Old amp upgrades?

[fastasulike]

The second question regarding old amps is this...

Assuming that an old amp has a good circuit design, would it be wise to replace some of the components with newer and maybe better items (although maintaining component values), such as capacitors, diodes and maybe a power supply?

[nigelwright7557]

Yes and no.

Things like capacitors of the same rating are fine to change.

Changing transistors could cause oscilation problems if care is not taken to match closely.

[jackinnj]

If it is cheap, has decent heat sinks and a good transformer knock your socks off.

I've modded a half dozen Crown amps replacing everything save the trafo -- for each I used one of the National Semi driver chips.

[ljm_ljm]

capacitor life is not long.
85C 2000 HOURS=16 000 HOURS 55C is universal

[fastasulike]

Interesting. What happens to the caps? Do they dry out?

[ljm_ljm]

Originally Posted by fastasulike

Interesting. What happens to the caps? Do they dry out?

of or relate to heat.
current ,resistance within the capacitor.

[sakis]

read this vintage amplifier repair/upgrade manual

you might find it handy

[peranders]

Originally Posted by fastasulike

Interesting. What happens to the caps? Do they dry out?

Yes. They have a fluid inside. It's very dependent of how they are used and temperature is a big factor.

[kirk57]

Originally Posted by sakis

read this vintage amplifier repair/upgrade manual

you might find it handy

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

[godfrey]

Originally Posted by kirk57

Also is there benefit/risk to using higher value on the rail cap?

Both. Higher value supply caps will reduce the ripple on the rails, but put more strain on the transformer and rectifiers.