[Audionautic]

 

Just swapped out what I thought was a blown midrange, and I still have the top end distortion. I say top end, but it really did seem to be coming from the midrange panel. Anyone have a theory as to what could be causing this? The other speaker is strong and clear. I'd switched speaker leads and the problem is in the one speaker. I guess it could be the tweeter or crossover?

[John Casler]

What are the exact details?

Did you replace 2 panels or just one in each speaker?

Did you replace with an actual "factory modded" panel(s)

Did you swap left and right speaker wires to make sure it wasn't the "signal"

Did you work the L-Pads from one stop to the other 40-50 times to make sure they are not oxidized or corroded?

Can you describe the sound you are hearing more specifically?  Is is a scratchy, or crackling sound?

[Audionautic]

John-
I replaced just the midrange in the distorting speaker. The panels are identical to the ones I took out. I did swap out the speaker cables and the problem didn't follow the signal. I worked the midrange L-pad maybe 10 times, and there was no change. When it distorts, it sounds like "break-up". Intro to The Lamb Lies Down on Broadway, snare drum roll is clear with each stick strike distinct from the left speaker, and a muddied jumble from the right. It still seems like it comes from the midrange panel, but it's tough to say. Thanks for the help.

[John Casler]

Hmmm. . .

Sounds like the replacement has the same issue as the original.

Did the replacement have the little silver bolts/screws with the small nuts like the other?

From your description, it sounds like typical panel failure, which happened often to the unmodded panels, and occasionally to even the modded panels.  The modded panels has the small screws and nuts to make the contact more secure from vibration.

You could try tightening the nuts just slightly, if possible to see if maybe that would secure the connection.

Be careful, as bumping them can break them loose.

You could also try said tightening the original panel and trying it again too.

[Stimpy]

New panels, but never modded.  Ask me how I know?   

As another experiment, try swapping panels between the speakers.  If the 'known' good panel, distorts in the suspect speaker, your issue isn't with the panels.  So, clean and rotate the L-pads again, double-check all connection points (internally and externally - also check for poor solder), to insure proper connection, and if those attempted fixes aren't successful, you could have a failed capacitor.  Not likely with poly caps.  But, anything is possible.  Then, maybe new L-pads, or a recap. 

[Audionautic]

Ok. New data.
Took out one woofer to get access to the L-pads from within. DeOxit D5 and Faderlubed both in the distorting unit. Rotated both on that speaker over a hundred times total, between sprays. Still sounds like one channel on the radio before you get it to exactly lock on with the quartz tuning. One thing I almost missed is that all those red TRT caps had at some point pulled the hot glue off the board they were adhered to, and are kind of hanging from their own wires. They don't look damaged, but I don't know if they were playing when that happened.    I can stand in front of the "good" speaker when it's cranked, and dig it. The other at same volume makes me wince a little. 

[John Casler]

New panels, but never modded.  Ask me how I know?   

As another experiment, try swapping panels between the speakers.  If the 'known' good panel, distorts in the suspect speaker, your issue isn't with the panels.   

As Stimpy suggests above.  Swapping panels is your only (or best) next step, since you have a "known" working panel. 

But remember "be gentle" with those panels as those connections can be fragile, even in the modded panels.

If the sound with the "known" panel is good then you have your answer.  If it still distorts, then more troubleshooting is in order.

[Audionautic]

Will do that tomorrow. Are the caps hot-glued to their board, or should that be repaired another way?
I'll get in and take a good look at that crossover tomorrow also, and post pics. I'm thinking that could be involved.
8 or 9 heavy caps jostling around as the woofers move could pull on those leads and make intermittent contact.

[John Casler]

Are the caps hot-glued to their board, or should that be repaired another way?

Yes, hot glued.

[Audionautic]

Not sure how I did this, but it turns out the speaker is fine. I still have an intermittent distortion in one channel of the Sansei G8000 receiver. At least that is something I've handled before. Thanks to all who helped. The silver lining is that I now have the hard-to-find replacement midrange panels I'll need to keep these great speakers running properly for ages, I hope.

[John Casler]

That is actually GOOD NEWS, since a new amp or receiver will make the LRC sound even better. 

Thanks for letting us know.

P.S. - Since that old Sansui has knobs, and push buttons, you might get some relief from the scratchies by taking EACH knob, and control, and turning it "fully" back and forth, and or pushing in and out, or up and down AT LEAST 50-100 times.

All those controls corrode at the contacts over the years, and this might help clean the contact a bit.

[Stimpy]

Not sure how I did this, but it turns out the speaker is fine. I still have an intermittent distortion in one channel of the Sansei G8000 receiver. At least that is something I've handled before. Thanks to all who helped. The silver lining is that I now have the hard-to-find replacement midrange panels I'll need to keep these great speakers running properly for ages, I hope.

Wow.  That's awesome to hear.  I wanted to ask if you'd made any progress, but was afraid to find out.  I didn't want hear bad news.  So, sweet, I'm so glad everything worked out.  Except for the G8000.  I hope it's repairable?  At least, now you have an excuse for an upgrade!  Maybe one of the newer Yamaha or Parasound integrated amps with built in DAC's?  Those are nice.     

[Audionautic]

The G8000 volume pots are easily accessible without removing boards. I flushed the living heck out of those with DeOxit, and ran them stop-to-stop about 100 times. Thats not it. It may be the main switch that takes the amplifier section out of the circuit so you can use the preamp only. Those switches are fairly notorious, and a pain to get at. Or its a bad cap or two, or a dirty relay...
I'll report back once I get this squared. Oh and thanks Stimpy. It's all good. I have the parts and my VMPS LRCs will live longer than I'll need them probably. But, without starting a war, I have to say I'm not such a huge Yamaha fan. I think the old Sansui "Big G's" sound pretty great. There sure is a lot more amplifier iron in them than some of the new receivers I've seen.