On 30 October 2020 at 03:47 DougF VK4OE <uwaves@...> wrote:
Greetings to all readers!
I am wondering please if someone reading this message has practical experience with the internal construction and circuitry of AVANTEK microwave amplifier modules such as the one whose picture I am attaching to this message.
Following an eBay transaction four weeks ago, an AVANTEK 3A80-1782 amplifier module arrived in the mail this week. Some scant technical information about it showing that it had been tested satisfactorily at an earlier time was supplied, but it is not exhaustive information. Briefly, this amplifier is labeled for use over the 12 to 18 GHz range and the information supplied with it indicated that I should expect to get +15 dBm output power. It is 3¼" long by 1¼" wide and the label says +12VDC.
Before testing it, I mounted it on a heat sink, which had been recommended. That done, the simple initial test was to discover that it was drawing 270 mA at +12V which seemed about right.
Next, I introduced an input signal on 14 GHz at -10 dBm and that produced an output power of about +15 dBm, after which I quickly found that it would deliver close to +17 dBm saturated output power from about -6 dBm input. Both of those measurements seemed about right for such a module. I recorded similar good results at 15 GHz and 16 GHz.
At that point I became distracted for a couple of minutes by something outside the "shack" and when I returned the output power meter was showing nothing and the current being drawn was now only 2 mA. I was, of course, surprised and disappointed, particularly in that I wasn't, in my view, pushing it hard.
Removing and reinstating the DC supply has not restored things, neither has waiting several minutes. It still draws only 2 mA.
Question 1: Do you know or have some insight into the mode of failure that may have occurred here, and a possible way to fix it?
Question 2: Having removed the heat sink and removed the eight screws holding the back plate of the module, the back plate does not want to "let go". It appears to be firmly attached to something under the 'output' end of the amplifier module, but there are no more screws to remove. Is someone on this list familiar with the way such amplifier modules are constructed internally, and who could give me some advice please?
Question 3: Should I just regard the module as a 'write off'' and don't wast time trying to repair it?
What do folk think?
Cheers and 73,
--Doug Friend, VK4OE.
p.s. I have already posted a similar message on the W1MBA microwave reflector but no-one with the experience I'm describing has emerged. Apologies to those who have read a similar message there.....