VA rating of the main Vectrex transformer
Dylan Smith
After 5 minutes of gaming on my Vectrex, the main power transformer died :/
completely without fuss or magic smoke.
I have checked the fuses (one in the plug - UK model, and one on the
small PCB inside the Vectrex) and both are OK, continuity checks out to
the wires that go to the main transformer. But the primary winding
has infinite resistance. (I also measured the resistances from the
unused centre tap on the primary winding, only one half of the transformer
gives continuity).
Unfortunately, it looks like the transformer is full of epoxy or something
similar - and the metal casing itself is soldered together, and I don't
have anything that will get that huge mass up to the melting point of
the solder (however, I am considering dremeling off part of the transformer's
case to see if it's just the wire to winding connection that's failed - I can
fix that easily enough).
From what I've been told so far, the transformer's secondary winding
is 9v-0v-9v - but if I need to replace the transformer, I don't know
what the VA rating needs to be - the service manual doesn't seem to tell
me and a dig around Google hasn't brought up any useful information.
If you can tell me, I would be eternally grateful :-)
Peter W.
Hmmm....
It is a mystery. Main rectifier diodes (1N5624) are rated for 3A. I
suspect that it is a 9V AC X 2 @ 2 Amp transformer. So it would be
about 36VA. Just a semi-educated guess.
Peteski
Dylan Smith
> It is a mystery. Main rectifier diodes (1N5624) are rated for 3A. I
> suspect that it is a 9V AC X 2 @ 2 Amp transformer. So it would be
> about 36VA. Just a semi-educated guess.
Thanks. And d'oh, why didn't I think of looking at the diode's ratings :-)
Interestingly, a few things are actually blacked out in the service manual -
the things listed as "must use exact replacement, critical for safety".
Someone I was talking with suggested these items are blacked out because
the incorrect item could result in the picture tube making unsafe levels
of X-rays if it caused the flyback transformer to make a too high voltage.
But then again, the fuse is one of the things blacked out, so there were
certainly more reasons than this (and if you're providing the correct
input voltage, then it should function as before - but I ought to test
it's right once it's got a new transformer, at least with a HV meter, if
not an actual test for X-rays)
Peter W.
Some of those components (like transformer and fuse) are considered
critical because improper fuse could cause overheating and fire while
specific transformer is certified to provide voltage isolation. Those
rules are dictated by the government (to be UL certified, etc.). Most
of the high voltage CRT circuitry is also critical as using non-
standard parts could lead to the CRT emitting more X-ray radiation
than it is allowed. That is governed by another set of rules. Those
disclaimers are in the diagrams to protect manufacturer from lawsuits.
While I agree that things like the power transformer should preferably
be replaced with identical units, if you can get a similar transformer
from a reputable source, it should work just fine. You might have to
get creative mounting the replacement transformer.
Peteski
Dylan Smith
> While I agree that things like the power transformer should preferably
> be replaced with identical units, if you can get a similar transformer
> from a reputable source, it should work just fine. You might have to
> get creative mounting the replacement transformer.
I have seen a 50VA transformer at Farnell which has the same size
mounting "ears" on the base of the transformer, the body is slightly
larger, but the transformer isn't really a tight fit in the Vectrex
anyway (apart from the back of the transformer, I may need to modify
the back part of the plastic mounting inside the case so the back end
of the transformer fits).
I've also spent a lot of time trying to find out more about the original
transformer, but none of the markings stamped on the case turn up anything
in Google searches.
I'll post up some specs of this transformer if it all goes well for
the record. (I noted from my earlier searches, I'm not the first
person to have the primary winding go on their Vectrex's main
power transformer).