Amplifier rectifier diodes

[Robee]

Hi guys.
I bought used Arcam Delta 290 integrated and power amp two years ago. I will save you the boring part of dissatisfaction for my setup and the result in my listening room...
Few days ago I thought the sound got even worse and was too bad to be normal and I opened up the integrated, that I use as preamp and to power high range of my speakers (basses are powered by the power amp), and I found the rectifier capacitors swollen. One had a leak of electrolite too.
I saw the filters caps had already been replaced with cheap Jamicon's. Thinking I should check for the cause too, I'm now checking the diodes of the bridge and I saw they are different from the service manual ones. Judging by the joints, they don't look replaced (?). I'm not an electronics savvy as you could see by my other request of help here, but reading in the service manual, they should be 1N4003 and the actual ones are BYW98. Reading on mouser website and comparing them, even though the meaning is not that clear to me, the BYW98 has a triple direct current (If) and double reverse current (Ir). Is that only to have more overhead or should I be concerned? You can see the attached picture (sorry, I'm Italian and I hope you will be able to read everything).

I'm also looking for the new capacitors. Is it true I might use 12.000 uF instead of the original 10.000? Do you think it would be better to glue the caps on the pcb for the vibrations? If not, what about using a plastic washer underneath?

Here is the service manual, in case of need

Thank you very much nad goodnight

 

[Harlow]

There's no problem using diodes with a higher current rating or higher reverse voltage rating unless they're so big they're impossible to fit.

Similarly, 12,000uF capacitors would be OK instead of 10,000uF, but make sure the voltage rating is the same as, or higher than the original caps. Depending on the amp, they might be 40V, 63V or 100V rating.

You also need to check the ripple current rating of the new caps. If the replacement capacitors are physically the same size or larger than the old caps, that's fine. If the new caps are physically much smaller, their ripple current rating may not be sufficient. Large high current caps often have dimples on their sides to aid cooling.

Really big amplifier PSU electrolytics are usually secured to the metal chassis with circular metal clamps. The electrolytics I used in home made amps were the size of baked bean tins. Smaller caps are often soldered to a PCB. Silicone sealant can be used to secure tall components from vibration.

I wouldn't advise the use of epoxy resin or similar adhesive. If you use silicone, as used around the edge of a bath, you can unpick the adhesive more easily if you ever need to replace the component.

 

[Robee]

Thank you @Harlow .
I didn't see any response and I went ahead looking on the web to find exactly what you recommend.
I did as you say: possibly higher voltage, as higer ripple current as possible, possibly same size. In certain cases I could not fit biggers ones, unfortunately. In others, there was no availability, then I ordered 10.000 uF again for the big caps. By the way, mine are not as big as baked beans at all I will use silicone or some rubber or plastic washer underneath, or maybe hot glue, which is easy to be taken off.
Waiting for the supply to arrive (from Texas, it seems! This big online suppliers... )
Thank you again!

 

[Robee]

@Harlow , can you explain me? The power stage of the amp is after the rectifier --> DC current. But the other wires of the toroid go to another area of the PCB.
Where does the preamp stage gets DC?

 

[Shrek]

I'm also looking for the new capacitors. Is it true I might use 12.000 uF instead of the original 10.000? Do you think it would be better to glue the caps on the pcb for the vibrations? If not, what about using a plastic washer underneath?

Don't worry about gluing them.

If you use silicone, as used around the edge of a bath, you can unpick the adhesive more easily if you ever need to replace the component.

Do not use household silicone sealant, it releases vinegar as it cures and this can badly damage the circuit board.

 

[Robee]

I didn't think of that problem. Thank you Shrek