Yep, I see that too on that page now. No idea where they get that from. Even they meant 15-0-15 then that would only give -/+22 volts or so.
Is it a 50watt/8 ohm amp. That's another check... the chips could swing to - or + 28 volts peak. 28 volts peak is 19.8 volts RMS which equates to 49 watts into 8 ohms.
So again, an 18-0-18 is called for. CPC ?
Is it a 50watt/8 ohm amp. That's another check... the chips could swing to - or + 28 volts peak. 28 volts peak is 19.8 volts RMS which equates to 49 watts into 8 ohms.
So again, an 18-0-18 is called for. CPC ?
The Bill of Materials list is headed "Cambridge Audio A2/A1 Mk three SE Differences BOM" so it seems like they're listing the differences between this amp and another, via a list of additions and subtractions. Very odd. Perhaps the 30VAC transformer is for the A2 amplifier, and the other listing is the transformer for the A1mk3SE (the one with no voltage specified)
Am I better off going with 2x18 or 2x20? The link Mike kindly provided above (thanks, Mike!) looks like a reasonable price for a 2x20VAC, or Maplin have a reasonably priced 2x18VAC which looks suitable (and cheaper than CPC again!)
2x18V 120VA Toroidal Transformer | Maplin
Am I correct in thinking that the only difference will be the maximum power output available? I'm not likely to ever drive this amplifier particularly hard anyway.
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Well I would go off the data sheet for the TDA1514 which quotes -/+30 volts as the absolute max supply voltage. I just looked up the data sheets for typical 120va toroids and they have a regulation of 10%. That means the 18 volts is just under 20 at low current. The toroids are also nominally 230vac rated which means that if your mains is over that then the output is higher again. The higher the va rating, the better the regulation due to thicker windings and more iron in the core.
I would stick to an 18-0-18 toroid tbh.
I would stick to an 18-0-18 toroid tbh.
Thanks again to everyone for all the helpful advice. I've ordered a 2x18V, since that seems like the simplest, safest option (and a few quid cheaper too).
Maplin were good enough to refund the 2x30V one I'd bought, so my mistake won't end up costing me anything, it just slightly delayed my repairing this and getting the amp up and running again.
I'm so glad I decided to double check the wiring info and that Mooly pointed out my mistake
I'll post back in a couple of days when the new transformer turns up.
Thanks again.
Maplin were good enough to refund the 2x30V one I'd bought, so my mistake won't end up costing me anything, it just slightly delayed my repairing this and getting the amp up and running again.
I'm so glad I decided to double check the wiring info and that Mooly pointed out my mistake
I'll post back in a couple of days when the new transformer turns up.
Thanks again.
New transformer has arrived (and same wiring colour scheme) so I'll have a play tonight.
I'll wire up the primary, along with a bulb tester and see what I get across the secondaries. Assuming that all looks good, I'll wire it up to the rest of the circuit and make sure everything else is in order. (all time permitting, of course)
I'll wire up the primary, along with a bulb tester and see what I get across the secondaries. Assuming that all looks good, I'll wire it up to the rest of the circuit and make sure everything else is in order. (all time permitting, of course)
Success!
Basic tests all checked out: primary and secondaries had reasonable AC voltages, bulb tester behaved as expected.
After connecting to the rest of the power amp board, I saw a steady +/-26v DC on the power rails.
After connecting the pre-amp board all was still well, so I hooked up some speakers and an input and was delighted to hear music coming through.
Thank you again to everyone who helped me out with this. I really appreciate it.
PS - They really don't design these amps for ease of service. Assembly and disassembly is a long and fiddly process...
Basic tests all checked out: primary and secondaries had reasonable AC voltages, bulb tester behaved as expected.
After connecting to the rest of the power amp board, I saw a steady +/-26v DC on the power rails.
After connecting the pre-amp board all was still well, so I hooked up some speakers and an input and was delighted to hear music coming through.
Thank you again to everyone who helped me out with this. I really appreciate it.
PS - They really don't design these amps for ease of service. Assembly and disassembly is a long and fiddly process...
It's a commercial product, not a DIY project or kit, goojimba. There is no PCB unless you buy an old amplifier
Cambridge Audio A1 MK3 integrated amplifier - Audio 4 Maniacs
Looks like it's my turn for a bit of thread necromancy. So, I have a CA A1mk2 which I've just got round to looking at. Only the left channel is working. A look around the board suggested one of the 100uF capacitors on the right channel had gone (brown discolouration) so I've replaced that and still nothing, but it did free up a chance to look more closely at the TD1514A IC which appears to be done in and there's some similar burning on the nearby resistor (?green rubber domey thing) As the TD1514 is out of production I'm wondering what the least hassle way of getting the amp back up and working properly is going to be? I read somewhere about getting LM3886's, mounting them upside down on the existing heatsink and running some short wires to the corresponding locations on the TD1514 points on the PCB? The LM3886 datasheet helpfully says the pins are LM3886 1 V+ 2 n/a 3 Output 4 V- 5 V+ 6 n/a 7 GND 8 Mute 9 V-in 10 V+in 11 n/a and my beginner (started googling a few hours ago) interpretation of the TD1514a suggests the pins are; TD1514A 1 V+in 2 SOAR? 3 V- 4 V- 5 Output 6 V+ 7 Vbootrstrap or connected to 6 8 GND 9 V-in So, by my reckoning so far; TD1514a pin goes to LM3886 pin 1 - 10 2 - 8 3 - 4 4 - 4 5 - 3 6 - 1 and 5 7 - 1 and 5 ? 8 - 7 9 - 9 (TD1514a pin 6 to LM3886 pin 1 and 1514 pin 7 to LM3886 pin 5?) So I guess this leads to multiple questions; 1. Is replacing the TD1514a's with LM3886's do-able by just re-routing the pins 1a. Have I got my pin routes correct? If not; Is there a noob friendly way of getting the amp working again, maintaining the existing inputs/selector, volume control for less than or equal to the cost of buying another a1 mk2 from ebay (~£40) ? The amp needs to power some Wharfedale Dovedale 3's, 6Ohm, 88dB sensitivity 50W max (or potentially some qAcoustic 2010i's if I ever get round to building the alcove cupboard) TIA
I haven't seen a CA A1 mk2 but there is an A1 version2. It seems there is no end to the ways UK manufacturers cling to popular model numbers and confuse people thoroughly with the model upgrade ID sequences. These were troublesome chipamps and it would be good to be shot of the whole power amp PCB.
However, I'm uncertain of your actual model with no details corresponding to your quoted model. Here are pics of A1 V2 (perhaps?):
This differs from Mk 3 in that the power supply is also included on the power amplifier PCB.
With care and ingenuity, I would scrap the whole power PCB and graft in a ready built and working chipamp module with its own power supply, like this one: LM3886TF LM3886 Hifi AMP Amplifier Board Assembled Finished Board | eBay
It is not simple tearing out the heart of the amplifier but grafting in very different chipamps to to the original types would be much harder and likely end in disaster unless your PCB modification and design skills are truly awesome. Use something that already works, then the transformer will work fine with it, with much the same power but with the better performance and internal protection of LM3886. At the lower power of the CA A1, the insulated pack these chips come with will be fine using a little heatsink grease, even though you may need to re-drill the mounting holes in the heatsink to suit the new spacing.
There are several more details to resolve, such as adding fuses to the AC from the transformer, as you see on the original board but in-line fuseholders could be fitted to the transformer secondary leads there. Check clearance height for the caps before buying, noting the PCB will need mounting pillars of suitable height too.
What say you?
However, I'm uncertain of your actual model with no details corresponding to your quoted model. Here are pics of A1 V2 (perhaps?):
This differs from Mk 3 in that the power supply is also included on the power amplifier PCB.
With care and ingenuity, I would scrap the whole power PCB and graft in a ready built and working chipamp module with its own power supply, like this one: LM3886TF LM3886 Hifi AMP Amplifier Board Assembled Finished Board | eBay
It is not simple tearing out the heart of the amplifier but grafting in very different chipamps to to the original types would be much harder and likely end in disaster unless your PCB modification and design skills are truly awesome. Use something that already works, then the transformer will work fine with it, with much the same power but with the better performance and internal protection of LM3886. At the lower power of the CA A1, the insulated pack these chips come with will be fine using a little heatsink grease, even though you may need to re-drill the mounting holes in the heatsink to suit the new spacing.
There are several more details to resolve, such as adding fuses to the AC from the transformer, as you see on the original board but in-line fuseholders could be fitted to the transformer secondary leads there. Check clearance height for the caps before buying, noting the PCB will need mounting pillars of suitable height too.
What say you
?
I say thank you kindly, Ian.
It is the a1v2 you've posted. As my PCB design and mod skills are somewhere between 'that thing is a PCB' and 'what does that symbol mean' a prebuilt, or at least pre-designed kit, like this is definitely the way to go.
If I've understood you and the schematic correctly. I get that kit, put inline T4A fuses on the yellow and purple wires from the transformer and connect those to the AC points on the power supply board, with the red and grey wires mounting to the GND point on the board.
The V-, V+ and GND outputs from the power supply board, then go to the corresponding 28V+, 28V- and GND IN on the existing tone board, and then from the tone board OUT in parallel to the V+, V- and GND IN on each of the LM3886 amp boards.
Pin 2 and Pin 4 of the tone board OUT connector go to the In on the respective amp boards (aong with a GND each) and finally the Out and GND from the amp boards go to the appropriate + and - speaker binding posts?
It is the a1v2 you've posted. As my PCB design and mod skills are somewhere between 'that thing is a PCB' and 'what does that symbol mean' a prebuilt, or at least pre-designed kit, like this is definitely the way to go.
If I've understood you and the schematic correctly. I get that kit, put inline T4A fuses on the yellow and purple wires from the transformer and connect those to the AC points on the power supply board, with the red and grey wires mounting to the GND point on the board.
The V-, V+ and GND outputs from the power supply board, then go to the corresponding 28V+, 28V- and GND IN on the existing tone board, and then from the tone board OUT in parallel to the V+, V- and GND IN on each of the LM3886 amp boards.
Pin 2 and Pin 4 of the tone board OUT connector go to the In on the respective amp boards (aong with a GND each) and finally the Out and GND from the amp boards go to the appropriate + and - speaker binding posts?
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