PDA

View Full Version : 2 amps, 2 issues



ryan s
02-22-2011, 01:14 PM
Of course, both my home setups are messed up at the same time :banghead:

Problem #1...Old school receiver, normal solid state...nothing special.

I turn it on, and once it's warmed up, whichever speaker is hooked to the right channel has a static/popping sound in the higher frequencies. It's intermittent, yet always present.

Sometimes, it's tied to the volume knob. I twist the knob and can make the static appear and it sounds like the pot itself is "scratchy." This is very hard to replicate and it's pretty rare.

Swapped speaker wires, swapped to other speakers with the same issue.

------------------------------------------------------------------------------------
Problem #2...2.1 computer system with a track record of amp failures and problems with the speaker connections, because it uses 3.5mm ends into the back of the satellites. No issues in almost 4 years, and I even bought it used.

It has a standard (though proprietary) plate amp in the sub enclosure and a "control pod" in the one satellite. From the pod, it has a 3.5mm input cable and a DIN cable going to the amp.

I swapped speaker wires at the amp, and the one amp channel produces very, very low output (left satellite channel...right sat and sub work fine). Last week, it would cut back to full output once in a while but I couldn't get it to do that yesterday.

Took the amp apart and I can't see anything cooked or burned...these are notorious for having one or two resistors fail. Most troubleshooting online deals with scratchy output or no output at all. It was working fine up till last week.

Anyone have any ideas? Probably difficult to diagnose online. I think I'm going to get that small Dayton amp from PE and just run a pair of speakers and sub I have sitting and get rid of the computer set. They sound sooooooooo nice, too :rolleyes: And the Dayton amp is sold out for another month :mad2:

Chad
02-22-2011, 04:00 PM
#1 has leaky electrolytic caps likely, if the noise gets bad is it ever enough to kick out the DC protect relay? OR, can you smack it around a bit to replicate the sound? Indicating a bad connection internally?

#2 is the DIN plug a small one, like the size of a PS/2 connector? Or is it a big one like MIDI or old skool keyboards? It could be int he DIN jack, they are notorious about breaking solder connections, a broken volume pot can also do this. Can you smack it around a bit to replicate the problem?

Seeing a pattern here?

The actual make/model helps. Can't go on a mechanics forum and say "I have this car, and it makes a funny sound."

ryan s
02-23-2011, 05:30 PM
#1 is an old Sherwood RA-1145R receiver. I played it for about an hour yesterday and the static only came on for about 30 seconds during that whole time. Later I opened it up and the 4 filter caps near the transformer are leaky. They're just regular old Korean ones (and the board is through-hole) so they shouldn't be too bad to replace.

It's never gone into protect mode or anything like that. The left channel always works, the right always has the static. I've hit it plenty of times...that's usually my go-to method for fixing things :lol:

#2 is a Klipsch Promedia 2.1 system. Luckily, there's a lot of info out there on fixing them, including full schematics Klipsch Promedia V2.1 Amplifier Repair (http://www.thompdale.com/bash_amplifier/2-1/2-1_bash_amp.htm)

It uses the standard PS/2 DIN connector, and there's a guy on ebay who sells all kinds of parts just for these systems including a replacement plug.

If you scroll down to the bottom of that page I linked, you can see how the amp is set up. Mine has about 4 times more glue and shit inside, so it's hard to tell if the caps are going. Klipsch slathered all kinds of adhesives everywhere inside these things. The control pod looks good inside and works properly.

Punching the plate amp doesn't do too much, unfortunately :gr_grin:

Thanks for the response!

Chad
02-23-2011, 09:12 PM
The Klipsch DIN connectors are simply NOTORIUS for failure.. every time.. check it the sub. I deal with it all the time at work. if not grab the plug, hold it steady, then move the wire, they sell the wire as an assembly IIRC.

Leaky caps remember, they glue them own, often times they LOOK leaky (due to the glue,) but are not. Replacement is still not a bad idea, without me searching, what vintage s the Sherwood?

Newer caps are MUCH smaller than the older counterparts. Just make sure the lead spacing is right, the package will be smaller.. I like panasonic 105 degree ones.

Chad
02-23-2011, 09:15 PM
I just looked up the receiver, it's not THAT old, but new enough to have shittier components. pop the top and tap around in there with a pencil with one of those "Adda-erasers" on the end of it. Listen for the noise.

Is it a "one chip wonder" amplifier?

ryan s
02-25-2011, 04:36 PM
Hey Chad,

I think my dad bought this receiver in '86(?)...somewhere in that area.

Here's some pics:

http://www.mobilesoundscience.com/members/ryan-s/albums/sherwood-receiver/250-imgp7265-copy.jpg

Here is a shot of one of the big caps right next to the transformer. Looking at the top of the transformer, it looks like there's similar glue on it...

http://www.mobilesoundscience.com/members/ryan-s/albums/sherwood-receiver/251-imgp7269-copy.jpg

These are the 2 caps near the vertical heat sinks in the lower left corner:

http://www.mobilesoundscience.com/members/ryan-s/albums/sherwood-receiver/248-imgp7268-copy.jpg

http://www.mobilesoundscience.com/members/ryan-s/albums/sherwood-receiver/249-imgp7267-copy.jpg

It could be glue, but I'd wonder why it looks so shitty and dusty if the electrolytic wasn't "wet" when the dust hit it? Strange...

I'll give the tap test a go and see what happens. Sucks that a bunch of resistors have the loose ceramic insulators on the leads...they always rattle around.

For the Klipsch, I hooked up the system again today, and there is NO output on the left channel. Wiggled the wire while holding the DIN plug, nothing :( Here's the replacement from ebay (http://cgi.ebay.com/Repair-cable-Klipsch-ProMedia-2-1-Control-Pod-DIY-/180631549971?pt=PCA_Speakers&hash=item2a0e7ab813).

ryan s
02-25-2011, 05:29 PM
Playing it now with the top off...can't reproduce the sound with my pencil. In fact, it's been going for 10-15 minutes without a sign of the static :confused: Of course, once the troubleshooting begins, the issues cease.

These Klipsch satellites play low and loud enough to rattle some of the resistor insulators inside the amp while they're on a different level of my desk, on top of some other speakers :lol: And that's just listening to some indie rock...

ryan s
04-05-2011, 03:17 PM
So, narrowed it down to control pod failure since the DIN plug tested fine. I got the brand new (revised) pod from Klipsch the other day and at least the left channel has sound.

But...it's exactly 50% as loud as the right :( I hardwired the satellites, eliminating the 3.5mm jacks...just like the replacement speakers from Klipsch now come with.

With the balance in Windows set to 100% R, 50% L the sound is balanced but I just have to turn it up more.

Well as I'm typing this I'm listening to the system...there are some crackles on the left channel. That, combined with the low output on one channel, means amp failure. Probably going to sell the set as-is, pick up a cheap Class T amp, and use my cheap RCA bookshelves and 10" sub for the time being. These Promedias sound soooo good, but man, are they garbage.

Edit: Hello, left channel again :wtf: