I have a fully functional HP8920B and some time ago I bought a replacement lithium battery for the controller board which I have not installed.

Questions:

1). What exactly does this battery back up should it fail or should I change the battery and fail to maintain voltage? Anything critical?

2) Does the old battery ever leak?

3) Is the battery voltage tested in any of the self check routines?

I asked the same question a while ago, but the thread took a quick turn to the 8920b with pcmcia cards.? 8920b cards can be programmed by
plugging them into adapters or laptops that have that connector.? You will have to cobble up an interface of your own for the 8920a Epson
cards that were formatted DOS or a lot more trouble to do it in LIF format.? I was able to put an Epson card DOS formatted in the 8920a
and transfer via serial port with a modem terminal program.? A manual about programming the 8920 family in HPbasic gives a lot of info about
ASCII transfers.? It describes equipment and the LIF file format that are not easy to obtain anymore so you must learn a lot of old tech and the
hard way of doing things, then somehow translate with newer equipment.? It makes no mention of binary file transfers.

As far as I could tell, the RFTOOLS in the files section are for the 8920a or b in DOS file format, and some of those are ASCII.? The text can be
uploaded into HPbasic screen then written to a card in the 8920a slot or formatted memory in the 8920a and saved.? I have not tried it yet
with RFTOOLS so I can't tell you if you may have to generate other files for each program in order to use them, but it does work for other programs..?

After looking at them in more detail, i didn't find RFTOOLS to be any more useful (to me) than other software that is available that will run on a
PC anyway.? My original goal was to back up various saved screens to a PC folder and be able to restore them at will via serial port, but it seems
they get saved in LIF.? It seemed that there are several theories of translating files and the file system to DOS, but I wasn't keen on testing my 8920 by possibly
forcing gibberish into it and bricking a great machine.
Good luck.

Hello everyone, my name is Enrico and I am a happy owner of an HP8920A. I have read that some of you have managed to use the RFTOOL SW on this machine. I wanted to know? how they had managed to transfer it and with which methods. I have the USB/GPIB 8235B cable HP8920a and PC WIN7 pcs communicate but i don't know how to write the files to be transferred to HP8920A. I also have SDRAM but i don't know how to program them either.
Greetings Enrico

Hi Wallace,

Thanks for your message and suggestion.

It's a very interesting blog and I've checked the listing but sadly he doesn't list the parts or modules I need. I have sourced some from a supplier in Poland and am awaiting their delivery.

Regards,

Frank.

Hi Bill,

Thank you for your suggestion.

I'll have a look as it might be a useful device to have anyway.

The diodes are in pairs in 2 x 4-pin SMD packages so should be closely matched I would have thought. There is a graph on the data-sheet showing the spread of Vf at different forward currents and for the bias of 40mA the spread is 2mV. Whether they are selected on-test for specific values I don't know, but I don't have that capability so will have to suck-it-and-see. They are low-noise Shottky barrier diodes configured as far as I can see in a forward-biased bridge arrangement to detect the RF waveform in + and - half cycles with additional diodes to compensate for the volt-drop. The voltages are summed by op-amps so the detector works at very low levels of input power as the diodes are already conducting.

I've got replacements ordered from a source in Poland which should arrive in the next few days, so I'll give an update once I've installed them.

73,

Frank.

I do not know your HP part number
But this fellow has a lot of real HP and Tek parts and is priced very reasonably
I did buy a couple unobtanium low leakage diodes from him. Just Recently.They were real and worked just fine.
He lists by HP part number. You could also e mail him from the EEVBLOG site.

https://www.eevblog.com/forum/buysellwanted/fs-new-test-equipment-repair-parts-hp-agilent-tektronix-fluke-etc/

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Hi Frank,

Just a suggestion on this quest.

I just bought a Cheap Chinese Transistor tester that does ESR and Resistor, Capacitors and Diodes off Ebay.

When testing a diode, it gives extra information like forward volts drop. I was thinking this would be handy for matching diodes and other devices. Your need may be to match some diodes that are not an exact match for you job.

?I am not familiar with HSMS-2015, but if it is in a bridge configuration, then if they are matched and, I.E., Silicon, Hot Carrier or the like, It may not matter that they are Not HSMS.

Enjoy the journey.

Bill M??? (VK6IC ... It has just changed)

Update 2nd Dec.

Further investigation has revealed the +10V rail is supplied from the Aux +12V rail not the main +12V, so I've changed the feed and now getting +/-10V on pins 23 and 24 of J7 correctly.

Checking the voltages around the op-amps and diodes appears to show CR101A is not conducting and reading 6.2V across it whereas all the others show about 2.6V (Correction: 0.62V) which according to the device data-sheet is about correct for the 40mA bias current passing through the diodes. Next job is to locate a pair of replacement HSMS-2015's, remove the devices from the board and replace both with new ones. I will replace both as I feel sure they will be matched for best balance of the bridge, thereby attempting to keep to spec as best I can.

I'll update this post as and when I have any more developments.

Hello All,

It's my first posting on here, although I've used other of the groups.io forums and find they are great.

I've got an 8924C which had been working fine, then one day when I turned it on recently, the alarm sounded with the message "Input Power exceeded - Reduce input level" or similar. It has always been used with 30db of external input attenuation and only a few watts from an FT-290R so I know it hasn't been overdriven. On selecting the analogue TX test screen, the TX power shows around 20W with no input, so that is what's triggering the alarm. The fault seems to have appeared after a local thunderstorm although no external inputs were connected at the time.

Anyway, Robert G8RPI from whom I purchased it a year or so ago kindly gave me some pointers as to where to look, but no luck so far with identifying the fault.
On his suggestion, I made up a breakout board for the 15-way plug into the input module to check all the supply voltages and they all appear OK.

Boot-up self test passes OK, but if I run the RFDiagnostics3 routine with the Duplex Out and Ant In sockets joined with a jumper lead per the test screen message, the alarm is silenced and the test halts and fails as no power is detected. Upon exit of the test routine, everything works fine except the RF power still shows between 12 and 20W depending on the selected RF frequency. The indicated power seems to reduce linearly from 19+ W at 1Gig down to about 12W at 50MHz. Also, selecting between the RF In/Out and Ant In as the source input confirms the issue to be only associated with the RF In/Out as the Ant In shows --- with no input applied.

I've now removed the Input Module for internal inspection and tests. I managed to get hold of a couple of 8922 Input Modules for spares and test-beds to experiment on before "going live" on the real module. Again on Roberts suggestion, I've started looking around the RF Peak / Detector Switched Gain Amp area as this seems the most likely cause of the problem. This area is powered from the +/-12 supplies via +/- 10V regulators in the module, so I've carefully applied the +/-12V rails to check the 6.2V reference supply to the detector op-amps which seems to be 6.0V - probably within spec. and the balance ref. to chassis 0V is correct at +/- 3.0V so is symmetrical.

As the output from detector op-amp U3B pin 7 seems to drive the switched gain amp section, my understanding of op-amps suggests the voltage in the absence of any input signal it should be 0V. However it's -2.3V. This suggests something is unbalancing what appears to be a "Bridge" arrangement of the op-amps, so further tests are required.

Has anyone here had any experience with this type of fault or fault-finding in this section of the module or can offer any guidance please?

I'm determined to get this beast going as it's a brilliant bit of kit which helps heat the shack and also stops it getting blown away in strong winds!

Many thanks,

Frank G0CFD.

you have to have Option 4 which is the signalling feature ...you can buy the board and add it without too much hassle ....there is firmware on the board which may need to match the unit you are plugging into but I would just give it a shot if you are adding the board.

If you have that look in the HP 8920 Application Guide for instructions

Is there a way to get the 8920 to send dtmf tones?

I just fixed my second power supply replacing that cap.? All the files with pictures and procedures are in the files section.??

Pat

Thanks to all for your help. Looked up the suggested file, and that was the problem. Replaced the cap and everything is back in operation.

Mike, WA9FDO

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?There was a document floating around ...should be in the files section ...on repairing the 8924 power supply.

basically a thousand screws later there is a small cap on the daughter board inside the supply.that usually fails.

This is the standby supply ( green LED) that is on all the time?

Normally everything else is fine.

There was a document floating around ...should be in the files section ...on repairing the 8924 power supply.

basically a thousand screws later there is a small cap on the daughter board inside the supply.that usually fails.

This is the standby supply ( green LED) that is on all the time?

Normally everything else is fine.

Rick at Amtronix (do a Google search) has helped me in the past with this issue. I highly recommend him and I am not associated with him or his busines. Just another happy customer.

Greetings all,
It looks like the power supply in my 8924C has died. The green light does not even come on. The fuse is ok. Any ideas? Is there anyone out there repairing them as I cannot find any info on the supply. Any help is greatly appreciated. Thanks,

Mike, WA9FDO

Yes, it's so easy to forget that there is a GFI.? I had the same thing happen with mine.?

Apparently, the GFI may trip when the unit is first plugged in or immediately when the power switch is turned on. It thus mimics the symptoms of an 8924C that has suffered the familiar failure of the capacitor(s) on the small board in the power supply. One has to remember that there is something simpler to check first on the 8935.

In my case, since I have another functional service monitor, I deferred repair of the 8935 for many months.?? After acquiring a Hakko desoldering gun, I was ready to tackle recapping the power supply.? I rediscovered the the GFI while removing the covers to make a list of capacitors to order.? After resetting it, all the unit needed was a new set of AA memory batteries.

I'll remember next time!

KE6CD