Ha, I can relate, Jinxie!? Between 12 hour workdays and about 2.5 hours a day on the freeway every day, I have zero time for extracurricular activities during the week.? Weekends I'm watching our son perform with the drum corps and/or running through the honey-do list, along with helping out with my mother-in-law, so minimal time then, too.? Such is life.? ? ? ? ? Jim Ford?
Sent from my T-Mobile 4G LTE Device
toggle quoted message
Show quoted text
-------- Original message -------- From: "Jinxie via groups.io" <paul666@...> Date: 4/14/24 12:15 PM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] Testing Scope Probes
JMR, thank you very much for the very thorough and well set out reply (and all your contributions on the topic as well of course). I'd be interested to see if I can duplicate your results with my own VNA just out of curiosity, as this is not something I've ever encountered before. Only problem is I don't get more than a couple of hours for this kind of pursuit each weekend and it'll be another 6 days before I i get the opportunity. :-(
|
JMR, thank you very much for the very thorough and well set out reply (and all your contributions on the topic as well of course). I'd be interested to see if I can duplicate your results with my own VNA just out of curiosity, as this is not something I've ever encountered before. Only problem is I don't get more than a couple of hours for this kind of pursuit each weekend and it'll be another 6 days before I i get the opportunity. :-(
|
Re: Source of measurements HP54542C
I went right through the manual again. The "Wform Save" button saves the waveform to one of 4 novolatile?memories. I cannot do a measurement on them, in fact the manual says you can't. So this is not the Memory used as a source. How do I delete a saved waveform? I can only overwrite what I saved. I can perform various Functions but not using the Blue shift button and F as the source. The exercises are interesting but do not cover more than using the Channel.? F and M are still a mystery to me.
Thanks JMR. I have been using most of the shift measurements like freq and risetime, all on any channel as the source. F seems to mean Function and M is for Memory. I don't know how to use them. Save saves the setup state but I don't think it saves the waveform, so how do I save it to memory?
But this, below, just adds confusion. I was thinking M could mean Measure or Markers. Apparently not.
I haven't used a 5454x scope in a long time, but the measurement tool is quite easy to use if you just want to do simple stuff.
To measure Vac rms on channel 1 simply press the blue (shift) button and this converts the keypad to the functions shown in blue text. Then press the Vac rms button near the bottom right corner of the keypad and then rotate the selection control as required to see C# (for channel) and then press 1 for channel 1 and it should then tell you the Vac rms of the waveform on channel 1 assuming channel 1 is turned on and active.
The user interface of this scope is generally quite awful in my opinion, but the measurement functions are quite easy (and fast!) to access.
I think that is how I used to use it. I generally hated using these scopes because the user interface was such a disorganised mess.
|
I also found an old VNA measurement of my 10073A scope probe. You can see from the blue trace that Cp falls up at VHF and UHF. It falls to about 5pF. You can also see the knee in the green Xp trace and then it starts falling again. This is fairly similar to the Xp plots from Tektronix, but obviously, I'm not measuring the same x10 scope probe as them. If you can now accept that I know how to use a VNA, and you accept that maybe (just maybe) Tektronix know how to do this too, then hopefully you can be convinced that the Cp of a typical x10 scope probe does reduce up at VHF. 
|
In case anyone claims that a 50R VNA can't reliably measure small capacitances at V/UHF, I've dug out an old VNA measurement I made of an exotic 3.3pF SMD cap up to 2GHz.? I measured it on a VNA and compared my result with the manufacturer's data as they provide VNA data for the same cap. I wanted to use the cap in an RF filter and needed to know how much the capacitance changes up at about 1500MHz. There will be about 1nH package inductance in the SMD part and this is why the capacitance creeps up above 1GHz. By 1600MHz it measures almost 5pF. I needed to be certain that the manufacturer's data was OK so I measured the cap in a suitable VNA fixture. You can see that my measurement was essentially the same as the manufacturer (ATC). If there had been even a 0.3nH parasitic error in my fixture then the result would have been very different up at 2GHz. My VNA test fixtures are generally good to many GHz. The blue trace starts at 400MHz because the manufacturer only measured the part above 400MHz. My measurement of the 3.3pF SMD cap is the red trace. 
|
This is getting ridiculous now... The Cp and Rp of a scope probe is very easy to measure up at VHF using a regular 50R lab VNA.? Here's another graph from Tektronix showing how Xp changes up at VHF. It looks like a hand drawn diagram but it looks reasonable to me. I've been measuring stuff with various impedance analysers for decades and this includes many, many scope probes. How come none of you have ever done this if you have access to test gear at home or at work? 
|
Re: Source of measurements HP54542C
Thanks JMR. I have been using most of the shift measurements like freq and risetime, all on any channel as the source. F seems to mean Function and M is for Memory. I don't know how to use them. Save saves the setup state but I don't think it saves the waveform, so how do I save it to memory?
But this, below, just adds confusion. I was thinking M could mean Measure or Markers. Apparently not.
I haven't used a 5454x scope in a long time, but the measurement tool is quite easy to use if you just want to do simple stuff.
To measure Vac rms on channel 1 simply press the blue (shift) button and this converts the keypad to the functions shown in blue text. Then press the Vac rms button near the bottom right corner of the keypad and then rotate the selection control as required to see C# (for channel) and then press 1 for channel 1 and it should then tell you the Vac rms of the waveform on channel 1 assuming channel 1 is turned on and active.
The user interface of this scope is generally quite awful in my opinion, but the measurement functions are quite easy (and fast!) to access.
I think that is how I used to use it. I generally hated using these scopes because the user interface was such a disorganised mess.
|
Not sure what the source of the graph is or the testing methodology, but there's also the possibility of measurement error rather than any quirk in the probe. Perhaps we're looking at an effect that doesn't exist?
|
Hi.
That's what I'm wondering too.? But...? the "wrinkle" in Xp at UHF, could perhaps be be due to stray low value inductance, or dielectric loss at UHF. I need to dig deeper.
As always, The Devil is in the detail.
73.
Dave 'KBV.
|
Re: Source of measurements HP54542C
I haven't used a 5454x scope in a long time, but the measurement tool is quite easy to use if you just want to do simple stuff.
To measure Vac rms on channel 1 simply press the blue (shift) button and this converts the keypad to the functions shown in blue text. Then press the Vac rms button near the bottom right corner of the keypad and then rotate the selection control as required to see C# (for channel) and then press 1 for channel 1 and it should then tell you the Vac rms of the waveform on channel 1 assuming channel 1 is turned on and active.
The user interface of this scope is generally quite awful in my opinion, but the measurement functions are quite easy (and fast!) to access.
I think that is how I used to use it. I generally hated using these scopes because the user interface was such a disorganised mess.
|
I'm not sure if there's still some confusion with the graph I posted up so I'll have another go... I've now amended it with markers at 1MHz, 10MHz and 100MHz. See the graph below. At 1MHz Xp is about 16k ohm. If you use the formula for capacitive reactance, this works out to be 10pF at 1MHz. At 10MHz Xp is about 1.6k ohm. If you use the formula for capacitive reactance, this works out to be 10pF at 10MHz. So the capacitance is fairly constant up to about 10MHz. At 100MHz Xp is about 225 ohm (green marker). If you use the formula for capacitive reactance, this works out to be 7pF at 100MHz. 7pF is less than 10pF so the graph effectively shows that the parallel tip capacitance Cp falls up at VHF. The compensation capacitor in the tip of the probe is going to be in series with a lossy transmission line (coax). Not all x10 scope probes are made the same way but many of them use resistance wire for the centre conductor in the coax. This helps damp the probe at high frequency. The net result of this is that the input compensation capacitance is in series with a loss resistance. If you plot the Cp vs frequency for a capacitor in series with a resistor, the Cp will fall up at higher frequencies. There's also a small amount of shunt capacitance at the tip and this prevents the capacitance from falling a lot up at VHF and UHF. The alternative is to simply measure it with a VNA. A VNA should be able to measure the Cp and Rp of a typical x10 scope probe across about 10MHz to several hundred MHz. Below 10MHz it becomes much harder for the VNA to measure Rp correctly as Rp becomes quite large. However, it should be able to measure changes in Cp across a few MHz through to several hundred MHz. 
|
Dave,
I *assume* he means capacitive *reactance* rather than pure capacitance..?
|
OK, so what is the physical mechanism that causes that? (Citation please.)
Dave KBV
|
Re: Source of measurements HP54542C
I have several manuals including a paper service manual. I went through the entire manual looking for the information. Unfortunately the manuals are adapted from the 54540A manual and the two are slightly different. I need to hear from someone who has figured out what these other selections mean.? Some menu items do not exist and some instructions do not work. If I had not noticed?the C, F, and M? and tried them then none of the Blue key options would work. The manual does not explain what to select. It just says select the Source and until I tried C nothing worked. Peter
On Sun, Apr 14, 2024 at 05:34 AM, peter bunge wrote:
54542C DSO.
Good morning Peter from Australia.? While I don't have this CRO (I have a HP 54600) I suggest look at?
for the resource information.?Specifically the Quick Start Guides. These are sometimes called QIG Quick install guides on differing products. Written to get you familiar with some basic measurements as a starting/learning point.?
Working through the QSG and once familiar with basic controls, terminology and functions referring to the user manual will make more sense. Sometimes there is an overall series manual that will be more informative in general terms.
Of course youtube will contain at least someone showing basic use, unpacking and use, repair and use etc. These can be useful in some way.?
Good luck.?
maxwelloau
|
Re: Source of measurements HP54542C
On Sun, Apr 14, 2024 at 05:34 AM, peter bunge wrote:
54542C DSO.
Good morning Peter from Australia.? While I don't have this CRO (I have a HP 54600) I suggest look at? for the resource information.?Specifically the Quick Start Guides. These are sometimes called QIG Quick install guides on differing products. Written to get you familiar with some basic measurements as a starting/learning point.? Working through the QSG and once familiar with basic controls, terminology and functions referring to the user manual will make more sense. Sometimes there is an overall series manual that will be more informative in general terms. Of course youtube will contain at least someone showing basic use, unpacking and use, repair and use etc. These can be useful in some way.? Good luck.? maxwelloau
|
Re: HP8568B battery replacement
Gianini, The reason that you had 2 different batteries in your 8568B (it used to be an A before the B mod), the person that did the mod did not remove the 3 cell battery pack, which he was supposed to do per the B installation note. The only battery used now is on the A15 brd. in the RF section. There are no calibration factors stored in this memory, only user settings are kept alive with this battery. If you run the self correction routine those values may be kept in the battery backed memory., until you run the correction routine again. The attenuator corrections are stored in the EProm that is replaced when you change the attenuator, IIRC it may be A15U8??.
|
Re: OT: low volt wiring, supercaps
On 2024-04-13 11:36 AM, John Griessen via groups.io wrote: Who would put some DC wiring in their house to be able to use solar PV to run
things like computers? I would and did. I have 48V solar with two 230AH battery banks in parallel (but can separate them if I need to); this runs a true sine wave 240/120VAC inverter. Some heavy 240/120VAC wiring to the central utility room, where it branches out on its own subpanel to transfer switches that I have tested to confirm break-before-make, so I can put individual loads (including the 240VAC well pump) on either solar or grid power at will. I also have 12V solar, similarly with four 230AH battery banks in parallel. I no longer use the inverter on this system, but have run #6/3 cable to its own breaker panel in the utility room (standard GE commodity circuit breakers are rated to 30VDC), with sub-circuits to run my ham radio gear, LED "candles" in the windows, assorted convenience lighting including some low-light safety lights near top and bottom of the stairs, outside each bathroom, and a few other critical areas, as well as kitchen lighting and reading lamps over our bed. When a storm knocks out grid power here, life continues pretty much normally - but the internet "doesn't work", giving a better excuse for family board games around the kitchen table. I just wish I'd have known what I know now, when we had the house built some 39 years ago, and the general contractor said "the tradesmen will handle it" when I demanded to see mechanical drawings for how the electric, plumbing, heating, etc. was going to run. I should have stood my ground. Steve Hendrix
|
Re: HP6643A - Blows Fuse When Activated
Appliance bulbs in particular.? Are halogen considered incondescent?
They are.? May not quite work the way you think, but they are. They're higher temperature than normal incandescent.? Definitely look for appliance bulbs.
Harvey
toggle quoted message
Show quoted text
On Sat, Apr 13, 2024, 5:15?PM Peter Gottlieb <hpnpilot@...> wrote:
They sell them in the local Home Depot, appliance bulbs and
halogens bulbs.
On 4/13/2024 6:23 PM, Michael Yellin wrote:
> I can't believe how difficult it is to find an incandescent
bulb.? Gotta wait
> to get one from Ebay.
>
> On Mon, Apr 8, 2024, 9:27?PM Michael Yellin via groups.io
<> <>
> <michaelhq54@...> wrote:
>
>? ? ?Will do.? Thanks for the offer, I plan to take you up on it.
>
>? ? ?On Mon, Apr 8, 2024 at 4:43?PM Peter Gottlieb
<hpnpilot@...> wrote:
>
>? ? ? ? ?Try starting with a 60 Watt incandescent.
>
>? ? ? ? ?If you need help troubleshooting the supply I would be
happy to assist.
>
>? ? ? ? ?Peter
>
>>? ? ? ? ?On Apr 8, 2024, at 7:33?PM, Michael Yellin
<michaelhq54@...> wrote:
>>
>>? ? ? ? ??
>>? ? ? ? ?Peter,
>>
>>? ? ? ? ?This idea "You could wire an incandescent bulb in place
of the fuse
>>? ? ? ? ?so you don't keep blowing them.? Find a wattage that
will allow the
>>? ? ? ? ?supply to boot, but then light
>>? ? ? ? ?up when the short occurs" is very interesting. How can
I choose the
>>? ? ? ? ?appropriate wattage of light?
>>
>>? ? ? ? ?Thanks,
>>? ? ? ? ?Michael
>>
>>? ? ? ? ?On Sat, Apr 6, 2024 at 7:05?PM Peter Gottlieb
<hpnpilot@...> wrote:
>>
>>? ? ? ? ? ? ?Could be a lot of things.? The manual is available
on the web.
>>? ? ? ? ? ? ?At quick glance
>>? ? ? ? ? ? ?it seems when the supply is "on" before being
enabled, the main
>>? ? ? ? ? ? ?transformer and
>>? ? ? ? ? ? ?rectifiers are live.? You can verify by measuring
at the main
>>? ? ? ? ? ? ?electrolytics.
>>
>>? ? ? ? ? ? ?My guess is something is wrong with the pass
elements and the
>>? ? ? ? ? ? ?supply crowbars
>>? ? ? ? ? ? ?but doesn't limit current and the fuse takes over.?
You may be
>>? ? ? ? ? ? ?able to max out
>>? ? ? ? ? ? ?the crowbar OVP limit and not blow the fuse but
that won't solve
>>? ? ? ? ? ? ?the problem.
>>
>>? ? ? ? ? ? ?You could wire an incandescent bulb in place of the
fuse so you
>>? ? ? ? ? ? ?don't keep
>>? ? ? ? ? ? ?blowing them.? Find a wattage that will allow the
supply to boot,
>>? ? ? ? ? ? ?but then light
>>? ? ? ? ? ? ?up when the short occurs.
>>
>>? ? ? ? ? ? ?Peter
>>
>>
>>
>>? ? ? ? ? ? ?On 4/6/2024 9:48 PM, Harvey White wrote:
>>? ? ? ? ? ? ?> if the fuse blows when activated, then something
downstream of
>>? ? ? ? ? ? ?the fuse, (once
>>? ? ? ? ? ? ?> activated) is likely a short. Assuming that the
high amperage
>>? ? ? ? ? ? ?fuse blows
>>? ? ? ? ? ? ?> roughly as fast as the low amperage fuse (don't
try to measure
>>? ? ? ? ? ? ?it......) then
>>? ? ? ? ? ? ?> you're likely looking at a dead short downstream
of the fuse.
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?> Harvey
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?> On 4/6/2024 7:18 PM, Michael Yellin wrote:
>>? ? ? ? ? ? ?>> Mates,
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>> Recently acquired an HP 6643A.? When the unit is
plugged in
>>? ? ? ? ? ? ?and turned on, it
>>? ? ? ? ? ? ?>> boots, and seems fine. However, as soon as the
unit is
>>? ? ? ? ? ? ?"activated" to
>>? ? ? ? ? ? ?>> generate voltage and amperage, the glass fuse
blows.? I don't
>>? ? ? ? ? ? ?have an endless
>>? ? ? ? ? ? ?>> supply of fuses, but I have tried some very low
and very high
>>? ? ? ? ? ? ?voltage and
>>? ? ? ? ? ? ?>> amperage settings, but that made no difference
(I didn't think
>>? ? ? ? ? ? ?it would, but
>>? ? ? ? ? ? ?>> well, it made me feel better to try) Opened her
up, looked
>>? ? ? ? ? ? ?around, and
>>? ? ? ? ? ? ?>> everything appears fine, no burnt parts, no
bulging caps, no
>>? ? ? ? ? ? ?melted wires,
>>? ? ? ? ? ? ?>> and nothing obviously shorted. Anyone have any
ideas what
>>? ? ? ? ? ? ?could be wrong, or
>>? ? ? ? ? ? ?>> can send me down a path to try and resurrect the
thing.
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>> TIA
>>? ? ? ? ? ? ?>> Michael
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>
>>
>>
>>
>>
>>
>
|
Re: HP6643A - Blows Fuse When Activated
Ahhh, I'll look again. Went yesterday, and everything I saw was LED.? I'll look at appliance bulbs in particular.? Are halogen considered incondescent?
On Sat, Apr 13, 2024, 5:15?PM Peter Gottlieb < hpnpilot@...> wrote: They sell them in the local Home Depot, appliance bulbs and halogens bulbs.
On 4/13/2024 6:23 PM, Michael Yellin wrote:
> I can't believe how difficult it is to find an incandescent bulb.? Gotta wait
> to get one from Ebay.
>
> On Mon, Apr 8, 2024, 9:27?PM Michael Yellin via <>
> <michaelhq54=[email protected]> wrote:
>
>? ? ?Will do.? Thanks for the offer, I plan to take you up on it.
>
>? ? ?On Mon, Apr 8, 2024 at 4:43?PM Peter Gottlieb <hpnpilot@...> wrote:
>
>? ? ? ? ?Try starting with a 60 Watt incandescent.
>
>? ? ? ? ?If you need help troubleshooting the supply I would be happy to assist.
>
>? ? ? ? ?Peter
>
>>? ? ? ? ?On Apr 8, 2024, at 7:33?PM, Michael Yellin <michaelhq54@...> wrote:
>>
>>? ? ? ? ??
>>? ? ? ? ?Peter,
>>
>>? ? ? ? ?This idea "You could wire an incandescent bulb in place of the fuse
>>? ? ? ? ?so you don't keep blowing them.? Find a wattage that will allow the
>>? ? ? ? ?supply to boot, but then light
>>? ? ? ? ?up when the short occurs" is very interesting. How can I choose the
>>? ? ? ? ?appropriate wattage of light?
>>
>>? ? ? ? ?Thanks,
>>? ? ? ? ?Michael
>>
>>? ? ? ? ?On Sat, Apr 6, 2024 at 7:05?PM Peter Gottlieb <hpnpilot@...> wrote:
>>
>>? ? ? ? ? ? ?Could be a lot of things.? The manual is available on the web.?
>>? ? ? ? ? ? ?At quick glance
>>? ? ? ? ? ? ?it seems when the supply is "on" before being enabled, the main
>>? ? ? ? ? ? ?transformer and
>>? ? ? ? ? ? ?rectifiers are live.? You can verify by measuring at the main
>>? ? ? ? ? ? ?electrolytics.
>>
>>? ? ? ? ? ? ?My guess is something is wrong with the pass elements and the
>>? ? ? ? ? ? ?supply crowbars
>>? ? ? ? ? ? ?but doesn't limit current and the fuse takes over.? You may be
>>? ? ? ? ? ? ?able to max out
>>? ? ? ? ? ? ?the crowbar OVP limit and not blow the fuse but that won't solve
>>? ? ? ? ? ? ?the problem.
>>
>>? ? ? ? ? ? ?You could wire an incandescent bulb in place of the fuse so you
>>? ? ? ? ? ? ?don't keep
>>? ? ? ? ? ? ?blowing them.? Find a wattage that will allow the supply to boot,
>>? ? ? ? ? ? ?but then light
>>? ? ? ? ? ? ?up when the short occurs.
>>
>>? ? ? ? ? ? ?Peter
>>
>>
>>
>>? ? ? ? ? ? ?On 4/6/2024 9:48 PM, Harvey White wrote:
>>? ? ? ? ? ? ?> if the fuse blows when activated, then something downstream of
>>? ? ? ? ? ? ?the fuse, (once
>>? ? ? ? ? ? ?> activated) is likely a short.? Assuming that the high amperage
>>? ? ? ? ? ? ?fuse blows
>>? ? ? ? ? ? ?> roughly as fast as the low amperage fuse (don't try to measure
>>? ? ? ? ? ? ?it......) then
>>? ? ? ? ? ? ?> you're likely looking at a dead short downstream of the fuse.
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?> Harvey
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?> On 4/6/2024 7:18 PM, Michael Yellin wrote:
>>? ? ? ? ? ? ?>> Mates,
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>> Recently acquired an HP 6643A.? When the unit is plugged in
>>? ? ? ? ? ? ?and turned on, it
>>? ? ? ? ? ? ?>> boots, and seems fine.? However, as soon as the unit is
>>? ? ? ? ? ? ?"activated" to
>>? ? ? ? ? ? ?>> generate voltage and amperage, the glass fuse blows.? I don't
>>? ? ? ? ? ? ?have an endless
>>? ? ? ? ? ? ?>> supply of fuses, but I have tried some very low and very high
>>? ? ? ? ? ? ?voltage and
>>? ? ? ? ? ? ?>> amperage settings, but that made no difference (I didn't think
>>? ? ? ? ? ? ?it would, but
>>? ? ? ? ? ? ?>> well, it made me feel better to try) Opened her up, looked
>>? ? ? ? ? ? ?around, and
>>? ? ? ? ? ? ?>> everything appears fine, no burnt parts, no bulging caps, no
>>? ? ? ? ? ? ?melted wires,
>>? ? ? ? ? ? ?>> and nothing obviously shorted. Anyone have any ideas what
>>? ? ? ? ? ? ?could be wrong, or
>>? ? ? ? ? ? ?>> can send me down a path to try and resurrect the thing.
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>> TIA
>>? ? ? ? ? ? ?>> Michael
>>? ? ? ? ? ? ?>>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>? ? ? ? ? ? ?>
>>
>>
>>
>>
>>
>>
>
|
Re: HP6643A - Blows Fuse When Activated
They sell them in the local Home Depot, appliance bulbs and halogens bulbs.
toggle quoted message
Show quoted text
On 4/13/2024 6:23 PM, Michael Yellin wrote: I can't believe how difficult it is to find an incandescent bulb.? Gotta wait to get one from Ebay.
On Mon, Apr 8, 2024, 9:27?PM Michael Yellin via groups.io <> <michaelhq54@...> wrote:
Will do.? Thanks for the offer, I plan to take you up on it.
On Mon, Apr 8, 2024 at 4:43?PM Peter Gottlieb <hpnpilot@...> wrote:
Try starting with a 60 Watt incandescent.
If you need help troubleshooting the supply I would be happy to assist.
Peter
On Apr 8, 2024, at 7:33?PM, Michael Yellin <michaelhq54@...> wrote:
?
Peter,
This idea "You could wire an incandescent bulb in place of the fuse
so you don't keep blowing them.? Find a wattage that will allow the
supply to boot, but then light
up when the short occurs" is very interesting. How can I choose the
appropriate wattage of light?
Thanks,
Michael
On Sat, Apr 6, 2024 at 7:05?PM Peter Gottlieb <hpnpilot@...> wrote:
Could be a lot of things.? The manual is available on the web.?
At quick glance
it seems when the supply is "on" before being enabled, the main
transformer and
rectifiers are live.? You can verify by measuring at the main
electrolytics.
My guess is something is wrong with the pass elements and the
supply crowbars
but doesn't limit current and the fuse takes over.? You may be
able to max out
the crowbar OVP limit and not blow the fuse but that won't solve
the problem.
You could wire an incandescent bulb in place of the fuse so you
don't keep
blowing them.? Find a wattage that will allow the supply to boot,
but then light
up when the short occurs.
Peter
On 4/6/2024 9:48 PM, Harvey White wrote:
> if the fuse blows when activated, then something downstream of
the fuse, (once
> activated) is likely a short.? Assuming that the high amperage
fuse blows
> roughly as fast as the low amperage fuse (don't try to measure
it......) then
> you're likely looking at a dead short downstream of the fuse.
>
> Harvey
>
> On 4/6/2024 7:18 PM, Michael Yellin wrote:
>> Mates,
>>
>> Recently acquired an HP 6643A.? When the unit is plugged in
and turned on, it
>> boots, and seems fine.? However, as soon as the unit is
"activated" to
>> generate voltage and amperage, the glass fuse blows.? I don't
have an endless
>> supply of fuses, but I have tried some very low and very high
voltage and
>> amperage settings, but that made no difference (I didn't think
it would, but
>> well, it made me feel better to try) Opened her up, looked
around, and
>> everything appears fine, no burnt parts, no bulging caps, no
melted wires,
>> and nothing obviously shorted. Anyone have any ideas what
could be wrong, or
>> can send me down a path to try and resurrect the thing.
>>
>> TIA
>> Michael
>>
>
>
>
>
>
>
|
Jinxie
maxwelloau