Golden oldies - Hill Audio amp LC800

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Hill Audio amp LC800

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Forum Name: Golden oldies
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Topic: Hill Audio amp LC800

Posted By: Alien
Subject: Hill Audio amp LC800
Date Posted: 04 July 2015 at 5:46pm

I have a Hill Audio LC800 Power Amp (initial test 20th Dec 1989) has been working fine but has now developed a fault in that the Channel 2 does not work, I can get around it as I can select bridge and Channel 1 feeds both Channels (lucky Channel 1 was OK) but I prefer both channels to work independently.

I have had the lid off and all miniature fuses (qty 6) are OK can't see any loose leads or signs/smells of burning, from other posts I can see there is a lot of expertise out there, any ideas gents!

Thanks,

Allen

Replies:

Posted By: opus jody
Date Posted: 05 July 2015 at 10:54am

Well, if it works ok in bridge mode, then all the output stages on both channels are working ok, as that uses both.
Chances are it's some sort of contact issue somewhere, as the amp is probably getting on a bit & has probably had many years of hot - cold - hot - cold etc.
I had a Hill KA3000 for years, which almost never worked on one channel until you 'blast it through' (probably not the technical term! haha)
try this:
set your amp for stereo
wire in a source with tonnes of gain control & lots of bass.
disconnect any speakers.
then blast a really hot signal into it & see if it wakes up.
If it does, turn it all back down again, fairly quickly, then hook up your speaker, & try it at normal level. If it's a contact problem, that fixed it, then it should run fine once it's up & running, but you may need to do the same thing next time you use it from cold.

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Posted By: service dept Steve
Date Posted: 06 July 2015 at 3:35pm

I'm not going to be able to say too much about repairing this amp BUT even if one channel is completely dead the amp would "seem" to work in bridge mode (red to red) but in fact the one working channel would drive against the flyback diodes of the "off" channel so I'm afraid to say you may be barking up the wrong tree UNLESS in bridge you can get a signal red to black chan 1 and then red to black chan 2, in which case you have an input fault.
The favorite failure of these amps is either the speaker protection relay or, more often, the fuse carriers (not the fuses), they come loose and are cured, at least temporarily, but simply tightening them up and refitting the fuse.

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