kenwood rxd-m45 stereo - schematic?

[b]

Problem is that on connection, the green power led flashes and there
is a click from the relay.No display etc. there is voltage on the
small secondary power transformer in the psu. I'd like to check the
rails, but don't have the schematic :-(
any ideas gratefully received....TIA
B

 

[Arfa Daily]

"b" <reverend_rogers@yahoo.com> wrote in message
news:9a16bcdf-006d-4c4a-9d88-0fa94f57ddd4@j19g2000vbp.googlegroups.com...

Problem is that on connection, the green power led flashes and there
is a click from the relay.No display etc. there is voltage on the
small secondary power transformer in the psu. I'd like to check the
rails, but don't have the schematic :-(
any ideas gratefully received....TIA
B

Just checked my Kenwood schems, but none for that model. If the unit has a
small power transformer and a big one, the small one will be providing the
standby supply for the system control micro and remote receiver etc. If the
relay that you hear click, does so as soon as you press the standby button,
then it will be the relay which switches power to the primary of the large
tranny, that you are hearing. The scenario that you are describing is very
common, symptom wise, of when the primary of the main power tranny is open,
usually because an internal non-replaceable thermal fuse has failed, and
also usually, for no good reason. I can think of several manufacturers'
products which suffer from this, and give those exact symptoms - Teac and
Denon are two that come immediately to mind.

Very often, the main power tranny's primary is connected to the PCB by a
plug and socket, in which case, it is easy to measure the primary's
resistance. If it does read open, and the tranny has pins to which the wires
are connected, look carefully to see if one pair of pins have the thermal
fuse connected to them - you can usually see two silver wires (as opposed to
laquered copper wires) disappearing down into the windings. If you find such
a pair of pins, you can measure between them, and confirm that the fuse is
o/c. You can then go ahead and solder a fuse resistor or wire ended fuse
across the pins, and see if that brings the unit back to life.

If it does, all you have actually done is proved the point that you need a
new tranny, as any external device cannot be left in place to sub for an
internal thermal fuse, for obvious safety reasons. However, if the unit is
your own, rather than a customer's it is of course up to you if you want to
take the risk of bypassing this layer of protection ...

Arfa

 

[b]

On 24 oct, 17:41, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
The scenario that you are describing is very

common, symptom wise, of when the primary of the main power tranny is open,
usually because an internal non-replaceable thermal fuse has failed, and
also usually, for no good reason.

Thanks a million Arfa, that has given me some good leads to go on.
I'll hopefully get to this again during the week, take a few
measurements and will update as- and- when.

cheers!
B

 

[b]

The transformer primary measured open. As this is for someone else and
there are safety concerns in 'repairing' the tranny, I'm not going to
pursue it further.
thanks again!

 

[Arfa Daily]

"b" <reverend_rogers@yahoo.com> wrote in message
news:99308b68-487a-4ee8-a664-92f0c0f63a2d@r36g2000vbn.googlegroups.com...

The transformer primary measured open. As this is for someone else and
there are safety concerns in 'repairing' the tranny, I'm not going to
pursue it further.
thanks again!

Hmmm. Pretty much as expected then. It's a shame to commit items to landfill
for problems like this, but even if you could persuade Kenwood to part with
a replacement tranny, the cost would likely be prohibitive.

OK also on the safety angle. As I said to you in my original reply, not so
bad if it's your own responsibility, but a definite no-no when a third party
is involved. It's also not fair on any service engineer that follows behind
you. I saw a unit a while back that had had an external fuse bodged across
the pins of the tranny where an o/c thermal fuse was connected. The fault
that the shop had taken it in for on this occasion, was nothing to do with
the power supply, but when I saw the fuse across the transformer, it left
me, and the shop, in a very difficult position, as a reputable outfit.

The customer had to be quoted for a replacement transformer, on top of the
cost of repairing the fault that it was in for this time, and the shop had
to try to explain to them why this was the case. Needless to say, they
rejected the quote, and had a pink fit when they were told that it would
have to come back to them no longer working at all, as the bodge repair that
had been done by someone else, now that it had been spotted by us, would
have to be removed for safety reasons, otherwise we could be seen legally as
condoning it. I guess we lost that customer for ever, even though we were
acting in their best interests, whilst also covering our own arses ...

Arfa

 

[b]

On 26 oct, 19:49, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

OK also on the safety angle. As I said to you in my original reply, not so
bad if it's your own responsibility, but a definite no-no when a third party
is involved. It's also not fair on any service engineer that follows behind
you. I saw a unit a while back that had had an external fuse bodged across
the pins of the tranny where an o/c thermal fuse was connected. The fault
that the shop had taken it in for on this occasion, was nothing to do with
the power supply, but when I saw the fuse across the transformer, it left
me, and the shop, in a very difficult position, as a reputable outfit.

The customer had to be quoted for a replacement transformer, on top of the
cost of repairing the fault that it was in for this time, and the shop had
to try to explain to them why this was the case. Needless to say, they
rejected the quote, and had a pink fit when they were told that it would
have to come back to them no longer working at all, as the bodge repair that
had been done by someone else, now that it had been spotted by us, would
have to be removed for safety reasons, otherwise we could be seen legally as
condoning it. I guess we lost that customer for ever, even though we were
acting in their best interests, whilst also covering our own arses ...

Arfa

Agree with you totally on this one. As far as I'm concerned, there is
not a cat in hell's chance I'm going to risk anyone's life or property
for a mini system which probably only cost about 60 quid new and whose
second hand value is probably less than a third of that. It's just not
worth the risk for that kind of silly money. Apart from that, it's
from a neighbour who lives a few floors below me- so it's an even
clearer- cut case! Don't fancy a towering inferno with myself as the
star.....
-B

 

[Bob Larter]

Arfa Daily wrote:

OK also on the safety angle. As I said to you in my original reply, not so
bad if it's your own responsibility, but a definite no-no when a third party
is involved. It's also not fair on any service engineer that follows behind
you. I saw a unit a while back that had had an external fuse bodged across
the pins of the tranny where an o/c thermal fuse was connected. The fault
that the shop had taken it in for on this occasion, was nothing to do with
the power supply, but when I saw the fuse across the transformer, it left
me, and the shop, in a very difficult position, as a reputable outfit.

The customer had to be quoted for a replacement transformer, on top of the
cost of repairing the fault that it was in for this time, and the shop had
to try to explain to them why this was the case. Needless to say, they
rejected the quote, and had a pink fit when they were told that it would
have to come back to them no longer working at all, as the bodge repair that
had been done by someone else, now that it had been spotted by us, would
have to be removed for safety reasons, otherwise we could be seen legally as
condoning it. I guess we lost that customer for ever, even though we were
acting in their best interests, whilst also covering our own arses ...

Personally, I would've given it back to the client in the same way I
found it, at no charge, & explained why I couldn't (legally) work on it.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
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