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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 23rd Sep 2018, 6:07 pm   #1
Sparky67
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Default Clansman IBMS - Low Volts Fault

Hi all,
My IBMS has developed a fault where its self-test routine says the input volts are low (VLO) and, due to that, the start-up tests don't progress. The input volts at the front panel DC connector are well within spec.
Before I take it apart, does anyone have a circuit for this unit please? I have already downloaded the IBMS docs held by VMARS.
Many thanks,
Martin
G4NCE
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Old 27th Sep 2018, 9:11 am   #2
trh01uk
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Default Re: Clansman IBMS - Low Volts Fault

Martin,

which EMER covers this unit?

Richard
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Old 27th Sep 2018, 12:30 pm   #3
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Default Re: Clansman IBMS - Low Volts Fault

Richard,
The Technical Description is AESP 6130-M-102-303 but the table of associated documents in there is blank for the base repair document number, showing it as 'not published'. Unless there is some way of interpreting this table which I haven't spotted! Apart from that I don't have any other info I'm afraid...
Cheers,
Martin
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Old 27th Sep 2018, 1:52 pm   #4
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Default Re: Clansman IBMS - Low Volts Fault

Martin,

yes, the IBMS is so recent that its post-EMER of course. Try Mike Buckley to see if he has the relevant AESP - but from what you say the info was not published. It could be a reference to the famous "BRIFs", which are always cited as holding all that info that you need to repair things - but which never escaped into the field because no-one in the field ever repaired anything.....

Richard
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Old 27th Sep 2018, 2:21 pm   #5
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Default Re: Clansman IBMS - Low Volts Fault

Thanks Richard. Maybe these boards went back to Widney Aish then? I will drop Mike an email. Fortunately the tech description has given me enough to start with. The PSU is open on my bench at the moment (next to a 1950s dynamo in bits...) and new tants are on order. Those will be the first pass. If that doesn't cure it I'm going to have to start tracing the DC circuit out by hand by the look of it.
Cheers,
Martin
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Old 2nd Oct 2018, 9:47 pm   #6
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Default Re: Clansman IBMS - Low Volts Fault

This fault turned out to be a s/c 10uF 25V tantalum cap on the 15V rail on the IBMU analogue board, which was dragging the +/-15V supplies down. These are supplied from the same IBEK DC-DC converter. Fortunately it survived and the unit is now back to normal.

Not the easiest of units to work on. The front panel is attached by a short ribbon cable one end and a 'flexi-rigid loom' the other, and has to be connected to get DC into the box and for the fault display to work, so the boards behind it can't easily be brought out on extender cards. I ended up testing the PSU out of the box on the bench, then soldering wires onto the voltage outputs of the 5 and 15V converters to be able to measure those externally and pulled the boards (with the power off) until the volts came back up. A DVM did the rest.

Also one edge connector is fitted reversed to the rest, which had me scratching my head when following the 28V supply paths initially. So pin 1 on one board becomes pin 32 on the next. Mmmm...

Martin
G4NCE
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