I was incredibly fortunate to come across an original HP mic on eBay a little over a year ago. ?I spotted it in a listing from a trusted seller of Motorola parts that I had bought from before¡ price was $5! Took a few fractions of a second to decide to hit the buy button¡.
Before I found the mic I had trouble finding any mention of it in the HP manuals let alone find a part number for it, but I knew they existed because I¡¯d seen one at a HP demo I went to for my work many years ago, now I found one.
The mic has been a lot of fun, it lets me turn my HP8920A into a low power transceiver. ?I set it for duplex mode with the tone encoder enabled and can bring up local 2m and 70cm repeaters when connected to my external antenna on the roof.
With little to no info on the mic specs, I opened up the back and it¡¯s very simple inside, just the mic element and ptt switch. ?Cable has 3 conductors and a shield braid. Two wires for the ptt switch, one wire (yellow) and shield braid to the mic element. See the attached photos. ?I took a fluke DMM and measured the mic resistance, it¡¯s 315 ohms.
Let me know if you would like me to check on any further details on the mic.
73,?
Dave - WR6Z
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On Mar 3, 2022, at 9:12 PM, wa6oxn@... wrote:
Anyone come up with a suitable replacement or modification for a mic to use with the 8920A?
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any high impedance microphone wired into the correct circular connector ...believe there are posts on the correct 8 pin DIN part number
they are available from the typical online parts sources but not all that cheap.
same connector that was used on later IFR's ( COM-120 vintage )
The factory version was small enough to fit in the front lid but pretty rare ...only saw one or two over the time I have worked on the 892X
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Re: HP 8920A Options 002 and 102
the original SA module only had 10db and 1db scales
The later 102 version had 1, 2 and 10 db scales and later versions added adjacent power measurement capability
believe there were other updates but those are the major ones I recall
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Anyone come up with a suitable replacement or modification for a mic to use with the 8920A ?
Thanks,
-Steve WA6OXN
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Re: HP 8920A Options 002 and 102
The 102 is a later hardware design of the spectrum analyser module. Slightly better performance, but basically the same.
Interestingly the SA module from a 8922x will fit in a 8920x. It throws a configuration error on boot but if you ignore that it seems to work. The modules are basically the same but these use a configurable / programmable IC (Motorola IIRC in a PLCC package) for which there is no available data even though it has a non HP part number. It is used in a number of the other modules.
Robert G8RPI.
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HP 8920A Options 002 and 102
Are options 002 and 102 the same thing? Spectrum Analyzer + Tracking Generator?
What, if any, are the differences and why the (2) Options #'s ?
Thanks,
-Steve / WA6OXN
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Re: Send out HP8921A or try to repair myself
Thanks for the advice.? I think I will send it to Amtronix.?
73
Jeff n1kdo
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Re: Send out HP8921A or try to repair myself
The RF I/O is the most difficult assembly? ?to repair in the 892X? series .? ?The other parts are easy to swap and usually not that bad to repair and often can be easily swapped with a used part ( which for the 892X series are plentiful )
There are some easy fixes like replacing the protection diodes? ( common part? actually used on a number of service monitors )on the BNC ports? but from there it can get challenging due to the complexity of the part and the components used.? Relay failures are my least favorite? due to the effort in getting the old one out .
The failure described may have started out as a simple port overload but it sounds like there were some underlying issues that did not show until the full RF diags were run .Looks like there may be multiple failures in that assembly.
Fairly typically scenario .? These units will often appear to run correctly but the diagnostics will fail or it will not pass verification/ calibration without repair.
The 8920 power supply should be re-capped proactively as well ....the PCB can be damaged if not caught in time.
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Re: Send out HP8921A or try to repair myself
I have worked with Rick @ Amtronix in the past and I am 150% satisfied with his work and service. I recommend him all the way if you do not want to tackle the repair yourself.
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I am not associated with him in any way I am just another happy customer.
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Peter
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Re: Send out HP8921A or try to repair myself
On Mon, Feb 21, 2022 at 08:00 PM, Bob Burns AK9R wrote:
I'd vote for Amtronix. Rick Bowman at Amtronix knows the 8920/8921/8924/8935 family very well and has many spare parts on-hand. The 8920B that I bought from him developed a problem, so I shipped it back to him. I think shipping with insurance was around $250. Rick diagnosed the problem, replaced a module, recalibrated the unit, and shipped it back to me for about $400.
I second Rick at Amtronics.? He repaired my 8921 twice over the last 5 years or so (for different problems) and also did a full factory cal on it. I was extremely pleased with his service and the quick turn around time!? If you haven't had the power supply caps changed, you should do it (not an easy job) or have it done before the electrolytics start leaking and damage the PWB. He is a pro at doing this. This will happen to all of the 8920/21/24 units after 20 plus years and it will happen without warning. I also had some "user error" that smoked the rx front end. He fixed that as well. I would NOT recommend you try this repair. It is a major mess to get it apart and then there is the issue of finding what's wrong down to the component level, and trying to find suitable replacement parts. He has a standard repair he does for this problem. Recal after this is a must!? best regards, Chuck Adams N5UN
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Re: Send out HP8921A or try to repair myself
I think i paid about $350 to auburn metrology.
Steve Flory W9KOP
"I like climbing towers because people look up to me"
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Re: HP 8935 Power Supply Capacitor List
Frederick, something like that is in the works based on Paul's recent successful recapping of a dead E8285A PS. _________________________________________________________________________________
On Tuesday, February 22, 2022, 01:20:07 AM EST, fwbray@... wrote:
Has anyone who has recently rebuilt the HP 8935 power supply compiled a
list of the capacitors?? Preferably with DigiKey or Mouser part numbers?
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HP 8935 Power Supply Capacitor List
Has anyone who has recently rebuilt the HP 8935 power supply compiled a list of the capacitors? Preferably with DigiKey or Mouser part numbers?
I need to rebuild mine and from pictures on the web it seems like there are 20+ on the top board and presumably more on other boards. It would be helpful to have the parts on hand before commencing the rebuild.
I may have asked this some months ago, but I am hopeful that perhaps someone has undertaken a rebuild in the interim.
Just for fun, I priced a used power supply from a commercial source and received a quote of around $800 including shipping! Makes sense to do it myself.
Thanks.
KE6CD
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Re: Send out HP8921A or try to repair myself
"If you have an HP 8920 unit in need of repair and calibration, we're your guys. With over 20 years experience and some 2000 repairs, we have the experience to repair any problem an 8920 might have, calibrate it, and provide full performance evaluation data on our automated system. Your unit will work just as it did when it left the factory.??
The cost for a calibration with full performance evaluation data is $450.00."
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Re: Send out HP8921A or try to repair myself
Steve how is their pricing compared to Amtronix for cal svcs?
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73,
Tim KB2MFS?
On Mon, Feb 21, 2022, 18:26 Steve Flory < sflory@...> wrote:
I use auburn metrology in bowling green ky? ?they do a good job on mine?
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Re: Send out HP8921A or try to repair myself
On 02/21/2022 2:30 PM, Jeff Otterson wrote: Some options are to ship to Amtronix I'd vote for Amtronix. Rick Bowman at Amtronix knows the 8920/8921/8924/8935 family very well and has many spare parts on-hand. The 8920B that I bought from him developed a problem, so I shipped it back to him. I think shipping with insurance was around $250. Rick diagnosed the problem, replaced a module, recalibrated the unit, and shipped it back to me for about $400. Bob...
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Re: Send out HP8921A or try to repair myself
If you don't think you are up to the task, it would be worth a call to Amtronix.
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73,
Tim KB2MFS
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Re: Send out HP8921A or try to repair myself
I use auburn metrology in bowling green ky? ?they do a good job on mine?
Steve Flory W9KOP
sflory@...
"I like climbing towers because people look up to me"
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Re: Send out HP8921A or try to repair myself
Depends entirely on the value you place on your time.
As the years pass more of those projects fail pass the test. Lol
Good luck!
Colin G4CWH. (8920 owner, living with its frailties.)
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Show quoted text
On 21 Feb 2022, at 19:48, Jeff Otterson via groups.io <otterson_nospam@...> wrote:
?My HP8921A is sick.
I believe there are problems with the input module.? The internal diagnostics tell me there are problems with the "antenna input detector" (it reads high when it should be zero), filter output detector (reads low), and auto-range attenuator (reads low on 20db
setting).
It also has the symptom of generating the RF overpower alert if even the smallest rubber duck antenna is attached to the antenna jack.
I have looked at the service manual and the "clips" for 8920, I believe the instruments are similar, I'd feel more comfortable if I knew the schematics matched the device...
I can repair stuff, but I am a little bit leery of taking this on.
Some options are to ship to Amtronix or carry locally to Trescal.? A new (used) one can be had for $3k-$4k.
I'm seeking advice and suggestions.
Thanks,
Jeff n1kdo
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Send out HP8921A or try to repair myself
My HP8921A is sick.
I believe there are problems with the input module.? The internal diagnostics tell me there are problems with the "antenna input detector" (it reads high when it should be zero), filter output detector (reads low), and auto-range attenuator (reads low on 20db setting).
It also has the symptom of generating the RF overpower alert if even the smallest rubber duck antenna is attached to the antenna jack.
I have looked at the service manual and the "clips" for 8920, I believe the instruments are similar, I'd feel more comfortable if I knew the schematics matched the device...
I can repair stuff, but I am a little bit leery of taking this on.
Some options are to ship to Amtronix or carry locally to Trescal.? A new (used) one can be had for $3k-$4k.
I'm seeking advice and suggestions.
Thanks,
Jeff n1kdo
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Jeff Otterson n1kdo