Products > Test Equipment
Agilent E4432b unlevel issue again
hackwell:
Hi everybody
I read many threads discussing the unlevel failure on ESG D signal generators and watched Shahriar's video about the E4433.
got 2 units off Ebay few months ago. One with the unlevel error and one with a bad display. So I thought I could end up with a working sig gen in the end. Well... nope ! |O
The first unit has the board with the famous 1GM1 4201 and all the RF amps are custom hybrid chips. After some investigations I found a dead output amplifier and the QAM modulator 1GG7 1234 was roasted.
You can get them from UTsource for abt 150 bucks each (NOS)
So after some checkings and measurements I replaced both of them. Got a good signal for about 30 seconds then the QAM modulator died horribly. I bypassed the whole stage from the input to the filter with a jumper wire, losing the benefit of QAM in the process.
It worked quite well for a couple of weeks , in spite I couldn't reassemble the top shielding because of the bypass wire.
Then it went back to unlevel condition again , this time because of the burst modulator!
So I overrid this by soldering 2 wires before and after the PIN diodes as mentionned in the thread about Shahriar's video. I'm wondering what wil be the next failure !
The second E4432b was sold with a bad display, I was quite confident the ouptut board was OK. I easily fixed it, a bad transistor in the VLCD circuit. and guess what? unlevel as well...
After some measurements I foud 3 (yes 3!!!) dead RF amplifiers |O |O All of them except the one that was bad in Shahriar's video :-DD
As I had some NBB310 in stock I tried his workaround and it worked for 1 minute before the one before the LPFs died...
Now I have 2 boat anchors!
I ordered a bunch of SHF-1089 but this time I lack confidence dunno why.
In the meanwhile I'll try some reverse engineering.
Does anybody managed to find the cause of the burst modulator failure ?
Or some info about the QAM modulator?
Or traced back the RF amplifiers bias circuits ? They all issued by Q920 but there's additional circuitry in between...
hackwell:
quick update :
as I wrote befor , my attempt to replace the bad RF amplifiers by NBB 310 failed. So I tried with ADL5602ARKZ and I have a signal. The unlevel error is gone , but the signal is 8dB below what it should and a bit noisy.
I left one of the NBB310 , gonna replace it as well and see the result.
The ADL5602 provide 20dB gain with a +5v bias and not 8v , so I have to find a workaroud to get 5V from the 8V bias without using bulge wires in order to put the top shielding back into place (maybe the reason why the signal is so noisy BTW)
Maybe a zener diode could do the trick ?
EDIT : the IQ calibration fails at 14% with error 517
hackwell:
here are some news:
I replaced the 5 amplifiers by SHF0189Z I finally received and I can call it a success. The output is -0.87 dB below , no more unlevel error , the tone is clean above 250MHz. AM and FM modulation work fine.
I still get the IQ calibration error 517. Gotta investigate this.
Now calibration is the next step. As I used the python script to turn it into a E4433B via GPIB it now can go to 4GHz but it lost its calibration data as expected. (made a backup of U106 and U107 beforehand. If someone is interested I can share the files)
YetAnotherTechie:
Hello,
Can you backup the entire memory with gpib? what about cal constants?
Thank you
hackwell:
Hi ,
It must be possible as the firmware update from Keysight works by GPIB but I don't know the needed commands. And I think we have to kwon the address of the firmware in memory.
A bit of reverse ingeeniring could do the trick. It's on my to do list.
I did the backup using my TL866 programmer.
Navigation
[0] Message Index
[#] Next page
Go to full version