SUGDEN A-48 RECAP Question

[budkor]

Hello All

I have an A-48, which needs new audio capacitors. The old ones seem in poor state. When I opened the cover, they looked a bit leaky.

I am planning to recapping it myself. I looked into the caps and read the spec.
They are 40 VDC & 10000 uF.

I did some search on the internet and found some capacitors, and thought these were the best, but could anyone confirm that they are right ones for the A-48?

VISHAY BC COMPONENTS|222210117103|CAPACITOR, 40V 10000UF | CPC

Thanks in advance

Dan.

 

[budkor]

Anyone with SUGDEN A-48 & experience of recapping please?

 

[latala]

Done this on a no of occasions without any problems The capacitors that you can get today are far better than when the Sugden was made !
The first thing to look for is size you will find you can get larger capacitance in the same size can as the origional the last A48 I did had 18000 uf at 80 volt in the same can as per the origional
Any good quality will improve the sound but by pass them with a 0.1 uf to minimise any Hf effect
regards Trev

 

[budkor]

Can I use 18000 uF at 80V per one can, instead of 10000 uF at 40V?
There are six cans to replace.

Sorry I am a newbie - and I am not sure what it means by - "by pass them with a 0.1 uf to minimise any Hf effect "

Thanks

Dan

Done this on a no of occasions without any problems The capacitors that you can get today are far better than when the Sugden was made !
The first thing to look for is size you will find you can get larger capacitance in the same size can as the origional the last A48 I did had 18000 uf at 80 volt in the same can as per the origional
Any good quality will improve the sound but by pass them with a 0.1 uf to minimise any Hf effect
regards Trev

 

[AndrewT]

Hi,
I would certainly increase the voltage rating from 40Vdc to 50Vdc and consider going to 63Vdc.

6cans, does that equal a single power supply feeding both channels?
Or is it two separate supplies each with 3caps on the single supply rail.

simply increasing the capacitance from 10mF to 18mF will improve the ripple due to audio demand but reduce the conduction duration for the mains charging and thus increase the rectifier current and the secondary current. One gain may exactly cancel the other loss and result in same performance. But I would not bet on that.

Post a schematic of the PSU and we can have a look.
Try measuring the DC voltage on the caps and the equivalent mains supply AC voltage. Be very careful measuring the mains LIVE voltage !!!!!!!!!!!!!!!
Try to get the device names from the PCB or devices themselves.

 

[budkor]

Sugden A-48 Inside photos

Hi Andrew

Thanks for your information. Here are a couple of photos of inside of the A-48. It has a single PSU. I think I do have the original manual with schematic diagrams somewhere. I will find it and upload them here too.

I will wait for more of your information prior to ordering the caps. I am trying to get the best ones for the reliability, compatibility and performance.

Thanks & regards

Dan

 

[AndrewT]

The second pic shows two bridge rectifiers.
I seem to remember that the A48 is a capacitor coupled output and uses a single polarity supply for the amplifier.

If that is the case then you have 4 PSUs in there.
1pr of 10mF for channel A output stage
1pr of 10mF for channel B output stage
1 off 10mF + 100r for Channel A input stage
1 off 10mF + 100r for channel B input stage.

Measure the voltage from chassis to all 12 pins on the caps. Keep the black probe on the chassis for all the measurements.

 

[latala]

You have a bit of strange thinking here with an A48
The transformer has two secondaries 1 for each channel its a kind of halfway house in between single or dual power supply it shares a common primary this will give improved channel seperation
To complicate things further each supply is split into two not as in a normal split supply amplifier but as a method of voltage sharing between the supply capacitors
That acounts for 4 of the large capacitors
The other 2 are output capacitors the amplifier is not! dc coupled to the loudspeaker
Please remember when the amplifier was built capacitors were not as good as modern units
As mentioned earlier modern units with a higher capacitance and voltage can be fitted with advantage
When I mentioned by passing the supply capacitors with a 0,1uf this is in order to improve the high frequency response /stabilty of the amplifier all it is is connected the smaller capacitance in parrallel with the largs 1
regards Trev

 

[budkor]

18000 uF at 80V or 63V caps - which one would be best? Any recommendations?
I am still looking for the original book for the A-48, although I would not understand much of it. I am going to upload here so both Andrew and Trev can have a look at it and give me more info and tips.

cheers

Dan

 

[Chrisr3521]

I'd go for 63v as 80v seems like overkill. Have a look at these although they are 15000uf not 18000

BHC COMPONENTS|ALT22A153DE063|CAPACITOR, 15000UF, 63V | Farnell United Kingdom

 

[AndrewT]

The BHC is reputed to be a good Audio electrolytic.
buy 10 @ bulk discount and keep 4 aside for your next project.

Are the slit foil caps the same as the BHC?

 

[budkor]

Hi All

I finally got this amp recapped, and all seems fine. I used 15000 uF 63V caps, and they were a lot smaller than the original caps. After a couple of hours soldiering and burning fingers, they are all in. When I switched on, the amp came on silently, and played Radiohead CD in most beautiful way.

I am totally surprised with ths improved sound quality of this amp after recapping.

It sounds a lot more powerful, rush and rich. Deep bass and lots of more details - huge sound stage. This amp made my QUAD 303 sounds like tinny, thin and weak.

I will add some more reviews and photos of the job soon when I can find more time.

Thanks for all the members who kindly shared information, and offered advice.


Dan

 

[ashok]

Hi Budkor,
We are waiting for the schematic diagram !

Thanks.