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
On 24 oct, 17:41, "Arfa Daily" wrote: The scenario that you are describing is very
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
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
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
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.
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W
. | ,. w , "Some people are alive only because
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