Did I fry my SDA-2s? Help!

**onepixel** · 03-09-2006 07:03 PM

Thanks in advance.

I'm relatively new to this forum and a simpleton when it comes to electronics. Last night my SDA-2s the ones with two tweeters, 3 mids and a bass, per speaker partially died. I recently got a vintage Marantz 4140 Quadradial 4 channel amp. Cosmetically looks mint, functionally it was scary scratchy. I cleaned the pots best as I could. Big improvement but still some scratchiness. I plugged the SDAs into the front and some vintage Infinitys into the rears. After gently fiddling around a bit I got awesome sound. WEEE! Then I noticed the tweeters in the right speakers had gone completely silent. AHHH!

I swapped a good tweeter from the left speaker with a bad one. Silence. AHHH!! I made more tests with another amp and found out that 3 of 4 tweeters were silent. Sob! More test and I found out all the tweeters worked but in only one position on the left speaker. Phew! I not sure but the rest of the drivers may be affected. The Infinitys sound just fine.

What did I do to my most favorite Polk speakers?!? The interconnects were plugged in at the time. Did the I fry the crossovers or something?

Also I can't get on to Club Polk from home. Sigh...

**jcaut** · 03-09-2006 08:07 PM

It seems unlikely to me that you would have fried anything, but I guess it's possible. Your tests prove that the tweeters are all okay. I'm not an SDA expert (someone who is will chime in shortly) but most of them have polyswitches that protect the tweeters. It sounds like a few of them may have opened-up. It's possible, from the scratchy controls.

Caig Deoxit will take care of the scratchy controls.

Jason

**F1nut** · 03-09-2006 11:26 PM

Could have been a non-common ground issue.

**dorokusai** · 03-09-2006 11:40 PM

I'm sorry to hear of your problem....BUT....you violated the first rule of used audio....NEVER hook up unknown gear to your main rig. You should always have BS gear or speakers to hook "new" stuff up. I bet you know now? Good troubleshooting BTW.

Know how to use a VOM? That would determine the common ground idea mentioned by F1Nut.

CAIG! Great suggestion, but get in behind that knob, not the front. If you saturate and let it sit for a day....work it....and it still sounds bad....look forward to another expense. Try it a couple times as hippies were dirty folks, and that ****e builds up.

If none of that works, polkcs@polkaudio.com...have credit card ready. I would buy one tweeter and troubleshoot further or find a used tweeter via Ebay or the Polk Flea Market. You'll like the new ones much better anyhow.

**dudeinaroom** · 03-09-2006 11:57 PM

Did you check to see if it has fuse on the back panel, and if it does give them a check.

**dorokusai** · 03-10-2006 12:09 AM

It shouldn't have a fuse.

**F1nut** · 03-10-2006 12:27 AM

He says he has the SDA 2's, so they should have a fuse. Regardless, fuse or polyswitch, if any of the tweeters in the same cabinet work the protection device is not the problem.

**dorokusai** · 03-10-2006 01:33 AM

He states, SDA 2's....I've owned a couple SDA2's....no fuses in any that I've owned.

I figure he has a brain, in regards to the earlier troubleshooting, and I don't recall him mentioning an outboard fuse.

Take a look at the schematic....see a fuse?

**F1nut** · 03-10-2006 01:45 AM

Lots of folks don't know that there's a fuse(s) back there. Let's ask him to look instead of fighting about it. However and more to the point, that's not going to be his problem.

**dorokusai** · 03-10-2006 01:57 AM

I defer to you Polk Guru.

**F1nut** · 03-10-2006 02:13 AM

Ah, cut the crap Mark.

The schematic in Raife's Compendium shows a polyswitch, but in the description area it's states " an external tweeter protection fuse." As usual, Polk changed things at will. From that info, either type could have been used on his speakers. However, I've only seen them with a fuse. I take it that you've seen them with a polyswitch. Again, neither of them are going to be his problem.

**TroyD** · 03-10-2006 02:24 AM

Maybe a B&K AVR317 or somesuch would solve his problem.

(hey, this thread is careening off the tracks anyway)

BDT

**dorokusai** · 03-10-2006 08:45 AM

Good catch F1Nut. I see the fuse caveat in the notes, just haven't seen it personally in three pairs.

**TroyD** · 03-10-2006 12:17 PM

Jeeze, Mark, what's with the attitude? Is it THAT difficult to admit the possibility that you were wrong without sounding like a complete *******? Hell, near as I can tell even if your premise is correct it STILL doesn't address the guys original problem. WTF?

Eff me for trying to inject a little levity into a thread was going pointlessly astray.

BDT

**Ricardo** · 03-10-2006 12:35 PM

Onepixel,

Don't let these guys bother you; that's the way they are..sometimes.

From what I read, all your tweeters work; the problem is that they do not work in the right speaker (and in one position in the left speaker, but that could be ok...I am not familiar with your particular SDA, but I know others have some tricky things in the crossovers that make tweeters only sound when they are supposed to...or maybe these SDA's have one tweeter as an SDA tweeter? Do you have the interconnect cable plugged in? Just thinking out loud here).

With the right speaker, it seems that the protection could be the issue, be it a fuse or a polyswitch in the crossover. I guess that by now you already looked if there is a fuse. If there is not, you can test if it's the polyswitch by bridging it in the crossover, and then getting one from Polk CS if that was the issue. This is how the polyswitches look; it will be easy to identify.
http://www.partsexpress.com/pe/showd...number=071-254

**onepixel** · 03-10-2006 01:25 PM

Hi Guys,

Thanks for all the advice and sorry if I caused a ruckus. I should've been more clear.

I did check out and clean the amp and tested it on some other speakers before I plugged the SDA-2s in. The amp wasn't 100% clean, but I couldn't help myself. Had to hear what it sounded like. The speakers were 100%. No scratchiness or faulty drivers. There is no fuse on the back and all the tweeters work. Just not where they are suppose to. Only on spot. The interconnects were plugged in when all this happened. It wa great while it lasted.

HTrookie,
Thanks for the heads up on the polyswtich. When you say "try bridging it in the crossovers", does that mean use some wire and bypass it? I'm still learning.

F1nut,
What does it mean "non-common ground issue"?

Could the 4 channel with the interconnects have done something?

Thanks a bunch guys!

**Ricardo** · 03-10-2006 01:42 PM

Yes, using a wire to bypass it will work.

SDA's need to have a common ground amp; this means that the "negative" outputs from the amp are common; you can test this with a multimeter. It should measure 0 ohms from one terminal to the other measured at the amp's output.

**dorokusai** · 03-10-2006 01:57 PM

Originally Posted by TroyD

Jeeze, Mark, what's with the attitude? Is it THAT difficult to admit the possibility that you were wrong without sounding like a complete *******? Hell, near as I can tell even if your premise is correct it STILL doesn't address the guys original problem. WTF?

Eff me for trying to inject a little levity into a thread was going pointlessly astray.

BDT

I never said I wasn't wrong, just that I have owned 3 different early SDA2 with no fuses. You may recall, upon reading, he never mentioned a fuse in the first place. The schematic definetly shows a notation about a possible fuse existing and I'm sure that in there has got to be a model produced with an inline fuse. Many early models have fuses, so it just makes sense.

**schwarcw** · 03-10-2006 02:53 PM

Originally Posted by dorokusai

. . . .as hippies were dirty folks, and that ****e builds up.

ROTFLMAO!!!!

**TroyD** · 03-10-2006 03:30 PM

Originally Posted by dorokusai

I never said I wasn't wrong, just that I have owned 3 different early SDA2 with no fuses. You may recall, upon reading, he never mentioned a fuse in the first place. The schematic definetly shows a notation about a possible fuse existing and I'm sure that in there has got to be a model produced with an inline fuse. Many early models have fuses, so it just makes sense.

In regards to the attitude, F you, how's that?

It certainly seems as though the possiblility of not being 100% correct is something that doesn't occur to you. Regardless, as was pointed out, if they are fused or use polywitches, if that were the problem, none of them should work in any position.

Eff me? Fine. Gotta hand it to you, Mark, It must be tough keeping your nose that high in the air and your head that far up your ass.

G'head and put me on ignore, we are done here.

BDT

**dorokusai** · 03-10-2006 04:33 PM

Troy - Give me a break, obviously we are not seeing either point that we are respectively arguing about. I suspect we've lost some skin layers recently? If we're done, then that's your decision not mine.

**TroyD** · 03-10-2006 04:53 PM

No Mark, maybe we don't.

Look, I love you like a brother and you know that, however, it seems of late that every comment is an venomous rather than acerbic or being argumentative simply for the sake of being argumentative. It's playing to an increasingly weary audience. Personally, I find it sad because people that really think a lot of you are becoming alienated at an alarming rate.

Again, I love you man (not everyone gets to pass out on my bedroom floor mid-bash or hack up half eaten sammiches on my counters) but all I'm asking (and this is all I got to say on the subject, seriously) is think about dialing back the acidity level.

Troy

**onepixel** · 03-10-2006 05:24 PM

Hey dorokusai and TroyD,

Both of you might be right about the fuse thing. I noticed that the SDA-2 speakers have two different variations. The ones I have, 2 tweeters, 3 mids and a bass have no fuse. There also a version that has 1 tweeter, 2 mids and a bass, not sure if it has a fuse in the back. And I'm not talking about the 2A or 2B versions. They are both called SDA-2. All my other Polk Monitors have fuses. Thats always confused me. But don't take my word, I'm still trying to figure things out.

Peace.

**onepixel** · 03-10-2006 05:29 PM

HTrookie,
Thanks, I got the bypass thing. But I'm clueless on everything you said next. I'm not up to speed on all the terminology.

**schwarcw** · 03-10-2006 05:37 PM

Welcome to the Forum onepixel!

Carl

**dorokusai** · 03-10-2006 06:15 PM

Originally Posted by TroyD

No Mark, maybe we don't.

Look, I love you like a brother and you know that, however, it seems of late that every comment is an venomous rather than acerbic or being argumentative simply for the sake of being argumentative. It's playing to an increasingly weary audience. Personally, I find it sad because people that really think a lot of you are becoming alienated at an alarming rate.

Again, I love you man (not everyone gets to pass out on my bedroom floor mid-bash or hack up half eaten sammiches on my counters) but all I'm asking (and this is all I got to say on the subject, seriously) is think about dialing back the acidity level.

Troy

Fair enough.

**dorokusai** · 03-10-2006 06:25 PM

Originally Posted by onepixel

Hey dorokusai and TroyD,

Both of you might be right about the fuse thing. I noticed that the SDA-2 speakers have two different variations. The ones I have, 2 tweeters, 3 mids and a bass have no fuse. There also a version that has 1 tweeter, 2 mids and a bass, not sure if it has a fuse in the back. And I'm not talking about the 2A or 2B versions. They are both called SDA-2. All my other Polk Monitors have fuses. Thats always confused me. But don't take my word, I'm still trying to figure things out.

Peace.

The easiest way to identify the revision is usually the driver compliment. Dual tweeters and triple mid-bass is typical SDA2 and SDA2A. The single tweeter is typical SDA2B. The only one that may have a fuse would most likely be the SDA2, since it's the oldest.

It's not suprising that they only say SDA-2 as other models are also numbered that same way, regardless of them being an A or B.

**BobMcG** · 03-10-2006 06:55 PM

Originally Posted by dorokusai

The easiest way to identify the revision is usually the driver compliment. Dual tweeters and triple mid-bass is typical SDA2 and SDA2A. The single tweeter is typical SDA2B. The only one that may have a fuse would most likely be the SDA2, since it's the oldest.

It's not suprising that they only say SDA-2 as other models are also numbered that same way, regardless of them being an A or B.

Mark's right onepixel.
You might find the A or B designations on the original boxes but not on a lot of the SDA cabinet backs.

**TroyD** · 03-10-2006 08:45 PM

As my esteemed colleague Mark and others have pointed out on numerous occaisons, Polk was notorious for changing things up during a production run for numerous reasons so to say that all Model 'X' speakers have 'y' and 'z' parts isn't always possible.

At this point, perhaps a call to Ken at Polk might be in order. Past a protection issue fuse/polyswitch....I'd just be guessing.

Good luck and rock on.

BDT

**Ricardo** · 03-10-2006 09:48 PM

Originally Posted by onepixel

HTrookie,
Thanks, I got the bypass thing. But I'm clueless on everything you said next. I'm not up to speed on all the terminology.

You need one of these (or any other brand/type multimeter):
http://www.partsexpress.com/pe/showd...number=390-730

Place the selector in any of the OHM scales; measure from one negative output to the other, it should read 0 or very close to 0; if it doesn't, it is not a common ground and probably the cause of your problem.

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