The label fell of IC13 the calibration data EEPROM x2816. DO NOT try anything to adventurous with this IC. It opens up a minefield of hassle to recalibrate with a lot of specialist equipment needed. IC9, 10, 11 are M27C128 and IC12 is a M27C64. As the EPROMs hold all the data for display it was more than likely the card that went loose. These are also the IC's required for firmware upgrades. the latest version is v16 but it only included GSM testing and required a 2957 D'AMPS unit. Avoid v15 as it has bugs and v16 and see if you can manage to get hold of V14. From v13 to V16 other than GSM the only advantage is a few extra GBIP commands. Some versions also omitted some accessory commands and needed the EPROM to be changed to enable this.Power heads, GPIB printer etc failed to detect.
Nice piece of gear, I used a Marconi 2947 at work for many years on VHF and UHF comm gear - very reliable and easy to use. I also used an HP 8920, but it was a little less user friendly. Great job getting it up and running!
I commented earlier today - & decided once & for all to pull the cards out & use a rubber - it’s now working great 👍 a Friday fix for me today too after years of waiting for it to play ball. Also cleared some bits of wax that were across a few pins. Correction: is working but now failed 2.1 error 23 2.2 error 26 2.3 error 28. Never had errors before / we’ll see what rabbit hole we’re gonna go down today. 👍
Cured the problem - by luck - decided to check a radio for output power to see if the Marconi still provides info - which it does. By doing this it cleared the errors mentioned above. I can only assume that the unit ‘sorts’ itself out having a bit of RF applied. I did clean up the card with the potentiometers on (calibration setting card I saw on your other video) and again gave the errors - but I applied a bit of RF & the unit passes all self tests. I did this without putting the metal screen cover over the cards - saved aggravation shows it can be done. So, for future repairs - & those watching - a clean up of the contacts was stage 1 - insert cards & self test - if fault still present - connect up to a radio and inject some audio / power into unit - turn on/ off - self test again - this might rectify the errors - call it an ‘energising’ of the boards from an external device. My laymans explanation. Cheers All the best
Good to see you got it working so easily. Nice piece of equipment. Just a thought about the "The pictures showed it working" part, don't forget that a seller could Photoshop the pictures to make it look like it was working when he sent it. Not saying that anybody would do that, but just something to consider as a possibility.
I think F38 was AM level circuitry, before dissassembling it try to do a calibration to write a new calibration table, if it still fails afterwards check the OM345 modules. If these amp modules seem to be dead try hooking a 4.7kOhms resistor between their first and last pin and if they come back to life with this hack the internal 3,9kOhm feedbackresistor on the ceramic substrate is blown. You can repair them by scraping off the orange paint on the capacitor area of the module ans solder a fresh 3.9kOhms resistor in parallel to it. Always do a selfcal after repair because nothing in these old buddies works linear ;) Once I owned the 2955B with extention unit and the 2968 from IFR, I know what I'm talking about.
I agree the OM345 modules can cause lots of issues on these. The work around as you said is to solder a 4.7K resistor across pin 1 to 5. But only do this after making some DC measurements on the OM345 otherwise you could blow a working module ! I good source of info on the OM345 and possible replacements or work around can be found here ea4eoz.blogspot.com/2017/09/repairing-om345-hybrid-module.html
I’m glad it started up. I expected it to be a loose card. Very occasional my 2955 does the same perhaps 1 time in 50 but then starts up normally. I had assumed it was the processor card but not got around to investigating it. A lot of these Marconi devices give error codes it may even work fine depending on the error certainly calibration can cause error codes.
It looked like it was stuck in reset, but fondling the boards did the trick :-D Even gold plated connections can play up, like p.c memory strips that you have to jiggle about to make them work. The wax sounds a bit odd, maybe it was on the deflection coils .
The moment I saw that garbled screen, and definitely by 14:00, I'm thinking you should re-seat all of the PCB cards - I've never found vibration during transport to be a good thing. Personally, I'd also check all the slots on the main board, especially with all those wax chips floating around. Loose guide rails can also wreak havoc. At 22:00 I'm glad to see the old gut feeling is still right sometimes.
good bit of kit had to replace all the om345 in mine and replace a transistor and a cap on one of the boards prefer the 2955 over the ct systems inc 3000b I have on my shelfs
What you failed to do is to switch it on & off again! 😉 well, there are posts I’ve seen where some say not to do as it can corrupt the eprom data - but I just had the garbled screen - switched it on & off couple times - & it’s back again. Mine has always been / still is a temperamental unit - works when it wants to e.g stays on first screen Receiver Test - possibly the OXCO at fault as I think this unit doesn’t lock in / temperature effects it
Bottom modules seemed unlikely as all that looks to be front end RF Functions. The top card cage is mostly the system processing and thus the displ ay processing. Thus garbage display is from that part. As it appears rather ststic not part of the RF front end ( underside). Still good to look everywhere.
The label fell of IC13 the calibration data EEPROM x2816. DO NOT try anything to adventurous with this IC. It opens up a minefield of hassle to recalibrate with a lot of specialist equipment needed. IC9, 10, 11 are M27C128 and IC12 is a M27C64.
As the EPROMs hold all the data for display it was more than likely the card that went loose. These are also the IC's required for firmware upgrades.
the latest version is v16 but it only included GSM testing and required a 2957 D'AMPS unit. Avoid v15 as it has bugs and v16 and see if you can manage to get hold of V14. From v13 to V16 other than GSM the only advantage is a few extra GBIP commands. Some versions also omitted some accessory commands and needed the EPROM to be changed to enable this.Power heads, GPIB printer etc failed to detect.
Thanks for the helpful info.
@@TheDefpom I forgot to add the VDA board is next to the board worth the EPROMS. This can also give display issues.
Nice piece of gear, I used a Marconi 2947 at work for many years on VHF and UHF comm gear - very reliable and easy to use. I also used an HP 8920, but it was a little less user friendly. Great job getting it up and running!
That's a relief it's working. Look forward to you investigating that self test error code.
I commented earlier today - & decided once & for all to pull the cards out & use a rubber - it’s now working great 👍 a Friday fix for me today too after years of waiting for it to play ball. Also cleared some bits of wax that were across a few pins.
Correction: is working but now failed 2.1 error 23 2.2 error 26 2.3 error 28. Never had errors before / we’ll see what rabbit hole we’re gonna go down today. 👍
Cured the problem - by luck - decided to check a radio for output power to see if the Marconi still provides info - which it does. By doing this it cleared the errors mentioned above. I can only assume that the unit ‘sorts’ itself out having a bit of RF applied.
I did clean up the card with the potentiometers on (calibration setting card I saw on your other video) and again gave the errors - but I applied a bit of RF & the unit passes all self tests.
I did this without putting the metal screen cover over the cards - saved aggravation shows it can be done.
So, for future repairs - & those watching - a clean up of the contacts was stage 1 - insert cards & self test - if fault still present - connect up to a radio and inject some audio / power into unit - turn on/ off - self test again - this might rectify the errors - call it an ‘energising’ of the boards from an external device. My laymans explanation.
Cheers
All the best
Link to RFMAN RFMAN UA-cam vid re the Marconi 2955 / superb walk through & videos
ua-cam.com/video/v7pS5ANUWWE/v-deo.html
Wow with all this great kit, I may move in next door to Scott.... ;)
Good to see you got it working so easily. Nice piece of equipment.
Just a thought about the "The pictures showed it working" part, don't forget that a seller could
Photoshop the pictures to make it look like it was working when he sent it.
Not saying that anybody would do that, but just something to consider as a possibility.
I think F38 was AM level circuitry, before dissassembling it try to do a calibration to write a new calibration table, if it still fails afterwards check the OM345 modules. If these amp modules seem to be dead try hooking a 4.7kOhms resistor between their first and last pin and if they come back to life with this hack the internal 3,9kOhm feedbackresistor on the ceramic substrate is blown. You can repair them by scraping off the orange paint on the capacitor area of the module ans solder a fresh 3.9kOhms resistor in parallel to it. Always do a selfcal after repair because nothing in these old buddies works linear ;) Once I owned the 2955B with extention unit and the 2968 from IFR, I know what I'm talking about.
I agree the OM345 modules can cause lots of issues on these. The work around as you said is to solder a 4.7K resistor across pin 1 to 5.
But only do this after making some DC measurements on the OM345 otherwise you could blow a working module !
I good source of info on the OM345 and possible replacements or work around can be found here
ea4eoz.blogspot.com/2017/09/repairing-om345-hybrid-module.html
I’m glad it started up. I expected it to be a loose card. Very occasional my 2955 does the same perhaps 1 time in 50 but then starts up normally. I had assumed it was the processor card but not got around to investigating it. A lot of these Marconi devices give error codes it may even work fine depending on the error certainly calibration can cause error codes.
That first comment made while bottom being opened!
It looked like it was stuck in reset, but fondling the boards did the trick :-D
Even gold plated connections can play up, like p.c memory strips that you have to jiggle about to make them work.
The wax sounds a bit odd, maybe it was on the deflection coils .
The moment I saw that garbled screen, and definitely by 14:00, I'm thinking you should re-seat all of the PCB cards - I've never found vibration during transport to be a good thing.
Personally, I'd also check all the slots on the main board, especially with all those wax chips floating around. Loose guide rails can also wreak havoc.
At 22:00 I'm glad to see the old gut feeling is still right sometimes.
good bit of kit had to replace all the om345 in mine and replace a transistor and a cap on one of the boards prefer the 2955 over the ct systems inc 3000b I have on my shelfs
I made my first comment while the bottom was being opened, good that it started after reseating the cards
Nice test set Scott i love mine but they dont like moist air conditions.
What you failed to do is to switch it on & off again! 😉 well, there are posts I’ve seen where some say not to do as it can corrupt the eprom data - but I just had the garbled screen - switched it on & off couple times - & it’s back again. Mine has always been / still is a temperamental unit - works when it wants to e.g stays on first screen Receiver Test - possibly the OXCO at fault as I think this unit doesn’t lock in / temperature effects it
Bottom modules seemed unlikely as all that looks to be front end RF Functions. The top card cage is mostly the system processing and thus the displ ay processing. Thus garbage display is from that part. As it appears rather ststic not part of the RF front end ( underside). Still good to look everywhere.
Be very careful using erasers to clean board contacts as the rubber contains sulphur that will contaminate the metal and create corrosion later on.
Hi,
what is the green cover you have on your bench ? I wanted to get something like that for my bench..
kevin rea
lancaster, calif. usa
K6REA
It is an anti static mat, you can buy it in different widths and lengths.
Error 38 is a error on the am test of 50% with it too high. do a calibration see if it clears it
.