Well it seems these have an inbuilt series resistance and so that makes testing much more difficult because we would need to test them at a high frequency and then derive the resistance from the measurements... and that assumes the cap is basically OK at the higher frequency.
It might be worth seeing if you could turn up anything from the part numbers on them (I had a quick look and failed).
It might be worth seeing if you could turn up anything from the part numbers on them (I had a quick look and failed).
Not sitting on my hands, this is what I’ve found:
Jensen Copper Foil, Paper in Oil, in an Aluminium Can | Hifi Collective
£1500 for the dozen I need?
No way.
Jensen Copper Foil, Paper in Oil, in an Aluminium Can | Hifi Collective
£1500 for the dozen I need?
No way.
Paper caps are notoriously unreliable, so they are probably toast, as would be any new old stock caps of the same variety. Resistors are usually placed in series with caps to dampen crossover filters, I haven't seen one actually put in the same casing as the capacitor though. If you find out the resistance value you can just use a regular plastic film cap and place a 10watt resistor in series.
Jensen are still around (Manufacturer of high voltage and power capacitors - A/S Tobias Jensen Production) - you could try asking them if they know what the resistance value is for that part number. Failing that, you could sacrifice one by opening up the can and seeing if there's an actual separate resistor inside. There may not actually be a separate resistor and 'internal resistor' might just refer to the high resistance of the paper construction itself. If that is the case then you'd probably have to guess/measure to work out what an appropriate resistance is. It will be something in the 1-30ohm range I would say.
Jensen are still around (Manufacturer of high voltage and power capacitors - A/S Tobias Jensen Production) - you could try asking them if they know what the resistance value is for that part number. Failing that, you could sacrifice one by opening up the can and seeing if there's an actual separate resistor inside. There may not actually be a separate resistor and 'internal resistor' might just refer to the high resistance of the paper construction itself. If that is the case then you'd probably have to guess/measure to work out what an appropriate resistance is. It will be something in the 1-30ohm range I would say.
Last edited:
Okay, okay, I know before you collectively say it!
I’m a pillock.
I did as was suggested and bought two cheap crossovers off eBay.
They arrived hot foot from China this morning and this afternoon I’ve wired them up (I mentioned I could solder)
Connected my Cambridge CD player and switched on and ........nothing.
Turned the amp up to almost max. and I could just hear my favourite Santana track. In fact if Santana had been playing in Manchester which is about 49 miles away I’m sure they would have been louder than in my workshop.
As I prefixed in my original cry for help from this esteemed forum I know ‘nowt’ about what I'm doing and suspect that my new crossovers and more suitable for the crystal set I had as a lad and not a Steemfort Sugden 40watt amp.
So,
before I throw myself on my sword I have another request from anyone who isn’t watching the Winter Olympics on TV tonight.
There are several crossovers on eBay, can someone suggest a reasonable pair for me to try before I take my pair of disappointments to the tip. A link would be appreciated.
I’m prepared to stretch my budget to about £50/60.00. There’s no point spending more when my grandson might find these a little old fashioned in appearance when fashion is most important to a lad who’s never heard true HiFi before.
David
I’m a pillock.
I did as was suggested and bought two cheap crossovers off eBay.
They arrived hot foot from China this morning and this afternoon I’ve wired them up (I mentioned I could solder)
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Connected my Cambridge CD player and switched on and ........nothing.
Turned the amp up to almost max. and I could just hear my favourite Santana track. In fact if Santana had been playing in Manchester which is about 49 miles away I’m sure they would have been louder than in my workshop.
As I prefixed in my original cry for help from this esteemed forum I know ‘nowt’ about what I'm doing and suspect that my new crossovers and more suitable for the crystal set I had as a lad and not a Steemfort Sugden 40watt amp.
So,
before I throw myself on my sword I have another request from anyone who isn’t watching the Winter Olympics on TV tonight.
There are several crossovers on eBay, can someone suggest a reasonable pair for me to try before I take my pair of disappointments to the tip. A link would be appreciated.
I’m prepared to stretch my budget to about £50/60.00. There’s no point spending more when my grandson might find these a little old fashioned in appearance when fashion is most important to a lad who’s never heard true HiFi before.
David
Well you should certainly be getting audio...
Take it one step at a time. First disconnect everything, by that I mean have the crossover and speakers not wired up to anything.
1/ Connect your amplifier directly across the woofer and just confirm that we have audio.
2/ Now connect the amplifier to the crossover input.
3/ Connect the woofer across (presumably) 'Bass 1' and again see if there is output. If its correct is should be more 'bassy' than before when it was directly connected to the amp.
4/ Now just try connecting the woofer to the 'Bass 2' output. Again thee should be audio but it will be less bassy, more like telephone quality midrange.
Lets try that first.
What is the switch supposed to do ?
Take it one step at a time. First disconnect everything, by that I mean have the crossover and speakers not wired up to anything.
1/ Connect your amplifier directly across the woofer and just confirm that we have audio.
2/ Now connect the amplifier to the crossover input.
3/ Connect the woofer across (presumably) 'Bass 1' and again see if there is output. If its correct is should be more 'bassy' than before when it was directly connected to the amp.
4/ Now just try connecting the woofer to the 'Bass 2' output. Again thee should be audio but it will be less bassy, more like telephone quality midrange.
Lets try that first.
What is the switch supposed to do ?
This should definitely work. The woofer is connected via a coil only.
You could measure the DC resistance of the coil for interest and also confirm that there is no short circuit between the two input connections and also no short between the two woofer connections (thinking whiskers of copper on PCB)
You could measure the DC resistance of the coil for interest and also confirm that there is no short circuit between the two input connections and also no short between the two woofer connections (thinking whiskers of copper on PCB)
Attachments
Nothing better to do on a Saturday night log.
I tried the check outs to crossover options as suggested, hardly a crackle even at full volume. Then, removed the shield cover from the amp and found a blown fuse to the right speaker. (Shown resting on a capacitor.
Made sure that the speaker lead ran from the side with two unblown fuses and then tried the treble, mid range and bass. Speakers there was Crackle from all.
Then Connected the new crossover and retested and sound was heard from all but even at full volume it wasn’t any louder than you would expect from a pair of headphones. On a scale from 1 to 12 it was about 1
Swapped both fuses and leads to the other side and the sound was louder put even at full power loudness test about 3.
So, have I blown the amp?
Is the volume dependant on having a complete left and right speaker Output through all four fuses?
I tried the check outs to crossover options as suggested, hardly a crackle even at full volume. Then, removed the shield cover from the amp and found a blown fuse to the right speaker. (Shown resting on a capacitor.
An externally hosted image should be here but it was not working when we last tested it.
Made sure that the speaker lead ran from the side with two unblown fuses and then tried the treble, mid range and bass. Speakers there was Crackle from all.
Then Connected the new crossover and retested and sound was heard from all but even at full volume it wasn’t any louder than you would expect from a pair of headphones. On a scale from 1 to 12 it was about 1
Swapped both fuses and leads to the other side and the sound was louder put even at full power loudness test about 3.
So, have I blown the amp?
Is the volume dependant on having a complete left and right speaker Output through all four fuses?
I wouldn't want to be trying this if DC is available at the amplifier outputs. Then, if testing the amp with a speaker connected is the only method you have I would be doing it with a single woofer, or at least with a speaker with a known working crossover.
The crossover you have is a simple affair, as has been suggested it should just work. Oh, and if at some point you decide to bin it, save the parts..
The crossover you have is a simple affair, as has been suggested it should just work. Oh, and if at some point you decide to bin it, save the parts..
Now just hang on minute, hold the front page.
‘‘Tis almost 11.30 and a tot of brandy calls.
And then, just as I was about to turn the amp off, what did I notice?
The tape button was depressed. Whoops!
Switched it off and turned the volume right down to 6 o clock ( the max is 4 o clock. )
Powered on increased the volume to 7 o’clock boy oh boy Carlos sounded good.
So there we are,Time to reassemble and put the stuffing back in to cover up my tracks.
“It was workin okay when I last used lad, honest”
Thank you all again for your patience and guidance XXX
‘‘Tis almost 11.30 and a tot of brandy calls.
And then, just as I was about to turn the amp off, what did I notice?
The tape button was depressed. Whoops!
Switched it off and turned the volume right down to 6 o clock ( the max is 4 o clock. )
Powered on increased the volume to 7 o’clock boy oh boy Carlos sounded good.
So there we are,Time to reassemble and put the stuffing back in to cover up my tracks.
“It was workin okay when I last used lad, honest”
Thank you all again for your patience and guidance XXX
So are we saying it all works after that ? Are we all happy with everything, or.......
So far so good. One crossover is working so I need to put the drives back into the cabinets and seal every thing up.
I’ve repaired the blown fuse with a strand and soldered the leads to the other crossover ready to repeat its fixing.
I shall miss all of this excitement. Not.
Do we know what blew the fuse ?
If things don't work as expected (no or low sound) then never turn up the volume more in hope. There could be a problem such as the amp working into a near short circuit......
Tbh, speakers are the last things where you would expect issues like that but lets be careful and sure.
Repairing the fuse with a strand...... I'll pretend I didn't see that
Also, never connect a tweeter (or mid) directly to an amplifier output. Anything more than a few hundred milliwatts power will burn the tweeter coil out, the mid would take a bit more.
If things don't work as expected (no or low sound) then never turn up the volume more in hope. There could be a problem such as the amp working into a near short circuit......
Tbh, speakers are the last things where you would expect issues like that but lets be careful and sure.
Repairing the fuse with a strand...... I'll pretend I didn't see that
Also, never connect a tweeter (or mid) directly to an amplifier output. Anything more than a few hundred milliwatts power will burn the tweeter coil out, the mid would take a bit more.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.