28-02-2011, 07:40 PM
The suppression / Mains Filter/ RFI, call it what you will, goes across the mains input you will find the cap in all radios and TV's, its C22 on the DAC90 schematic, its listed as 0.1uF although this value is not critical at all. The original old waxy will normally be found with it's guts spewed up on the top behind the dropper, completely dead but will not stop the set from working.
It's there to reduce mains Hum / interference but to be honest you can run without it it will not matter. If you do decide to put one in circuit it only needs to be 250VAC, you do not need 400V.
Finally I have restored many DAC90's and other radios all have a 250VAC caps fitted as Mains Filter and I know others who do the same, I also fit these in TV's and they also are fine. I guess it's horses for courses and myths can develop.
The main debate I've encountered over this cap has been around should it be X, X1 rated or X2 rated. Like I say you can leave it out and will not notice the difference at all. If you decide to put one in that's the consideration. I settled on X refusing to get caught up in the nanny state, these were designed with the old waxies in place which were not, so a modern X is far better than the original and good enough for me and whats more I have about 500 of them! so I'm going to use them.
Remember if you use DC caps you must multiply by a factor of 4, so a DC cap in a 250 AC position must be 1000VDC. Had a 400VDC cap been used the again divide 400VDC by 4 would have only give 100VAC so no good.
HTH
Chris
It's there to reduce mains Hum / interference but to be honest you can run without it it will not matter. If you do decide to put one in circuit it only needs to be 250VAC, you do not need 400V.
Finally I have restored many DAC90's and other radios all have a 250VAC caps fitted as Mains Filter and I know others who do the same, I also fit these in TV's and they also are fine. I guess it's horses for courses and myths can develop.
The main debate I've encountered over this cap has been around should it be X, X1 rated or X2 rated. Like I say you can leave it out and will not notice the difference at all. If you decide to put one in that's the consideration. I settled on X refusing to get caught up in the nanny state, these were designed with the old waxies in place which were not, so a modern X is far better than the original and good enough for me and whats more I have about 500 of them! so I'm going to use them.
Remember if you use DC caps you must multiply by a factor of 4, so a DC cap in a 250 AC position must be 1000VDC. Had a 400VDC cap been used the again divide 400VDC by 4 would have only give 100VAC so no good.
HTH
Chris
