Electronics > Repair

E4407B Tracking Generator Repair

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analogRF:

--- Quote from: smgvbest on October 17, 2020, 11:16:33 pm ---
--- Quote from: analogRF on October 17, 2020, 12:28:35 pm ---
--- Quote from: smgvbest on October 16, 2020, 11:29:44 pm ---Looking for help in identifying some components
in PICT0007.jpg   looking to identify all marked ones.  the one I put a D on,  the D is the only marking on the component.   I think this is a dual diode package for the peak detector.

I loose allot of power at the point of this component.   like -25dB.   this is suppling the 786.5hz RF to the Mixer (5x that but I can't measure on my 1.5Ghz SA)
in  IMG_2867-1.jpg

--- End quote ---

the white elements are most likely resistors. you can check with multimeter
the "D" element is most likely HMPP-3890 single schottky diode by Agilent/Avago but are you 100% sure about the marking? sometimes it is tricky to read the labels
seems that all 4 pins of it have been used  ??? also for a good temperature compensated peak detector it makes sense to have two diodes in one package but if the marking is only a "D" then I couldn't find anything other than HMPP-3890 which is still applicable...

the element with red dot is what is used to generate 5th harmonic if i remember correctly from previous discussions, so it is probably a diode of some kind.

--- End quote ---

The White elements do read as resistors of 50 and 125 ohm

for the part with the D marking.   see image for best I could get 
Using the Diode test here are reading for all 4 pins (see image for pin numbering used)  all reading Vdc

1-2  1.3908v/1.447v
3-4  1.6304v/0.1447v
1-3  0.0691c/0.0691v
2-4  1.4398v/1.3723v

for the damaged element

Did multiple checks
Resistance Open
Capacitance 0
Diode open

see image for better view

--- End quote ---

see the picture for my comments.
are you sure about the diode test voltages? you have a 1.447 and a 0.1447? which one is correct?
what was the test current of your multimeter diode test? 1mA as usual? in that case you are reading 69 ohm between 1 and 3 but I think that's because of the outside resistors forming a loop. I think 1 and 3 are in fact not connected in the device

w.r.t. the discolored component it is definitely a capacitor and it cannot be zero of course. if you want, you need to measure it with a LCR meter
with at least 10KHz or above because it is definitely just a few pF or maybe several 10s of pF
I dont think it is damaged otherwise your TG wouldn't work at all.

analogRF:

--- Quote from: smgvbest on October 17, 2020, 11:25:19 pm ---
--- Quote from: analogRF on October 17, 2020, 12:32:46 pm ---
--- Quote from: smgvbest on October 16, 2020, 11:37:11 pm ---these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

--- End quote ---

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter ::)

--- End quote ---

Here are reading for CR1/CR2 Forward and reverse voltages  meter set for 15V test

CR1  0.789v/2.773v
CR2  0.789v/2.763v

--- End quote ---

so they are 2.7V zener diodes.

what is your multimeter by the way?

smgvbest:

--- Quote from: analogRF on October 18, 2020, 12:28:00 am ---
--- Quote from: smgvbest on October 17, 2020, 11:25:19 pm ---
--- Quote from: analogRF on October 17, 2020, 12:32:46 pm ---
--- Quote from: smgvbest on October 16, 2020, 11:37:11 pm ---these 2 Sot-23's marked 8F I think are 5.1v zeners but 8F can be a NPN transistor as well
both read strange but reading is in-circuit.  one reads 24.7K forward and reverse and other is like 30meg forward and reverse.   I'll get them out of circuit to test but they are connected to V1/V2

--- End quote ---

clearly they are not transistors (they are marked by CRxx) and they are definitely diodes. seems to be used for clipping/clamping a signal or a dc voltage (from top and bottom)

use diode test mode not resistance mode in your multimeter ::)

--- End quote ---

Here are reading for CR1/CR2 Forward and reverse voltages  meter set for 15V test

CR1  0.789v/2.773v
CR2  0.789v/2.763v

--- End quote ---

so they are 2.7V zener diodes.

what is your multimeter by the way?

--- End quote ---

in this case I'm using the eevblog 121GW

on the 2.7 zener though.  isn't a 8F a 5.1V zener?

smgvbest:
at peak detector I did have a typo
this is the correct value
1-2   1.3908v/0.1447v

in PICT0042-1.jpg

the Cap did clean up as seen and the LCR at 10Khz says 9.65pF

smgvbest:
Would this be of any value in doing.

my Rigol 815 only goes to 1.5Ghz.
I need to look at signals up to 6hgz (LO)

I go have a Divide by 4 that's good up 8Ghz
what if I ran my probe into the /4 then into the SA. adjust reference to give good readings

The 3.92Ghz would come out at 981.875Mhz if present.   

I would also be able to see the LO sweeping

I know its not ideal but working with what I have would that be useful to do?


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