Luxman L-430 stuck in protection. Help please.

[Binkman]

it must be caused by something else

This is why they (posters with same issue) are trying to eliminate the actual protect circuit vrs. another cause. Unfortunately there is no voltage references in the sm schema's. There are a few more transistors OP's need to check.

You may have a clue, though. perhaps not dc issue but over current sense circuit?? wonder if there are any fusible resistor types gone open, if any. like 10ohm typical? without v references kinda a lot of guess work. needless to say day jobs to work on.

 

[bktheking]

Why would you say it's incorrect, I measured, it rises and drops to near zero at turn on and stays in protection- there's something wrong in the protection circuit. I'd like to understand what this AC reference is referring to- that part of the circuit has an SIBV 20 being fed from a tap and another pair of diodes going to the 1uf cap, wouldn't that be DC? I'll measure the bases of those transistors for voltage.

 

[llwhtt]

Haven't seen much in the way of voltage checks. FIRST make sure you're using the correct schematic, L-430 and NOT L410. The relay is energized by Q828, what are the voltages on Q828? Q828 is turned ON by Q827, what the voltages on it? Q826 should be ON because the base is connected to the lightly filtered PS of C813 and associated parts. Q829,30 and 31 are the DC detectors and all of them should be OFF. If any of the detectors are ON the base of Q827 will be grounded causing the relay to de-energize. Since there are no voltages on the schematic we'll have to wait until they are checked then we can make some sense out of them. The only voltage that I can determine is the base of Q827 should be about 6.7VDC by way of the 6.1V Zener and D809.

Craig

 

[Binkman]

https://www.hifiengine.com/manual_library/luxman/l-430.shtml
confirmed being referenced.

Aside: Here's an Aussie mate/member @Trevor White who recently did an extensive overhaul.. may help.
Luxman L-430 Recap / Overhaul | Audiokarma Home Audio Stereo Discussion Forums

 

[llwhtt]

I just checked the schematics, there are TWO different ones for the L-430!!!!!!! Are both of these L-430s the same? Which schematic should we be using? Are the protection circuit transistors Q82x or Q83x?

Craig

 

[bktheking]

Where? There's an alternate scan which is was better than the first one I downloaded. Same schematic though.

 

[llwhtt]

One of the L-430 schematics is labeled FIRST LOT in the lower right corner of page 25. The other schematic doesn't have that and is different. The FIRST LOT schematic has a couple more transistors in the protection circuit.

Craig

 

[bktheking]

Tested all components, passed- hit the relay with 24v and now it comes on with no delay on turn on - shorted q832.

 

[llwhtt]

I know which L-430 you have now, FIRST LOT.

 

[bktheking]

Yes, i'm still tracking the issue.

 

[chammerbeck]

Just check my q832 and q834 tested good with my meter....

 

[bktheking]

1uf cap- replace it . C813 = click, 5 second delay

 

[bktheking]

Just so you know I’m actually working on one.

 

[chammerbeck]

Looks like 1uf I changed earlier...I put in non-polarized replacement. Just changed it again. No go

 

[chammerbeck]

Proof I'm working on one too! LOL....next pic I just acquired these for $100 total. Not starting
them till the Luxman is running. One at a time.

 

[bktheking]

So all caps in the protection circuit have been replaced?

 

[chammerbeck]

just finishing up a snack. going to dive back in an verify what I have replaced.

 

[kramden]

If these units were not purchased in the same country, they very well could be different versions.

 

[bktheking]

Also verify your orientation of the caps you replaced.

 

[chammerbeck]

Just got done swapping out a ton of caps. unable to do the two very large and the 4 470uf/100vdc ones.
My warm up light stays on for a long time too....still no relay click. I always double check my cap polarity...not a pretty sight when those blow lol