BRIGHT Replacement LCD for 8753/8720 VNAs with dim LCD displays
Dr. David Kirkby (Kirkby Microwave Ltd)
I have both an 8720D and an 8753ES. Both are LCD, but the displays are rather dim. I see a VNA in eBay which was advertised as having a brighter replacement LCD. Does anyone have any experience of these?
I know that there are LCD replacements for older VNAs with CRTs, but I am not looking at those.
Dr David Kirkby
Managing Director
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3 6DT, United Kingdom
Registered in England and Wales as company number 08914892
Tel 07910 441670 / +44 7910 441670 (0900-2100 GMT)
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Thanks, David - great advice! I'll start planning by making a drawing of the A9 board changes and then acquire the necessary parts. I'll let you know how things progress.
Best regards,
Joe, KN5U
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Re: Spring loaded Old Style Front Panel Buttons
I have advocated washing the assembled keyboards with
91 or 99% IPA before on this board. It changes the
character of the keys from something that feels like
you are going to do damage, to something that feels
nice.
I think that HP put the grease on the springs to modify
the feel.... perhaps preferring a strong click? The grease
will stick the spring to the plunger until it abruptly
gives way, and the key pushed down.
I think it was a bad idea given the adverse long term
effects of dried grease.
I have left all of my keyboards dry, and they seem
perfect.
-Chuck Harris
Barry n4buq@... [hp_agilent_equipment] wrote:
toggle quoted message
Show quoted text
Hi Adrian,
Okay - I may give that a try. I wonder if there was any grease originally in the
mechanisms that has dried up and possibly should be replaced after cleaning?
Thanks, Barry - N4BUQ
----- Original Message -----
From: "Adrian Nicol fenland787@... [hp_agilent_equipment]"
<hp_agilent_equipment@...> To: "hp agilent equipment"
<hp_agilent_equipment@...> Sent: Wednesday, February 24, 2016
9:52:43 AM Subject: Re: [hp_agilent_equipment] Spring loaded Old Style Front
Panel Buttons
Hi Barry, short answer is yes, that is the reason and the fix is dead easy and
really effective, if my experience is anything to go by. There is a parallel
thread running where I and others have posted their solutions - I just did a
3456A and 3455A as well as an 8566A and other gear - but this is what I did:
Remove the switch PCB from the panel, flood spray the switches with IPA (Isoprop
alcohol) and operate each a few times, within just three or four operations they
free up like magic going from clunky 'feels-like-something-is-about-to-bust' to
almost silky smooth! Then blow it off with an air-gun and give it another dose
for luck. Works for me anyway!
On Wednesday, February 24, 2016 3:09 PM, "Chuck Harris cfharris@...
[hp_agilent_equipment]" <hp_agilent_equipment@...> wrote:
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Re: HP 8901A assistance needed.
This is most interesting, thank you for the help!
2 of 3 instruments does not respond according to the manual. John and Joe, have you tried your instruments with GPIB??
I suppose there could be a error mode in the instruments where the GPIB adressing stops working.?
BR. Thomas.
?
Thomas -
My 8901B gives exactly the same responses as Joe's 9802A.. John - WB4YJT
-- ?Please? avoid sending? me? Word? or? PowerPoint? attachments. ?See? <> PDF is an better alternative and there are always LaTeX!
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I do not think the reconstruction has to be that comprehensive. The
MAR type devices have the same pinout except for one lead which is
power on the stock amplifier and ground on the MAR amplifier. Since
that lead is decoupled, removing the series resistor and jumpering the
decoupling capacitor and will turn it into ground for the MAR
amplifier. Then a resistor needs to be added from the output of the
MAR amplifier to the +15 volt supply; the value of the resistor
depends on the supply voltage and which specific MAR device is used.
The peak detector is used to determine if a suitable signal is present
at the input to the divider so no changes need to be made. It only
cares about the total signal level at the divider.
I would be more worried about oscillation of the MAR amplifier. The
minimum lead lengths should be used and removing the existing socket
so it can be soldered directly into the board will probably help with
this as well. I would attach the output bias resistor close to the
MAR amplifier and decouple it as well. The parts changes I
recommended in my earlier post are an easy way to do that by reusing
the existing series resistor location to hold the decoupling
capacitor.
toggle quoted message
Show quoted text
On 24 Feb 2016 09:13:39 -0800, you wrote: Good thoughts, David and Ignacio.
It should be fairly straight forward to cut out and rebuild the traces on the A9 board to accommodate the new Minicircuits amplifier. Especially since only the amplifier chip needs to be added. Everything else is already there (probably need to change values to control the low frequency rolloff to around 150 MHz) and amplifier biasing for optimum gain. The maximum frequency would be 1.3 GHz due to the limitations of the decade counter just after the amplifier stage, so extending the frequency range is not likely.
There is also the consideration of the peak detector components just after the amplifier, but since this is isolated from the amplifier by a blocking capacitor, bias voltage in the peak detector should not affect the amplifier. It may take some tweaking to get the peak detector to work properly with any variations in amplitude due to different gain figures from the new amplifier chip. I thinks some critical measurements of a working A9 board are in order.
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Re: HP 8901A assistance needed.
Thomas -
My 8901B gives exactly the same responses as Joe's 9802A.. John - WB4YJT
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Re: OT Rod terminating resistor
Hi,
Have you tried asking them for a sample? you would be surprised what results a nice letter or even email can get.
Robert G8RPI
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Re: 08410-60146 source control cable that goes between an 8350B and an 8410[BC]
I know this is an old post but did anyone ever come up with the wiring for this cable?
Regards,
Tom
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OT Rod terminating resistor
Hi fellows,
Looking for ONE small rod 50 ohm resistor for repair one terminator.
Found same model at Emc-rflabs.com TRM 4-12 50 but price and minimal quantity
out of my budget.
Thankful for help,
Milan
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Re: Need HP34401A GPIB help
On Tue, Feb 23, 2016 at 11:06 PM, iphi@... [hp_agilent_equipment] <hp_agilent_equipment@...> wrote:
Hi,
I am controlling my HP34401A multimeter via GPIB with a Prologics adapter, which works quite nicely.
My only problem is that the measurement speed it rather low at about 1 measurement per second.
The reason for this is apparently the fact that the GPIB command
meas:volt:dc?
automatically switches the instrument to highest resolution, i.e. slowest speed.
But I am not a GPIB expert.
Thus, the manual is not very helpful for me in this respect. It states:
MEASure
:VOLTage:DC? {<range>|MIN|MAX|DEF},{<resolution>|MIN|MAX|DEF}
Can someone tell me please, how to set the range and resolution in the measure command?
All my attempts ended with an error beep.
Thanks!
For maximum measurement speed you could use one of the following commands, depending on what voltage range you already know you want to use: "MEAS:VOLT:DC? 0.1, MAX" "MEAS:VOLT:DC? 1, MAX" "MEAS:VOLT:DC? 10, MAX" "MEAS:VOLT:DC? 100, MAX" "MEAS:VOLT:DC? 1000, MAX"
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8555a indicator/cord replacement or modification
Hello all.
Broke the indicator cord on my 8555a. Is there a good fix? Are there supposed to be very small pullies on those posts that are now lost on the floor? Is there any way to get the output from the oscillator controlled by the frequency know and display it on a counter? I'm thinking that if there is, some presets and a counter could give me a frequency display independent of the cord type display.
Thanks and 73
James Hickox
AA5AO
Abilene Texas
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Re: Spring loaded Old Style Front Panel Buttons
Now that I see how they're made, I can understand why lubrication should not be necessary. I plan to disassemble mine and give it the treatment. That nasty clicking is unnerving.
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "fenland787@... [hp_agilent_equipment]" <hp_agilent_equipment@...>
To: "hp agilent equipment" <hp_agilent_equipment@...>
Sent: Wednesday, February 24, 2016 11:45:14 AM
Subject: Re: [hp_agilent_equipment] Spring loaded Old Style Front Panel Buttons
I wondered about that too but advice on this forum was "no, clean and leave
dry" and that's what I did. So far it seems fine, I guess I'll need to check
again after another 30 years of use or so.....?
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Re: Spring loaded Old Style Front Panel Buttons
I wondered about that too but advice on this forum was "no, clean and leave dry" and that's what I did. So far it seems fine, I guess I'll need to check again after another 30 years of use or so.....?
|
Good thoughts, David and Ignacio.
It should?be fairly straight forward to cut out and rebuild the traces on the A9 board to accommodate the new Minicircuits amplifier. Especially since only the amplifier chip needs to be added. Everything else is already there (probably need to change values to control the low frequency rolloff to around 150 MHz) and amplifier biasing for optimum gain. The maximum frequency would be 1.3 GHz due to the limitations of the decade counter just after the amplifier stage, so extending the frequency range is not likely.
There is also the consideration of the peak detector components just after the amplifier, but since this is isolated from the amplifier by a blocking capacitor, bias voltage in the peak detector should not affect the amplifier. It may take some tweaking to get the peak detector to work properly?with any variations in amplitude due to different gain figures from the new amplifier chip. I thinks some critical measurements of a working A9 board are in order.
|
As Ignacio points out, these parts are designed to operate in a
transmission line environment so a daughter board will be difficult to
implement.
The pins on the package from Minicircuits are probably too thick to be
bent and inserted into the existing collet socket pins because they
were intended to be soldered into a microstrip environment. I would
either solder them to the exposed top of the collets or remove the
collets and socket that HP used and solder the MAR device into place.
toggle quoted message
Show quoted text
On 23 Feb 2016 19:47:04 -0800, you wrote: ...
So at this point, the best route is probably to acquire a modern MMIC and use a daughter board to connect to the original board holes. It should be fairly easy with the MIcrocircuit's amplifier. Except for the physical connections, the design, supporting parts, and supply voltage are very close to the original.
Thanks again for all of the great responses! I'll post again when I have a working solution.
Best regards,
Joe, KN5U
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Re: HP 8901A assistance needed.
Hi Thomas,
I have a HP 8902A and the command structure is very similar to the 8901A.
If this helps, here are the responses: The response to 21.0SPCL was 1111.000 The response to 61.0 SPCL was 0.0 The Response to 61.2 SPCL was 0.0
Best of luck!
Joe, KN5U
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Re: Spring loaded Old Style Front Panel Buttons
The video on the page really helps!
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "pianovt@... [hp_agilent_equipment]" <hp_agilent_equipment@...>
To: "hp agilent equipment" <hp_agilent_equipment@...>
Sent: Wednesday, February 24, 2016 10:40:39 AM
Subject: Re: [hp_agilent_equipment] Spring loaded Old Style Front Panel Buttons
There is this from Roberto Barrios:
Also, I have written about this a few times on this forum. Search for my
posts.
Vladan
|
Re: Spring loaded Old Style Front Panel Buttons
There is this from Roberto Barrios:
Also, I have written about this a few times on this forum. Search for my posts.
Vladan
|
Re: Spring loaded Old Style Front Panel Buttons
Hi Adrian,
Okay - I may give that a try. I wonder if there was any grease originally in the mechanisms that has dried up and possibly should be replaced after cleaning?
Thanks,
Barry - N4BUQ
toggle quoted message
Show quoted text
----- Original Message ----- From: "Adrian Nicol fenland787@... [hp_agilent_equipment]" <hp_agilent_equipment@...>
To: "hp agilent equipment" <hp_agilent_equipment@...>
Sent: Wednesday, February 24, 2016 9:52:43 AM
Subject: Re: [hp_agilent_equipment] Spring loaded Old Style Front Panel Buttons
Hi Barry, short answer is yes, that is the reason and the fix is dead easy
and really effective, if my experience is anything to go by.
There is a parallel thread running where I and others have posted their
solutions - I just did a 3456A and 3455A as well as an 8566A and other gear
- but this is what I did:
Remove the switch PCB from the panel, flood spray the switches with IPA
(Isoprop alcohol) and operate each a few times, within just three or four
operations they free up like magic going from clunky
'feels-like-something-is-about-to-bust' to almost silky smooth! Then blow it
off with an air-gun and give it another dose for luck.
Works for me anyway!
On Wednesday, February 24, 2016 3:09 PM, "Chuck Harris cfharris@...
[hp_agilent_equipment]" <hp_agilent_equipment@...> wrote:
? Hi Martin,
The easiest thing is to find the spring that fell out. It
is sticky with grease, so it will often stick to something.
If it is in the instrument, you must find and remove it, as
it can cause short circuits.
If you can't find the spring, you will have to get one from
other instrument's keyboard. There are plenty of scrap hp
front panels with keyboards on ebay.
You can make a new spring, but it is very critical in its size,
finish, and temper. I have heard that some have had success
making springs out of steel "feeler gages" Tin snips will
cut them, but make sure that you snips don't have a serrated
blade. I seem to recall that they are 0.0015" thick. The
size is somewhere in the archives. Shim stock will not work!
It is too soft.
On occasion, while I was waiting to find the correct spring, I have
made a coil spring and placed it so that it pressed on the keytop,
and the key mechanism. It doesn't click, but otherwise suffices.
-Chuck Harris
Martin.Hepperle@... [hp_agilent_equipment] wrote:
I got a 9915 computer which uses the same leaf-spring loaded front panel
buttons
as many older HP instruments (/e.g. the 3456A DVMs).
Three of the springs have fallen out and I need to fix that.
Are there any sources for these parts or ways to obtain similar springs or
even
complete switches?
Any well known repair procedures that I should know?
I could possibly obtain some flat sheet spring steel and grind a spring to
shape
using Dremel tools etc. but that sounds like a difficult and very time
consuming
task. Also the length of these springs must probably quite accurate.
Otherwise I would have to try something with external helical springs, glue
and
other ugly constructions...
Thanks, Martin
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Re: Part Needed Ge Diode HP 1910-0016
David:
Send me your address privately and I'll mail you one for free...
Dan in Chandler, AZ
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David Hess