Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Cracking open a Galaxy Audio PA amp Hot Spot PA5X140 Spot Monitor

I'm dredging up this old subject from 2010 which isn't really worthy of
reading since it's mostly personal attack exchanges, but the point worth
mentioning* is:

Remove the 6 front panel screws AND 1 screw in the back *plus the nut on the
1/4" jack.

The reason I was looking for looking for info regarding this unit (already
had it opened) is because I bought one today for $10US.
I routinely open and inspect any used equipment before I apply power.. just
a habit, although I usually can't resist opening new equipment either, after
I've used it for a while.

A schematic is available at Galaxy Audio's site
http://galaxyaudio.com/schematics.php

The seller said this unit was for parts/repair, and that it had been working
fine for years, then suddenly didn't.

Inspection hasn't been very thorough yet, although I didn't notice any
fuses, but also didn't notice anything burnt.
I saw pics of a board which had a burnt circuit trace on the large board
near where the edge of the board makes an inside corner and is close to the
speaker magnet.

There are a couple of spots of heat-induced discoloration around the leads
of D21 & 22, but it's minor.
These diodes are tied to/across the plus and minus supplies from the PSU.

In addition to the 15V supplies, there are also +/- 23V and +/- 50V
supplies.

A description of the unit states it's a Class H amplifier with 4 output Qs..
2 for low voltage (always in use), and 2 for high voltage which kick in when
demand exceeds the capacity of the LV pair.

--
Cheers,
WB
..............


"David Nebenzahl" wrote in message
.com...
I inherited a repair job that I can't get started because I can't get the
damn amp open.

It's a Galaxy Audio Core PA5X140 all-in-one PA. It's a tough little unit,
with a die-cast metal chassis set into a thick rugged plastic
(polypropylene?) case, that can sit on top of a mike stand. Similar to
this one: http://galaxyaudio.com/MSPA.jsp. The front of the chassis has 6
screws into the case, and there's one on the back I removed, but I still
can't get the chassis out of the case. I tried prying the case, thinking
there might be some cast-in lugs I could open, but no luck, and I didn't
want to risk chewing up the edge of the case.

Does anyone have any idea how to open up this unit?


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)


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Default Cracking open a Galaxy Audio PA amp Hot Spot PA5X140 Spot Monitor

When powerd on, there was definitely no output, not even the slightest tick
noise.
With an external speaker connected, the output appears to be normal as far
as hum and crackle when the input signal line is touched.

It turns out that the 5" driver coil is open.. and examination of the face
of the cone revealed that someone had altered/tampered with it before. The
cone has some kinks in the pleated cone surround, and there is some
significant distortion/warpage of the cone itself (although there doesn't
appear to be any rubbing between the coil form and pole piece).
The dust cover shows 2 distinctly different applications of black goop, and
one compound appears to be RTV silicone.
From the back/frame side of the cone, it appeared as though one of the
eyelets was working it's way out thru the back of the cone.

I put some small dabs of paint stripper (methanol and methylene chloride)
around the eyelets where the tinsel wires are soldered to the voice coil
wires (beside the center dust cover).
After a while I started poking around/scraping at the black goop, expecting
it to have been softened by the stripper, but it was rubbery like RTV.

The dust cover appeared to have been previously replaced and seemed to be
sitting fairly high above the cone, so I cut the cover away to reveal more
of the area where the coil form meets the cone.
After pulling quite a bit of the goop off, I located the fine voice coil
wires cemented to the cone leading to the eyelets.. and found the break in
the fine wire.
Ohm meter check shows that the coil is likely still intact, so I may attempt
to solder a jumper across the break.. just for grins.
I think the eyelets in the cone need to be secured to the cone with
something solid (a glue that dries hard) to ensure that they can't move.

--
Cheers,
WB
..............


"Wild_Bill" wrote in message
...

A schematic is available at Galaxy Audio's site
http://galaxyaudio.com/schematics.php

The seller said this unit was for parts/repair, and that it had been
working fine for years, then suddenly didn't.

Inspection hasn't been very thorough yet, although I didn't notice any
fuses, but also didn't notice anything burnt.


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Default Cracking open a Galaxy Audio PA amp Hot Spot PA5X140 Spot Monitor

After soldering jumpers (wirewrap 30ga) across the voice coil wires adjacent
to the coil form, and extending to each eyelet (where the tinsel wire is
joined to the coli leads in production), the driver/speaker appears to
function normally.

Dabs of a hard-drying glue (Seal-All) were applied to the back side of the
cone around the eyelets to try to secure them to the cone, especially the
one that appeared to be pulling out the back side (which is also the same
coil lead that was broken).
I suspect that the loose eyelet was passing stress/movement to the very fine
coil wire, leading to the break.

The center dust cover was glued back in place (Seal-All) and allowed to dry
for 2 days on a mildly warm heater.
I expect this is the last attempted rescue for this speaker.

A new Galaxy Audio S5N-8 replacement is on its way.. I found a large audio
dealer in Kansas on eBag that accepted an offer of $49 delivery included.

--
Cheers,
WB
..............


"Wild_Bill" wrote in message
...

It turns out that the 5" driver coil is open.. and examination of the face
of the cone revealed that someone had altered/tampered with it before.


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