Re: 8711B tantalum disease
There were a lot of 3 legged tantalums which I hadn't seen before. The two outside leads were negative and center positive.? The ground plane on the processor board seemed unusually heat-sinky and I had a really hard time desoldering those leads.? It would be a massive chore to have to replace all the tantalums.
Not for an old 75 ohm 8711B, anyway.
Peter
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On 4/27/2024 8:24 PM, Mark Weedon via groups.io wrote: Peter,
I agree - tantalums are a pest.? Perhaps the problem isn't the tantalums but our fascination with equipment from the dodgy tantalum era.? We can replace tantalums, dried electrolytics, leaky backup batteries etc but who really wants to cure that fascination?
The tantalums exposed to immediate voltage at turn on are the most likely to fail. Those in timing circuits, charged via a resistor seem to be OK.
A scan of the circuit should identify the tantalums being hit at turn on - replace these as a precaution.? That solves some of the issues but obviously tedious if you have a memory or logic board with decoupling tantalums on every chip.
Sometimes it can work to your advantage: I bought a Racal RA6790 RX cheap on ebay - advertised as not working.? It was tedious - tantalums distributed all over the board decoupling power rails. Got that radio going and then it stopped again!
Cheers
Mark
VK2WU
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Re: 8711B tantalum disease
Peter,
I agree - tantalums are a pest.? Perhaps the problem isn't the tantalums but our fascination with equipment from the dodgy tantalum era.? We can replace tantalums, dried electrolytics, leaky backup batteries etc but who really wants to cure that fascination?
The tantalums exposed to immediate voltage at turn on are the most likely to fail. Those in timing circuits, charged via a resistor seem to be OK.
A scan of the circuit should identify the tantalums being hit at turn on - replace these as a precaution.? That solves some of the issues but obviously tedious if you have a memory or logic board with decoupling tantalums on every chip.
Sometimes it can work to your advantage: I bought a Racal RA6790 RX cheap on ebay - advertised as not working.? It was tedious - tantalums distributed all over the board decoupling power rails.? Got that radio going and then it stopped again!
Cheers
Mark
VK2WU
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Re: Interesting power supply issue!
Acronym?? Like VPS,? VNA Power Supply?
And how is the best way to refer to this series?? A bunch of different models with many similar assemblies.
871x?
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On 4/27/2024 1:18 PM, maurit via groups.io wrote: I think it is useful for many to also write the acronym of the instrument concerned in the title of the Post.
In this case HP 8711B.
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Re: Interesting power supply issue!
I think it is useful for many to also write the acronym of the instrument concerned in the title of the Post.
In this case HP 8711B.
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Re: Requesting HP 33120A VFD
They may not have them but they definitely will sell to individuals.? I bought a new VFD display for one of my 34401's a few months ago, as an individual.? I could have done it through one of the companies I work for but that wasn't necessary.? Tons of engineers these days have non-traditional working arrangements. Part of this is to reduce the reliance of purchasing agents for repair and prototype parts; simply let the engineers buy what they need then reimburse them.
Find the HP/Agilent/Keysight part number and search for it on ebay and the web.
Peter
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On 4/27/2024 11:45 AM, alberto.vaudagna via groups.io wrote: Nope keysight has not it. (Anyway I read somewhere that in general keysight is not more prone on selling stuff to individual people, but only sells stuff if you are applied to some kind of repair program and is only for company anyway)
So still looking for something.
I really feel like an idiot ? it was basically the one thing I always said I should not broke??
Il sab 27 apr 2024, 16:08 Peter Gottlieb via groups.io <> <hpnpilot@...> ha scritto:
See if Keysight has them in stock.? May not be that expensive.
Peter
On 4/27/2024 10:03 AM, alberto.vaudagna via groups.io <>
wrote:
> I burn, as an idiot, the VFD of my 33120A (Plugging the main power
connector
> backward, it seem the instrument still functioning anyway) .
> Anyone have some to sell, or anyone has the entire front panel to sell?
> Best regards,
> Alberto V.
>
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Re: Requesting HP 33120A VFD
Nope keysight has not it. (Anyway I read somewhere that in general keysight is not more prone on selling stuff to individual people, but only sells stuff if you are applied to some kind of repair program and is only for company anyway) So still looking for something. I really feel like an idiot ? it was basically the one thing I always said I should not broke??
Il sab 27 apr 2024, 16:08 Peter Gottlieb via <hpnpilot= [email protected]> ha scritto: See if Keysight has them in stock.? May not be that expensive.
Peter
On 4/27/2024 10:03 AM, alberto.vaudagna via wrote:
> I burn, as an idiot, the VFD of my 33120A (Plugging the main power connector
> backward, it seem the instrument still functioning anyway) .
> Anyone have some to sell, or anyone has the entire front panel to sell?
> Best regards,
> Alberto V.
>
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Re: Requesting HP 33120A VFD
See if Keysight has them in stock.? May not be that expensive.
Peter
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On 4/27/2024 10:03 AM, alberto.vaudagna via groups.io wrote: I burn, as an idiot, the VFD of my 33120A (Plugging the main power connector backward, it seem the instrument still functioning anyway) .
Anyone have some to sell, or anyone has the entire front panel to sell?
Best regards,
Alberto V.
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I burn, as an idiot, the VFD of my 33120A (Plugging the main power connector backward, it seem the instrument still functioning anyway) .?
Anyone have some to sell, or anyone has the entire front panel to sell?
Best regards,?
Alberto V.?
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Re: 2-Port Vector Network Analyzer Recommendations
Hi Matt,
The dim screen is actually a pretty easy fix.? What happens is that there is a mylar film that acts as a reflector around the lamp that ages and curls up around the lamp over time.? All you have to do is remove the front panel (about 5-7 screws, top and bottom), unplug the connector to the unit, remove the LCD module (4 screws I think) and then finally the backlight (2 screws).? You carefully remove the florescent tube then replace the damaged mylar with a little strip of aluminum foil which can be held in place with some tiny pieces of foam at the end if you like to keep it from moving around.? It's about a 15 minute job if you know what you're doing.? I actually recorded a video of the process that I'll try to get up on youtube.? ?You can replace the light for about $20 as well, but I find that this is rarely required.? The mylar replacement usually does the trick.
As for the reversed screen, even easier.? It turns out that there's a connector inside that front panel that goes bad over time.? It is a 8 pin flex to board connector (z axis) that is about 3-4 inches in length.? It goes from the keypad side of the panel over to the LCD.? Just unplug it and replug it in 2-3 times and you should be good for at least 2-5 years of additional use without any issues.
By the way, I still have two 8753ES 6 GHz units that I repaired up for sale at the bargin bin price of $2500 per unit (or a fair offer).? I still think that they're a great way to go if you don't need a lot of speed.
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Re: 2-Port Vector Network Analyzer Recommendations
I bought a 8753ES about a year ago and yeah Im about to deal with those issues.? I think I paid around $3500 for the 6ghz model.??
My screen is dim so I have a new led backlights to replace the tubes with.? However I maybe needing to build a 5vdc boost converter to run the led strip lights.??
I also have had once my screen invert on me.? Annoying to say the least, but have yet to break the cal stickers to opener up to work on it.??
Matt
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Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
There isn't anything directly in parallel with it.? Each side is connected to a separate rail so that's a possibility for invalid reasons.? In any case, with the new one in circuit, the DMM diode checks normal.? I was just concerned that some diodes - perhaps all diodes - (and I think Schottky is in the list) can have small amounts of reverse current and I wanted to make sure that wasn't what was tripping up my DMM.
I just really prefer having a fairly solid reason to desolder a component before doing that.? If I had a really nice desoldering station, then maybe I wouldn't be as hesitant.? I've seen how well those clean out a via and I really wish I could justify one.
Thanks for the new acronyms, Barry - N4BUQ
Or, perhaps more likely, due to something else in parallel with it.
You simply can't check devices in circuit with any reliability. Yes,
if you read an open in both directions, it's obviously a dead diode.
But Things in Parallel with Other Things (TPOT) can produce reduced
resistances, so lower than normal resistance readings don't tell you
much.
So, lift one pin and retest. Then you'll know. And a heckuva lot
faster than taking the time to post!
(And fyi, a diode -- whether made of silicon, germanium or Marmite
-- should conduct only one way)
--
Prof. Thomas H. Lee
Faculty Co-Director, SystemX Alliance
Director, Stanford-Samsung Research Initiative
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 4/26/2024 7:44 AM, n4buq wrote:
Yes, that helps.? I plan to test a new Schottky and if it
doesn't have that same reverse voltage, then I'll lift one leg
of the existing diode and check it.? If it still tests
differently than a new one, then I'll replace it.? I just
wasn't sure whether that was due to it being germanium or
whether it's just bad.
Thanks for the info!
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Re: 8711B tantalum disease
Hi Peter, It seems to be a combination of a couple of bad brands of capacitors, and an engineering thing. The biggest issue is capacitor rating voltage vs applied voltage. It should be greater than 2x for best life. The other issue is source-able current. If the power source for the capacitor can source a lot of current into the capacitor, it will destroy (melt down) what would have been an otherwise self healing capacitor. So, my philosophy is when one pops, if it is being run close to its rating (eg. 5V on a 6V cap, 15V on a 20V cap, I just replace it and any others similarly applied. If it is more like 15V on a 35V cap, I replace them all. -Chuck Harris On Fri, 26 Apr 2024 17:21:57 -0400 "Peter Gottlieb" <hpnpilot@...> wrote: This would apply to all this series.
I got a 8711B with a bad power supply.? I tracked that down to an
open trace caused by corrosion in one of the mag amp circuits.
The unit still wouldn't power on, traced it to a shorted tantalum
capacitor on the +15 volt bus.? Replaced it, reassembled everything,
the unit ran about 2 minutes then shut down again.? This time it was
a shorted tantalum on the +12 bus, different assembly.
If this is like other gear I have had experience with, unless I go
through and replace every single one of those suckers it will remain
a crapshoot as to whether it will turn on each time.
It might be the age of these instruments.? My expectation is that
every one of this series will have these failures and be unreliable.
Peter
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This would apply to all this series.
I got a 8711B with a bad power supply.? I tracked that down to an open trace caused by corrosion in one of the mag amp circuits.
The unit still wouldn't power on, traced it to a shorted tantalum capacitor on the +15 volt bus.? Replaced it, reassembled everything, the unit ran about 2 minutes then shut down again.? This time it was a shorted tantalum on the +12 bus, different assembly.
If this is like other gear I have had experience with, unless I go through and replace every single one of those suckers it will remain a crapshoot as to whether it will turn on each time.
It might be the age of these instruments.? My expectation is that every one of this series will have these failures and be unreliable.
Peter
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Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
Yes, Lift One Leg (LOL) to coin yet another Three Letter Acronym (TLA).? A YAT (Yet Another TLA).? Et cetera, etc cetera, ad nauseam.? About the only Latin I remember from junior high school 40+ years ago....? ? ? ? ? ?Jim Ford?
Sent from my T-Mobile 4G LTE Device
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-------- Original message -------- From: Tom Lee <tomlee@...> Date: 4/26/24 10:47 AM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP-1404A - Question regarding hot-carrier diode A10-CR4
Or, perhaps more likely, due to something else in parallel with it.
You simply can't check devices in circuit with any reliability. Yes,
if you read an open in both directions, it's obviously a dead diode.
But Things in Parallel with Other Things (TPOT) can produce reduced
resistances, so lower than normal resistance readings don't tell you
much.
So, lift one pin and retest. Then you'll know. And a heckuva lot
faster than taking the time to post!
(And fyi, a diode -- whether made of silicon, germanium or Marmite
-- should conduct only one way)
--
Prof. Thomas H. Lee
Faculty Co-Director, SystemX Alliance
Director, Stanford-Samsung Research Initiative
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 4/26/2024 7:44 AM, n4buq wrote:
Yes, that helps.? I plan to test a new Schottky and if it
doesn't have that same reverse voltage, then I'll lift one leg
of the existing diode and check it.? If it still tests
differently than a new one, then I'll replace it.? I just
wasn't sure whether that was due to it being germanium or
whether it's just bad.
Thanks for the info!
|
Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
Or, perhaps more likely, due to something else in parallel with it.
You simply can't check devices in circuit with any reliability. Yes,
if you read an open in both directions, it's obviously a dead diode.
But Things in Parallel with Other Things (TPOT) can produce reduced
resistances, so lower than normal resistance readings don't tell you
much.
So, lift one pin and retest. Then you'll know. And a heckuva lot
faster than taking the time to post!
(And fyi, a diode -- whether made of silicon, germanium or Marmite
-- should conduct only one way)
--
Prof. Thomas H. Lee
Faculty Co-Director, SystemX Alliance
Director, Stanford-Samsung Research Initiative
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 4/26/2024 7:44 AM, n4buq wrote:
toggle quoted message
Show quoted text
Yes, that helps.? I plan to test a new Schottky and if it
doesn't have that same reverse voltage, then I'll lift one leg
of the existing diode and check it.? If it still tests
differently than a new one, then I'll replace it.? I just
wasn't sure whether that was due to it being germanium or
whether it's just bad.
Thanks for the info!
|
Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
I've tested a few of these 1901-0347 diodes that came from some 3702/3 boards I was given, after checking the color bands match those in the HP 209A I have. The component tester can only do 12V, reverse voltage must be higher than this as I got a flat line.
David
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Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
Out of circuit, the old part tested as a small-value capacitor.? I replaced it with a new Si Schottky and it works like it should.? No more fat traces in CHOP mode!
Thanks, Barry - N4BUQ
Yes, that helps.? I plan to test a new Schottky and if it doesn't have that same reverse voltage, then I'll lift one leg of the existing diode and check it.? If it still tests differently than a new one, then I'll replace it.? I just wasn't sure whether that was due to it being germanium or whether it's just bad. Thanks for the info! Barry - N4BUQ HP part numbers have the type of component etc coded in the first four numbers, some examples below;
Diodes:
1901 = silicon
1902 = zener
1906 = dual/bridge
1910 = germanium
1912 = tunnel
0122 = varactor/tuning
Transistors;
1850 = germanium PNP
1851 = germanium NPN
1853 = silicon PNP
1854 = silicon NPN
1855 = FET
Matched diode sets start can with 5080 and parts sold by HP (later Avago) under 5082 numbers.
Hope this helps.
David
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Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
Yes, that helps.? I plan to test a new Schottky and if it doesn't have that same reverse voltage, then I'll lift one leg of the existing diode and check it.? If it still tests differently than a new one, then I'll replace it.? I just wasn't sure whether that was due to it being germanium or whether it's just bad.
Thanks for the info!
Barry - N4BUQ
HP part numbers have the type of component etc coded in the first four numbers, some examples below;
Diodes:
1901 = silicon
1902 = zener
1906 = dual/bridge
1910 = germanium
1912 = tunnel
0122 = varactor/tuning
Transistors;
1850 = germanium PNP
1851 = germanium NPN
1853 = silicon PNP
1854 = silicon NPN
1855 = FET
Matched diode sets start can with 5080 and parts sold by HP (later Avago) under 5082 numbers.
Hope this helps.
David
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Re: HP-1404A - Question regarding hot-carrier diode A10-CR4
Thanks David, very useful.
Renaud
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Re: HP5315B 100MHz counter
I have an 5316A/B OCXO listed on EBAY that should work in the 5315A/B since they used a similar module.
I have only tested it in a 5316B.
Pins 1 and 6 are 7.5V unregulated power
Pin 2 is 10MHz
Pin 3 is ground
Pin 4 and 5 are no connect.
Does your unit have the battery pack? The OCXO takes more power than the TCXO option.
ed
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maurit
factory
