HP 204C
Forum rules
Use tags for the type of equipment your topic is about. Include the "repairs" tag, too, when appropriate. If a new tag is needed, request one in the TEAdministration forum.
Use tags for the type of equipment your topic is about. Include the "repairs" tag, too, when appropriate. If a new tag is needed, request one in the TEAdministration forum.
Re: HP 204C
Glad you managed to get into it. I couldn't be bothered to work out how to get into the 204D I had. Peeled one layer off and there was another one!
Tags:
Re: HP 204C
Once I accidentally discovered that the PSU board plugged into the main board the rest was easy. But for quite a while I was scratching my head.
An old gray beard with an attitude. I don't bite.....sometimes 
Re: HP 204C
Started re-cap of the PSU board which is attached to the rear panel.
And we have a date.
And we have a date.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
Re-cap of the main board. C11 is the huge axial 300uf/10V non-polarized capacitor on the output. I was unable to find an axial capacitor of that value and type but I did find a Panasonic radial 330uf/10V non-polarized. Look at the size difference.
The only other capacitor changed is the blue one in the front (100uf). All those other capacitors are axial leaded tants. Have you priced them lately? Now I could try to stuff radial leaded beaded tants in those confined spots but decided against it. Why? Well in order to replace them all I'd have to pull the main board. That's gonna be a freaking jigsaw puzzle. So it's not happening. Now am I taunting Murphy? Absolutely. And am I getting lazy and smart in my old age? Yes.
Left to do. Re-assemble then test/calibration.
The only other capacitor changed is the blue one in the front (100uf). All those other capacitors are axial leaded tants. Have you priced them lately? Now I could try to stuff radial leaded beaded tants in those confined spots but decided against it. Why? Well in order to replace them all I'd have to pull the main board. That's gonna be a freaking jigsaw puzzle. So it's not happening. Now am I taunting Murphy? Absolutely. And am I getting lazy and smart in my old age? Yes.
Left to do. Re-assemble then test/calibration.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
Calibration was a bit fiddly but finally fell into place. Will burn-in for at least 2 hours then this project is complete.
Displaying 1MHz Sine.
Displaying 1MHz Sine.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
Oh no it isn't! Not until the spectral purity of that sine wave is checked out on a spectrum analyzer!
Re: HP 204C
No gots a spectrum analyzer. My tired old eyeballs are good enough.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
Not even a simple 12-bit Swiss army knife like the Analog Discovery? Tut, tut, tut <slowly sucks breath in through teeth>
Re: HP 204C
You must have a distortion meter somewhere.
-
nixiefreqq
- Posts: 192
- Joined: Fri Oct 28, 2022 12:41 pm
- Location: commonwealth of pennsylvania
Re: HP 204C
suggesting that med acquire a distortion analyzer is........just plain mean. it might cause him to go off searching for an hp334. (DON'T DO THAT!)
maybe he has a scope with an fft function? my hp54622 will measure distortion with an fft.
not being a tek guy i don't know for sure, but they must have made something similar? and doesn't med already have one each of every scope those guys in oregon ever made?
maybe he has a scope with an fft function? my hp54622 will measure distortion with an fft.
not being a tek guy i don't know for sure, but they must have made something similar? and doesn't med already have one each of every scope those guys in oregon ever made?
free range primate since 2011
Re: HP 204C
You guys kill me. Suggesting I go down all sorts of rabbit holes.
My Siglent SDS1052DL does have some basic FFT functions but I trust my crusty old eyeballs.
My Siglent SDS1052DL does have some basic FFT functions but I trust my crusty old eyeballs.
An old gray beard with an attitude. I don't bite.....sometimes
-
nixiefreqq
- Posts: 192
- Joined: Fri Oct 28, 2022 12:41 pm
- Location: commonwealth of pennsylvania
Re: HP 204C
hey. even my old 54601a does an fft.
https://www.hpmemoryproject.org/an/pdf/hp54600_fft.pdf
edit ok...it was purchased maybe 6 or 7 years ago, but it was only 75 bucks.
sure, a spectrum analyzer would be a lot cooler. but 75 bucks and it will measure distortion. (that's a win).
https://www.hpmemoryproject.org/an/pdf/hp54600_fft.pdf
edit ok...it was purchased maybe 6 or 7 years ago, but it was only 75 bucks.
sure, a spectrum analyzer would be a lot cooler. but 75 bucks and it will measure distortion. (that's a win).
You do not have the required permissions to view the files attached to this post.
free range primate since 2011
Re: HP 204C
Go on, try it. See what it can do and what the noise floor is
Or get a Keithley 2015THD, and use the suffix
-
Cubdriver
- Posts: 417
- Joined: Sat Oct 22, 2022 8:23 pm
- Location: Southeastern Litchfield County, CT
- Contact:
Re: HP 204C
Well, this is the TEA forum... <whistling>
Have you forgotten that being enablers is part of our charter?
-Pat
Re: HP 204C
I'm shocked that you so readily believe that your e-friends are trying to mislead you.
These are not rabbit holes and it's nothing like Alice in Wonderland - well not quite. We are merely encouraging you to embark on a delightful voyage of discovery (and expense, and obsession).
Since this goes up to 1.2MHz a distortion analyzer is only a part of the picture. An HP 8903 would do nicely up to 100kHz. Spectrum analysers typically start at 9kHz. So they are another part of the picture. There are audio spectrum analysers such as the HP 3580A - only goes to 50kHz, but it's a classic. If you want to cheap out, there are Heathkit distortion analysers, some with tubes.
As for the Siglent SDS1052DL, a fine instrument in its day, but you are not still struggling along with that old thing are you? You could be the envy of your neighbours with a Siglent SDS804X-HD 4Ch, 70MHz, 2GSa/s, 12 Bit scope, which you could hack to be the SDS824X-HD 4Ch, 200MHz, 2GSa/s, 12 Bit number.
Only trying to be helpful. I'm sure you know that.
Re: HP 204C
OK gang, here it is. I have really no clue what it all means. Comments welcome.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
Well, I have no clue what that specific instrument's display is trying to tell us, so only a few generic observations:
- expand the signal vertically so as to almost fill the whole screen. That will maximise the frequency domain peak relative to the noise
- the various window functions allow better/worse frequency resolution vs amplitude resolution. They also reduce artefacts related to not capturing an integral number of cycles
- most useful initial display shows 0Hz on the left and >5*fundamental on the right, thus making harmonics visible
- play around with signals having known harmonic distortion, e.g. a square wave. Once you can see those you will be in a position to be sure what you aren't seeing with your "real" signal
- play around with capturing more/fewer cycles, to see effect on the frequency domain display
- play around with other scope controls; some cheap scopes only process the screen display rather than the whole buffer
- play around with various averaging operations, to try to lower the noise floor
Re: HP 204C
You require a slower timebase setting on Siglent DSO’s when doing FFT.
Experiment with 50 or more cycles on the display.
If required I’ll pull out a DL when home in a day or so and show screenshots.
Siglent Distributor NZ, TE Enabler
Re: HP 204C
We've been trying to persuade him that he can't expect to get anywhere with his totally inadequate TE or his crusty old eyeballs. He thinks we are pulling his leg or maliciously leading him down rabbit holes. Perish the thought.
I'm sure as an experienced Siglent salesman and self-confessed TE enabler, you will be able to lead him to reason.
I haven't tried it, but I believe a very respectable distortion analyser can be made from a PC with a sound card and some software. There may be open source software.
I'm sure as an experienced Siglent salesman and self-confessed TE enabler, you will be able to lead him to reason.
I haven't tried it, but I believe a very respectable distortion analyser can be made from a PC with a sound card and some software. There may be open source software.
Re: HP 204C
Show me the way to Nirvana.
An old gray beard with an attitude. I don't bite.....sometimes
Re: HP 204C
I've got a Siglent SDS1102CML+, about the same vintage as your SDS1052DL. It's better spec'd and may be a bit later.
I played with the FFT function and was never very impressed or saw it as particularly useful. I may not have discovered how to drive it properly, but it seems to be a bit limited.
Sorry about the picture quality, I just snapped them off. I should get to grips with dumping screen shots to thumb drive, but I rarely need to do it. I took tautech's advice and slowed down the sweep and also averaged the display over 16 samples. It's a 10kHz signal.
FFT on the CML+ showing a sine wave. FFT on the CML+ showing a square wave. There's a difference between the sine and square waves, but it's hard to see what the levels or frequencies are.
FFT on an SDS2104X plus - a much modern, capable and expensive scope.
Showing a sine wave. Showing a square wave. Levels and frequencies are annotated, and you have control over what's displayed.
I think the FFT function on affordable DSOs from ten years back or so, was mainly a throwaway feature. As for the HP204C, I doubt you intend to use it for anything serious, such as testing amplifiers, so if the output looks like a good sine wave, it is a good sine wave.
I played with the FFT function and was never very impressed or saw it as particularly useful. I may not have discovered how to drive it properly, but it seems to be a bit limited.
Sorry about the picture quality, I just snapped them off. I should get to grips with dumping screen shots to thumb drive, but I rarely need to do it. I took tautech's advice and slowed down the sweep and also averaged the display over 16 samples. It's a 10kHz signal.
FFT on the CML+ showing a sine wave. FFT on the CML+ showing a square wave. There's a difference between the sine and square waves, but it's hard to see what the levels or frequencies are.
FFT on an SDS2104X plus - a much modern, capable and expensive scope.
Showing a sine wave. Showing a square wave. Levels and frequencies are annotated, and you have control over what's displayed.
I think the FFT function on affordable DSOs from ten years back or so, was mainly a throwaway feature. As for the HP204C, I doubt you intend to use it for anything serious, such as testing amplifiers, so if the output looks like a good sine wave, it is a good sine wave.
You do not have the required permissions to view the files attached to this post.
Re: HP 204C
I suppose this is much more meaningful?
An old gray beard with an attitude. I don't bite.....sometimes