Voltage doubler caps
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From: N_Cook on 10 Feb 2010 10:01 <Meat Plow> wrote in message news:3gr6ps.bnh.19.11(a)news.alt.net... > Working on a Silvertone Twin Twelve 1484 amp. Uses a voltage doubler > for the HV. Output should be 480 but seeing only 375. I'll assume > these caps being 45 years old are weak resulting in the 100 volt loss. > > Funny thing printed on the capacitors "Guaranteed for One Year" LOL What is the sag in the rectifier tube/s?
From: Dave Plowman (News) on 10 Feb 2010 11:43 In article <3gr6ps.bnh.19.11(a)news.alt.net>, Meat Plow wrote: > Working on a Silvertone Twin Twelve 1484 amp. Uses a voltage doubler > for the HV. Output should be 480 but seeing only 375. I'll assume > these caps being 45 years old are weak resulting in the 100 volt loss. > Funny thing printed on the capacitors "Guaranteed for One Year" LOL This application seems hard on caps. Had four identical tuners where a cap performing this function failed on all at nearly the same time. -- *Beauty is in the eye of the beer holder... Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: hr(bob) hofmann on 10 Feb 2010 22:15 On Feb 10, 10:43 am, "Dave Plowman (News)" <d...(a)davenoise.co.uk> wrote: > In article <3gr6ps.bnh.19...(a)news.alt.net>, > Meat Plow wrote: > > > Working on a Silvertone Twin Twelve 1484 amp. Uses a voltage doubler > > for the HV. Output should be 480 but seeing only 375. I'll assume > > these caps being 45 years old are weak resulting in the 100 volt loss. > > Funny thing printed on the capacitors "Guaranteed for One Year" LOL > > This application seems hard on caps. Had four identical tuners where a cap > performing this function failed on all at nearly the same time. > > -- > *Beauty is in the eye of the beer holder... > > Dave Plowman d...(a)davenoise.co.uk London SW > To e-mail, change noise into sound. Power surge??
From: Phil Allison on 11 Feb 2010 02:22 <Meat Plow> > > I don't understand why a conventional full way bridge was not used. ** Lower voltage electros are cheap. > Doublers aren't known for their ability to supply high current so > even in new condition this supply is going to sag more than traditional. ** No such difference exists between a full wave doubler and a bridge circuit. The doubler simply use two caps of half the voltage and double the uF compared to a bridge. Music Man amps all use doubler supplies for the HT - which has the additional benefit of giving a half voltage supply for the output tube screens. ..... Phil
From: hr(bob) hofmann on 11 Feb 2010 13:00
On Feb 11, 9:43 am, Meat Plow wrote: > On Thu, 11 Feb 2010 18:22:20 +1100, "Phil Allison" > <phi...(a)tpg.com.au>wrote: > > > > ><Meat Plow> > > >> I don't understand why a conventional full way bridge was not used. > > >** Lower voltage electros are cheap. > > A 100uf @ 450 vdc can't be much more expensive than a 250 vdc of the > same value. And a doubler has twice the caps as a bridge correct? > > >> Doublers aren't known for their ability to supply high current so > >> even in new condition this supply is going to sag more than traditional. > > >** No such difference exists between a full wave doubler and a bridge > >circuit. > > >The doubler simply use two caps of half the voltage and double the uF > >compared to a bridge. > > >Music Man amps all use doubler supplies for the HT - which has the > >additional benefit of giving a half voltage supply for the output tube > >screens. > > I know the MM 112 has a 700v HT didn't know it was derived from a > doubler. I was taught that doublers are less able to supply a constant > current than a bridge. That was back in the 70's. ELectricity still works the same way as far as I can tell. |