Electronics > Repair
Rohde & Schwarz - IQ Modulator A240 (1084.9800.02) - Level Problem
rg58:
Could it be possible that this rubber pad is not even a thermal pad, but only used as a spacer?
You might be right that they ONLY use the source terminals for heat dissipation. From the FETs package, S-terminals, on to the bulkhead, then to the radiator (thermal paste), then to the upper lid (thermal paste again). There was no thermal paste between the pad and the FETs.
rg58:
Alright. The other board (1084.9800 printed on the PCB) turns out to be 1084.9800.10 - a higher revision. So at some point R&S decided not to print the revision number on the board anymore, rather putting a sticker on it. I overlooked this on top of the metal. It also has another tiny sticker "MGA1" on it, whereas the older faulty one (.02) has "MGA5" written on it.
Also I forgot to mention that right after finding Vds is too low, of course next I checked was the supply voltages to the gate and drain - which were OK.
wriely:
I was just looking at my SMIQ03B and wondering if it may be possible to get probes on the IQCON board without an extension card and extending the myriad of RF cables.
How? Well, the front panel easily comes off of the unit. Behind it is a metal bracket that is secured by what I count to be 8 screws. With that out of the way, one could have direct access to the front side of the IQCON board with ease.
I've not gone any further than taking the front panel off of my unit so I can't say for certain whether this work, but it could be a major time saver if it does.
Walt
lcharman:
Your sharing helps me a lot!! :-DD THX!
My SMIQ03B got error reference voltage oot while perform internal calibration of vector calibration.
I check the output stage of IQMOD module.
V144 Vds=4.6V
V103 Vds=0.64V (It should be 7V)
V104 Vds=7.3V
The symptom seems to similar to yours but the Rds values of V144, V103 and V104 are about 3ohm (in-circuit measurement & no power).
I am waiting my SHF-0186K. Hope have luck.
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