JBL HTPS400 Subwoofer Plate Amp Repair

Thread Starter

Daren Howard

Joined Feb 10, 2017
2
I recently picked one of these up at an estate sale (former Braves player, moving, Andruw Jones), but the plate amp is not working. Service Manual can be found here. I did find one bad capacitor on the EMI Board (page 25) assembly (C502) and have swapped it. I will likely swap the capacitor labeled C501 as well as it is from the same manufacturer and same cap. I also swapped the (U502) (LM7905CT) voltage regulator as well as it tested bad. One thing the page does not explain is what the voltage coming off this card feeding the next power supply should read. Does anybody have an answer to what it should be? I would rather know I am sending the right voltage there before powering the whole assembly up.

The next thing I noticed was that the feature board has a G-Luxon cap. It looks a little dirty but I was thinking this was likely flux. The rest of the caps seem to be name brand and good quality. I don't have any experience with these caps so am asking if this looks like leakage and are these quality caps? I suspect they are not quality and this is one I would likely want to swap out. Any assistance would be appreciated.

FYI: When powered on the speaker initially LED did come on showing standby and when went to on position turned green. Beyond that no sound from speaker and suspect amp is the issue. Have hooked the speaker (minus amp) to the center channel and it works. Only $100 in it so far so not too worried if I need to get a new plate amp but would really like to get this one working. It seems very high quality, is THX certified, and is a 1000W amp. Sealed speaker would necessitate a powerful amp as you get much less sound from sealed vs. ported. Amp is a Bash model. Other than the one dirty cap nothing looks like it is failing and all solder connections look solid.
 

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AlbertHall

Joined Jun 4, 2014
12,338
The voltage between DC+ and DC- should be about 1.4 times your mains voltage.
Note these two points should both be considered as live mains connections - no shorts; no fingers!
 

Thread Starter

Daren Howard

Joined Feb 10, 2017
2
The voltage between DC+ and DC- should be about 1.4 times your mains voltage.
Note these two points should both be considered as live mains connections - no shorts; no fingers!
Thank you Albert, I have not done electrical trouble shooting since the 80's so am a little rusty. Well, ok, I'm rustier than a 50 year old salt truck. I'm being very cautious for that very reason. I have a ton of respect for electricity. Have a great day.
Daren
 
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