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Display module repair (IFR A-8000 Spectrum analyser)  

 
jimmc101
(@jimmc101)
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I have a faulty display module (COMPUTRON MOD # 115-35 DMK7) in my spectrum analyser (vintage 1987).

I confess I'm not familiar with TVs but to me it looks a bit similar to a monochrome set of that era.

It is a 7" display similar to a TV but with the scan coils turned to give a vertical raster.

(I think that the external connections show the rotated names but parts of the circuit diagram refer configuration before rotation.)

Would anyone like to hazard a guess as to what IC101 is, I would like to get some idea what signals to look for before I dismantle half the unit to get at the display module.

I forgot to mention the fault is total lack of any picture.

Jim

Schematic
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Posted : 26/03/2020 7:47 pm
jimmc101
(@jimmc101)
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I've done a bit more reading, I was wrong, all Horizontal and Vertical references are to the unrotated  state.

Horizontal sync is a 19.608kHz squarewave, Vertical sync unknown but does not matter as it's shorted out by the modification that replaces C116A by a short.

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Posted : 26/03/2020 10:36 pm
Nuvistor
(@nuvistor)
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No idea about the chip, hopefully may just be a PSU fault otherwise is multimeter and scope.

 

Frank

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Posted : 26/03/2020 11:12 pm
jimmc101
(@jimmc101)
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Well I managed to get it apart and found that a lot of corrosive glue had been used to hold large components and cables down.

CRUD

 The ribbon cable connects to the CRT base and the worst corrosion occurred on the G2 conductor at both ends.

Board cleaned and recapped where necessary and ribbon cable connections remade.

I hope to reassemble it all tomorrow.

IC101 remains a mystery, It really annoys me when manufacturers sand off the type markings.

 

Jim

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Posted : 27/03/2020 8:01 pm
Nuvistor
(@nuvistor)
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Hope that sorts it out, that glue really is corrosive.

Frank

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Posted : 27/03/2020 8:50 pm
jimmc101
(@jimmc101)
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I'm pleased to say that that the analyser is working now.

It lives

Jim

 

 

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Posted : 28/03/2020 8:23 pm
turretslug
(@turretslug)
Reputable V-Ratter Registered

Blimey, that's a shocking example of how destructive something apparently innocuous like glue can be. Must have been a considerable relief to have it come back to life.

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Posted : 28/03/2020 8:59 pm