UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)

Notices

Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

Closed Thread
 
Thread Tools
Old 23rd Feb 2018, 7:55 pm   #1
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Hacker LS1100s - one bass driver down

I bought a Hacker Centurion Mk2 a few weeks ago sans speakers. Then Herald 1360 got in touch to offer the pair of speakers here to go with it (many thanks again Chris). One of the bass drivers wasn't working but it checks out fine (battery and continuity). I first suspected the 15uF cap in the x-over and replaced that with 2 NP 8uF caps in parallel....but that did no good.

The chokes all check out for continuity. Can anyone suggest what might be stopping this bass driver working? My knowledge of x-over design doesn't extend much beyond a capacitor in series to block LF! The x-over model is SK1848. Also does anyone know who made the bass driver?
Attached Thumbnails
Click image for larger version

Name:	P1230941.jpg
Views:	92
Size:	106.6 KB
ID:	158120   Click image for larger version

Name:	P1230942.jpg
Views:	83
Size:	105.9 KB
ID:	158121   Click image for larger version

Name:	P1230943.jpg
Views:	88
Size:	110.0 KB
ID:	158122   Click image for larger version

Name:	P1230944.jpg
Views:	121
Size:	95.4 KB
ID:	158123  
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 23rd Feb 2018, 8:40 pm   #2
Ted Kendall
Dekatron
 
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
Posts: 3,657
Default Re: Hacker LS1100s - one bass driver down

I think it's a case of tracing the circuit through from the input terminals to the driver. I'm assuming the driver isn't jammed solid - unlikely, admittedly...
Ted Kendall is offline  
Old 23rd Feb 2018, 10:33 pm   #3
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Hacker LS1100s - one bass driver down

Yes, it's worth connecting it directly to an audio source, just to makes sure the unit is OK. And of course, you could swap the bass drivers around to see if the fault stays with the box or moves with the woofer...

From what I can see, L1 is in series with the woofer, and C1 is in parallel with the woofer. It appears that everything else is for the tweeter (quite complicated for the class of speaker). More photos (from different angles and with more diffuse lighting - perhaps outdoors?) would be interesting, but probably not essential to solving the immediate problem. I presume the tweeter is OK?

Just for info, if the capacitor fails O/C, then that won't stop the woofer working, but it will sound a bit different to the other unit. If it was to fail S/C - much less likely - then the amplifier wouldn't enjoy that! I know you've already replaced it, but I thought it was worth mentioning what it is going on...

The woofer is made by Peerless. Luckily for you, it's one with a rubber surround. I had a pair of later Hacker speakers that had foam surrounds, and they'd rotted away. Also Peerless.
mhennessy is offline  
Old 23rd Feb 2018, 10:38 pm   #4
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Hacker LS1100s - one bass driver down

It’s not going to cause this fault but is C1 a reversible electrolytic, if so when you have fixed the fault it may be worth either fitting a reversible cap or put two in series back to back?
__________________
Frank
Nuvistor is offline  
Old 23rd Feb 2018, 11:45 pm   #5
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
Default Re: Hacker LS1100s - one bass driver down

Quote:
Originally Posted by mhennessy View Post

The woofer is made by Peerless. Luckily for you, it's one with a rubber surround. I had a pair of later Hacker speakers that had foam surrounds, and they'd rotted away. Also Peerless.
These speakers had foam fronts- they've rotted away quite nicely, I had to vacuum them up from the boxes.

Sorry one's duff, I never powered them up so I had no idea.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline  
Old 24th Feb 2018, 1:00 am   #6
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Re: Hacker LS1100s - one bass driver down

Hello Chris - I think the foam you hoovered up was from the grilles. I am not familiar with these but it looks like they had foam filled grilles backed with hardboard panels. The bass driver surround is rubber and it's fine. I have tracked down the fault - and it is in the driver. I did as Ted suggested and followed the track on the pcb through and there's nothing wrong with that. As MHennessy noted, a failed C1 wouldn't stop the woofer working anyway.

I connected the woofer direct - worked fine. I connected just the woofer through the x-over - worked fine. BUT in all these scenarios the woofer was sitting on its magnet or sitting on its cone - as soon as I turned it through 90 degrees (to where it would be on the baffle) - it failed. Oddly, I have always thought there should be potential for a work-hardening weakness in that moving electrical connection between the signal and the speech coil - but in 50 odd years of fiddling around with these things, this is the first example I have come across of that actually happening.

I shall be looking for a replacement 8" driver with a circular basket (so I can use Hacker's nice little bolted clamps to fit it) any suggestions welcome. And, as ever, many thanks for the spot on advice!
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 24th Feb 2018, 1:26 am   #7
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Hacker LS1100s - one bass driver down

Are the pigtails connecting the voice coil to the connectors OK, common problem and easy to replace?
__________________
Frank
Nuvistor is offline  
Old 24th Feb 2018, 12:07 pm   #8
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Re: Hacker LS1100s - one bass driver down

Thanks Frank - it's worth a try. The connections at the basket end are OK. What should I expect to find if I scrape away the glue(?) from the contacts on the cone?

Peerless? Is that the Danish firm that makes nice tweeters?
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 24th Feb 2018, 12:29 pm   #9
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Hacker LS1100s - one bass driver down

Connect your test meter across the speaker terminals and just move the pigtails about, if the connection makes or breaks you know you need to replace them.
__________________
Frank
Nuvistor is offline  
Old 24th Feb 2018, 9:19 pm   #10
RojDW48
Nonode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
Default Re: Hacker LS1100s - one bass driver down

I did as you suggested Frank with no problems but manipulating the cone brought it on. So, nothing to lose, I gave the connectors on the cone a little melt with a soldering iron and that seems to have cured the problem. Running for several hours now without mishap....and very nice they sound too. Many thanks - Roger
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline  
Old 24th Feb 2018, 9:52 pm   #11
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Hacker LS1100s - one bass driver down

Quote:
Originally Posted by RojDW48 View Post
Peerless? Is that the Danish firm that makes nice tweeters?
Yes. Known as Tymphany today: https://www.tymphany.com/peerless/

Well done on the repair - I've done a few like that over the years. How do they sound?
mhennessy is offline  
Old 24th Feb 2018, 10:27 pm   #12
Nuvistor
Dekatron
 
Nuvistor's Avatar
 
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
Default Re: Hacker LS1100s - one bass driver down

Good, glad you have it working.
__________________
Frank
Nuvistor is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 5:34 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.