RE: BU406D (was Wintron install: Does this look right?)

I'm not sure wether I should take this off line (tell me if
I should) but I suspect other hackers like myself
appreciate these tips...

To test using a trace do you find a spot and scratch off
the laminent look for some sort of larger exposed junction
elsewhere along the same trace. I suppose either should be
fine but I have resisted removing any of the laminent for
testing purposes.

Dan

--- Bret Pehrson <bret@infowest.com> wrote:
> I've always tested w/ the components (BU406D) in place.
> Just use care, and
> you shouldn't have a problem w/ HV (remember, it comes
> out of the HVT to the
> second anode on the CRT). From what I understand, the
> voltage regulators
> need a load to regulate properly.
>
> As for testing -- don't try your luck w/ trying to
> connect to the actual
> pin/leg of the reg. Test from the solder-side of the
> board, and use a
> *trace* that goes to the pin you are testing -- it is a
> lot easier and
> safer, even w/ std probes. See what I'm saying?
>
> > -----Original Message-----
> > From: owner-vectorlist@synthcom.com
> > [mailto:owner-vectorlist@synthcom.com]On Behalf Of Dan
> Rasmussen
> > Sent: Wednesday, October 24, 2001 10:54 AM
> > To: vectorlist@synthcom.com
> > Subject: RE: VECTOR: BU406D (was Wintron install: Does
> this look right?)
> >
> >
> >
> > Bret,
> >
> > Thanks for the clarification. This is helpful. I was
> > getting -33 (as I recall) from pin 3 of the 7924 and I
> was
> > getting +21.6 (as I recall) from pin 3 of the 7824.
> >
> > I'll check the other pins. By the way, I find taking
> these
> > measurements difficult due to the fact that my tools
> are
> > limited. My DMM probes are pretty standard fare and
> sort
> > of "large" for this particular job. I sometimes wonder
> > what damage can be done if I slip. Keep in mind I was
> > taking these measurements with the bu406d removed (If
> HV is
> > running, I am not touching that board).
> >
> > Thanks.
> >
> > Dan R.
> > --- Bret Pehrson <bret@infowest.com> wrote:
> > > Just to clarify on reg voltages:
> > >
> > > These regulators take in +30 and -30 to output +24
> and
> > > -24. The input
> > > voltages come pre-filtered from the deflection board.
> > > Although spec is
> > > +30/-30, I typically see +33/-33.
> > >
> > > To test input voltages on the HV, check pin 1 of the
> 7824
> > > (VR1) and pin 2 of
> > > the 7924 (VR2). If your 7924 tests real low or 0,
> > > check/replace the wire
> > > jumper W1 on the deflection board.
> > >
> > > To test output voltages on the HV, check pin 3 of the
> > > 7824 and pin 3 of the
> > > 7924. Spec is +24/-24.
> > >
> > > > -----Original Message-----
> > > > From: owner-vectorlist@synthcom.com
> > > > [mailto:owner-vectorlist@synthcom.com]On Behalf Of
> Dan
> > > Rasmussen
> > > > Sent: Wednesday, October 24, 2001 6:16 AM
> > > > To: vectorlist@synthcom.com
> > > > Subject: VECTOR: BU406D (was Wintron install: Does
> this
> > > look right?)
> > > >
> > > >
> > > > Hey,
> > > >
> > > > I'm following up to my own post.... I found the
> > > following
> > > > on the archives (after my sig), seems applicable.
> I'm
> > > just
> > > > not sure if that 21.6V on the 7824 is too low and I
> > > have
> > > > other problems besides (possibly) the bu406d.
> > > >
> > > > In summary, the posting below states, even though a
> > > bu406d
> > > > may test good, it may not be good and that the best
> way
> > > to
> > > > check is to first get good readings from the
> 7824/7924
> > > and
> > > > then, if the HV still seems to be dead (as mine
> seems
> > > to
> > > > be), try replacing the bu406d.
> > > >
> > > > My main question is this: is the -33 V from the
> 7924
> > > and
> > > > the 21.6V on the 7824 too far out of range for me
> to
> > > > consider them good?
> > > >
> > > > If it makes sense to try a known good bu406d now,
> can
> > > > anyone around here (Boston area) help me with a
> BU406D
> > > > (Joel!!!)... My 9YO son's birthday party is
> Saturday
> > > and
> > > > I'm trying to get it back up for it. If someone
> can
> > > lend
> > > > me one, I'll replace it as soon as I can get a hold
> of
> > > a
> > > > new one.
> > > >
> > > > Thanks.
> > > >
> > > > Dan Rasmussen
> > > >
> > > > From: jwelser@ccwf.cc.utexas.edu
> > > > Date: Tue Oct 21 1997 - 13:40:05 CDT
> > > >
> > > > On Tue, 21 Oct 1997, Joel Rosenzweig wrote:
> > > >
> > > > > How have you all gone about testing the BU406D?
> > > >
> > > > The BU406D is a wierd one. There shouldn't be a
> diode
> > > drop
> > > > from C -> B, or from C -> E (I think I got that
> > > right...the
> > > > case where the diode across C and E is reverse
> biased
> > > > should be infinite impedance, of course, is what
> I'm
> > > > saying.)
> > > >
> > > > Even on good BU406D's, the B -> E and E -> B will
> show
> > > low
> > > > impedance, because there is an internal resistor
> (in
> > > > addition to the diode) from B <-> E
> > > >
> > > > The way I fixed a bunch of HV units: Test the
> BU406D.
> > > If it
> > > > tests bad, throw it out (obviously) if it tests
> good,
> > > > you're still not out of the woods yet, because I
> had a
> > > > couple that caused no HV, even though they tested
> good.
> > > >
> > > > > When yours have failed, do they open up, or
> short, or
> > > ???
> > > >
> > > >
> > > > Short from C <-> E just like most other
> transistors...
> > > >
> > > > > I have three more Amplifone HV units that I'm
> trying
> > > to
> > > > repair. I
> > > > > suspect the HV transformer in all cases, but I'd
> like
> > > to
> > > > know how to
> > > > > tell if the BU406D is at fault or not.
> > > >
> > > > No HV, heater, etc. Same symptoms as the bad HV
> > > > transformer, shorted regulators, etc.
> > > >
> > > > > One last thing .. I have 4 HV boards in total,
> all
> > > with
> > > > red Hv
> > > > > transformers. One of the HV units actually works.
> (I
> > > > know, a rare
> > > > > breed) Similar to what Clay mapped out with a DMM
> for
> > > the
> > > > Wells Gardner
> > > > > HV transformer, I performed similar type
> measurements
>
=== message truncated ===

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Received on Wed Oct 24 12:44:14 2001