Hi

Do you have access to a signal generator >3GHz?

It would help a lot, because that can help you to figure out where the problem is.

So if low band is low and high band is ok, the failure is most likely low band first mixer or second converter, or any signal/power feeding them.

If both low and high band is low, the you should check the IF path, by injecting a signal into the third mixer and checking what level you get on the display, compared to what it should be compared to the service manual.

You might of course have more than one failure...

I once fixed a 8563A that had low level on only the low band, problem was in the second converter, on the pcb.

When this converter was made, the one soldering the trough hole components cut the leads after soldering, and cutting down into the solder, over the years the stress on the solderings made them break.. Would think that HP would know better.. At least when I was trained for soldering certificate, I was told this was a big NO-NO. If you did do this, you should reflow.

Best of luck

Askild

On Sat, Apr 13, 2019 at 5:34 PM amirb <amir.borji@...> wrote:

oh, was it heating up? had you measured the bias voltage and DC current draw in that MMIC?
that usually (not always as I learned recently in repairing a R&S SME) gives you enough clue about the state the MMIC is in when you compare the values with datasheet


On Sat, Apr 13, 2019 at 11:02 AM, Dave Ireland wrote:

Amir

?

Haven't done much to day but I am starting to get obsessed again about the 100MHz level as when looking at the circuit third converter for the reason that might be 20dB down I realised that the local oscillator for the third converter is 300MHz derived just from the 100Mhz tripler.

?

I was just about to try injecting the 600Mhz from a sig gen and try selecting SIG ID which appears to switch in a 298MHz LO instead of the 300MHz to see if it makes up the 24dB but as fate would have it the MMIC in the 100Mhz oscillator has died and now the 300MHz has disappeared.

?

Off to order the MMIC.

?

Dave

?

?

?

On 13/04/2019 7:44 pm, amirb wrote:

When working on RF circuits only a proper RF active probe such as 85024A (ideal) or 1152A or 54701A or etc....will work
forget about passive probes unless accurate amplitude measurement is not your concern and you just want to see the signal
even for that purpose sometimes passive probes load your oscillator (depending on where you probe it) such that it stops oscillating!
The total system bandwidth (probe + scope or SA) is the key parameter.

Anyways, how do you measure the 600MHz? Do you have the proper connector (SMB or SMC i forgot) and do you measure it with 50 Ohm SA?

There are a couple of MMIC ampifiers in the final stages of the 600MHz REF, I would check them for DC bias voltage, DC current draw and? temperature to see if they are dead
of course with an active RF probe you could check their gain.

I would still focus on the mixers, for now you can just inject a 600MHz into the second converter
because if the low band mixer or the second converter is dead they are very expensive to repair or replace specially the second converter used to cost a fortune as I recall
and you might find it beyond economic repair. the 600MHz ref is easy to repair and its cheap. those MMICs can be found on ebay and they are cheap
or you might conclude that the 1st and 2nd mixers are fine and there is a problem in the IF and log amp, that is usually easy and not expensive to repair.



On Fri, Apr 12, 2019 at 08:11 PM, Dave Ireland wrote:

Amir

?

I think you are correct about the 100Mhz. I have become obsessed with the level without a proper method of measuring it. All the 300Mhz stuff following is working so can't be much wrong with it.

?

I am still however worried about the 600Mz level as this is being measured at the proper alignment point but another day dawns here in Australia and I have to leave it for a while.

?

Thanks for your help to date.

?

Dave

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?

?

Sent from my Samsung GALAXY S5

-------- Original message --------
From: amirb <amir.borji@...>
Date: 13/04/2019 00:00 (GMT+08:00)
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP8560E Low Level

I still doubt that there is anything wrong with the ref osc and 600MHz lo, really. it could be just a measurement trap.
how are you measuring those 9dBm and 17dBm in-circuit amplitudes? remember that only and only a proper RF active probe?
with careful grounding can give you the correct value. Any passive probe even the best 500MHz passive probe will give you totally out of whack values. I have been there...
even with an active probe (cap <1-2pF) still the precise point at which you measure it, is very critical. If the 100MHz is like 10dB low I am sure
you would be getting errors because the PFD will probably fail to work and the loop becomes unlocked.?

Moreover, as you explained, even when you inject 600MHz Lo from the outside your second IF is still 24dB low. That has nothing to do?
with the ref osc anymore.

another thing that puzzled me is that when you inject 310.7MHz to the third converter you get a trace at -32dBm? it should be much higher, close to -10dBm I think.
(adjust your atten to 10dB and ref level to 0dBm) How is the level of 300MHz third converter LO drive??

your 'default' noise floor is too low (it must be around -65 to -70dB as I recall from the units that I had in the past)
usually that means a mixer is not working but it can have other reasons further down the signal path

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