"N_Cook" wrote in message
...
Arfa Daily wrote in message
...
"N_Cook" wrote in message
...
According to owner , bought it off company rep a few years ago and is
export
version prototype.
Blew a fuse a few weeks back , runs still ,after fuse change (self
heeled
cap?) but excessive hum.
450V rating ps electros but I measure 488V on the HT rail and varying
ac
(4
to 5 volt ac measured via 1uF, 1500V polyprop), perhaps seriesed-up,
but
3
in there, I've not taken apart yet.
The neon lit mains switch looks more like a light bulb , runs too hot
to
keep your finger on, I suspect droppers for USA mains inside. No serial
number on the chassis. Have yet to test the valves but I suspect
probably
ok, any advice on dealing with the HT/caps issue? What is the HT rail
supposed to be for USA issue ones ? Any schematic for the pa / ps
anywhere
?
"BV" = Blue Voodoo series. 150 similar to 60 but with more O/P valves
maybe
?
http://www.schematicheaven.com/newam...voodoo_60w.pdf
This also uses 350v and 450v rated caps and max quoted HT is 460v. This
is
coped with by 350v cap pairs series'd up, with v-share Rs across them.
Arfa
I was wondering where the "B" came from and assumed V was for valve,
despite
USA amp. I will download that schema and compare
I should have said previously only the 110V and 230V fuse ratings stated
on
the chassis, not 2 separate fuseholders, so someone might erroneously
think
it was an "intelligent" ps , no external selector switch or helpful
labelling of selector matrix inside, I'll explore that later today.
All valves test ok except one 6L6 which, apart from heater, is totally
dead,
no gain at all at any anode current. There is opaque stain on the envelope
in area above pins 4 and 5, localised in that area, although it could pass
beyond the non-round, mica spacers. I assume some metal melted and
evaporated/jetted onto the glass like the getter process. I assume this
could have been plasma arc to anode and excessive current and blown mains
fuse, as that part of the amp history. What would have happened here ? I
will break into the base/glass pip/cut-ring the envelope and remove the
innards to have a good look as presently cannot see anything through the
deposit. A melted hole in the anode? what would physically stop any valve
action? the getter is still silvery.
Not yet retubed (that one plus another removed for balance) and tried out
on
reduced mains yet.
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
Assuming no obvious internal o/c connections to electrodes, then a stripped
cathode is about the only thing. However, I don't quite understand your
statement "no gain at all at any anode current". It seems to me that if you
are able to see *any* anode current, then the valve is, to whatever degree,
'working', and hence has at least some gain ?? How does the tester control
the anode current ? By varying the g1 voltage ? If it does, then that would
confirm that the grid is not o/c. Thinking a bit more, you might well see
some anode current, but little 'gain' if the g2 connection was open ?
The schematic for the '60 that I pointed you at, has a detailed diagram set
of the primary connection arrangement for different voltages. Probably a
similar scheme to the '150 ?
Arfa