Hi All.
Helping a friend sort out some issues with his Technics SB-E100 Loudspeakers.
He's getting no sound from the left Midrange Driver.
The Technics is quite a fiddly build.
It looks like the crossover board is sandwhiched between a circuit board and a faceplate and soldered together.
Quite involved getting it apart.
I've been able to isolate the driver.
I'm thinking it's either:
Faulty driver.
Faulty reset arrangement.
Faulty wiring or
Faulty midrange tone control.
The manual indicates a Breaker value of 1.6A.
There's are reset buttons for the tweeter and mid so maybe there's some electronic devices, maybe thermisters involved??
Was hoping for some directions on how to identify where the problem is coming from.
Cheers
Cliff
Helping a friend sort out some issues with his Technics SB-E100 Loudspeakers.
He's getting no sound from the left Midrange Driver.
The Technics is quite a fiddly build.
It looks like the crossover board is sandwhiched between a circuit board and a faceplate and soldered together.
Quite involved getting it apart.
I've been able to isolate the driver.
I'm thinking it's either:
Faulty driver.
Faulty reset arrangement.
Faulty wiring or
Faulty midrange tone control.
The manual indicates a Breaker value of 1.6A.
There's are reset buttons for the tweeter and mid so maybe there's some electronic devices, maybe thermisters involved??
Was hoping for some directions on how to identify where the problem is coming from.
Cheers
Cliff
Attachments
Last edited:
Hi,
They are able to take multiamplification standard. You have multiple input at filter.
Locate the medium way and the multiamp switch, turn it to multiamp then test the midway ( at low volume!).
If you have sound it is either the pad ( very probably from my experience with 'old' Technics speakers) either the polyswitch ( the protection), either the passive filter which gone the dodo way. ( multiamp mode disengage the filter and all components between input and driver).
A bit of documentation may help:
https://www.vintageshifi.com/repert...e.php?pdf=Technics-SBE-100-Service-Manual.pdf
https://www.vintageshifi.com/repert...ge.php?pdf=Technics-SBE-100-Owners-Manual.pdf
They are able to take multiamplification standard. You have multiple input at filter.
Locate the medium way and the multiamp switch, turn it to multiamp then test the midway ( at low volume!).
If you have sound it is either the pad ( very probably from my experience with 'old' Technics speakers) either the polyswitch ( the protection), either the passive filter which gone the dodo way. ( multiamp mode disengage the filter and all components between input and driver).
A bit of documentation may help:
https://www.vintageshifi.com/repert...e.php?pdf=Technics-SBE-100-Service-Manual.pdf
https://www.vintageshifi.com/repert...ge.php?pdf=Technics-SBE-100-Owners-Manual.pdf
I selected the 200 ohm scale.
Made sure the red terminal aligned with the positive meter prod.
Reading is 5.4
Made sure the red terminal aligned with the positive meter prod.
Reading is 5.4
So it is probably the pad.
Take a look at both service manual and user manuals you'll info about components how to disconnect/dismantle them, etc,etc,...
Try to power the mid in multiamp mode ( i repeat low volume as there isn't filter anymore!).
Take a look at both service manual and user manuals you'll info about components how to disconnect/dismantle them, etc,etc,...
Try to power the mid in multiamp mode ( i repeat low volume as there isn't filter anymore!).
Thanks K.
I have the manual print out.
There are multiple wire lead plugged into "system circuitry".
I'll unplug it and plug it into the one marked "multi amp"
How do I then test the midway circuit?
Do I run the speaker cable from the Amp, directly to the midway terminals (in and out)?
Isn't this harmful as it will receive full range sound (bypassing crossover)?
If it is either pad, the polyswitch ( the protection), or passive filter , how do I overcome these issues?
Cliff
Last edited:
sorry but where exactly are you getting this reading from?
as i understand it there's a harness connector that has to be switched from internal x-over to the multi-amp terminal we want the portion that's going to the drivers, sans x-over connected for now.
as i understand it there's a harness connector that has to be switched from internal x-over to the multi-amp terminal we want the portion that's going to the drivers, sans x-over connected for now.
and yes it can be harmful to drive the mid with an unfiltered signal so very low volume or better yet just use a 1.5 V battery and do a "click" test to confirm the driver makes sound.
What gear do you have at hand?
( playback source, amp, electronic components,..)
To test the passive filter ( mid) i would connect a 6ohms ( 15w or more) resistor in place of driver and monitor if you have a voltage. If you haven't a high power resistor a 8ohm driver could be ok to check if there is a signal present.
The passive filter is kind of 'modular' in that you have ( in reverse order): driver>pad>filter>polyswitch. So by locating the input/output of each section you can isolate the faulty part.
It may be a pita but worth it ( if driver is not dead).
Could be C3 in the filter too (6,8uf/50v bipolar electrolytic schematic in first link given 'service manual').
Turk is right: where do you read this 5.6r? If you had not disconnected the pad it could be its own value you have ( instead of the driver dcr). 5.6r is inline with the driver Z though ( 6r) so it is encouraging.
Be careful with drivers as they are unobtainable and this is a nice loudspeaker set! For the mid driver if you have a capacitor >68uf to put between driver and amp it will gives a safety protection for test.
A last suggestion: the subject belong more to multiway than fullrange subforum. Ask a moderator to move it in there you may have more answers.
( playback source, amp, electronic components,..)
To test the passive filter ( mid) i would connect a 6ohms ( 15w or more) resistor in place of driver and monitor if you have a voltage. If you haven't a high power resistor a 8ohm driver could be ok to check if there is a signal present.
The passive filter is kind of 'modular' in that you have ( in reverse order): driver>pad>filter>polyswitch. So by locating the input/output of each section you can isolate the faulty part.
It may be a pita but worth it ( if driver is not dead).
Could be C3 in the filter too (6,8uf/50v bipolar electrolytic schematic in first link given 'service manual').
Turk is right: where do you read this 5.6r? If you had not disconnected the pad it could be its own value you have ( instead of the driver dcr). 5.6r is inline with the driver Z though ( 6r) so it is encouraging.
Be careful with drivers as they are unobtainable and this is a nice loudspeaker set! For the mid driver if you have a capacitor >68uf to put between driver and amp it will gives a safety protection for test.
A last suggestion: the subject belong more to multiway than fullrange subforum. Ask a moderator to move it in there you may have more answers.
Last edited:
I pulled the midrange driver free from the rig.
I'm reading from the speaker terminals (+ve to -ve).
Ok so driver motor seems to be ok.
Next step would be to try it connected to an amp.
What source and amp do you have?
Next step would be to try it connected to an amp.
What source and amp do you have?
Thanks.
5.4 reading was the driver alone free from the Loudspeaker and testing for ohms.
Regarding C3 a full set of poly replacement caps have been ordered.
I have a Marantz PM6A Amp and currently a Pioneer PD 7050 CD Player.
well i would do a "click" test with a 1.5 V battery just to be certain it still emits sound first.
^Turk is right.
About the set of caps... have you checked they'll fit? I fear not in the actual filterboard/pcb. And i have other things to tell about caps conversions ( from bipolars to Poly 'audiophile') with my own technics loudspeakers ( SB-M2. A clue: i ended up multiamp and dsp filter! But i'm a lost cause... 😉 ) and other vintage loudspeakers too ( Wharfedale TSR112).
Ok your amp is powerful so you'll have to be verycareful!
Do you have a cd recorder/printer? I could process and send you a filtered file to test the driver from your cd/amp.
About the set of caps... have you checked they'll fit? I fear not in the actual filterboard/pcb. And i have other things to tell about caps conversions ( from bipolars to Poly 'audiophile') with my own technics loudspeakers ( SB-M2. A clue: i ended up multiamp and dsp filter! But i'm a lost cause... 😉 ) and other vintage loudspeakers too ( Wharfedale TSR112).
Ok your amp is powerful so you'll have to be verycareful!
Do you have a cd recorder/printer? I could process and send you a filtered file to test the driver from your cd/amp.
Last edited:
Could be but mine are still ok 40 years later. I can't say the same from the Lpad...
That said mine are 'younger' than the E100 and component sourcing could have been different... well a nice joke coming from Panasonic mothership! The components were goods in japan at this time! But electrolytics age.
That said mine are 'younger' than the E100 and component sourcing could have been different... well a nice joke coming from Panasonic mothership! The components were goods in japan at this time! But electrolytics age.
Last edited:
well we both want to help Cliff so let's see if we can walk him through his diagnosis...i'm starting with the first thing in the chain...
^ i don't see it as a contest Turk and agree with all you said!
And i know you have experience and you're a trustable source. I just put my own bias and experience about mine on this... 😉
About breakers they could be 'isolated' easily as they have dedicated wire to them from the pcb: it is just needed to short them at pcb ( or at their legs).
And i know you have experience and you're a trustable source. I just put my own bias and experience about mine on this... 😉
About breakers they could be 'isolated' easily as they have dedicated wire to them from the pcb: it is just needed to short them at pcb ( or at their legs).
Last edited: