EB5AGV's Marconi 2955A


Welcome to my Marconi 2955A page!

Marconi 2955A Marconi 2955A


My 2955A

My unit was bought at an on-line Auction as a faulty unit. And, indeed, it was faulty!. Here you have some info I wrote on it:

Let's see it in perspective... some days ago I bid on a FAULTY 2955A which seemed to be in good external condition. Failures included the dreaded LOW POWER ones (in the eBay auction, they showed a picture with errors 11, 21, 23, 25, 27 and 37). Despite of this I bid and won the item.

Today it has arrived and upon powering, situation is still worse. None TEST passes!. So I get these errors: 12, 14, 16, 18, 1A, 21, 23, 25, 27, 33, 35, 37 and 39. I think there should be more errors which are just not shown. Ok, so it seems I have some problems ahead...

Another thing I have found is that there is one metal cover missing in what seems a power amplifier... Not a good thing!

Also, there are a couple of fried and replaced coils in one of the plug-in cards.

Here you have some pictures of my unit:

Top side view

Bottom side view

AA1 assembly

AA2 assembly (in red, OM modules)

AA3 assembly (in red, OM modules)

AA4 assembly (in red, OM modules)

Keypad

Power Supply (cover out)

Rear panel (covers out)

Error Codes

Upon further work, I found the following:

Ok, it seems TX TEST works fine. I have measured frequency, deviation, power and checked oscilloscope and it seems accurate enough (as a sample, I got 145.349999 measuring a 150MHz walky). So this points out that basic frequency generation and counter are working (I would love to have a block diagram of the set!). So I am, in a first guess, narrowing down the problem to the RF, RF amplifier or attenuator sections.


Repair

Main problem with 2955/2955A sets is the failure of some special Philips OM series hybrid amplifier modules which are now obsolete. Modules used are these:

Marconi 2955

Marconi 2955A

I am in need of two OM-345 (or OM-2045) to repair my unit. Please, let me know if you can help. Thanks!

UPDATE: I have located some extra Philips OM-2045 and OM-350 modules. Please, check my Marconi 2955 SPARE PARTS page for more information!


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