Electronics > Repair

E4407B Tracking Generator Repair

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analogRF:

--- Quote from: analogRF on September 24, 2020, 09:08:41 pm ---not sure if the golden mixer is HMC129. The packaging does not match. still it could be an old version of hmc129 with different specs...

another peculiarity here is that MNA6 (bottom right) is specified as 0.5-2.5GHz amplifier. So the signal in that path cannot be 3.92GHz as we expect.
I am thinking maybe that path is 1.96GHz and the golden mixer H129, actually does a harmonic mixing (mixing with the second harmonic of 1.96) ?
I wish you could do some tests and verify what frequency is there..

--- End quote ---

or maybe the signal is 1.96GHz at the MNA6 amplifier but then they multiply it by 2 using something similar to a diode at the bottom edge of the PCB right before the bandpass filter. So after that the BPF, filters in the 3.92GHz. This looks more plausible....that BPF must be very sharp with such widely spaced resonators.

smgvbest:

--- Quote from: analogRF on September 24, 2020, 09:08:41 pm ---not sure if the golden mixer is HMC129. The packaging does not match. still it could be an old version of hmc129 with different specs...

another peculiarity here is that MNA6 (bottom right) is specified as 0.5-2.5GHz amplifier. So the signal in that path cannot be 3.92GHz as we expect.
I am thinking maybe that path is 1.96GHz and the golden mixer H129, actually does a harmonic mixing (mixing with the second harmonic of 1.96) ?
I wish you could do some tests and verify what frequency is there..

--- End quote ---

What specifically would help the most to test?   I will work on doing that.
It is a 600Mhz in to this unit in the upper right.
the section you mark oscill? freq?   there are 3 pins this coming from the other side of the board as seen in the attached image

the other image is of the signals on the 10pin header input coming from the control board.  ALC_MON goes back to a OPAMP on the control board
ALC_EXT is suppose to be on same page but I cant' locate it.


analogRF:

--- Quote from: smgvbest on September 25, 2020, 02:15:36 am ---
--- Quote from: analogRF on September 24, 2020, 09:08:41 pm ---not sure if the golden mixer is HMC129. The packaging does not match. still it could be an old version of hmc129 with different specs...

another peculiarity here is that MNA6 (bottom right) is specified as 0.5-2.5GHz amplifier. So the signal in that path cannot be 3.92GHz as we expect.
I am thinking maybe that path is 1.96GHz and the golden mixer H129, actually does a harmonic mixing (mixing with the second harmonic of 1.96) ?
I wish you could do some tests and verify what frequency is there..

--- End quote ---

What specifically would help the most to test?   I will work on doing that.
It is a 600Mhz in to this unit in the upper right.
the section you mark oscill? freq?   there are 3 pins this coming from the other side of the board as seen in the attached image

the other image is of the signals on the 10pin header input coming from the control board.  ALC_MON goes back to a OPAMP on the control board
ALC_EXT is suppose to be on same page but I cant' locate it.

--- End quote ---

what pins are coming out of that area? can you mark them? do they connect to the other board?

w.r.t. tests, as I mentioned, i would start by just looking at the yellow marked area with an RF probe (even a home made 450ohm series resistor with RG316 cable. you can use two back to back female sma-to-board connectors and solder the SMD resistor between the center pins of the two and solder the surrounding pins together to make a cage around the resistor and then insert a pin inside the center and solder a solid wire to the body as ground pin. The other side is connected to your measuring device with standard RG316 SMA cable. I'll post a picture of mine tomorrow. It has worked for me flawlessly up to 7GHz before)
or if you can even check at low frequencies by an oscilloscope. Check to see if you have a good  signal at the input to the IGG5 hybrid or not when the error occurs. and if not, work your way back to the two amplifiers. Check their supply voltage (seems to me it should be 12V by the value of series resistor they used for biasing)
one thing that is important is to see if your unlevel errors happen at all frequencies or only at certain ranges. because that makes a big difference in strategy

Jay_Diddy_B:
Hi,

I don't know what documents you have. I found this one:


https://www.testworld.com/wp-content/uploads/service-guide-agilent-e4402b-e4404b-e4405b-e4407b-e4411b-e4403b-e4408b.pdf

In this document there is this block diagram for the tracking generator:




This is very useful. It shows that the course steps 8 dB steps are set by A2A3.
The LO oscillator is levelled by the A2A1 to +16dB
The fine control of the TG output level comes from modulating the level of the 600MHz A2A2J5 -11.5dBm to -4dBm

I don't know what instruments you have to confirm the signal levels.

But I suggest setting the SA to a low frequency say 10MHz and zero span. This will cause the TG output frequency to be fixed and easy to measure with a scope. Terminate in 50 \$\Omega\$.

You could measure the output at A2A2J2. As you change the TG output level the signal should change in amplitude by 8dB (2.5x) and then go back to times 1.

Once you have measured the output of A2A2J2 you can reconnect the A2A3 attenuator and measure the output again. This will confirm the attenuator is working. It seems be doing the 8dB steps, but it may have a high insertion loss.

After this it is measuring the A2A1J1 which is the LO drive at 3.9 to 6.9 GHz and 16dBm. This is going to be hard without another SA or a power meter.

You should also measure the signal level on the 600 MHz signal at A2A2J5.

If you don't have a suitable instrument, consider a power detector demo board.

Regards,
Jay_Diddy_B

smgvbest:
Probably I should say I have the following equipment (test probes are where I am short) and limitations

My lab is not accessible at the moment so I'm not near the equipment, I am pulling things out as I need them
*Oscilloscope  Rigol 100Mhz
SA   *Rigol 815TG ((1.5 and most accessible) and Agilent E7495A (2.7Ghz)
*Tekbox Probes (near/far field)
2.5 Ghz Active Probe (untested, got off ebay)
*U2001H (USB 6GHZ)
HP E4418B w/ E4412
*Nano VNA

Those I starred are easy to access and move to the E4407/TG for testing

Note:   I did Terminate A2A2J2 with 50ohm and checked attenuator settings and had same "Source Unlevel" message, if it helps but seeing as it's measured before the A2A3 that may be expected?

it sounds like plan is
1. I need to re-assemble the TG and verify if "Source Unlevel" is at all frequency's (initial test was at 3Mhz-3Ghz) or some as well as the attenuator values
2. check 600Mhz in to TG at A2A2J5 (note SMB not SMA)
3. Check RF out at A2A1J1 (zero span and set based on finding in #1)
4. Make @analogRF RF Probe.
5. figure out how to measure Yellow section,  will likely have to make or find some extender cables to be able to access the board without the shielding on.  shouldnt' be hard. just need to do it

there's more I'm sure but a start

@analogRF
A2A1P1 to A2A2J1 Cable sends back ALC_MON to the A2A1 Driver board

I have both the service guide and CLIP but CLIP only shows the A2A1 board, 

Attached is where I mention the ALC_MON from the A2A2 board is feed back to the A2A1 board and into OP AMP to create the Unlevel Signal

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