Sony SA-WM40 problem

[joe1234]

I have a Sony SA-WM40 subwoofer that has seen approximately 3 years of heavy use. As many people know, its a great sub after the polyfill and mod-podge mods. However, the problem I recently started noticing is that after playing a CD for a few songs, it spontaneously cuts off during the middle of a song for anywhere between 5 to 10 minutes and then comes back on randomly. It then proceeds to switch on and off at random intervals. Its like it has a mind of its own. What is weird is the power light stays on and stays green throughout. I do hear a "click" like as if it were shutting off or switching or something when this happens though.

Has anyone else encounteed this problem with this sub? I thought it might be the "power save auto turn on/off" function that is built in, so I switched it to manual but the same thing happened anyway. I figure the cheap, built in amp is just plain wore out and old. Is it time to get a new sub, or is there an easy cheap fix for this?

Jose

[MikeyBC]

Could be as simple as a cold solder joint that when it reaches a certain temperature decides to break contact somwhere in the signal path. Send it out for an estimate.

[abulgan]

I have a Sony SA-WM40 subwoofer that has seen approximately 3 years of heavy use. As many people know, its a great sub after the polyfill and mod-podge mods.
Jose

what type mod is that?thinking to add a s.woofer to my stereo system with reasonable price but i see it is good sub after some work on it some kind of upgrade

[joe1234]

what type mod is that?thinking to add a s.woofer to my stereo system with reasonable price but i see it is good sub after some work on it some kind of upgrade

You basically fill the inside of the enclosure with "Poly-fill" to get rid of the overly "boomy" and inaccurate sound that it produces from the factory. You can find good info and pictures of this mod here: www.nonsensicalgibberish.com/sony.html

Being a relatively cheap sub, Sony uses a regular untreated paper woofer to keep costs down. So what many people also do is treat the woofer with "Mod-Podge," which is a glue like substance that when applied to the flimsy paper woofer, stiffens the paper and adds some structural rigidity and weight to the woofer. This helps tighten up the sound even more. Most people do 3 coats to the front and 2 coats to the back of the woofer waiting 15 to 20 minutes in between coats. Some people go even a step further and replace the woofer altogether with something better.

You can find both "Poly-fill" and "Mod-Podge" at any local handcrafts store or even walmart for few bucks each. However, you probably won't find a new SA-WM40 on the market anymore. Your best bet is to find one on e-bay. For around $100 bucks you won't find anything that touches it.

Jose

[abulgan]

thanks,can find lots of poly-fill material

and u r right but i can find Sony SA-WM200 and 250

can u or somebody suggest these speakers for stereo application

[bfalls]

To help with the original question. It sounds like the amp is shutting itself down. There's probably a relay which opens when a heat sensor on the heat-sink of the output transistors/IC gets too hot. When it cools enough the relay closes and the speaker comes back on. This is why the power light stays on, it's only shutting down the output until the relay can reset. The time it's off will vary depending on how warm the outputs were and how easily they can cool. If the amp is internal it's possible the poly-fill is impeding the air flow and not allowing enough air around the heat-sink to dissipate the heat. I read Sony standard receivers (not the ES series) had underpowered power supplies which resulted in the amp clipping and cause speaker damage. I haven't heard anything about their subs. It's possible you're just overdriving the sub and the problem is not related to the upgrade. But if you didn't have the problem prior to the upgrade, heat dissipation is worth looking into.