Re: 8924C video out using a GBS-8200 to vga questions
either will work.
On 19/04/2021 13:02, William Verstelle
wrote:
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The 50k resistors, how critical is that value, I have 47k and
56k will either of these work? I guess I could use 2x100k if
needed.?
Bill N7OQ
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Re: 8924C video out using a GBS-8200 to vga questions
The 50k resistors, how critical is that value, I have 47k and 56k will either of these work? I guess I could use 2x100k if needed.?
Bill N7OQ
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Re: 8924C video out using a GBS-8200 to vga questions
Wow again, great information, I get my lm-1881 Thursday or wed. Will let you know how it works out, thanks everyone,
Bill N7OQ
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Re: 8924C video out using a GBS-8200 to vga questions
To use the GBS-8200 converter with the hp-8924c service monitor to use with an external VGA monitor.
Obtain:
50 K ohm SMD resistors 4 required
LM1881N IC sync seperator .1 UF capacitor--2 required 680 K? ohm resistor
To be mounted on the GBS8200 board will be 4 SMD 50 K ohm resistors.?? Without the resistors the display will seem to work for? about 30 seconds and fade out. That is what it did for me.
On the LM1881 connect pin 1 to the # 4 (gray wire) pin of the 8 pin RGBS input connector. Pin 2 to a .1 UF capacitor and then to? the Green input of the 8 pin RGBS connector? A wire from that junction goes to the input from the 8924C. Pin 4 to ground. Pin 6 has a .1 UF and 680 K resistor in parallel to ground. Pin 8 goes to 5 volts. Pins 3,5,7 are not used.
The 4 SMD 50 K ohm resistors are soldered across capacitors 29,32,33, and 36 on the? GBS8200 board.? They are in a row between the 3 pots and an IC.
This will provide a green video output to a VGA monitor.
On Sunday, April 18, 2021, 02:05:33 AM EDT, William Verstelle <bverstelle@...> wrote:
Hi group, I want to replace the CRT monitor in my 8924 and bought a GBS-8200 board. Well I saw a picture where they plugged it into the green (Y) rca jack on the 8200 board and this worked to a degree but the display was black and white and the right hand side was cut off. I tried the vga/ega connector without a sync and nothing,?reading another article and blog they used a lm1881 sync separator to extract the V and H syncs. ?So here are my questions
1. does the composite video on a HP 9824c ?have the Sync pulses in it? ?(The article was for a different HP analyzer)
2. The schematic shows the V and H sync pulses are already at the CRT monitor plug can I use these pulses?
3. it there any other way to connect or modify the board to make it work?
It seems like a lot of the info was lost in the move from Yahoo to here like a lot of my other groups so I¡¯m getting bit and pieces. The reason I want to replace the crt monitor is because it has a lot of burn in on the screen and it is only time before I have problems with it. Plus LCD screens are easier to read on my old eyes.?
thanks, Bill N7OQ
?
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Re: 8924C video out using a GBS-8200 to vga questions
My guide:
?
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Re: 8924C video out using a GBS-8200 to vga questions
Bill
Here are a couple of old things i saved re getting the GBS-8200
workings with 8924 from the old Yahoo groups.
There is also one on power supply repair plus some notes on power
supply caps I replaced a while back - maybe useful for ordering
replacements.
73s om de chris zl1cvd
On 18/04/2021 18:05, William Verstelle
wrote:
toggle quoted message
Show quoted text
Hi group, I want to replace the CRT monitor in my 8924 and
bought a GBS-8200 board. Well I saw a picture where they plugged
it into the green (Y) rca jack on the 8200 board and this worked
to a degree but the display was black and white and the right
hand side was cut off. I tried the vga/ega connector without a
sync and nothing,?reading another article and blog they used a
lm1881 sync separator to extract the V and H syncs. ?So here are
my questions
1. does the composite video on a HP 9824c ?have the Sync pulses
in it? ?(The article was for a different HP analyzer)
2. The schematic shows the V and H sync pulses are already at
the CRT monitor plug can I use these pulses?
3. it there any other way to connect or modify the board to make
it work?
It seems like a lot of the info was lost in the move from Yahoo
to here like a lot of my other groups so I¡¯m getting bit and
pieces. The reason I want to replace the crt monitor is because
it has a lot of burn in on the screen and it is only time before
I have problems with it. Plus LCD screens are easier to read on
my old eyes.?
thanks, Bill N7OQ
?
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8924C video out using a GBS-8200 to vga questions
Hi group, I want to replace the CRT monitor in my 8924 and bought a GBS-8200 board. Well I saw a picture where they plugged it into the green (Y) rca jack on the 8200 board and this worked to a degree but the display was black and white and the right hand side was cut off. I tried the vga/ega connector without a sync and nothing,?reading another article and blog they used a lm1881 sync separator to extract the V and H syncs. ?So here are my questions
1. does the composite video on a HP 9824c ?have the Sync pulses in it? ?(The article was for a different HP analyzer)
2. The schematic shows the V and H sync pulses are already at the CRT monitor plug can I use these pulses?
3. it there any other way to connect or modify the board to make it work?
It seems like a lot of the info was lost in the move from Yahoo to here like a lot of my other groups so I¡¯m getting bit and pieces. The reason I want to replace the crt monitor is because it has a lot of burn in on the screen and it is only time before I have problems with it. Plus LCD screens are easier to read on my old eyes.?
thanks, Bill N7OQ
?
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Re: HP 8924C power supply issue
Thank you everyone, I¡¯ll order 105 degree caps and do a recap. So far everything else seems to be working. This is a great forum.
Bill N7OQ
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Re: HP 8924C power supply issue
As others said, it is most likely the capacitors.? About 90% or more switching supply problems are the capacitors.
I had an 8924c that acted similar.? I took a hot air gun from a SMD rework station that had some small tips and could blow hot air on one capacitor at a time.? Found the one that was causing the problem,but replaced several other ones while I had the 8924c open.? After going through all the trouble of removing all the screws I felt it worth while to replace many of the electrolytic capacitors .
Ralph ku4pt
On Saturday, April 17, 2021, 03:34:03 AM EDT, William Verstelle <bverstelle@...> wrote:
Hello group, thanks for letting me join,? My name Is Bill and call is N7OQ.?
I got a free HP-8924C that the guy said needed a new power supply. Well I put Some power to it and nothing, then I removed the PS and opened it up looking for any obvious problems. I cleaned it up everything looked good, no burned components or over heating areas so I put it back together and plugged it in and the green light came on. Now the unit powers up, had the clean display adjustment post to keep a display Going and now that works good too.?
Well this morning I hit the switch and nothing, it was in the garage and was cold, so I put a little heat into the PS with a hot air gun and it came right back to life. Has anyone seen this problem? As long as I keep the unit plugged in even with power off it stays warming enough and will fire right up. But who how long that will last. Thanks
._,_
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Re: HP 8924C power supply issue
there is a write up in the files section ...or at least there used to be from the old hosting service.
usually you are missing the green led on the rear of the unit which is the 15 volt standby supply.
That should be there anytime the unit is plugged in ....which is why it dies ...used to power the internal reference as well as the on/off voltage IIRC
This comes from a small daughter board on the back corner and the cap on that board fails.
not usually all of the caps ...just the small one on the daughter card.
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Re: HP 8924C power supply issue
It is a very common issue with these power supplies. All the electro caps go faulty. Especially the little ones on the small boards. You need to change them all for 105 degree rated caps. The old 85 degree caps dry out. Also do the caps in the regulator PCB - its separate to the power supply. You may also see the odd tantalum cap smoke, bang or go faulty in the rest of it. Takes allot of time to replace them all but well worth it. The very best general purpose analogue test gear ever made.
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HP 8924C power supply issue
Hello group, thanks for letting me join,? My name Is Bill and call is N7OQ.?
I got a free HP-8924C that the guy said needed a new power supply. Well I put Some power to it and nothing, then I removed the PS and opened it up looking for any obvious problems. I cleaned it up everything looked good, no burned components or over heating areas so I put it back together and plugged it in and the green light came on. Now the unit powers up, had the clean display adjustment post to keep a display Going and now that works good too.?
Well this morning I hit the switch and nothing, it was in the garage and was cold, so I put a little heat into the PS with a hot air gun and it came right back to life. Has anyone seen this problem? As long as I keep the unit plugged in even with power off it stays warming enough and will fire right up. But who how long that will last. Thanks
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Re: hp11758a Multipath fading test set & rf Power Meter
All I found is this user manual:
An interesting piece.? What is the matter with a 3v battery that reads 3.1v??? did you slip with the test prod?? is it leaking?? do you think you have corrupted data?
A lot of equipment must be kept powered when you replace these so you dont lose data u cant get back.
Probably easier to find the Panasonic specs and sub a more common battery.
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hp11758a Multipath fading test set & rf Power Meter
Hello
I have a HP11758 Multipath test set and it contains an rf power meter that I suspect is similar to HP437 power meter.? This unit has a soldered-in Panasonic 3 volt lithium battery and it currently measures 3.1 volts.? Do both the multipath set and the power meter utilize this battery to hold constants?? Or is just necessary for only the test set?
I can't find a service manual on this unit.?
Thanks
KC5WYA, Henry
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Re: Where the 10MHz reference is located on E8285A?
There are 2x OCXOs in the E8285A. High stability and CDMA which is pll locked to the high stability. The location is shown on page 89 of the E8285-90033 Agilent Technologies E8285A CDMA
Mobile Station Test Set Assembly Level Repair manual. You'll find it online. Download it and learn more about the inside of your gear. I use an GPS locked OCXO to calibrate all my analyzers specifically the Samsung EP92-01704A UCCM-LP. You can pick them up on eBay quite easily. They were used in cellphone towers to synchronize the network. The E8285A manual indicated above also gives detail on how to calibrate the frequency and measurement unit of your analyzer. 73s de chris zl1cvd
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Re: Where the 10MHz reference is located on E8285A?
Find a list of ATSC pilot frequencies.? They are usually network disciplined.? Try several - I see 2hz variation between them in my area.? This way you can judge the warmup drift of your instrument.? For Ham use, TCXO is plenty good if you calibrate it at lab temp, and you wont have to worry about warmup drift with the OCXO.? If I am really picky, I will let the OCXO warm up for at least 1 hour, but maximum stability is reached by 2 hours.? At room temp, the TCXO will be ready for use while the OCXO will have to wait at least 20 mins to do better.
My other answer was to get one of those surplus e-bay 105243 OCXO, build up a clean power supply for it and leave it running all the time. This is as accurate as warming up the OCXO in my 8920a for 2 hours.
I wonder if there are any issues with keeping the internal OCXO warm with 9v or so from an external dc supply with diode isolation?
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Penultimate update to the LCD saga
(link to my blog not to load the group. Google translator is your friend)
Penultimate because now I gotta model something to install this LCD on its placa and make the 2 boards fit inside the E8285A
Hope you like it!
73 de PU2SEX Alexandre
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Re: Where the 10MHz reference is located on E8285A?
It should be listed in options somewhere on the menu screens or on a sticker on the back. The High Precision unit is a big plug in metal box about 10 cm square and 1 cm deep metal can along with several plug in units in a row ...RF etc boards. I had units with high precision and regular oscillator. I swapped the high precision unit and I really did not notice any difference.? You calibrate the oscillator from a menu function using an external?time base?I think the time base has to be several hundred MHz as I recall, I might be wrong about the freq of external time base. I use another HP unit with a GPS disciplined osc in it to cal the 8395 at 500 MHz. I concluded that at the normal price of a high precision time base for this unit, an external?time base was much more accurate and cheaper. The actual oscillator in the high precision time base is not very big and I think it is a temp comp osc not an oven.
Wally KC9INK
On Tuesday, March 16, 2021, 11:08:04 PM EDT, Alexandre Souza <alexandre.tabajara@...> wrote:
Greetings! I want to know if my HPE8285A has the high-precision reference unit. Where should it be located? If it doesn't have it, how can I install? Ok, I know I can use an external GPSDO signal
Thanks Alexandre, PU2SEX
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Where the 10MHz reference is located on E8285A?
Greetings! I want to know if my HPE8285A has the high-precision reference unit. Where should it be located? If it doesn't have it, how can I install? Ok, I know I can use an external GPSDO signal
Thanks Alexandre, PU2SEX
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Re: Firmware update for 8935 E6380A
It would be nice to have a backup of the present system. I ran into the same problem with another Agilent unit. E7495
I had to alter the code on the update card and re install the update. It made me nervous.
But it worked OK.
I do not know how to get a backup off these units. Maybe someone else does.
Wally KC9INK.
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Chris, ZL1CVD
Alexandre Souza