Panasonic SU-HTB770 (surround sound system) - Page 1
Forum section: electronics / repair

author: SquattingDog
author_rank: Contributor
timestamp: September 17, 2019, 04:35:31 pm
content: I have a Panasonic SU-HTB770 that quit working. It does not power on. I was wondering if you think this can be fixed by me, a non electronic type person. <g> I have the tools just not the knowledge to trouble shoot. I'm not an electronic guy but more than willing to try. It just quit working. I did hear a loud pop one day but I didn't pay any attention to what it was. I think the pop was my surround sound system box shown here. Maybe a capacitor (just a guess)? I noticed some fuses but haven't a clue how to test or remove them and didn't want to mess something up being a noob. I wasn't sure if they pulled off or I had to remove the board. I wasn't able to find a wiring schematic for it either.https://pbase.com/smokedaddy/image/169740307

author: rfengg
author_rank: Regular Contributor
timestamp: September 19, 2019, 12:39:33 am
content: There is nothing in the pic that shows evidence of something damaged.......could you post a pic of the whole board?Do you see any soot or evidence of any component damage on the board? Do you have access to a multimeter?Working with mains AC is deadly, so make sure you know the risks before going ahead.

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 12:53:34 am
content: Quote from: rfengg on September 19, 2019, 12:39:33 amI did post a link to the full board which is a large image as well. No, I didn't noticed any soot etc., from something blowing. Yes I have a Fluke 179. Yea, I know I can get fried, that's why I'm here along with some hand holding. I'd never do anything without asking first.https://pbase.com/smokedaddy/image/169740307-JW:

author: rfengg
author_rank: Regular Contributor
timestamp: September 19, 2019, 01:03:10 am
content: Sorry missed the linkFirst things first......REMOVE the mains PLUG.Could you check the continuity on the fuse F1 on the small green board marked as 50 12?Is it possible to remove the PS board and check the back side for any signs of damage due to the blast you heard?To test the fuse, put the multi meter on the beeper mode and touch the lead ends together.......you should hear a beep sound when the leads are touched together.Then , put the probe ends , red and black , to the 2 ends of the F1 (where the sine wave like symbol is shown).....if your fuse is good , then you should hear a beep sound.

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 05:01:37 am
content: The continuity was fine on the fuse. I think I found the problem. You can see the crack and stuff oozing out of that blue thing. I don't know what it's called but it's definitely a problem and maybe the only problem. Ceramic capacitor? I can't see any numbers on it.-JW:

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 05:18:22 am
content: I know nothing about this or the nomenclature printed on it nor where to purchase a couple but here's a close up. Should I assume they're both the same since I can't read the one that's blown? I might have to replace them both if they're stuck together.

author: rfengg
author_rank: Regular Contributor
timestamp: September 19, 2019, 06:22:33 am
content: The thing "oozing" out of the caps is not an issue.......its some sort of epoxy that the manufacturer puts on to hold the caps together.Are you sure there is a crack on one of the caps? Its very hard to see if there a crack indeed cos of the epoxy on top.Ceramic caps have no liquids for some to ooze out of as they are built of solid ceramic dielectric.......only electrolytics have liquid like electrolytes which form the dielectric.The cap in question is a 470pF, 250V rated for X and Y applications for EMI/RFI suppression but I doubt if its blown......the part is anyways easy to get from Mouser/Digikey are and cheap as chips.

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 06:54:26 am
content: ... and I thought I was on to something.Can the cap be tested somehow just in case it's history? IF so do I need to buy something like this? I don't mind spending a little money if there's something better. The reviews aren't that great.https://www.amazon.com/gp/product/B01H6QKVOU/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

author: rfengg
author_rank: Regular Contributor
timestamp: September 19, 2019, 07:52:58 am
content: There are better cap meters like the Anatek Blue ESR tester but they give ESR's (Equivalent Series Resistance) properly only for caps above 1uF , so its not very helpful for you.See link below......https://www.amazon.com/Blue-ESR-Tester-Fully-Assembled/dp/B00O0BMIYQ/ref=lp_10347381011_1_1?srs=10347381011&ie=UTF8&qid=1568878712&sr=8-1Let's take it one step at a time......First, let us know where C5704 and C5705 are connected to? My guess is one of them is connected between line and neutral and the other one is between neutral and earth.If so, remove these two caps and switch on the unit again......my guess is that there would be no difference in the unit operation status (i.e. unit would remain dead) , indicating that this is not where your problem lies.Are you comfortable with measuring voltages on the power supply board?If you have never done it before, I would not advice messing with main voltage powered supplies........switching supplies just make the whole story worse.Am surprised that you heard a loud bang and can't see any visual damage on the board.

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 04:06:24 pm
content: I'm probably wasting your time but I appreciate the help. I'm pretty much a wussy when it comes to electrical stuff that can kill me. I have a lot of nice vintage tube amps but I didn't rebuild them. Sure wish I had the skill but don't. Here's a pic that shows the solder side of the board. I put some annotation on it for the cap location and power leads.https://pbase.com/image/169788402and here is an image of the top side (in that area).

author: SquattingDog
author_rank: Contributor
timestamp: September 19, 2019, 07:11:35 pm
content: BTW, before I forget, what is a "fuse point check mean" in the very first image I posted mean?