Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
The is also a modification for a second harmonic trim which uses feedback around the fet via a 2k trimmer. I have implemented this in a clone I built of the oscillator section and it makes a very marked improvement in reducing the 2H level.?
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
The oscillator IC is the Harris HA2625 which is discontinued. I believe the LT1468 is a suitable replacement. The HA2625 is also used as the product amplifier to drive the true RMS converter IC, an AD536 (still available albeit expensive). The HA2625 is used elsewhere in the unit, once you know one HP part number you can find all the similar ICs. The AD536 is a great chip for RMS if you drive it with a large signal. It’s very accurate below about 200-300khz. The AD637 is better if you want more frequency response but the pins are completely different (I digress). The oscillator uses a VCR2N fet for level control. You can find them second hand or try a 2N4091 or 2N4092 which are available from Mouser. The 4091 being the better choice.?
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
Hi Jim, et al.
I have an HP339A on my bench so I'm following this discussion thread with interest. My unit was manufactured in 1983 and currently needs some TLC. I offer some of the things that I have learned as I used my unit.
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On Sun, Sep 8, 2024 at 06:54 PM, Jim wrote:
...I looked through the schematic at the section for the monitor output and it's a simple path from the main meter circuitry (which appears to be working) - just a resistor, fuse and then the isolation relay. I hear the relay get activated/deactivated, so once I have the unit open again I will probe that path and see where the signal stops. I am hoping that it's just the 0.062A fuse.?
Note that the monitor output is disabled when the OSCillator LEVEL FUNCTION is selected. Reference manual sections 3-28 & 3-37. I did need to replace the 62mA fuse in my unit after I inadvertently applied an external signal to the front panel Output Monitor terminals. I was very happy to learn that the instrument was protected from such operator mistakes.
On Sun, Sep 8, 2024 at 06:54 PM, Jim wrote:
Did I read somewhere where HP did not include the schematic for the 339A's oscillator itself in the service manual?
My manual does include a foldout schematic of the oscillator circuits. However, the oscillator circuit uses two OP Amp ICs that are listed as manufactured by HP.
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When I was considering the purchase of my unit it was still easy to talk to a live person at an HP service center. The rep told me that "The most common failure in the 339 is the switches which wear out or get dirty. The frequency switches wear out the most with the distortion range switch next. It takes about 2 hours to change the switches so they often just change the complete PCB assembly. Both approaches are expensive. They don’t use any special cleaner just a good quality contact cleaner."
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Enjoy your 339A Jim.
Cheers,
Tom.
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
I have a 339A that I am about to press into service unfortunately it hasn’t been switched on for over 5 years so will probably require a bit of attention I have uploaded the service manuals to this sight Could I ask if you find any information or notes that you upload them to the files on this sight I am also interested in the baseline measurements on the 339A you talk about Regards Paul ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Jeremy B
Sent: 09 September 2024 20:13
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read) ? Great find. The 339A is a great improvement over the 333. I have the 339A and 334A, both are very useful instruments. Mine has been seeing a lot of work lately with my current project. Let me know if you need any baseline measurements on the 339A and I’ll try and help you out. Once you get it working I’d recommend checking online for the improvements which can be made. There’s a very comprehensive list on one of the audio forums (audio karma I think). Mine bottoms out around 0.0012% at 1khz but that can be improved.?
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
Great find. The 339A is a great improvement over the 333. I have the 339A and 334A, both are very useful instruments. Mine has been seeing a lot of work lately with my current project. Let me know if you need any baseline measurements on the 339A and I’ll try and help you out. Once you get it working I’d recommend checking online for the improvements which can be made. There’s a very comprehensive list on one of the audio forums (audio karma I think). Mine bottoms out around 0.0012% at 1khz but that can be improved.?
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Re: E4438c display problem, controler memory location please
I'll? sure check out the psu caps. This gen has about 40000 hours on the clock. Original seal's intact. When I opened it up found it's like new inside. No dust or dirt anywhere, my guess is it must have spent it's working life in a clean room. Has all board's fitted and a number of options. I didn't make a proper note but think it was drawing over 200W.
Many thanks John
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Re: E4438c display problem, controler memory location please
On a more general note, I would strongly recommend that you check/replace the main bulk capacitor in the main switched mode PSU module if it hasn't already been done. This is a known weak point once the E4438C sig gen has seen a lot of use. It failed in mine but luckily the previous owner immediately stopped trying to use it once it failed.
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Keysight looked at it and claimed that they couldn't repair it (they said the PSU module is obsolete) so I was able to??acquire the E4438C sig gen as BER.?Once it was mine, I replaced the cap and it has been fine ever since. There are plenty of pictures online of failed PSUs in these sig gens. If the bulk cap fully fails with low capacitance and high ESR then other components in the PSU are likely to fail in a big way. So it is worth replacing this cap.
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I think I used this 220uF 400V cap from Mouser with Mouser part number ?661-ETXH401N221MR35S. It is a higher spec version of what was already in the PSU with a longer lifetime and it only costs about ?4. Same manufacturer, same dimensions. However, the voltage rating is the same at only 400V. It might be worth trying to find one rated to 450V.?
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The other thing to be aware of is that these sig gens consume a lot of power when running. Mine has lots of hardware options fitted and it can exceed 200W power consumption when I measure it under certain operating modes. The datasheet says <300W. It isn't really suited as a general purpose sig gen because of this. I only use it when I need the special features or the high performance it offers.
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Re: E4438c display problem, controler memory location please
Thank you Mark
I have seen that part of the clip. Mine is a different release, not sure if newer or older but made in 2005 or 6. All lcd drive circuits appear to be on cpu card. Can't find a lcd controler chip so assume is been put in fpga. Have ordered both ram chips, will start with the 4Mb one.
John
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
Hi Tony what Distortion level did you manage to get the 339 down to ? also
what is the level flatness you have managed to achieve between say 75 hz to
20 Khz ?
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-----Original Message----- From: [email protected][mailto: [email protected]] On Behalf Of tony sayer Sent: 09 September 2024 11:28 To: [email protected]Subject: Re: [HP-Agilent-Keysight-equipment] HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read) In message < [email protected]>, Jim via groups.io <james_buttons@...> writes Thanks Dave.
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I'll look into that next. During my initial testing I did look at
the freq. output of the oscillator and I didn't see anything that
looked outrageous re: actual vs. setting, but I didn't run the math
to see if in spec. I the cases where the input LED was on,
sometimes the oscillator freq was spot on and other frequencies
where the LED was on freqs. seemed off from spec, but not too far
off. I think it may be a little bit of both - notch filter center
freq. being off in some cases, oscillator freq. off in others.
?
I looked through the schematic at the section for the monitor
output and it's a simple path from the main meter circuitry (which
appears to be working) - just a resistor, fuse and then the
isolation relay. I hear the relay get activated/deactivated, so
once I have the unit open again I will probe that path and see
where the signal stops. I am hoping that it's just the 0.062A fuse.
?
?
I am going to let the unit "bake" for a week or so. After 24 hours
the freq. that starts requiring the vernier is now down from 3.5
KHz to 3.3 KHz.
?
Did I read somewhere where HP did not include the schematic for the
339A's oscillator itself in the service manual?
? I think it is there are some versions for this unit online here and there had one for years very reliable;! Whilst your at it make sure of you change the power supply caps this improved the distortion reading on mine by a decent amount supply ripple i suppose?>. -- Tony Sayer
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
Re feet there is a file for feet to make them using a 3 D printer ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Roy Thistle
Sent: 09 September 2024 17:53
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read) ? On Sun, Sep 8, 2024 at 08:40 AM, Jim wrote: missing bottom feet
Yes, they often walk away here... hide amongst a large number of friends... in an un-labeled? cardboard box somewhere... and eventually...enjoy the ride... to their final home... the dump. There are models for them... and they can be 3D printed...by the local teenager... and if all you are interested is in functionality... from a distance... they look reasonably similar. The bright orange PETG print threw me off at first... but, one can't see it when the unit is on the bench... and the 'feet' keep the case from contacting the bench... which is a 'no no' here. But of course... nothing beats the bone fides. You can always find those on Ebay, for 10.00 to 20.00 USD + plus 50.00 USD shipping. I think scrappers, junk magnets, and metal hounds, keep the feet, and 'throw' the instrument away.
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
On 9/9/24 12:53, Roy Thistle wrote: missing bottom feet
Yes, they often walk away here... hide amongst a large number of friends... in an un-labeled? cardboard box somewhere... and eventually...enjoy the ride... to their final home... the dump. Wow, Roy. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
On Sun, Sep 8, 2024 at 08:40 AM, Jim wrote:
missing bottom feet
Yes, they often walk away here... hide amongst a large number of friends... in an un-labeled? cardboard box somewhere... and eventually...enjoy the ride... to their final home... the dump.
There are models for them... and they can be 3D printed...by the local teenager... and if all you are interested is in functionality... from a distance... they look reasonably similar.
The bright orange PETG print threw me off at first... but, one can't see it when the unit is on the bench... and the 'feet' keep the case from contacting the bench... which is a 'no no' here.
But of course... nothing beats the bone fides.
You can always find those on Ebay, for 10.00 to 20.00 USD + plus 50.00 USD shipping.
I think scrappers, junk magnets, and metal hounds, keep the feet, and 'throw' the instrument away.
?
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Re: 8566B attenuator removal
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Some Hp 8568b attenuator repair guidance, with photos, can be found here:
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rick
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Re: E4438c display problem, controler memory location please
I am not sure this covers the 4438B specifically, but the CLIP for the 4400 family shows that they use the 66510 LCD controller, at U607.? This controller uses a dedicated 514260 256k x 16 DRAM, at U610-A.
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Hope this helps,
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-mark
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Re: HP 8568B from hell to Heaven... a restoration story!
The RF unit
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I decided to first test the RF unit and leave the display for later. The RF unit was miraculously complete with all the boards. However, several screws and the plastic covers protecting the boards were missing. Additionally, the entire cooling fan assembly was not present. The tuning knob was missing from the front panel (fortunately i have some spares), and the covers were, of course, not there.
First, I installed a temporary fan to avoid overheating the unit, hoping to find the original one in the future. Then I turned on the unit and crossed my fingers...
The first power-up didn’t go well, no image on the screen, and the right red LED was on. The CPU board showed the fourth LED lit during the self-test, indicating an I/O error. The manual explains the possible causes of the problem: it could be two faulty PALs or many other reasons. While I was inspecting the device, I noticed that the I/O board wasn’t properly seated in its socket. I proceeded to remove, clean, and reinsert the board, and on the next power-up, I no longer had any errors, and the RF unit was alive!
Clearly, the backup battery was signaling depletion, so I replaced it. However, a big issue remained: there was no sweep, so the trace was stuck. I checked the amplifier board and noticed that someone had switched the input and output cables. Incredible... Once they were corrected, we had a perfect sweep.
At this point, I ran the first calibration, feeling quite confident, but unfortunately, it failed, even after adjusting the calibrator and frequency align to -10 dBm. I noticed that the calibration failed when it started exercising the attenuator. Indeed, there were some attenuator positions that didn’t work.
I manually exercised the attenuator, and after 3 or 4 switchings, it started working perfectly again. There was clearly some oxidized contact. I relaunched the calibration, and this time, everything went well. The RF part works perfectly.
After testing some sample signals, I loaded the HP DLPs via GPIB and declared the repair finished...
Now it’s time to move on to the 85662A…
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Re: 8566B attenuator removal
Well, I've ordered a range of sizes just to be on the safe side. Unfortunately they won't be arriving any time soon (yeah, China) so there won't be any updates for at least a week I'm afraid. Anyway, now I've got the attenuator out, this thread's objective has been achieved, so I'll begin a new one for the actual overhaul process when those parts are finally here.
Many thanks for your assistance! :)
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Re: HP 339A Distortion Test Set repair/refurbish (hamfest find) (long read)
In message < [email protected]>, Jim via groups.io <james_buttons@...> writes Thanks Dave.
?
I'll look into that next. During my initial testing I did look at
the freq. output of the oscillator and I didn't see anything that
looked outrageous re: actual vs. setting, but I didn't run the math
to see if in spec. I the cases where the input LED was on,
sometimes the oscillator freq was spot on and other frequencies
where the LED was on freqs. seemed off from spec, but not too far
off. I think it may be a little bit of both - notch filter center
freq. being off in some cases, oscillator freq. off in others.
?
I looked through the schematic at the section for the monitor
output and it's a simple path from the main meter circuitry (which
appears to be working) - just a resistor, fuse and then the
isolation relay. I hear the relay get activated/deactivated, so
once I have the unit open again I will probe that path and see
where the signal stops. I am hoping that it's just the 0.062A fuse.
?
?
I am going to let the unit "bake" for a week or so. After 24 hours
the freq. that starts requiring the vernier is now down from 3.5
KHz to 3.3 KHz.
?
Did I read somewhere where HP did not include the schematic for the
339A's oscillator itself in the service manual?
? I think it is there are some versions for this unit online here and there had one for years very reliable;! Whilst your at it make sure of you change the power supply caps this improved the distortion reading on mine by a decent amount supply ripple i suppose?>. -- Tony Sayer
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Re: hp 5480A Signal Analyzer I/O Connector Question
I have both the user manual (in paper form) and the service manuals that are scans from microfiche:
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Christopher
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Re: hp 5480A Signal Analyzer I/O Connector Question
As this is a relatively old instrument as far as bus/remote control is concerned, I am wondering if the connectors are possible BCD format for local i/o. ? Presumably this is documented in the main user manual? Do you have that? Regards Nigel ?
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From: [email protected] <[email protected]> On Behalf Of Christopher Tucker via groups.io
Sent: 07 September 2024 13:09
To: [email protected]
Subject: [HP-Agilent-Keysight-equipment] hp 5480A Signal Analyzer I/O Connector Question? I am working with an hp 5480A Signal Analyzer, especially its connection ports on the rear, as a programming exercise with a RaspberryPi: Concerning 18 and 19: The manual says J18 is something called a?Correlation Synthesizer while J19 points to an I/O Connector hp 5495A Would anyone have any information on either of these, what they consisted of?
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Re: HP 5342A blowing fuses on switch on
Jack,
I would check CR1 and CR2 (the bridge rectifiers) 1st. One might be shorted. Assume you have a DVM and know how to do this.
(with the board removed of course)
Mark
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My 5342A freq counter has started blowing fuses on switch on.
I removed the A19 board which just left the filter, fan and oven transformer in circuit. No blown fuse and the fan runs.
Replaced the A19 board and BANG.
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I am seeing a kit of PSU boards for a 5343 which, by the board numbers, look the same.
Should I just get these 3 and replace then all of does anyone have some insight?
I do not have an isolation transformer and am very hesitant to work on this while it's connected to the mains.
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Thanks
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Tom Phillips
Paul Bicknell
Dave McGuire
Jinxie
Christopher Tucker