ALPS motor/servo function selector switch

[N Cook]

On 1993 Arcam Delta 290 amp, for R/C use and also manual front panel knob.
Before I take the whole amp apart to remove it.
Poor switch contacts. Has anyone taken one apart to renovate or even just
clean them, any hidden traps? odd springs, awkward indexing or anything?

 

[Tim Schwartz]

On 1993 Arcam Delta 290 amp, for R/C use and also manual front panel knob.
Before I take the whole amp apart to remove it.
Poor switch contacts. Has anyone taken one apart to renovate or even just
clean them, any hidden traps? odd springs, awkward indexing or anything?

Nigel,

I've worked on many of these. The switches don't come apart easily,
and often get damaged just removing them from the board, which you would
have to do to take one apart. My experience is that they don't hold up
for more than a few months if you spray them out. You can put some
contact cleaner or lubricant on the new switch if you like, and that may
help it last longer than the original one.

Arcam still has them in stock, part number A1207. E-mail them at
[email protected].

Regards,
Tim Schwartz
Bristol Electronics

 

[N Cook]

Nigel,

I've worked on many of these. The switches don't come apart easily,
and often get damaged just removing them from the board, which you would
have to do to take one apart. My experience is that they don't hold up
for more than a few months if you spray them out. You can put some
contact cleaner or lubricant on the new switch if you like, and that may
help it last longer than the original one.

Arcam still has them in stock, part number A1207. E-mail them at
[email protected].

Regards,
Tim Schwartz
Bristol Electronics

But any specific hidden hazards beyond taking any switch or pot apart ?
As its an otherwise unpopulated area of board I intend hot-air gunning it
off.
Also intend taking apart to renovate, presumably cleaning off CuS corrosion
going by other parts in the amp, rather than happy-squirting and original
part replacement would be a back-stop.

 

[Tim Schwartz]

But any specific hidden hazards beyond taking any switch or pot apart ?
As its an otherwise unpopulated area of board I intend hot-air gunning it
off.
Also intend taking apart to renovate, presumably cleaning off CuS corrosion
going by other parts in the amp, rather than happy-squirting and original
part replacement would be a back-stop.

Nigel,

Nope, as I recall you can unbend the front tabs and remove the front
metal casting with the motor drive. The individual wafers can be
unclipped. Just mind the positions of everything, as it is possible to
to get a section 180 degrees out of phase with the others. I'd clean
out the old goo with alcohol on a cotton swab, use a synthetic oil and
reassemble. I've done it once or twice, and it is a 2 hour job, making
the new switch seem cheap. Occasionally, some of the pins on the switch
will break off as you remove the switch from the board, and then you
need a scrap switch to make one good one, if the pin is used.

The board is double sided with plated through holes, so be careful when
removing it not to pull out the plate through holes.

Regards,
Tim Schwartz
Bristol Electronics

 

[N Cook]

Nigel,

Nope, as I recall you can unbend the front tabs and remove the front
metal casting with the motor drive. The individual wafers can be
unclipped. Just mind the positions of everything, as it is possible to
to get a section 180 degrees out of phase with the others. I'd clean
out the old goo with alcohol on a cotton swab, use a synthetic oil and
reassemble. I've done it once or twice, and it is a 2 hour job, making
the new switch seem cheap. Occasionally, some of the pins on the switch
will break off as you remove the switch from the board, and then you
need a scrap switch to make one good one, if the pin is used.

The board is double sided with plated through holes, so be careful when
removing it not to pull out the plate through holes.

Regards,
Tim Schwartz
Bristol Electronics

I would not fancy desoldering that one by conventional means. No broken pins
or lifted tracks/pads. Desoldered the motor and straightened the bent over
pins while melting solder before hot-airing apart the whole switch
mechanism.
All conductors covered in black corrossion, but does all come apart quite
safely, after labelling. I will note the contact connections in a specific
position for anyone coming a cropper with another one of these.

 

[N Cook]

Nigel,

Nope, as I recall you can unbend the front tabs and remove the front
metal casting with the motor drive. The individual wafers can be
unclipped. Just mind the positions of everything, as it is possible to
to get a section 180 degrees out of phase with the others. I'd clean
out the old goo with alcohol on a cotton swab, use a synthetic oil and
reassemble. I've done it once or twice, and it is a 2 hour job, making
the new switch seem cheap. Occasionally, some of the pins on the switch
will break off as you remove the switch from the board, and then you
need a scrap switch to make one good one, if the pin is used.

The board is double sided with plated through holes, so be careful when
removing it not to pull out the plate through holes.

Regards,
Tim Schwartz
Bristol Electronics

That was the easy part, no one said anything about replacing it back onto
the board.

What has round pin sockets of .156 inch spacing , 2 row , staggered ?
If it was symmetric you could line it up on the other side of the board.

So either engineer a gauge plate with 41 holes , .156 in spacing in 7 rows
staggered .
or drill 2 holes in the pcb to allow rotational symmetry and lining up on
the reverse side of the board.
or put pins in all the pcb holes and caste a gauge plate in epoxy or
something

 

[N Cook]

Lined up the pins visually in both senses, opened out the topside holes with
a dart point and at the third time of offering up / viewing on reverse side/
adjusting, got it replaced

 

[N Cook]

bloody thing
I tested the switches and also that bending the wipers had not produced
trouble with extra back torque and driving round via the motor.
Now its all soldered in, the safety clutch operates in one position, too
much back torque. I had tested before fixing the metal casing back into
place around the switch sections and there must be some sort of additional
strain/misalignment.
Anyway it will desolder easier this time.