Re: HP8920 displaying over 1.5 MW!!!
Hi, the problem is on the control board of the input module. We had several do that and just replaced the board.
Rick
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Re: HP8920 displaying over 1.5 MW!!!
I have never seen that issue but I suspect the usual? parts going bad ...input detection diodes and op amps.
It would be good to verify the power detect output as the power in scales ...I would bypass the input attenuator to test so you can use some reasonable power levels.
Just adjust the config and the RF off with +14db? assuming a standard? 60W power input.
Who knows it may be the DVM board ...you could verify the +-5 volt references first just for something easy.
You could also inject a DC level at the power detect and sweep that? to see if that board and scaling correctly
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HP8920 displaying over 1.5 MW!!!
?Hi all...
This is a weird one...? ?I have been servicing HP8920's / 8922's for years for a radio shop but this one is above all...? ? ?HP8920, option 011...
When connected to a 25W or less transmitter, the rf power display is excellent (particularly for a test set of this age!), but as soon as I use a radio above 25-30 watts, the display goes completely out of this world.
?
Power levels of about 1500000 watts, 92 dBm, or 9000 rf volts!!!? All scales seem to correlate with each other but with an incomprehensible +47 dB offset!!!!? Suddenly, when RF drive rises from 25 watts to 30 watts, no glitch, no warning, from 30 to 1500000 watts!
?
?Outside of that offset, everything else is ok. Rock solid OCXO, generate levels, audio... Only this rf power offset!!!?
In [BLUE] [CONFIG], all rf offsets are at 0 dB.
?
?Has anyone ever seen such a behavior?
?
?One thing sure: HP engineers had real fun designing a radio comm test set able to display over 1 megawatt!!!!
?
?73 de Normand VE2UM
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Re: 8924C video out using a GBS-8200 to vga questions
Skip,
Thanks for your followup post.? The picture did not attain the quality that could have been achieved.
A few of the new members are close to posting correctly on Groups.io, but not getting it quite right.
I'll be in contact with you in a few minutes by email about how to both email pics and upload pics to?HP8920/8935 Family.
Hank _______________________________________
On Sunday, January 14, 2024 at 06:14:50 PM EST, Skip wrote:
Yes, valid point,? image attached (I hope).? It looks a LOT worse "in real life".?
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Re: 8924C video out using a GBS-8200 to vga questions
Yes, valid point,? image attached (I hope).? It looks a LOT worse "in real life".?
Additionally I had it on while doing other things and it eventually turned completely white.? I guess I need to add those 50k?
mentioned here.
While researching all things gbs8200 I came across? the "GBS control" project so now I'm interested in that!
https://ramapcsx2.github.io/gbs-control/Wiki/
73's Skip WB6YMH
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Re: 8924C video out using a GBS-8200 to vga questions
Skip and the whole gang,
?I guess?I can't say this enough:? Pictures!
Help potential responders (like A.S., but he's not the only one) be able to help you.
Hank ________________________________________________________
On Sunday, January 14, 2024 at 05:26:38 PM EST, Skip wrote:
Hi Alexandre, I followed your guild and it kind of works, but my display is nowhere near as sharp as yours. I can't get my display centered vertically and there's lots of garbage below the image and floating around the screen.?
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Re: 8924C video out using a GBS-8200 to vga questions
Hi Alexandre,
I followed your build and it kind of works, but my display is nowhere near as sharp as yours. I can't get my display centered vertically and there's lots of garbage below the image and floating around the screen.?
I've screwed around with the settings *A LOT* and I think the "clamp st" and "Clamp sp" values might be the answer.? Can you share you settings from the Geometry menu?
My monitor is a Viewsonic 10725 which has a native resolution of 1280 x 1024.? I've used it successfully with dozens of other computers @ 640 x 480 as well as other resolutions and it always looks great.
I've tried all of the available resolutions in the display menu and I can't say another are better than the others.
I have an 8924c, not an E8285A, perhaps they aren't the same?
73's Skip WB6YMH
I've tried
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Re: 8924C POWER SUPPLY DEAD
Hi Dean, I would check R3 that goes open a lot. It's a 470K and is near the 120 or 240v fuse holder.
Rick
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Re: Adjustment of the power reading on the HP 8920A
Thanks John, I'll check it.
Thanks for your response
Regards
Bill M.
On 11/01/2024 1:23 am, John Yelmgren wrote:
Normally the A24 attenuator is easily verified.? If it's the standard 60 Watt input than you should see 14 dB.
But if brings the measurement back in line than you should see something different.? ?You should also be able to verify the resistance values.?
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Re: FS: Flash card w/HP tools & SRAM card
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FS: Flash card w/HP tools & SRAM card
These are duplicates that I don't need. I haven't tried every one of the programs in my HP8920B, but the ones that I did seem to work fine. It looks like the EDACS tools also does conventional channels. NOT FOR HP8920A - DIFFERENT TYPE OF CARDS.
The Flash card is a SMART 4 MB that contains these HP tools:
HP 11807: Opt 001 - NA FM Tools, Opt 003 - AM Tools, Opt 011 - EDACS Tools, Opt 100 - RF Tools
The card is formatted to about 2MB, as when formatted to 4 MB, my HP8920B didn't recognize it.
If I remember, years ago when this was hosted on Yahoo, someone posted a few minor mods to make some of these programs work on the HP8924. That's for you to figure out.
The SRAM card is a SMART 256KB with internal rechargeable battery. Not sure how long it will hold a charge, as it is used. Stick it in your HP to charge it once in a while. An SRAM card is useful to store your programs and data. You can't (easily) write to the Flash card.
$50 for both cards, including USPS Priority Mail shipping. Not sure how messaging works on here, but my gmail address is mojoehand.
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Re: 8924C POWER SUPPLY DEAD
Yes, well no.? Not ON, plugged in!? If nothing else the fan noise would have driven me (more) insane by now!
73's Skip WB6YMH
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Re: Adjustment of the power reading on the HP 8920A
Normally the A24 attenuator is easily verified.? If it's the standard 60 Watt input than you should see 14 dB.
But if brings the measurement back in line than you should see something different.? ?You should also be able to verify the resistance values.
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Re: 8924C POWER SUPPLY DEAD
With the 8924C, leaving it on is quite different to leaving it plugged in. I can understand not leaving it on. Besides the wear and tear, it consumes a fair amount of power, and more importantly to me, it is quite noisy. Leaving it plugged in, keeps the OCXO warm, and ready for use. It is meant to stay plugged in all the time.
Good idea to not leave it on.? 14 years of solid ON is really extreme and probably a "personal best" for all of us gathered here.  ______________________________________________________________
On Tuesday, January 9, 2024 at 05:44:17 PM EST, Skip wrote:
... I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.
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Re: 8924C POWER SUPPLY DEAD
?
Good idea to not leave it on.? 14 years of solid ON is really extreme and probably a "personal best" for all of us gathered here. ______________________________________________________________
?
On Tuesday, January 9, 2024 at 05:44:17 PM EST, Skip wrote:
?
... I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.
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Re: 8924C POWER SUPPLY DEAD
Confirming the usual, replacing the 47 uF fixed it.?
That capacitor had been replaced in 2009. I don't use my 8924C regularly, but it's been plugged in 24/7 since 2009 "just in case".?
I really don't want to do this again so I'm not going to leave my 8924C plugged in any longer unless I have an active project that I need it for.
73's Skip WB6YMH
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Re: Adjustment of the power reading on the HP 8920A
Thanks.? I have replaced the load resistor in the A24 assy., so It is a lot better than it was before. It looked like the user had left the TX on while he went for lunch!
I think I will believe the 50 ohms I measured whilst installing the new load, and the calibration in the HP.? Bird had a 'D' slug in it.
It is not that critical any way to ham radio applications such as mine. I do appreciate your comment though.
Many thanks
Bill M.
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On 8/01/2024 10:36 pm, John Yelmgren wrote:
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Re: 8924C POWER SUPPLY DEAD
Hi Bill,
I have an 8920 and the power supply is also dead. A fellow ham said he could fix it - but that is now 2 years ago. I know nothing about switchmode power supplies so am not prepared to touch it. I replaced all caps but had no luck.
I'm in VK5 land. Is there anyone over there that has experience with switchmode supplies ?
Regards,
Dean
VK5HMV
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Re: Adjustment of the power reading on the HP 8920A
On the 8924, which is like 8920's, there is a PERCAL or periodic Calibration internal routine. You need well calibrated 6 digit voltmeter & one of the steps is to enter reading of + & - rails on the measurement unit. This calibrates power meter and basically everything the measurement unit measures. The only other thing is frequency calibration & I can't recall if it was part of PERCAL or another routine. The 8920 will have same/similar routines as the measurement unit is the same along with almost everything else except the CDMA boards..
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Re: Adjustment of the power reading on the HP 8920A
Tru Dat!?
I have found as much disagreement among a handful of Bird slugs and/or cables.? There is actually a closed loop test for the 8920 to verify your cables first.
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On Mon, Jan 8, 2024 at 06:36 AM, John Yelmgren wrote:
I would tend to trust the 8920 more than the Bird.
IIRC correctly the Bird wattmeters are +-5% of full scale ...not sure what slug you have in the Bird .? If that's a 100 W VHF slug you are +- 5 Watts? which pulls those numbers pretty close.
As was mentioned I would test/compare? the 8920 with some other device.? ?Usually an easy check is? a known good signal gen from @ 0, 10 and 20 dbm.? ?Make sure you zero the 8920 power meter first and set the scale to dbm as well.
Normally I have a number of power meters? and the 8920's I fix are very close.
You may have an issue on the RF i/O assembly ...not really an adjust per se on the watt meter.
I have had to replace leaky diodes in the power detect circuit? ...they actually met spec at higher levels but below 0 dbm the leakage became a factor.
Most of your typical through line wattmeters? are not supper accurate ....and then you have your cabling and terminator that needs to be verified as well.
I have? at least two of everything? so that if anything looks off I have another one to validate with?
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Normand MARTEL
Chris, ZL1CVD