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Marconi 2022E RF signal generator repair and refurb
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bd139:
That’s a a great idea actually. Thanks for the suggestion. Those also won’t fall out when soldering!
George Edmonds:
Hi

Just a quick word.

The ones used on the AA4 board in a 2955 are critical for overall dimensions due to the limited space available.

PLEASE use soft pins for the legs, the last ones I used could not be cut with small side cutters, I had to use piano wire cutters to cut them, not a good idea.

G Edmonds
G0HZU:
Note that the reverse isolation of a typical MMIC won't be quite as good as the original OM345. This might not matter in some locations in the 2022 sig gen but it probably does matter for the IC1 location at least.

The OM345 reverse isolation is typically 22dB at about 100MHz and the MAR7 manages just 18dB here. The 22dB reverse isolation of the OM345 may already not be enough to prevent some FM modulation occurring on the AM for frequencies up to about 62.5MHz. IC1 acts as an isolation buffer between the AM modulator and the 160MHz VCO. I've checked several 2022 sig gens and they all suffer from a bit of unwanted FM when AM is selected below 62.5MHz. This includes the ones at work and these all have the original OM345 fitted. There's a good chance the MMIC replacement for IC1 will increase the amount of unwanted FM that occurs here.

I designed a high reverse isolation alternative for IC1 but never got around to trying it out. This had about 50dB reverse isolation at 160MHz.

factory:

--- Quote from: bd139 on July 30, 2022, 03:35:54 pm ---That’s a a great idea actually. Thanks for the suggestion. Those also won’t fall out when soldering!

--- End quote ---

They were used in stuff at work, no-one knew what they were and some boards we had made (supposed to be an exact copy) they fitted right angle pin headers, they were a pain to remove, after we found the boards didn't work (eventually I found the problem).

Many many years later, some of the leadframe connections turned up in the TEA thread and I asked to find out what they were. Seems there is lots of choice for, pitch, size & board thickness.

David
bd139:

--- Quote from: George Edmonds on July 30, 2022, 06:53:50 pm ---Hi

Just a quick word.

The ones used on the AA4 board in a 2955 are critical for overall dimensions due to the limited space available.

PLEASE use soft pins for the legs, the last ones I used could not be cut with small side cutters, I had to use piano wire cutters to cut them, not a good idea.

G Edmonds


--- End quote ---

Thanks for the heads up. I located a picture of AA4 in the 2955 and it looks like my replacement module would fit in there.

As for the soft pins, agreed. See my later reply from user factory which I haven't written yet as I post this :)
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