Agilent ESG E4435B signal gen - no output at some frequencies

[Leo Bodnar]

I have an E4435B with unknown past.  It has problems with output loss at some frequencies: 250...375MHz, 500...750MHz, etc
The signal disappears on both front panel output and Aux Out "coherent carrier" SMA jack at the back.
Looks like synthesizer board loses lock in the 0.5-0.75GHz range.
Does anybody have quick hints or had the same problem?

I recall seeing an error message towards some RAM constants being bad in flash.  If this is calibration related - is there a way of rstoring them?

Cheers
Leo

[Tony_G]

I have a 4436B with a similar issue. I think it is the Frac-N IC but I haven't had a chance to go any further yet. Check out the HP group over at groups.io for the messages about it.

Interested in what you find.

TonyG

[nctnico]

I'd check the multipliers and filter sections on the synthesizer board.

[Leo Bodnar]

Multipliers and filters must be OK because the problem equally affects all multiples: 250MHz+, 500MHz+, 1000MHz+
I am probably looking at replacing dodgy 1GC1-4210 http://literature.cdn.keysight.com/litweb/pdf/E4435B-01E.pdf
Possibly, with another dodgy 1GC1-4210...
Leo

[Leo Bodnar]

Here is A24 synth board for future reference.
Suspect IC is U313 1GC1-4210
Cheers
Leo

[tautech]

I should have probably started this in "Repair" section... Please someone move it on occasion.

You can move it there yourself with the Move Topic feature. Look for it at the foot of the page.

[nctnico]

When I fixed my ESG generator I left the cover off the modules and soldered some wires to interesting test points to see if there was a signal or not (with the module fitted into the signal generator so it had airflow). I'd rather verify before replacing chips based only on a hunch.

[Leo Bodnar]

I'll see what I can find.

[Tony_G]

Nice - Look forward to seeing what turns up.

Out of interest, what connectors and crimping tool (for the cables, I don't have one right now but it looks like a good excuse to get one) did you use?

Thanks,

TonyG

[Leo Bodnar]

I have used DIN 1.0/2.3 connectors but they are 75Ω impedance.  I am looking for 50Ω version.
Leo

[Melt-O-Tronic]

I agree that it's likely the PLL chip (corrected:  Frac-N chip is what I meant -- that's where my testing seemed to point as well.  Good luck finding new chips!).  I had the same problem with my E4433A and was fortunate to find a complete working synthesizer board from an eBay seller in Moscow.  One day, I'll repair the original board.

For connectors, I learned somewhere on here that the board RF connectors are compatible with D-sub coax connectors.  I've bought Harting 09-69-281-7140 (female), 09-69-181-7140 (male) and also 09-69-181-5140 (male) and none work.  The center pins are all too thick.

Leo, do you think this might work?  It's 50 ohms.  (Better option at this link)




*BTW, Leo, I'm suddenly a fan of yours after seeing your pulse generator on The Signal Path (Hugoneous' YouTube channel) and then checking out your web site!   

[Tony_G]

Today at DigiKey I found out that the Connector Style filter is not sorted alpha numerically - Imagine my surprise when 1.0/2.3 showed up at the bottom of the list....

Anyway, I found these that might be applicable:

https://www.digikey.com/product-detail/en/amphenol-rf-division/102-799-04/ARF1976-ND/3593509
https://www.digikey.com/product-detail/en/amphenol-rf-division/102-913-06/ARF1986-ND/3593470

I was thinking of getting the bulkhead jack because it had a 10GHz maximum frequency, the in-line jack was limited to 2.5GHz - That said, seeing that my 4436B is only 3GHz I might be able to get away with using an inline jack.

For what it is worth, one of the connector datasheets I was reading strongly advised against using 75Ohm connectors due to center pin damage but I have no idea if it is a big or small thing or related to multiple use etc.

As for the ribbon cables - Are they just standard 0.1" headers? For some reason I was thining they're a more complex piece.

TonyG

[Leo Bodnar]

Thanks, Melt-O-Tronic!

I have found that Frac-N and VCO/PLL are fine and dandy.  The problem is in the U313 integer divider.  It is supposed to maintain its division ratio all the way through 4GHz to 8GHz input.  However, I can see it changing its division ratio between 4.0 and 5.5GHz to what is essentially half of what is required so the output doubles in frequency.  It is then hitting the wrong LPF and gets filtered out, otherwise you could have seen it at the instrument output.  The switchover at ~5.5GHz is not clean and very metastable and noisy.

I'll see whether this is the problem of U313 or the U311 analogue SPST that is controlling its ratio.

I don't want to use the IC that has fundamental problems with it.  I might just bodge modern Hittite prescaler in instead and be done with it.

I have just tested D-sub coax connector from CSA803A sampling head and 1.0/2.3 does not fit at all even without the central pin.

Leo

I agree that it's likely the PLL chip (corrected:  Frac-N chip is what I meant -- that's where my testing seemed to point as well.  Good luck finding new chips!).  I had the same problem with my E4433A and was fortunate to find a complete working synthesizer board from an eBay seller in Moscow.  One day, I'll repair the original board.

For connectors, I learned somewhere on here that the board RF connectors are compatible with D-sub coax connectors.  I've bought Harting 09-69-281-7140 (female), 09-69-181-7140 (male) and also 09-69-181-5140 (male) and none work.  The center pins are all too thick.

Leo, do you think this might work?  It's 50 ohms.  (Better option at this link)




*BTW, Leo, I'm suddenly a fan of yours after seeing your pulse generator on The Signal Path (Hugoneous' YouTube channel) and then checking out your web site!   

[Leo Bodnar]

I was thinking of getting the bulkhead jack because it had a 10GHz maximum frequency, the in-line jack was limited to 2.5GHz - That said, seeing that my 4436B is only 3GHz I might be able to get away with using an inline jack.

Middle coax connector (J1) carries 4..8GHz signal irrespective of the model.  But you should still be able to make it work.

For what it is worth, one of the connector datasheets I was reading strongly advised against using 75Ohm connectors due to center pin damage but I have no idea if it is a big or small thing or related to multiple use etc.

Do you have the link, Tony? I have tested the 75Ω and they fit nicely - not too tight, not too loose.  Agilent connectors don't see many mating cycles - unlike 75Ω version that are mostly used in broadcasting patch panels.  It might be a problem there.

As for the ribbon cables - Are they just standard 0.1" headers? For some reason I was thining they're a more complex piece.

Yes, they are 0.1" IDCs, highest frequency is 10MHz reference clock.  Pay attention when you are making them and try not to swap top and bottom pins.  Test twice.

Leo

[Tony_G]

Thanks Leo - Appreciate it.

I went looking for the info and it wasn't in a datasheet but on this page (note that it is for a different connector type):

http://www.coax-connectors.com/products/connectors/41626-(din)/29-005-d36-ab-din-41626-75-ohm-coax-crimp-crimp-straight-plug-insert.aspx

However, now that I look back at it I see that it was referring to another DIN spec - Before I discovered that 1.0/2.3 was available on DigiKey, I was trying to find something that would let me find it connectors here in the US so I was looking for the original spec number to try and get proper physical requirements to find what they're called in the US. Looks like I messed up on remembering where that warning was.

Sorry for the inconvenience.

TonyG

[Leo Bodnar]

OK, I call it "fixed" for now.

I have deadbugged 1,2,4,8 Hittite prescaler in and it is plodding along fine.

It needs another ÷2 stage in front of this mother of all bodges.  Then I can bolt the lid down and put it back together.

Leo

[Tony_G]

Nice - What Hittite part did you use? Was that just because it was on hand?

From the sound of it the original U313 part did  divide by 2,4,8,16.

TonyG

[Leo Bodnar]

I had HMC862 on my desk for another project so used that.  Twice, because I have managed to blow one up.
Leo

[Leo Bodnar]

Finally fully fixed now, one up on Agilent.  All frequency ranges are working as they should.
Leo

[Melt-O-Tronic]

Congratulations!  Awesome work.     Do you have a schematic to work from?

Best I can find for my E4433A is the block diagrams in the service manual.  Can't find any trace of the elusive schematics for it.  My synthesizer board is substantially different from yours too.  There are some similarities, but they're mostly different.

[Leo Bodnar]

I have made this available for purchase from my website.

Tested and confirmed to operate through the whole of 250kHz-4GHz range.

Cheers
Leo

[Tony_G]

Outstanding - Thanks Leo, just bought one.

TonyG

[Melt-O-Tronic]

Mildly interesting point for reference:  Your 2 GHz E4435B's A24 synthesizer board is much more sophisticated than my 4 GHz E4433A's A12 synthesizer.  I don't even have a U313.

[Leo Bodnar]

Mildly interesting point for reference:  Your 2 GHz E4435B's A24 synthesizer board is much more sophisticated than my 4 GHz E4433A's A12 synthesizer.  I don't even have a U313.

This is because you have ESG-D model as opposed to ESG-DP model which uses YIG oscillator to lower the phase noise level.
The good news is: you don't have to worry about U313 expiring on you. Norwegian Blues stun easily, major.
Leo

[thorswait]

Hi there,
I was wondering, how are you able to manage to generate a 4GHz signal using an E4435B ? Wasn't this unit stuck at 2GHz ? Also I would like to tell you great work on the prescaler !