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 Post subject: Source for replacement speakers?
PostPosted: Dec Wed 26, 2018 10:07 pm 
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Joined: Mar Thu 29, 2012 8:51 pm
Posts: 260
Location: upper midwest
Back around 1988, I bought a pair of HH Scott 6.2a bookshelf speakers for my Dad for Christmas.

After he passed in 2012, I ended up taking them back.

After starting to use them, the foam rings went to crap and I posted here some time back about replacing the rings and problems with glue that came with the kit.

Any rate, I've had continued problems with one of the drivers with the connection from the litz wire to the cone windings. I have "fixed" this several times and it keeps breaking. Not sure there is anything left to fix now.

At this point, I am thinking just replace the drivers themselves. These are 6-1/2" drivers, 8 ohms. Probably only rated 30W continuous given the size of fuse on the terminal box.

Any suggestions on a vendor selling decent replacement parts for this sort of thing? I've perused a few online sellers looking for close matches, etc.


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 Post subject: Re: Source for replacement speakers?
PostPosted: Dec Wed 26, 2018 11:05 pm 
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Joined: Aug Fri 12, 2016 1:49 am
Posts: 747
Location: Houston, TX
Do you mean the wire keeps breaking free of the cone at the adhesive or that the wire itself breaks in two?

I don't know what you've been using, but maybe this is better? https://www.simplyspeakers.com/speaker- ... lwk-1.html


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 Post subject: Re: Source for replacement speakers?
PostPosted: Dec Wed 26, 2018 11:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 14862
Location: Fernandina Beach, FL
The orientation of the wire from the terminal to the voice coil much be such that the wire flexes in the middle. Push the cone in and out and see if the wire is flexing at the connection.

Replacing the drivers will be a crap shoot because the entire "system" is matched components. What model Scott is it, something like S-10 or S-14 etc.?

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Don


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 Post subject: Re: Source for replacement speakers?
PostPosted: Dec Fri 28, 2018 5:27 pm 
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Joined: Mar Thu 29, 2012 8:51 pm
Posts: 260
Location: upper midwest
I had the connection from the litz to the coil break a couple of times despite putting glue on there to keep it from moving at the surface of the cone. The last time I may have overdone it. Its been either the solder joint with the litz or now I think its the magnet wire itself is cracked?

But, now what happens is it cuts out intermittently with low levels but will work if I turn up the volume. I think if I try to dig the glue out of there again there will be nothing left.

Tweeters went open circuit and I replaced those but I think they are bad again. I am sure I undersized them.

At this point, I am probably looking to gut and restuff the cabinets.

These get used attached to a 90s ?? era Teac AG-680 receiver that is also attached to my desktop PC/soundcard. Usually its NPR radio or youtube videos from the PC so I don't often have them "loud" so the intermittency on low levels is annoying.


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 Post subject: Re: Source for replacement speakers?
PostPosted: Dec Fri 28, 2018 7:46 pm 
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Joined: Sep Tue 30, 2014 6:08 am
Posts: 4772
Location: Norfolk, VA
Parts Express has a wide range of speakers - I've used them once, in the past.

https://www.parts-express.com/cat/midra ... PortalID=1

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Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Source for replacement speakers?
PostPosted: Mar Sat 02, 2019 9:06 pm 
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Joined: Mar Thu 29, 2012 8:51 pm
Posts: 260
Location: upper midwest
Thought I would post a follow up to this....

I was always pretty sure the problem was this one speaker in the system. I have a 90's era Teac AG-680 receiver I inherited and have these Scott speakers on the front pair and a pair of early 80's Realistic speakers I got for xmas in the early 80s on the rear. This is all setup in my office.

It sure seemed to be that the LF would cut out intermittently and would come back if you turned up the volume a bit.

Then in January, I happened to notice that BOTH the front and rear left were cutting out. Hmmm.

The receiver has 2 switches on the front that control some relays inside (can hear them click) for selecting which pair or both pair of speakers are ON. Wondered if the problem was a bad relay with intermittent contacts. Seemed like clicking them a few times MAY fix the problem temporarily.

Last week it got worse and was so annoying I turned the balance all to the right so I would save my sanity when listening to something.

Now that I was thinking the current problem NOT the speaker, it was time to open up the receiver and have a look for cold solder joints, etc someplace as some prior experience with a similar symptom problem on another old stereo turned out in that case to be a cold joint on a wire attached to the volume pot.

This unit has a mother board for most of it with a front panel board for the VFD and control buttons and 2 amplifier boards that plug into the mother board and are screwed down to the heatsink. I pulled the amp boards and then the mother board to get a look at the backs to examine the solder joints. These are all single sided through hole construction. Nothing obvious with any of the solder joints but I reflowed the ones for the relays and the connectors on the amplifier boards.

Since both front and rear were cutting out, the problem had to be upstream of the speaker selector relays.

There were a couple of electrolytic caps on the amplifier boards, a 4.7uF and a 100uF. The 100uF ones sitting really close to a small power transistor and those obviously run hot and the PCB is darkening around them.

For some reason, I thought to check the capacitance of these with my DMM. First board, the 100uF was measuring about 33uF. Well, that could be thrown off from parallel circuit elements so I didn't think too much of it. Then the other board, I was getting < 1uF. That was unexpected as these boards appear to be identical so would expect to have identical readings.

Those caps WERE running right next to those hot transistors and one was even bent over and nearly touching it too.

So, I scrounged my parts until I managed to find a pair of 100uF radial caps that were the right physical size. One was the correct 16v but the other I had to use 25V. Checked both out of circuit (these parts are new, unused, but at least 20yrs old).

I removed one of the suspect caps and installed a new one in place. Checking it with the DMM, I got the correct C value so the problem was not parallel circuit paths. the loose removed bad part still measured off.

Replaced the other cap on the other board and put it all back together.

I have run the receiver all this past week and so far so good!!

I can only wonder if the "open" cap was reconnecting internally if the volume was turned up. I would expect the other one being low would affect the bass response but I don't usually have that turned up or listen to thumpy type stuff and maybe would not notice. I assume these must have been signal coupling caps someplace in the amplifier signal path but don't have a schematic to be sure.

So, this begs the question as to why I thought it was ever the speaker in the first place? Well, after I redid those foam rings, I DID have problems with breaking litz wire as the speaker would quit but them work again if I nudged the cone with my finger. Seems it must have been a bad coincidence this other problem with the receiver seemed to have almost the same symptoms.


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 Post subject: Re: Source for replacement speakers?
PostPosted: Mar Thu 07, 2019 10:46 pm 
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Joined: Feb Fri 15, 2019 11:19 pm
Posts: 12
By far, the most common cause of speakers cutting out at low volume is contaminated speaker relay contacts. There is some debate over the need for relay replacement vs just cleaning the contacts, but I can say that I've had excellent results with cleaning in every case where the contacts weren't pitted from arcing.


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