Every couple of years we go round and round on this board.
The "version" is a compromise that should cover them all.
Worst case the board doesn't have a D1, nor a D7 and D8. So you end up with 3 extra diodes... That's why I didn't go to 2x or 3x on the D7, D8 replacements...
It COULD also have stv-3 diodes at D7 and D8, which ARE LEFT IN PLACE if OK.
first, PLEASE be specific!!!
Some may have the 032-0 board and some may have the 032-D board. My board is a D board which I will refer back to post #8. The D version removed a diode and replaced it with two jumper wires, lower right corner of the board.
So I would recommend checking your version of the board before replacing all the diodes as some are STV diodes as in mine.
Someone may chime in and let us know which version of the board the list belongs to.
Thanks again.
PLEASE mention the number of the removed diode for precision, for those of us actually trying to track things down...
And what the jumpers are doing / where they are going would help too. I assume it's the d1 area you are talking about.
The 44 meg Hi-res manual doesn't even have internal consistency.
On the 12.7 power amplifier assembly (awh-032-0) page the schematic does NOT show the D7 and D8 diodes THAT ARE CLEARLY VISIBLE ON THE PC BOARD LAYOUT DIAGRAM RIGHT BELOW IT!!!!!
D7 and D8 when added were first 1s1885's, then were upped to stv-3 (NOT stv-3H!!) diodes for their additional voltage drop.
UF4004 x 1 each were subbed, but 2x or 3x UF4004 strings can be used as per Echowars.
The other changes are in the voltage divider strings that develop the voltages for the VR1 DC offset voltage adjustment pot.
First, there are versions without D7 and D8:
http://www.audiokarma.org/forums/showpost.php?p=2322349&postcount=301
On 1010 Power Amp Board AWH-032-0, I'm wondering why you replaced diodes D7 & D8, which were each originally a single 1S1885 diode (rating: VRRM 100 Volt, IFSM 66 Amp) with two Fairchild UF4004 (rating: Repetitive peak reverse voltage 400 Volt, Peak one cycle surge forward current 30 Amp) in series. This seems like less protection rather than more in terms of the current capability of the replacements. Am I missing something?
I attach ccheath's illustration of the components from his earlier posting and a pic of my original unmodified board.
Here's why, when I was working on Maddart's sx-1010, it had stv3's instead of 1s1885 diodes and one was bad.
then this (post 60):
http://www.audiokarma.org/forums/showthread.php?p=1494762#post1494762
explains EVERYTHING.
The D7 and D8 diode are there to prevent the driver stage from saturating the output transistors too hard. In this case, Pioneer originally thought 1 diode drop would do it, and evidently decided later that they'd like a little more breathing room for fools who like to get a bit too frisky with the volume control.
You do not need to find more STV diodes to replace the bad ones. If this were my own receiver, I'd replace the dead diode with a good, fast (*speed is important! 1N4004 or similar is too slow!), rugged 1A diode, such as a UF4004, and call it a day. But, do replace both D7 and D8 if you do either.
If this really bothers you, make a string of two UF4004 diodes in series ('A'-frame mode), and replace the STV-3 with it. I can't think of a way to do this with three diodes that won't look like sheeite.
*1N4004 - Trr = not specified, since it is designed to deal with 60Hz
UF4004 - Trr = 50nS
Then there is the change to "the lower right corner" DC offset voltage generator section.
There are versions (IIRC) where D1 is replaced with a resistor....
And versions where the diode d1 is just left open
and versions where the diode d1 is just left open AND R5 is shorted with a jumper.
Not to finally mention that the placement of the two STV-3H diodes were altered, from two on the driver heat sink, to one of the driver heat sink and one remotely mounted in the correct position on the OUTPUT'S heat sink.
