read this http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
you might find it handy
you might find it handy
Yes.
They have a fluid inside. It's very dependent of how they are used and temperature is a big factor.I'd like to upgrade my Superphon
I did read this post. I have (2) Superphon DM220 amps (cannot locate schematic unfortunately). These amps are 23 years old now and I've had a peek inside one. The caps are (this for one channel):
(2) 100uF 35v Marcon brand?
(2) 100UF 50v no name I can see, just Malaysia
(1) 10uF 50v no name I can see, just Malaysia
and the (rail?) capacitors are (2) 10000 uF 50v National brand
all of the above are electrolytics of course.
I do not intend to change the output devices.
I see a comment that replacing higher quality caps can make a difference.
I have some 100uF 50v Blackgates that I can use for the smaller ones.
What would be considered a higher quality cap brand to replace the 10K uF National?
Also is there benefit/risk to using higher value on the rail cap? I have some more room in the case.
I do have a scope, but no signal generator, and a dummy load I can get at Radio Shack. I have not worked much with amps since getting my EE 10 years ago, but this seems pretty straightforward. I did recap my preamp, and it's working just fine...
I appreciate what advice is offered.
Thanks
Kirk
I did read this post. I have (2) Superphon DM220 amps (cannot locate schematic unfortunately). These amps are 23 years old now and I've had a peek inside one. The caps are (this for one channel):
(2) 100uF 35v Marcon brand?
(2) 100UF 50v no name I can see, just Malaysia
(1) 10uF 50v no name I can see, just Malaysia
and the (rail?) capacitors are (2) 10000 uF 50v National brand
all of the above are electrolytics of course.
I do not intend to change the output devices.
I see a comment that replacing higher quality caps can make a difference.
I have some 100uF 50v Blackgates that I can use for the smaller ones.
What would be considered a higher quality cap brand to replace the 10K uF National?
Also is there benefit/risk to using higher value on the rail cap? I have some more room in the case.
I do have a scope, but no signal generator, and a dummy load I can get at Radio Shack. I have not worked much with amps since getting my EE 10 years ago, but this seems pretty straightforward. I did recap my preamp, and it's working just fine...
I appreciate what advice is offered.
Thanks
Kirk
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Both. Higher value supply caps will reduce the ripple on the rails
, but put more strain on the transformer and rectifiers.
caps related to filtering on the pcb of the amp and the power supply can always replaced with bigger and better .... very correct, will add some stress to the rectifier and trafo
though as its writen in the tutorial if you go from 10k to 15or 20 will be just fine ...but if you go from 4k7 to 33.000 then you probably going to blow the rectifier on start up
electrolytics might be also used in the feedback cirq of the amp there you may change things regardingquality but not the value ....
as about signal generator you may download almost a zillion of them free from the internet that work through your sound card ...not especially acurate but will show more or less a few things
regards sakis
though as its writen in the tutorial if you go from 10k to 15or 20 will be just fine ...but if you go from 4k7 to 33.000 then you probably going to blow the rectifier on start up
electrolytics might be also used in the feedback cirq of the amp there you may change things regardingquality but not the value ....
as about signal generator you may download almost a zillion of them free from the internet that work through your sound card ...not especially acurate but will show more or less a few things
regards sakis
Thanks for responses! Looks like I can go to 150000 without issues...
Actually I do have a tone generator on my PC, forgot about that one.
Last question: Is there any qualatative difference between Mallory, Vishay, Cornell-Dubilier, etc as used on the rail cap? These are computer grade caps.
Any preferences? I need the screw terminals so limited to those brands.
Both. Higher value supply caps will reduce the ripple on the rails
For a tube rectified amp this is true -- there's only so much a tube rectifier can take and it is usually specified in the data sheet.
For SS rectification, if you have inrush issues you can use a thermistor like a CL-60. On the Pass power supplies they use a pair on the primary of the transformer and one to connect the DC supply ground to the chassis ground. These devices have a high "cold" resistance which drops as it heats up.
if the choice of the arrangement has been made as for the capacitors with the blue shrink tubing - see left side on the first photo about
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(and right side of the attached jpg)
near behind the two output power tubes - then the expected lifetime is further reduced - especially if there are shrink tubing in a dark versions.
A desin error that I have sometimes observe, not only by tube amplifiers.
Therefore I replace in all such cases capacitor devices through a version with transparent or white shrink tubing, so that the heat radiation is reflected rather than absorbed.
The developers of this integrated tube amp say me, that would be nonsense (after the cover caps of the original capacitors were already swollen through the influence of high temperature)
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