replacement? From the cross reference I have, it's reported as equivalent to SN75491 display driver. Best regards Frank
|
Re: HP 1725A oscilloscope, first displayed cycle is weird
On 08/28/2011 09:35 AM, honolulusnowwhite wrote: I know that the vertical output has adjustments for frequency response, but wouldn't those adjustments affect all displayed pulses, not just the first? Only if the pulses are all similar time scale. Not enough info to say. If the second pulse is after enough time that all has gone back to steady state quiet, no more current flowing, then the 2nd pulse should look just like the first, or suspect the scope and path between, not the generator. John
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I guess no one is interested in these, as I've gotten no offers. If I don't sell them here for a small price, later in the week I'm going to list them on ebay. They seem to fetch a rather ridiculous price there.
As for whether they work, as I said, I have no way to test these. However, they came from a shop that was in the habit of tagging defective equipment and putting it in a back room. These probes were not tagged and were in the shop area with the working equipment. Based on this and the fact that all the other equipment in the shop worked, I'd say that these probes are most likely OK.
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--- In hp_agilent_equipment@..., "mojoehand" <mojoehand@...> wrote:
I have two HP 54701A 2.5 GHz Active Probes in plastic cases. They look complete and almost new, but I have no way to test these. I'll sell these cheap, so make me an offer. Shipping within the US will be $10 extra for Priority Mail.
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For Sale: Agilent 34330A 30A Current Shunt
This is a new, unused current shunt with the following specs:
DC - 1 kHz +/- 0.3 %
1 kHz - 5 kHz +/- 5.0 %
15 amp: Continuous
30 amp: 15 minutes Max
Priced at $ 50 includes shipping within the U.S.
PayPal is accepted - please reply offline.
Steve
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For Sale: HP 85672A cards 1 and 2
I have a set of cards 1 and 2 (missing card 3 of 3) of
the HP 85672A Spurious Response Measurement Utility for use with the following spectrum analyzers:
8560A/E
8561A/B/E
8562A/B/E
8563A/E
8564E
8565E
Asking price $ 50 includes shipping within the U.S. - PayPal is OK.
Please reply offline - thanks.
Steve
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HP436A LED Display Driver IC - HP1820-1361 - 9374DC - Where to get?
Hi Group, I've got a HP436A with a defective LED display decoder IC (A1U1...U4 - all same type of chip). Only 1 IC is bad, the others are fine. I can't seem to find a replacement or substitute. Does anyone know where one can get a replacement?
|
Re: Looking for probe tips for an HP8405A Vector Voltmeter
If you solve this riddle, I would like to get some as well.
Joe
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-----Original Message-----
From: hp_agilent_equipment@...
[mailto:hp_agilent_equipment@...]On Behalf Of m_elec_guy
Sent: Sunday, August 28, 2011 12:08 PM
To: hp_agilent_equipment@...
Subject: [hp_agilent_equipment] Looking for probe tips for an HP8405A
Vector Voltmeter
Hi Group, I was wondering where I could get some probe tips for an HP8405A
Vector Voltmeter? I would like to 3 if possible. Any ideas?
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Looking for probe tips for an HP8405A Vector Voltmeter
Hi Group, I was wondering where I could get some probe tips for an HP8405A Vector Voltmeter? I would like to 3 if possible. Any ideas?
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HP 1725A oscilloscope, first displayed cycle is weird
Dear all,
I've continued to work on the 1725A and most recently replaced 32 capacitors (mostly tantalum, one electrolytic and one tubular ceramic that looked weird) on the three boards for main and delayed sweep, and the vertical preamp board. The sweep triggering works quite well now.
The scope has one remaining glitch: using my HP 3325A as a signal source, when a square wave signal is displayed with a frequency of around 7 MHz or more, the top of the first pulse is irregular (with slightly wavy ups and downs in the signal) compared to the following pulses. Similarly, when a sine wave is displayed, the first pulse looks slightly irregular compared to the others.
When I press the 20 MHz bandwidth button, the signal clears up. Of course the square wave then looks more curved, more like a sine than a square.
Is this indicative of a fault in the vertical section or the horizontal sweep?
I know that the vertical output has adjustments for frequency response, but wouldn't those adjustments affect all displayed pulses, not just the first?
Thanks for your comments.
Patrick Wong AK6C
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Re: Want to buy: HP 3325A attenuator board
Hi Dickson,
The Omron low signal relay that I used to replace the original Aromat relay in the div by 100 position has a manufacturer PN of G6AK-274P-ST-US-DC12 and at Mouser Electronics is priced at $5.43 plus shipping.
The new relay is rectangular. I positioned it to minimize the lead length from the relay to the PCB holes that lead to the input RCA jack and to the next relay.
I suggest you measure the resistance between the positive voltage wiring harness connectors (pins 1 and 2) and ground. If you do not measure this to be rising to infinity as the capacitors charge up, then you'll know that at least one of the 14 0.1 uF 50V capacitors is bad.
A 51 ohm resistor (R1) on the board was missing so I replaced that with a 51 ohm 1W Xicon carbon film resistor. The board has a copper layer serving as a ground plane, and that is a very good heatsink so my 25W soldering pencil did not produce sufficient heat to properly solder the end of the resistor connected to ground. I had to get out my 100W soldering gun to solder that one connection.
Using my oscilloscope to monitor RF voltage output and switching between the various functions, I have noticed that *occasionally* the voltage is less than it should be, for example, 2V p-p instead of 3V p-p. I don't think this is a relay problem since the voltage difference is too small to be caused by a relay.
Good luck and 73.
Patrick Wong AK6C
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--- In hp_agilent_equipment@..., "Dickson" <dicksonfuhk@...> wrote:
Hi all,
My 3325A has the attenuator board marked as "03325-66523 Rev B" which uses 4 yellow "PRINTACT" Latching Relay (12 BW4LD).
I think Patrick's attenuator board is the newer "03325-66523 Rev C" which used the relay made by Aromat (Japan). I think Aromat is being merged with the Japanese giant Panasonic.
It seems to me "Rev C" is a cost down version because it is not longer having the gold plated PCB.
Regards,
Dickson Fu
VR2WHF
P.S. Really wanted to know the model number of the Omron relay used to replace the original Amron relay.
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