Teardown and Repair of a Fluke PM6303A Automatic RCL Meter

[Hugoneus]

You can watch the video here: [27 Minutes]
youtu.be/vd9VdphNst4

More videos at The Signal Path:
http://www.TheSignalPath.com

[BravoV]

Thanks, great video. 

Just for reference, the PM6303A's bigger brother -> PM6306 Teardown Photos or the whole thread about it -> PM6306 Discussions

[TiN]

Neat work. Like frequency of new vids too 
Can share service manual as well?

[HighVoltage]

Thanks for another great repair video.

I will upload the service manual to the FTP today for everyone.

[HighVoltage]

All PM6303A manuals, including service manual uploaded to ko4bb

[Hugoneus]

All PM6303A manuals, including service manual uploaded to ko4bb

Thank you again. Very much appreciate that you shared these.

[AF6LJ]

Thank you for the video, it made for good viewing while I finish my last cup of coffee.

Good Stuff.

[plesa]

Nice vid, thanks. It looks like you have lab almost full. How often you use repaired equipment?
Or it is more like addiction ?    I have the same disease.

[vaualbus]

Good video, but I guess the network analyzer repair video would be more interesting.
That network analyzer is in the background of three video. As far as we can see it have a lot of boards! 

[PA0PBZ]

I'm puzzled by the inductor increasing the value when you take the ferrite out, it seems wrong.
Afaik the inductance of an air coil is lower than one with a ferrite core 

[Hugoneus]

I'm puzzled by the inductor increasing the value when you take the ferrite out, it seems wrong.
Afaik the inductance of an air coil is lower than one with a ferrite core 

You are correct. If you look closely, you can see that the instrument is not in AUTO mode and is selecting the parallel L/R mode with the R as the dominant component. This impacts the computation of L and reverses the trend in its value versus the position of the ferrite core. I added a note to the video as well. Thanks!

[Hugoneus]

Good video, but I guess the network analyzer repair video would be more interesting.
That network analyzer is in the background of three video. As far as we can see it have a lot of boards! 

I know, I know! Sorry.

[HighVoltage]

May be I missed it, but did you press the "Trim" button above the cable connector once with open connection and once with shorted connection to compensate for wire capacitance and inductance. It usually makes a big difference on this instrument.
After it is done with the compensation, it will show "PASS" in the display. (At least in my unit with FW v1.1)
This might had an influence on the inductor measurement as well.

[Hugoneus]

May be I missed it, but did you press the "Trim" button above the cable connector once with open connection and once with shorted connection to compensate for wire capacitance and inductance. It usually makes a big difference on this instrument.
After it is done with the compensation, it will show "PASS" in the display. (At least in my unit with FW v1.1)
This might had an influence on the inductor measurement as well.

Yes! I actually did do that right before the last segment of the video. I should have mentioned it in the video.

[Earendil]

Good video, but I guess the network analyzer repair video would be more interesting.
That network analyzer is in the background of three video. As far as we can see it have a lot of boards! 

I know, I know! Sorry.

Wow, is that an Anritsu 373XXA? Very impressive. 
I can't wait seeing the repair and hopefully upcoming VNA measurement videos too

[Vgkid]

Just got around to watching it, nice video.

[CrazyFin]

@Hugoneus: Wonderful video! 

I´ve had a working PM6303A for many years and when I was clumsy enough to partially make bad due to forgetting to discharge a 4700 uF electrolytic cap before making a measurement my PM6303A was showing bad measurement values.

I was able to partially fix my PM6303A thanks to your video (had the complete service manual since many years but your video really helped me out  ).

My remaining issue now is that when I measure electrolytic caps that have higher capacitance than somewhere around 200-300 uF, I get quite low readings. I do have the DC BIAS set to on (and it does output 2.00 VDC).

A 4700 uF shows up at approx 3500 uF in auto mode and if I turn off automode and select Ls/Cs mode then the value jumps up a little bit to around 4200 uF. If I take the same cap and measure it with my ESR-Micro 4.0 I get almost a spot on value of 4710 uF.

A 470 uF cap shows up at approx 390 uF. Lower caps, for example cheramic caps and polyester caps below 100 uF and down to pF-levels shows up correctly.

I am wondering if something else than the input diodes and resistors are bad. I've checked the 4.7V zeners in the PSU area and replaced one that was showing too low value so both zener voltages there are correct (+4.62V and -4.68V).
Could it be the LF356N (N101) on the input stage being bad or even the 74HC4053 (D101) since this would take a direct hit of a non-discharged cap connected to the front panel? Are the coils or caps on the connector board at the front panel at risk as well (fig 53 on the schematics, unit 3)?

Can anyone of you who also have the PM6303A measure a 4700 uF cap and see what values you get please?

I also realised that my firmware is older than yours, I have 1.2 while your video seems to indicate that you have firmware revision 1.4. Would it be possible to purchase a firmware copy of your chip?