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Beginner wants help retrofitting old PC speakers
Beginner wants help retrofitting old PC speakers
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Old 4th December 2020, 08:35 PM   #21
planet10 is online now planet10  Canada
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Beginner wants help retrofitting old PC speakers
Loss of channel could well be the umbilical to the other speaker as well as a broken amp.

dave
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Old 5th December 2020, 02:42 AM   #22
ElBjorno is offline ElBjorno  Australia
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Quote:
Originally Posted by Galu View Post
As far as I can see, you still haven't confirmed whether that is due to a faulty left speaker or a faulty left channel of the amplifier.

Swapping the speaker drivers over will reveal the culprit, as I suggested earlier.
OK, finally got around to pulling the second speaker apart and properly testing both drivers.
I must have mis-remembered, because it's clear that it's the RIGHT driver (the one in the same box as the amp) that's misbehaving, not the left. I tested both drivers on both channels, and every time the same driver is about half the volume and much scratchier than the other one. This is actually a surprising improvement, because in the past I could barely even hear it at full volume.
Either way, the drivers obviously need replacing. The board (while cheap and crummy) works.

Quote:
Originally Posted by planet10 View Post
3.6 litre. Small for a 4”, ideal for some Alpair 6.2m (metal), but A6.2p (paper) could also fit. No need for a tweeter. These are amoungst the very best FR drivers available in this size (an IMO smoke the FE103 [FE103 SOL excluded]).

Both discontinued but d’Archer still has some A6m
Mark Audio 6M

The vent would likely need tweaking, bass resonse anechoic expected to be circa low 60s, F6, low 50s F10. Very good mids and extended top.

You will have to work the box over to come near getting the most out of the drivers. Get the amp good enuff and people will be stunned when you fire them up.

An adaptor may be needed, but the large bezel on these MA Alpairs makes them closer bezel size to common 4”.

https://frugal-phile.com/boxlib/markaudio/A6x-dims.pdf

Exact dimensions of the cutout and the bolt circle (or how far apart in the case of the tweeter).

As to the amp, yours could be toroughly reworked with caps etc, how much could be squezzed out depends alot on the chip under that heat sink. And rework the power supply, that can make for huge benefits. How good a chip amp can be (depending of course on chip) from crappy to really quite good depending on what surrounds it and the implementation. Yours is cheap so compromises on parts supply, everything.

I expect you could get a solid 1-2 w out of it.

The small Class D amps are a very good suggestion. Easiest if you lose the tone controls. I had/have some tiny (really small) Dayton that were surprising good.

If you want to go over the top, a diy preamp specifically designed to purpose driving separate Class A amps outside the box.

Done right one could get a lot of WTF when people come over and listen.

dave
That's a lot of good info, thanks!
Some of the stuff about modifying the vents etc. might be a bit above my head, but I'll keep it in mind.

Now I'm just torn as to whether I should try refurbishing the current board or replacing it with a brand new one. It looks like it might actually work out cheaper to replace the whole board! But staying with the current one would be less work and fiddling/adapting to fit.
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Old 5th December 2020, 03:47 AM   #23
diyiggy is offline diyiggy
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peereless TC9 ? 8 ohms... 20 USD


drivers seems 6 ohms ?
Maybe a cleaner picture of the bord to understand,ho it is made , where is the rectifiers, etc...
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Old 5th December 2020, 03:59 AM   #24
planet10 is online now planet10  Canada
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Beginner wants help retrofitting old PC speakers
Again, what is the size of the bolt circle on the 4”? Hole size? max vert height of the rebate.

The reason i ask is that the rebate is the shape of an FE103. The new one has a bit differetn bezel, but if the dimensions are close a vinatge FE103 might drop right in. If it nominally wants a bit bigger box you can then turn that to your adavatage by damping the port (stuff it with fluff.

dave
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Old 5th December 2020, 05:41 AM   #25
ElBjorno is offline ElBjorno  Australia
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Quote:
Originally Posted by planet10 View Post
Again, what is the size of the bolt circle on the 4”? Hole size? max vert height of the rebate.

The reason i ask is that the rebate is the shape of an FE103. The new one has a bit differetn bezel, but if the dimensions are close a vinatge FE103 might drop right in. If it nominally wants a bit bigger box you can then turn that to your adavatage by damping the port (stuff it with fluff.

dave
Hole size is 104mm (~4.1''). Diagonal distance between the screws is 115mm (~4.5'')
Tweeter hole is 47mm(~1.85''), diag hole distance is 65mm (~2.6'')

Quote:
Originally Posted by diyiggy View Post
peereless TC9 ? 8 ohms... 20 USD

drivers seems 6 ohms ?
Maybe a cleaner picture of the bord to understand,ho it is made , where is the rectifiers, etc...
My multimeter put them at 4 ohms. (Well, 4.5)

Here's some pics of the rectifier (it's separate to the board, attached to the back of the box):
Click the image to open in full size.
Click the image to open in full size.

Not sure how better to frame pictures of the board. What should I focus on in particular?
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Old 5th December 2020, 04:26 PM   #26
Galu is online now Galu  Scotland
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Quote:
Originally Posted by ElBjorno View Post
My multimeter put them at 4 ohms. (Well, 4.5)
Your multimeter reads the DC Resistance of the driver. It's Nominal Impedance (opposition to AC) is around one third higher i.e. 4.5 + 1.5 = 6 ohm.
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Old 5th December 2020, 04:30 PM   #27
Galu is online now Galu  Scotland
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P.S. The object you are holding is a step-down transformer. The rectifiers are located alongside the other boarded components.
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Old 5th December 2020, 04:41 PM   #28
Galu is online now Galu  Scotland
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Quote:
Originally Posted by ElBjorno View Post
Not sure how better to frame pictures of the board. What should I focus on in particular?
Focus on providing a sharp and larger (expandable) version of the attached photo that you posted earlier, which will allow us to see clearly down to individual component level.
Attached Images
File Type: jpg Amp Board Close Up.jpg (19.7 KB, 24 views)
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Old 5th December 2020, 04:44 PM   #29
diyiggy is offline diyiggy
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or a 3/4 view to see caps value... the metal thingy is a radiator fo an amplifier ic I surmise...

The red and green caps has to be keeped (film caps). The lytic long can caps are certainly good enough if less 20 years old... however if you see bumped top or leaks at the bases...think tpto a cap refurbishing... Very few thing to improve on the caps side but to avoid a futur refurbishing if you listen everyday... Sometimes some caps have a subjective better snap that can help those mini speakers but it mainly depends of the ic circuitry....

Last edited by diyiggy; 5th December 2020 at 04:48 PM.
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Old 5th December 2020, 04:46 PM   #30
Galu is online now Galu  Scotland
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Yes, that looks like the heat sink for an amplifier ic. It would be nice to identify that ic.
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