"N_Cook" wrote in message
...
Gareth Magennis 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
?





What is the voltage on the heaters? If this is excessive then the whole
transformer is probably running too high.



Gareth.



I didn't think of that, all valves out for testing at the moment

No mains voltage stated at the IEC inlet, just fuses for 110 or 240V, 7
wires to the primary side of the tranformer and jumper spade matrix
inside.
As the rep was going around Europe , not just the UK , I wonder if if it
is
internally set to 210V.
Anyone know what the secondary voltages should be ? or how to unravel ?
power up and look for voltages 30 or 40 V off from 0,110 or 240 I suppose.
No smoothing choke for this amp it would seem, unless its in with the
mains
transformer .

As the mains switch is made for 110V use then anything is possible





Your best bet IMHO is trying to get the 6.3v heater winding correct via a
variac and then make a judgement.



Gareth.