I have had a Velodyne SPL-8 series sealed subwoofer for 6 years with no problems, but as of late it has had issues with the plate amplifier. very audible distortion, severe, loud motorboating, and doesn't fully work unless it has a hair dryer applied to the plate amp. (lol!)
I would assume this is something to do with caps, or bad solder joints? I have tried to diagnose it but there wasn't anything obviously burnt up or broken when I opened it. After it warms up it's fine, so if I leave it on 24/7- it doesn't come back. When it gets cold the issue comes back- it sounds almost as if a preamp is the only thing driving the sub, and there's hardly any amplification at all. Lots of squeaky distorted noises and such- and when it warms you can hear the full punch hammering in and out like a car engine trying to cold start. Any suggestions are appreciated, I love this subwoofer and wouldn't want to replace it for anything.
I would assume this is something to do with caps, or bad solder joints? I have tried to diagnose it but there wasn't anything obviously burnt up or broken when I opened it. After it warms up it's fine, so if I leave it on 24/7- it doesn't come back. When it gets cold the issue comes back- it sounds almost as if a preamp is the only thing driving the sub, and there's hardly any amplification at all. Lots of squeaky distorted noises and such- and when it warms you can hear the full punch hammering in and out like a car engine trying to cold start. Any suggestions are appreciated, I love this subwoofer and wouldn't want to replace it for anything.
Update?
Not sure if I'm allowed to bump a thread but I'd really love it if anyone had any suggestions about how to go about repairing this or diagnosing the issue. It's still a recurring issue every time I turn it on and sometimes can take quite a while to start functioning correctly. Thanks so much.
Not sure if I'm allowed to bump a thread but I'd really love it if anyone had any suggestions about how to go about repairing this or diagnosing the issue. It's still a recurring issue every time I turn it on and sometimes can take quite a while to start functioning correctly. Thanks so much.
Posting some well-lit, in-focus photos of the internals of the amp would be a good place to start.
Update with pictures of the board.
Just took some. Looks as if the mains voltage had caught a terminal at one point!
http://bassblitzed.net/share/IMG_0287.JPG
http://bassblitzed.net/share/IMG_0289.JPG
Big burnt area that looked like some kind of short had been made at one time. That didn't make sense to me that it would be heat-reactive or something of the sort, so I didn't think that was the issue I was facing. I made a jumper for the terminal and resoldered the offending joint that had contacted the board somehow, but alas to no avail. (forgive my crappy soldering, I have thick solder laying around and literally a chisel tip on my iron. I really need a tiny cone)
http://bassblitzed.net/share/IMG_0300.JPG
http://bassblitzed.net/share/IMG_0302.JPG
bassblitzed.net/share/IMG_0303.JPG
I have a strong feeling that it's the caps that are going bad however. http://bassblitzed.net/share/IMG_0304.jpg This thing was made in 2001, and has lasted 18 very hardy years with being played quite a lot. I'm really impressed that the surround has made it this long, but the used some very hard rubber with a big surround.
Just took some. Looks as if the mains voltage had caught a terminal at one point!
http://bassblitzed.net/share/IMG_0287.JPG
http://bassblitzed.net/share/IMG_0289.JPG
Big burnt area that looked like some kind of short had been made at one time. That didn't make sense to me that it would be heat-reactive or something of the sort, so I didn't think that was the issue I was facing. I made a jumper for the terminal and resoldered the offending joint that had contacted the board somehow, but alas to no avail. (forgive my crappy soldering, I have thick solder laying around and literally a chisel tip on my iron. I really need a tiny cone)
http://bassblitzed.net/share/IMG_0300.JPG
http://bassblitzed.net/share/IMG_0302.JPG
bassblitzed.net/share/IMG_0303.JPG
I have a strong feeling that it's the caps that are going bad however. http://bassblitzed.net/share/IMG_0304.jpg This thing was made in 2001, and has lasted 18 very hardy years with being played quite a lot. I'm really impressed that the surround has made it this long, but the used some very hard rubber with a big surround.
Would anyone have any suggestions to what could cause this or a way to test my hypothesis about the capacitors? Any feedback is greatly appreciated. Thanks!
Sorry but your pics are too fuzzy and don't show anything informative about the burning damage you mentioned.
You could be right about the caps after that period of time but if you choose to replace them in hope of a fix, make sure the grade of replacement caps is compatible or better since this is (I presume) a switchmode power supply i.e. no power transformer and the duty for the caps in the power supply is an arduous one. They are usually low ESR type caps which are quite expensive in large sizes. Fitting the wrong type where it matters can cause nasty overheating and venting, if not explosion so be careful with the quality of your replacement types.
Testing capacitors is done with a particular type of instrument - an ESR meter and a good one will cost as much as a replacement plate amp. (possibly your best option actually) Yes, you can buy test gear cheaper from China but there's often no indication of limitations and just because a manufacturer says their gadget tests everything imaginable doesn't mean it gives reliable results. Given the large size of the caps, it may just be cheaper to replace them anyway.
You can use the manufacturer's datasheets at their tech. websites to locate the specs and dimensions for your caps and compare with other brands and grades online.
BTW, have you contacted Velodyne service for their suggestions?
You could be right about the caps after that period of time but if you choose to replace them in hope of a fix, make sure the grade of replacement caps is compatible or better since this is (I presume) a switchmode power supply i.e. no power transformer and the duty for the caps in the power supply is an arduous one. They are usually low ESR type caps which are quite expensive in large sizes. Fitting the wrong type where it matters can cause nasty overheating and venting, if not explosion so be careful with the quality of your replacement types.
Testing capacitors is done with a particular type of instrument - an ESR meter and a good one will cost as much as a replacement plate amp. (possibly your best option actually) Yes, you can buy test gear cheaper from China but there's often no indication of limitations and just because a manufacturer says their gadget tests everything imaginable doesn't mean it gives reliable results. Given the large size of the caps, it may just be cheaper to replace them anyway.
You can use the manufacturer's datasheets at their tech. websites to locate the specs and dimensions for your caps and compare with other brands and grades online.
BTW, have you contacted Velodyne service for their suggestions?
If it only faults when cold a can of Freeze Spray might help locate the offending area. Electrolytic caps can fault in a way that is heat sensitive. They appear to loose capacitance when cold. (I've seen this before). Be very judicious when spraying and try to only freeze one component at a time. Good luck.
Be advised that that decade-old warning about "the bad capacitor syndrome" can be a part of this if the vendor had those defective caps.
Some manufacurers in order to cut costs may use "old stock" and from time to time it'll rear its ugly head.
A friend of mine purchased (new) a Polk sub on sale at HH Gregg.
Just a year or so later, it developed a "tick tick tick" while on standby.
We had one in the shop that did the same thing.
Some manufacurers in order to cut costs may use "old stock" and from time to time it'll rear its ugly head.
A friend of mine purchased (new) a Polk sub on sale at HH Gregg.
Just a year or so later, it developed a "tick tick tick" while on standby.
We had one in the shop that did the same thing.
in reply to Ian Finch and irext, I might try the freeze spray method to diagnose the issue. I'd prefer not replacing the stock amp but at this point I'm not sure if I would be able to correctly repair or even if the caps were indeed defective. the amp is 18 years old at this point so I figure it's served a good life. and wiseoldtech, yeah I agree. I have some ancient JBL Model L212's in my room with wax and paper capacitors in the crossover network, they work fine and those are old as dirt!
Give the freeze spray method a go and report back. If it's electrolytics then replacing them shoudn't be too difficult with a good soldering iron and some solderwick. They are all radial types fortunately (according to the pics) and seem accessible. Use leaded solder as that's what would have been used when it was made. You've got nothing to loose and left as it is it may fail completely and be a much bigger repair or a write off.
Sounds good and will do, sounds like a great project for this weekend! By freeze spray you mean upside down compressed air duster right? Also, I appreciate the good suggestions, fingers crossed that it's the caps so I can repair it easily. I'm not worried about my soldering skill, but moreso that it'll be something else not so easily testable. I had thought it might be them from the start due to the fact that if the amp was heated up considerably it would function as normal. After reading that electrolytics gain capacitance at higher temperatures, it seemed like a fitting reason. My guess would be (if it was the capacitors) that they are losing their total capibilities and somehow this is affecting the power input (back to my previous statement about sounding underdriven, as if it was a teeny preamp getting massively overdriven) and coupled with the motor sound of it constantly bumping in and out of it's full volume. (very distracting) Makes me wonder if the mosfets, when undervolted or underdriven will make such noises. Anyway, yeah I'll give that a go this weekend and post some better (not fuzzy haha) pics. I don't have a macro lens for my canon so it's difficult to get up close shots that don't seem to have a massive glare on something that small.
Since that sub amp is around 18 years old, that would put manufacture year at 2001/02, which was as far as I know, the beginning of that "bad cap" run.
Look for physical leakage under the cap leads, bulging tops, perhaps black goo.
If a cap is unsoldered, and it has a "fishy" smell, there's your problem.
Mitsubishi TV's made around that time were famous for that problem.
I had to replace hundreds of them caps in the shop.
Freeze spray comes in a pressure pack can and is specifically made for fault finding. You will find it at an electronic supply store (I'm in Aus so I can't recommend one in the States). The can will have an extension tube which you poke into the nozzle so that you can direct it at individual components.
Another little thing that plagues electronics and causes "hard to locate" issues....
GLUE.
An ivory color, tan, brown, or black "goo" glue used to anchor and keep components from moving.
usually anchoring larger capacitors, but can be on anything.
It, over time, becomes conductive, sometimes changing color (tan glue turns dark brown)
If spread around on resistor leads, etc, it's like another "path" for signals/electricity to creep, causing all kinds of crazy issues.
One way to determine if it's "gone bad" is to get your digital multimeter probes on the glue, almost touching each other - and see if you get a reading on the OHMS scale. (K ohms, or meg ohms will show something)
Glue that reads "open" is OK.
I worked on a "high end" Rotel 7 channel surround receiver for a customer - loaded with that crap.
I had to pry, scrape and curse my way through the muck, but I got it functioning again.
GLUE.
An ivory color, tan, brown, or black "goo" glue used to anchor and keep components from moving.
usually anchoring larger capacitors, but can be on anything.
It, over time, becomes conductive, sometimes changing color (tan glue turns dark brown)
If spread around on resistor leads, etc, it's like another "path" for signals/electricity to creep, causing all kinds of crazy issues.
One way to determine if it's "gone bad" is to get your digital multimeter probes on the glue, almost touching each other - and see if you get a reading on the OHMS scale. (K ohms, or meg ohms will show something)
Glue that reads "open" is OK.
I worked on a "high end" Rotel 7 channel surround receiver for a customer - loaded with that crap.
I had to pry, scrape and curse my way through the muck, but I got it functioning again.
Last edited:
- Status
- Not open for further replies.