Vintage Pioneer SX-838 receiver - UPDATE

[Bob Larter]

GregS wrote:

In article <gvon7t$lei$1@news.eternal-september.org>, "William Sommerwerck" <grizzledgeezer@comcast.net> wrote:
If I understand it correctly, poking the tranny (something I would never
do!) caused the corresponding channel to drop in and out.

So... are you ready to swap trannys?

(I'm a bit confused. Does this unit actually use driver transformers? It's
hardly a recent model, but I thought driver transformers had disappeared a
few years before this series.)



I think he meant trany istor.

Used to have bad transistors in some Tek scopes that ran hot.
over time the internal connection would become unstable and poking
would bring it back. Probably just the solder joint.

That'd be my diagnosis too. Happens all the time with heatsinked parts,
because the pins don't get hot enough to 'wet' properly when they go
through the wave-soldering machine at the factory.

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[GregS]

In article <gvpbbk$rv5$6@blackhelicopter.databasix.com>, Bob Larter <bobbylarter@gmail.com> wrote:

GregS wrote:
In article <gvon7t$lei$1@news.eternal-september.org>, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:
If I understand it correctly, poking the tranny (something I would never
do!) caused the corresponding channel to drop in and out.

So... are you ready to swap trannys?

(I'm a bit confused. Does this unit actually use driver transformers? It's
hardly a recent model, but I thought driver transformers had disappeared a
few years before this series.)



I think he meant trany istor.

Used to have bad transistors in some Tek scopes that ran hot.
over time the internal connection would become unstable and poking
would bring it back. Probably just the solder joint.

That'd be my diagnosis too. Happens all the time with heatsinked parts,
because the pins don't get hot enough to 'wet' properly when they go
through the wave-soldering machine at the factory.

Thats what happens to boards, but I'm not saying that. Its
the connections INSIDE the transistor that were going bad.
Poking the transistors vibrated the internal connections.
The only way to fix the problem was to install new transistors.
These were the ones in the 5000 series for the vertical and horizontal
drives.

greg

 

[Bob Larter]

GregS wrote:

In article <gvpbbk$rv5$6@blackhelicopter.databasix.com>, Bob Larter <bobbylarter@gmail.com> wrote:
GregS wrote:
In article <gvon7t$lei$1@news.eternal-september.org>, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:
If I understand it correctly, poking the tranny (something I would never
do!) caused the corresponding channel to drop in and out.

So... are you ready to swap trannys?

(I'm a bit confused. Does this unit actually use driver transformers? It's
hardly a recent model, but I thought driver transformers had disappeared a
few years before this series.)


I think he meant trany istor.

Used to have bad transistors in some Tek scopes that ran hot.
over time the internal connection would become unstable and poking
would bring it back. Probably just the solder joint.
That'd be my diagnosis too. Happens all the time with heatsinked parts,
because the pins don't get hot enough to 'wet' properly when they go
through the wave-soldering machine at the factory.


Thats what happens to boards, but I'm not saying that. Its
the connections INSIDE the transistor that were going bad.
Poking the transistors vibrated the internal connections.
The only way to fix the problem was to install new transistors.
These were the ones in the 5000 series for the vertical and horizontal
drives.

I wasn't arguing with you about the Tek parts, just talking about the
likely cause of the OP's problem. ;^)

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Arfa Daily]

"Bob Larter" <bobbylarter@gmail.com> wrote in message
news:gvpb6g$rv5$4@blackhelicopter.databasix.com...

Readily Visible wrote:
The tranny in question is 2SD358 on the left channel side. It is one of
those that drives one of the output trannies. The solder joints are hard
to access, but look to be well soldered,

On heavy parts - especially heatsinked ones - it's entirely possible for a
good looking joint to be dry internally. I'd desolder all the pins &
resolder them from scratch.


--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

Which makes my point exactly ...

Arfa

 

[Bob Larter]

Arfa Daily wrote:

"Bob Larter" <bobbylarter@gmail.com> wrote in message
news:gvpb6g$rv5$4@blackhelicopter.databasix.com...
Readily Visible wrote:
The tranny in question is 2SD358 on the left channel side. It is one of
those that drives one of the output trannies. The solder joints are hard
to access, but look to be well soldered,
On heavy parts - especially heatsinked ones - it's entirely possible for a
good looking joint to be dry internally. I'd desolder all the pins &
resolder them from scratch.

Which makes my point exactly ...

Indeed!

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Deke]

"Readily Visible" <abc@xyz.com> wrote in message
news:ED3Tl.19070$D32.4605@flpi146.ffdc.sbc.com...

When I put the top and bottom back on the unit and plugged in all the
various RCA plugs and speaker wires and 300 ohm antenna, the same
problem reasserted itself, the left channel bugged out.

Then I pulled the top and bottom and set the unit up on its side and it
has been playing all day without a hitch.

So I am thinking the problem is either heat related or position related.

As far as position related goes, this time the unit is standing up on
the opposite side as before, so I think the problem is heat related. As
long as the top and bottom are off, the left channel does not go out.
That makes a problem because as long as the problem does not assert
itself with the top and bottom off I cannot poke and prod and measure.

Got it!

I will simply leave the top and bottom off and put the unit on its side
and live with it.

I had this problem once a long time ago with another brand amp, a Proton, I
think. Turns out I was putting a screw back in the wrong place. It was
just long enough that when it was placed on its feet, it shorted to the
circuit board.