Re: BU406D

Before I buy 30 of these ($50 minimum order)....

I would appreciate it if someone could verify that this is
right -- :

http://www.galco.com/scripts/wsisa.dll/WService=Galco-Web/WA/wcat/itemdtl.r?listtype=Catalog&pnum=BU406D-NTE

Price listed is $2.83. At quantity 30, they are $1.94.
I'll make 20 or so available to the list (for cost +
postage). I just want to make sure I'm getting the right
thing.

Thanks again.

Dan

--- Dan Rasmussen <sscanf@yahoo.com> wrote:
> 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
> on
> the Amplifone
> > HV transformer units. Every last one of them (including
> the working
> > one) had the same measurements. Yet, only one of them
> actually works.
> > The ohm test seemed pretty logical to me, and it
> sounded
> like it would
> > be a surefire way to detect an open or shorted winding
> ... but
> > apparently, that's not the whole story. If the windings
> appear to be
> > good, what else is wrong with these transformers? The
> BU406D's that I
> > can't test? :-) :-) :-)
>
> I measured the same on good and bad Penn-Tran/Wintron HV
> units. I think what sometimes happens is that the
> insulation between turns breaks down, and the effect is
> that the transformer has fewer windings, so the HV drops.
> From the schematic of the HV unit from Wintron, it looks
> like there is a diode IN the HV transformer, so maybe
> that
> breaks down too, but I'd guess you could test for that
> <shrug>
>
> > I have not removed the HV transformers and swapped them
> into the known
> > good HV board, but I have checked every component
> except
> for the BU406D
> > and MC1, whatever that is?? Aside from that, these
> units
> have basically
> > been rebuilt! Any ideas?
>
> I just repaired a half-dozen of these boards, and the
> most
> common failures are the 7824 and 7924 regulators (The
> 7924s
> failed in all but one instance) If you're getting good
> +/-
> 24V, then try the BU406D. I found a bunch of creative
> replacements that previous techs had done (but all
> incorrect) for the BU406D, so check to make sure that the
> transistor that's there is actually a BU406D. If you've
> got
> those cheesy brown jumpers (W1, etc) on the board, check
> them out, because they DO open up. If you're not getting
> +/- 24V (or the +/- 30V input to the board) check the
> brown
> jumpers on the deflection board. I had this happen in 1
> case.
>
> Joe
>
>
>
> =====
> ------ replies to sscanf@yahoo.com ------
>
> Anything that appears after this sentence is inserted by
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>
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=====
------ replies to sscanf@yahoo.com ------

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Received on Wed Oct 24 07:09:06 2001