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Re: For Sale: E4402B and 8644B
Hi there, Mark.
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Can you provide eBay links to the auctions? Many thanks! dwayne At 07:32 PM 3/19/2019, Mark Bielman wrote: Hi Group. |
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Analysis of HP 3466A DC zero circuit
Can someone explain how the DC zero on the HP 3466A works? The manual with the full schematic is on the Keysight web-site:
The first thing to note is that the topology of the input amplifier is non-inverting on the 20 mV and 200 mV ranges, and is switched to inverting on the higher ranges. Figure 8-19 "Ohms Current Source and Input Amplifier Schematic", on page 8-31 of the manual, shows the essential parts of this circuitry. Here's a schematic excerpt showing the switching around the plus (+) input of the input amp: On the 20 mV and 200 mV ranges, Q105 is on and connects the DC input to the plus input of the amplifier. Presumably Q107 is off. On the higher ranges, Q105 is off and Q107 is on, thus connecting the plus input of the amplifier to circuit common. Now the puzzling bit is that the DC zero control, R134, applies an offset voltage to the drain of Q107. This makes sense for the ranges where the input amplifier is in its inverting configuration. However, the manual has you set the DC zero on the 20 mV scale. As I analyze it, that means that to the first approximation, Q105 is conducting and Q107 is not, so I don't see how the DC zero can affect the non-inverting configuration of the input amplifier on the 20 mV and 200 mV ranges. My analysis must be wrong, so I'd appreciate someone setting me straight. -- Steve Byan steve@... |
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Signal Generator Comparison Chart ?
Hi all,
I was wondering if there is a sig gen comparison chart somewhere. Googling around I only found a pdf from Keysight of their latest generators. Personally I'm in the market for something that goes to 26Ghz ( Id like to go higher but the $'s start to get crazy for a hobbyist!) and I've been looking at 8673's but they're not the only ones out there. Scanning ebay for kit, I keep bumping into HP model numbers I've not heard of before and then run down that rabbit hole investigating the model. It'd be nice if there was a definitive list of all HP/Agilent/Keysight sig gens to look at. Does such a thing exist ? thanks Tim de VK2XAX |
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Re: 8970b
kevin kearns
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Thanks John
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? ----- Original Message -----
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Re: Possible to repair HP 8120-2292 (part of HP 11853A accessory kit) coax cable?
On Mar 20, 2019, at 21:08, johncharlesgord via Groups.Io <johngord@...> wrote:
Or more simply, TDR it. Needs a pulser, a T connector, and a scope. Pulser and scope of course must be fast enough so you still can see something; for a 600 mm cable, round trip is on the order of 6 ns. Pulsers (square wave oscillators, actually) with fast enough rise time can be built from a 74AC14, a couple resistors, a capacitor, and a USB power supply cable. All this is documented in easy to find youtube videos. Gr¨¹?e, Carsten |
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Re: HP 8664A signal generator repairability
On Wed, Mar 20, 2019 at 04:52 AM, amirb wrote:
yes, it seems the SA is having an issue.?Yes, I'm quite certain now that the displayed problem above is due to the SA and not the 8664. I was able to flatten out the response shown in the upper band by (1) reducing the SA sweep time (to give things more time to settle and (2) playing with the preselector peak. The response still isn't perfect as far as absolute amplitude, but there's some adjustments that I can do to fix that. I also showed a picture of a much narrower sweep right around the area of that bad dip in the pic above. As you can see, it's about as flat as you like. With the flatness of the response seen from 10 kHz to 2.5 GHz, I seriously doubt that the final 500 MHz is as bad as that original photo showed. Honestly, after doing much testing yesterday looking at CW from the 8664 in narrow spans, I can't really find any faults with how it is functioning. I'd say I agree with the others above that it's worth keeping and repairing (and adjusting as needed). Sean |
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Re: Possible to repair HP 8120-2292 (part of HP 11853A accessory kit) coax cable?
Dave,
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You might want to measure the capacitance at each end to get an idea where the open is.? Then you can keep the good end intact while you attack the problem end. --John Gord On Wed, Mar 20, 2019 at 12:54 PM, David Feldman wrote: I have a HP 8120-2292 coax cable (24", N Male connectors) which is DC open on center conductor path, and no measurable RF continuity up to 3 GHz. No sign of damage, and it arrived in this condition so I have no prior history with it. I've not been able to ascertain where the open is (but am guessing at one or the other of the connectors.) |
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Possible to repair HP 8120-2292 (part of HP 11853A accessory kit) coax cable?
I have a HP 8120-2292 coax cable (24", N Male connectors) which is DC open on center conductor path, and no measurable RF continuity up to 3 GHz. No sign of damage, and it arrived in this condition so I have no prior history with it. I've not been able to ascertain where the open is (but am guessing at one or the other of the connectors.)
Is it possible to remove the N-type connectors for inspection and re-attachment (if so, any suggestions as to how)? I've tried pushing the plastic "boot" (cover over the coax/connector joint) backwards to expose more of the connector, but that hasn't been successful (perhaps boot glued in place?) As the cable is not useful in it's current condition, I thought of cutting away the boot at each end, but if there's a way to avoid this step, I'd like to learn of it. Thanks for any advice, Dave |
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Re: 8970b
Kevin,
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Yes.? Look at measurement mode 1.4 in the manual (08970-90022). The noise source operates at 144MHz while the 8970B looks at the 28MHz output. --John Gord On Wed, Mar 20, 2019 at 10:26 AM, kevin kearns wrote:
I have a rf converter (144MHz to 28 MHz) can I use the 8970b to measure it's noise figure, how do I do it if possible? |
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Re: HP 8664A signal generator repairability
yes, it seems the SA is having an issue.?
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you can center around those frequencies where the amplitude was way off with a small span and try to tune the preselector (peaking) on the SA and see how the amplitude is On Tue, Mar 19, 2019 at 06:33 PM, @0culus wrote:
On Tue, Mar 19, 2019 at 12:03 PM, @0culus wrote: |
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Re: HP 8664A signal generator repairability
Are you sure about these measurements and about the SA?
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If you look at 2.0-2.5GHz sections in pic #2 and pic #3 they look very different, why? what happens if you center at 2.05GHz which looks very bad in pic #2 with a small span like 1MHz or less? do you get any amplitude error (which usually means ALC is unlocked) anywhere? if the amplitude is that much off as I see in these pictures, the instrument must have? given amplitude error and the amplitude must be unleveled UNLESS there is a problem after the output amplifier in A7 (module 5). Which only means: connectors and rigid cables or the attenuator or the pulse modulator (option 008) if you have it or the RPP switch right at the end. if something is wrong in those parts, the ALC loop will not see that. In that case the output of A7 must be OK if you measure it directly at the SMA connector on top of that board one reason that I wanted the test at high amplitude like 13dBm was to eliminate all attenuator pads from the signal path On Tue, Mar 19, 2019 at 03:03 PM, @0culus wrote:
On Tue, Mar 19, 2019 at 05:00 AM, amirb wrote: |
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Re: HP5335A fan replacement
By the way, the original fan was 120 VAC, but repair note changed the fan to 24 VDC. This was precipitated by the power supply relay and socket overheating. The repair note had a description of a circuit mod using a diode and also replacing the fan and socket. I have done a few of these mods and this a fairly simple fix. Let me know if you need a copy of the change.
Joe, KN5U |
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Re: HP5335A fan replacement
Dan,
This is a great question. My experience is that the critical parts for cooling consideration are the input amplifier U3 and U4 (Schmitt amplifier). These are highly susceptible to shortened life due to heating. Of the 200+ units I have refurbished, interestingly, those that had underpowered fan replacements also had one or both Schmitt amplifier chips not working. So my suggestion is to replace the fan with one of the proper air flow. Especially considering that the Schmitt amplifiers are no longer available. Regards, Joe, KN5U |
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For Sale: E4402B and 8644B
Hi Group.
I've put two items up for sale on Ebay. Both are working "perfectly" and are in great condition. The 8644B is really nice! I'd love to keep it but it's SO big and heavy. But really is nice. I like the dual audio generator feature. Great for IM measurements on transmitters, amplifiers and such. Please let me know if you are interested. Not inexpensive as they cost a bit prior to repairing them. Cheers! Mark in Oregon |
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Re: HP5335A fan replacement
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On Mar 19, 2019, at 5:13 PM, Stephen Hanselman <kc4sw.io@...> wrote:
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Re: HP 8664A signal generator repairability
On Tue, Mar 19, 2019 at 12:03 PM, @0culus wrote:
Here's some pics at 0 dBm. I have to toddle off to take care of some other things, so I'll do higher amplitude later. I'm starting to think there might be something off in the 2-22GHz band of my 8566A, looking at the sweeps of different spans. I can't do a full 0-3 GHz due to the way the 8566 bands are laid out.I believe there might be an issue with the preselector in the upper band in the 8566A, so I'll need to look into it. It is very flat in the 0-2.5 band, so I'm inclined to think the signal generator is working fine. I'm testing narrowband CW in each synthesis band now to see if any spurs show up. Sean |
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Re: HP5335A fan replacement
¿ªÔÆÌåÓýGotta love HP, I can¡¯t find that in my manual.? Page number? Thanks steve ? From: [email protected] <[email protected]> On Behalf Of Steve - Home
Sent: Tuesday, March 19, 2019 2:53 PM To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP5335A fan replacement ? I have the same manual as you but I looked in y parts unit and it has the DC fan.? Steve ? ? ?
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Re: HP5335A fan replacement
¿ªÔÆÌåÓýI tried to post a reply to your blog but didn¡¯t want to start an account. ? On 29sep16 ¡°1980s_john¡± posted a picture of a small piece of metal that dropped out of his unit.? It is a spring for one of the front panel switches.? They drop out all the time and are easily put back in place ? steve ? ? From: [email protected] <[email protected]> On Behalf Of Orin Eman ? There was a change to a DC fan as well as a re-wiring of the relay and replacement of the relay and socket. ? See the service note attached to my post here: ? ? ? On Tue, Mar 19, 2019 at 2:02 PM Stephen Hanselman <kc4sw.io@...> wrote:
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Steve Byan
