Re: Looking for power supply schematic of Agilent 83751A
On Sun, Feb 20, 2022 at 10:46 PM Dave McGuire <mcguire@...> wrote:
I've seen plenty of capacitors fail shorted, but never an
electrolytic, I guess I've been lucky there.
I've seen exactly 2 aluminium electrolytics failed short circuit so far in maybe 20 years of repairs, both were inside HP instruments: one into a HP-3456A ad one was in a HP-5328A They were enough dead short to pop fuses and blow one pass transistor in the case of the 5328A. Just for the record anyway Frank
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Re: Looking for power supply schematic of Agilent 83751A
Failing shorted is indeed unusual for these caps. Of the few that I've seen, a good fraction had actually been installed backwards at the factory. Even HP occasionally makes that error, surprisingly enough. The 8657A that I own had failed because of that.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 2/20/2022 13:46, Dave McGuire wrote:
? I've seen plenty of capacitors fail shorted, but never an electrolytic, I guess I've been lucky there.
? What I HAVE seen them do is "almost" short, like 100 ohms or so, boil their electrolyte and blow the wad out the end like a party streamer.
? A very stinky party streamer. ;)
?????????? -Dave
On 2/20/22 15:51, Glydeck via groups.io wrote:
I¡¯ve seen caps fail short and with spectacular results.
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Glydeck
On Feb 20, 2022, at 6:39 AM, Dave McGuire <mcguire@...> wrote:
?On 2/20/22 01:28, Lincheng Xiu via groups.io wrote:
After 6 hours troubleshooting, it is fixed. The reason is C35 short. 100uF/50V electrolytic capacitor.
Here is what I traced the partial schematic of HP83751A power supply.
?After C35 short, the PWM controller does not drive the MOSFETs.
Also checked the ESR of C1, which is too much, 2 ohm, it will soon fail, just replaced with a new one. ?Wow, I see electrolytic capacitors like that dry out and lose capacitance all the time, but I don't think I've ever seen one shorted. Nice troubleshooting!
?????????-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
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Re: Looking for power supply schematic of Agilent 83751A
I've seen plenty of capacitors fail shorted, but never an electrolytic, I guess I've been lucky there.
What I HAVE seen them do is "almost" short, like 100 ohms or so, boil their electrolyte and blow the wad out the end like a party streamer.
A very stinky party streamer. ;)
-Dave
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On 2/20/22 15:51, Glydeck via groups.io wrote: I¡¯ve seen caps fail short and with spectacular results.
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Glydeck
On Feb 20, 2022, at 6:39 AM, Dave McGuire <mcguire@...> wrote:
?On 2/20/22 01:28, Lincheng Xiu via groups.io wrote:
After 6 hours troubleshooting, it is fixed. The reason is C35 short. 100uF/50V electrolytic capacitor.
Here is what I traced the partial schematic of HP83751A power supply.
?After C35 short, the PWM controller does not drive the MOSFETs.
Also checked the ESR of C1, which is too much, 2 ohm, it will soon fail, just replaced with a new one. ?Wow, I see electrolytic capacitors like that dry out and lose capacitance all the time, but I don't think I've ever seen one shorted. Nice troubleshooting!
?????????-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
--
Dave McGuire, AK4HZ
New Kensington, PA
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Hi Chris,
yes, I have reduced the input to the phono preamp so as to have the output signal not clipped in the whole band from 20 Hz to 20 kHz (seen on oscilloscope).
With my friends we have made several phono preamps both tube and solid state. No problem with solid state preamps (fet or low noise opamps), while with tube ones they are fine, but it is very difficult to eliminate the hum at the mains frequency (50 Hz) that is heard especially when the turntable arm is raised from the vinile disc.
-- Cheers
? ? Attilio
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Re: Looking for power supply schematic of Agilent 83751A
I¡¯ve seen caps fail short and with spectacular results.?
?
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On Feb 20, 2022, at 6:39 AM, Dave McGuire <mcguire@...> wrote:
? On 2/20/22 01:28, Lincheng Xiu via groups.io wrote:After 6 hours troubleshooting, it is fixed. The reason is C35 short. 100uF/50V electrolytic capacitor.
Here is what I traced the partial schematic of HP83751A power supply.
?After C35 short, the PWM controller does not drive the MOSFETs.
Also checked the ESR of C1, which is too much, 2 ohm, it will soon fail, just replaced with a new one.
?Wow, I see electrolytic capacitors like that dry out and lose capacitance all the time, but I don't think I've ever seen one shorted. Nice troubleshooting! ?????????-Dave-- Dave McGuire, AK4HZNew Kensington, PA
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Hi?Attilio,
Make certain your test signal doesn't exceed 5 mV (as a number) or you may drive the phono preamp beyond it's linear range (a lot lower than clipping).? That will drive distortion numbers up.? Also, a tube stage has much lower transconductance than solid state designs, so you will have much higher distortion figures as you have much lower feedback than a line stage will have, even lower in the lower frequencies.? So do not expect very low distortion figures from (especially) simple phono gain stages.? Tubes also are inherently more noisy than a solid state stage given the same care in design.? I design with tubes, transistors and ICs and you have to match your expectations to the technology you are using.? With tubes, power supply noise is critical as well.
I used an HP 339A with the output to a 3585A, and also a ShibaSuko AD725C.? The new audio analysers are more than a magnitude better, but you do what you can.? You may find that a really good sound card can enhance your capabilities, but they do not tolerate input voltages over 5 Vpk? max.? That's a problem with tube stages and also solid state, so you need to condition and limit the input.? Calibrating this isn't too hard.
-Chris
The 8903B is a fine analyser within it's limitations.? I wish I could afford either of the two current audio analysers, but like you I can't.
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Re: HP65 software and memory strips?
I wasn't so much scolding you about being OT, as pointing out that you may get more interest on other mailing lists.
-Dave
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On 2/20/22 14:26, Tony wrote: Hi Dave,
Apologies - didn¡¯t mean to post OT.
I¡¯ll take it off line from now on.
T.
On Sun, 20 Feb 2022 at 19:14, Dave McGuire <mcguire@... <mailto:mcguire@...>> wrote:
On 2/20/22 13:33, Tony wrote:
> While sorting through packing material to dispose of I found a
package
> that came with my HP85 but which I not noticed.
>
> I had to do some research but realised it contains a big
collection of
> HP65 calculator programmable strips and some HP software pacs. See
> attached pics.
>
> I was wondering if these strips are still readable after many years?
>
> I have no use for them but also have no idea if there is any
interest in
> these sorts of items now?
>
> There is also something that looks like a battery pac charger -
it has
> an electrical connector on the bottom. But no idea what it is for.
? ?This really isn't the right place for it, but HP calculators and
early computers have a HUGE following.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
--
--
Dave McGuire, AK4HZ
New Kensington, PA
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Re: HP65 software and memory strips?
Yes, that is the charger for the early HP calculators, including the models 35, 45, 55, 65, 67, 70, 80.
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On Feb 20, 2022, at 13:24, Mark Bielman <mbielman@...> wrote:
?
If I remember correctly, the HP75 uses the same battery pack.
Mark
It is possible that the cards are still readable and even if they are not they can probably be re-written if you go over to MoHPC
? I am sure you would find someone interested The battery charger is an external charger for the battery pack that the HP-65 used among others.
Paul.
On 2022-02-20 14:33, Tony wrote:
Hi,
While sorting through packing material to dispose of I found a package that came with my HP85 but which I not noticed.
I had to do some research but realised it contains a big collection of HP65 calculator programmable strips and some HP software pacs. See attached pics.
I was wondering if these strips are still readable after many years?
I have no use for them but also have no idea if there is any interest in these sorts of items now?
There is also something that looks like a battery pac charger - it has an electrical connector on the bottom. But no idea what it is for.
thanks
Tony
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Re: HP65 software and memory strips?
Hi Dave,
Apologies - didn¡¯t mean to post OT.
I¡¯ll take it off line from now on.
T.
On Sun, 20 Feb 2022 at 19:14, Dave McGuire < mcguire@...> wrote: On 2/20/22 13:33, Tony wrote:
> While sorting through packing material to dispose of I found a package
> that came with my HP85 but which I not noticed.
>
> I had to do some research but realised it contains a big collection of
> HP65 calculator programmable strips and some HP software pacs. See
> attached pics.
>
> I was wondering if these strips are still readable after many years?
>
> I have no use for them but also have no idea if there is any interest in
> these sorts of items now?
>
> There is also something that looks like a battery pac charger - it has
> an electrical connector on the bottom. But no idea what it is for.
? ?This really isn't the right place for it, but HP calculators and
early computers have a HUGE following.
? ? ? ? ? ? -Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
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Re: HP65 software and memory strips?
If I remember correctly, the HP75 uses the same battery pack.
Mark
toggle quoted message
Show quoted text
It is possible that the cards are still readable and even if they are not they can probably be re-written if you go over to MoHPC
? I am sure you would find someone interested The battery charger is an external charger for the battery pack that the HP-65 used among others.
Paul.
On 2022-02-20 14:33, Tony wrote:
Hi,
While sorting through packing material to dispose of I found a package that came with my HP85 but which I not noticed.
I had to do some research but realised it contains a big collection of HP65 calculator programmable strips and some HP software pacs. See attached pics.
I was wondering if these strips are still readable after many years?
I have no use for them but also have no idea if there is any interest in these sorts of items now?
There is also something that looks like a battery pac charger - it has an electrical connector on the bottom. But no idea what it is for.
thanks
Tony
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Re: HP-8753E Options Activated
Well done Rich.
Sounds like you have confirmed that 8753D and 8753E have the same EEPROM layout after all.
I did some service guide digging this morning and found some indications that they could be the same.
Br
Marcus
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Re: HP65 software and memory strips?
It is possible that the cards are still readable and even if they
are not they can probably be re-written if you go over to MoHPC
? I am sure you would find someone interested The
battery charger is an external charger for the battery pack that
the HP-65 used among others.
Paul.
On 2022-02-20 14:33, Tony wrote:
toggle quoted message
Show quoted text
Hi,
While sorting through packing material to dispose of I found a
package that came with my HP85 but which I not noticed.
I had to do some research but realised it contains a big
collection of HP65 calculator programmable strips and some HP
software pacs. See attached pics.
I was wondering if these strips are still readable after many
years?
I have no use for them but also have no idea if there is any
interest in these sorts of items now?
There is also something that looks like a battery pac charger -
it has an electrical connector on the bottom. But no idea what
it is for.
thanks
Tony
|
Re: HP65 software and memory strips?
On 2/20/22 13:33, Tony wrote: While sorting through packing material to dispose of I found a package that came with my HP85 but which I not noticed.
I had to do some research but realised it contains a big collection of HP65 calculator programmable strips and some HP software pacs. See attached pics.
I was wondering if these strips are still readable after many years?
I have no use for them but also have no idea if there is any interest in these sorts of items now?
There is also something that looks like a battery pac charger - it has an electrical connector on the bottom. But no idea what it is for. This really isn't the right place for it, but HP calculators and early computers have a HUGE following. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Thanks Radu,
I understand that the new audio analyzers are the best, but for now I make use of the HP8903B (which I really like) with the help of the PC to view, save and print the graphs.
I also saw the U8903B, very interesting but it costs too much for my finances.
-- Cheers
??? Attilio
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Hi Chris,
thanks I also think that the reverse RIAA also helps me to reduce the noise and to obtain a more realistic measure of the distortion. The HP8903B in my opinion is still an excellent audio analyzer, certainly the U8903B would be the best but its price is prohibitively expensive for me. With the help of the PC, a GP-IB - USB interface and specific software I can also save and print the sweep graphs from HP8903B.
Hello John Lyles,
I filtered the band that interested me, but I have very high distortion values ??at 20 - 30 Hz and between 12 kHz and 20 kHz, not realistic because viewing the waveform at those frequencies with the oscilloscope distortion (values ??up to 10%).
Hi Radu,
I expected very low distortion values, the line preamp test gave me a result from 20 Hz to 20 kHz below 0.07% of distortion.
I have tried to minimize mains frequency interference (50Hz), but with the tube phono preamp it is not easy (there is a disturbing signal at 50Hz of about 4mV pp at the output). Between the output of the HP8903B and the input of the phono preamp I have inserted a resistive divider to adapt the input level.
-- Cheers
? ? Attilio
|
HP65 software and memory strips?
Hi,
While sorting through packing material to dispose of I found a package that came with my HP85 but which I not noticed.
I had to do some research but realised it contains a big collection of HP65 calculator programmable strips and some HP software pacs. See attached pics.
I was wondering if these strips are still readable after many years?
I have no use for them but also have no idea if there is any interest in these sorts of items now?
There is also something that looks like a battery pac charger - it has an electrical connector on the bottom. But no idea what it is for.
thanks
Tony
|
Re: HP-8753E Options Activated
All:
I apologize, the second bullet below is for OPT 11.
Rich?
On Sunday, February 20, 2022, 01:28:20 PM EST, Rich Miller via groups.io <av8torrich@...> wrote:
All:
Today, I pulled the EEPROM from the A9 CPU Board and took a look at it's binaries. With the help of another member of the group (Joe), who has been very supportive, I was able to finally figure how to activate all options on the 8753E. The bottom line is:
- Address 0x00 - 0x02 must be populated with "F7 F7 F7"? (NOTE This activates OPT 006, 10, and 02)
- Address?0xBC - Populate with 01 to activate and 00 to disable.
This is before the serial number of the VNA. If this is done, then you will be greeted with the enclosed boot up screen. I was also pleasantly surprised to see that "ALL INT TEST PASS".?
Now that I have all these Binaries, and notes I took while figuring this out, would it be benificial for me to store these on the files portion of the Groups.io page?
Thanks for everyone's input!
Rich?
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HP-8753E Options Activated
All:
Today, I pulled the EEPROM from the A9 CPU Board and took a look at it's binaries. With the help of another member of the group (Joe), who has been very supportive, I was able to finally figure how to activate all options on the 8753E. The bottom line is:
- Address 0x00 - 0x02 must be populated with "F7 F7 F7"? (NOTE This activates OPT 006, 10, and 02)
- Address?0xBC - Populate with 01 to activate and 00 to disable.
This is before the serial number of the VNA. If this is done, then you will be greeted with the enclosed boot up screen. I was also pleasantly surprised to see that "ALL INT TEST PASS".?
Now that I have all these Binaries, and notes I took while figuring this out, would it be benificial for me to store these on the files portion of the Groups.io page?
Thanks for everyone's input!
Rich?
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Re: Mixing 'n' matching S parameter test sets
HP stuff in general is very serviceable as I'm sure everyone here knows. The 8754A I have has been apart quite a few times since I've owned it. It's a dream to work on and pretty much infinitely reparable into the future. That's another great attraction for me with vintage test equipment. If you buy new today you haven't a hope in hell of fixing it if it goes wrong. So it seems to me, anyway, but of course YMMV.
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Re: HP8903B - THD measure on Phono RIAA preamplifier
Chris, Attilio, Indeed, an AP box greatly enhances one's ability to do such measurements. I've used an HP8903B w/ Pete's software for a bit some years back, and it's been good, but I've since?switched to AP. Different ballgame, all this is packaged into the unit/software and you can do orders of magnitude?more things,?and quite a bit more straight forward too.?
Not to discourage you, Attilio, on the contrary, this is really fun and gives you quite a bit of ability to perform measurements?and assess your units or designs. Once you nail this, I recommend looking into one of those instruments. Audio Precision is the leader in this field, and System Ones are not quite so expensive these?days. Even?System Twos, if you have a bit more to put into this.?
Radu.?
On Sun, Feb 20, 2022 at 10:09 AM bhome1959 < bhome@...> wrote: Hi??Attilio,
A reverse RIAA network is what I use.? You can check the accuracy of the EQ curve as you are doing, or if you characterise the reverse RIAA network it becomes more simple.? One thing the network will do for you is reduce the noise floor of the 8903B so you can get better readings.
One thing I had to do is move to a modern audio analyser such as a U8903B or Audio Precision in order to get noise floors low enough.? I was lucky enough to grab an RTX 6001 when they were briefly available, coupled with Multi-instrument (M.I.) software, it is an effective tool.? ARTA also works for quick jobs.? I understand that these are very expensive options, so I hope the 8903B with the reverse RIAA? can give you measurements adequate for your needs or expectations.? I dearly wish I could afford a Keysight U8903B.
-Chris
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Dave McGuire
Attilio
Glydeck
Jinxie