Sunfire HRS8: Screws removed, how do I remove rear plate??? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 14 Old 07-04-2018, 08:40 AM - Thread Starter
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Sunfire HRS8: Screws removed, how do I remove rear plate???

Hi - I have a 8+ year old Sunfire HRS8 Subwoofer that has developed a hum. I get the hum with no inputs connected, and I tried locating the subwoofer in different places in my house, on different circuits/phases/etc. I also tried different power cords (including a 2-prong one). I believe it's a filter cap. I'd like to take a look (and also, some repair places ask you to send just the amp, not the whole subwoofer).

I've removed the 12 screws around the back, but I cannot budge the rear plate out of the box. Help?

Thanks!
/j

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post #2 of 14 Old 07-04-2018, 02:55 PM
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Ive never removed a Sunfire amp but I dont see why anything else would be holding it in. If you dont want to pry anymore pull the driver and see if somethings hung up.

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post #3 of 14 Old 07-04-2018, 02:56 PM - Thread Starter
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Thanks!

was trying to avoid messing with the driver - sometimes these are hard to put back in properly... After I remove the 12 screws (3 outer most on each of 4 sides of the back panel), the back panel should what, just drop out?
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post #4 of 14 Old 07-04-2018, 07:24 PM - Thread Starter
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Hmmm - after wiggling it a bit - it just came loose. Nothing inside looks obviously broken though. Pics at http://kwcpa.com/HRS8
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post #5 of 14 Old 07-05-2018, 08:04 AM
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A bit late now but the advice I got from a UK subwoofer manufacturer was to use a hair drier or heat gun to loosen the seal. As it was winter and the central heating was on I placed it in front of a hot air vent for a couple of minutes.

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post #6 of 14 Old 07-05-2018, 08:08 AM - Thread Starter
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Thanks - sending it to EBC electronics for repair...
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post #7 of 14 Old 07-05-2018, 12:31 PM
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Do the caps look swollen? http://kwcpa.com/HRS8/20180704_220232.jpg Or is it just me imagining it?
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post #8 of 14 Old 07-05-2018, 12:35 PM - Thread Starter
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Not obviously - I ran my finger around them and didn't detect any imperfections. I'm sending it out for repair (EBC Electronics) anyway. Unless I saw 1 cap obviously hosed that looked easy to replace, it's beyond my meager skillset to repair :-)
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post #9 of 14 Old 07-06-2018, 09:02 AM
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Quote:
Originally Posted by jeffw_00 View Post
Not obviously - I ran my finger around them and didn't detect any imperfections. I'm sending it out for repair (EBC Electronics) anyway. Unless I saw 1 cap obviously hosed that looked easy to replace, it's beyond my meager skillset to repair :-)
Capacitors are often bad, but not visually, and must be tested with an ESR Meter or Leakage Detector to be found. ESR meters can be found cheap on Ebay (and generally speaking the cheap no-name ones do work fine). But yes if it's beyond your ability you can either send it out for repair, or you could add some terminals to the sub, hook those up to the driver, and use an external amp. Leave the plate amp on just so you don't have a giant hole in the side of your sub box. Don't actually hook it up to anything.

But repair is fine. I have no experience with that company so I don't know if they're a good repair shop or not.
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post #10 of 14 Old 07-06-2018, 11:00 AM
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Quote:
Originally Posted by DonoMan View Post
Capacitors are often bad, but not visually, and must be tested with an ESR Meter or Leakage Detector to be found. ESR meters can be found cheap on Ebay (and generally speaking the cheap no-name ones do work fine). But yes if it's beyond your ability you can either send it out for repair, or you could add some terminals to the sub, hook those up to the driver, and use an external amp. Leave the plate amp on just so you don't have a giant hole in the side of your sub box. Don't actually hook it up to anything.

But repair is fine. I have no experience with that company so I don't know if they're a good repair shop or not.
https://www.ebay.com/itm/3-7V-of-ind...item2cd6232131

Is something like this sufficient, or do I need to get something a little better in the $30-40 range? I have some vintage amps and a Sunfire so I think I need to learn how to do this if I want to keep the stuff running without spending a lot.

I happened to fix my Sunfire after seeing this post and watching some youtube videos. I think I had a cracked solder joint. I could not see well enough to reflow all the components, however I did the caps and seems to have fixed my Sunfire now. I had a whole evening without humming


Now I want to learn more and check all the caps so I can replace any that are starting to fail. Maybe I can even add an additional Sunfire to the theater soon
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post #11 of 14 Old 07-06-2018, 11:12 AM
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that will be fine, just a bit less convenient to use - if it has no case then make sure not to set it down on anything metal and short it out

but it will work fine

I have the ~$40 MESR-100 one and it works great. I have relatively expensive multimeters from Agilent, Fluke and Klein (one each and the Klein one is a clamp-on), but I'm happy with the cheap ESR meter.

https://www.youtube.com/watch?time_c...&v=7Br3L1B80ow -- Dave Jones from EEVBlog thinks these are pretty decent also. This video is about the LCR/transistor model which is slight different but it's close and should be applicable.

Sometimes these work well in-circuit and sometimes not. But here's a general tip: if an ESR meter says your cap is bad, it is definitely bad. If it says it is good while out of circuit, it is almost definitely true. If it says it's good in-circuit, it may or may not be true. It can get confused in-circuit when you have a capacitor in parallel with other capacitors, or with low value resistors. Personally I always test in-circuit first, and move onto out-of-circuit testing if I deem that necessary.
NNG and LotsaBoxes like this.

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post #12 of 14 Old 07-06-2018, 12:27 PM
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Quote:
Originally Posted by DonoMan View Post
that will be fine, just a bit less convenient to use - if it has no case then make sure not to set it down on anything metal and short it out

but it will work fine

I have the ~$40 MESR-100 one and it works great. I have relatively expensive multimeters from Agilent, Fluke and Klein (one each and the Klein one is a clamp-on), but I'm happy with the cheap ESR meter.

https://www.youtube.com/watch?time_c...&v=7Br3L1B80ow -- Dave Jones from EEVBlog thinks these are pretty decent also. This video is about the LCR/transistor model which is slight different but it's close and should be applicable.

Sometimes these work well in-circuit and sometimes not. But here's a general tip: if an ESR meter says your cap is bad, it is definitely bad. If it says it is good while out of circuit, it is almost definitely true. If it says it's good in-circuit, it may or may not be true. It can get confused in-circuit when you have a capacitor in parallel with other capacitors, or with low value resistors. Personally I always test in-circuit first, and move onto out-of-circuit testing if I deem that necessary.
Thanks, I watched the video and ordered a Mega 328 on amazon with case for $16 shipped to me. I just did a search on ebay for esr when I posted the link.

Last edited by LotsaBoxes; 07-06-2018 at 01:03 PM.
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post #13 of 14 Old 07-10-2018, 09:25 AM
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I'm in the similar boat in many ways. A few non-working built-in sub amps with interest in DIY repairs. I will look to get the same ESR tester to aid in locating bad caps. The other issue is getting the replacement caps without having to buy larger lots.

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post #14 of 14 Old 07-16-2018, 08:43 PM
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Looks like my problem is not a cracked solder joint the hum came back after a few days. I'm not sure I'm using the meter correctly to check caps while on the board. I'm getting higher ESR and Vloss values while measuring on board. I'm still putting my list of caps together before I order. I still think the caps are bad. I happened to have a few 2200uF 25V caps on a amp board for a project I parted out. Decide to practice desolder some caps, and happen to notice they were some of the ones I needed. Did a quick test on the meter and these caps looked much better. Very low ESR values, very low Vloss, and capacity much closer to spec. I put the 2 2200uF caps onto the Sunfire board, and for now the problem seems to be fixed. I still want to replace more caps as I think they are going bad from age, I believe these are the original and the sub is close to 20 years old. This post shows 6 bad caps, 4 1000uF 25V and 2 2200uF 25V, https://www.ecoustics.com/electronic...io/618938.html When people say replace all the caps, are these the only 6, or should I be replacing all 40+ caps on the 2 boards?


Sub sounds good now, but to be sure I want to replace all the needed caps so I can enjoy the hum free sounds for years to come.
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