Vintage Pioneer SX-838 receiver- I MISDIAGNOSED !

[Bob Larter]

Dave wrote:

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:h0159p$bdi$1@news.eternal-september.org...
I have an excellent -- indeed, I'd say exceptional -- sense of how to go
about diagnosing problems. But I don't have the in-depth, day-to-day
experience Arfa, et al, have.

I used to service most of my own equipment, but consumer electronics have
become so complex and so fundamentally un-repairable that I rarely repair
anything. The last item I fixed was one of my electronic crossovers,
replacing an output drivers. (Believe it or not, John Curl helped me
diagnose the problem, by pointing out something I'd overlooked.)

One of the reasons I'm here is that I like to see what's going on in
electronic servicing, and get a better view of how the "new stuff" works.
You never know when it might come in handy.


I'm about the same as far as experience goes. Background in electrical
engineering (long long time ago), used to repair just anything, but have
never had the urge to move into SMD work, my eyes probably aren't good
enough anyways. Most of the repairs of newer TV's, multi-channel amps,
etc. seem to be board replacements, which holds no interest for me... I
like the troubleshooting process itself and get great pleasure from
being able to take a doorstop that cost somebody $1,000 long ago and
turn it back into a great amplifier or TV or washing machine or for the
cost of a few caps and a $1 regulator or $5 IC. My collection of TV's,
stereo equipment, etc. was in large part received for free in
non-working condition, and I doubt I've got $100 in any single piece.
My wife calls me a packrat but doesn't complain about my rates...

I'm a bit of a noob here, but I racked up about 5 years as a service
tech for computers, faxes, laser printers & inkjet printers. Then
another few years as the national Technical Specialist (ie; the go-to
guy for the entire country) for laser faxes & photocopiers, then a few
years doing actual electronics design work, followed by about 5 years
running a service department for laptops, lasers, inkjets & PCs. Since
then (10 years?), I've worked in networking, security & general IT
consulting. I don't know that much about troubleshooting consumer goods
(other than what I've done for myself or friends), but I do know my
stuff in my areas.

This group is a gold mine for experience, and it annoys me to no end
when people dare to complain about ABSOLUTELY FREE advice and
assistance. Advice gleaned here has helped me to repair items of which
I initially had little or no understanding.

Ditto. The gang here helped me repair my Tek oscilloscope, & were about
as nice & helpful as you could possibly imagine. I can't think of
anywhere else I could go, & get that quality of expertise. And it was
FREE! What kind of moron would argue with that?

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

 

[Meat Plow]

On Mon, 1 Jun 2009 10:38:36 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net>wrote:

Given all the time that people have spent, at no charge to yourself, to
help
you fix a problem which, honestly, you don't seem competent to diagnose
and
repair yourself, I find it in incredibly poor taste to make the comments
you
have. This group has a very talented and extremely experienced core group
of techs like William Sommerwick...

I appreciate the implicit support, but I am nowhere nearly as experienced as
others in this group.

I don't think that was implied. You seem to be well informed and have

an air of modesty about you. That often is better than pure on the
bench experience where the Average Joe stumbling across tech groups is
concerned.

I myself am considerably out of the loop on current day consumer
electronics by choice. I prefer pro audio equipment more specifically
things with glowing tubes in the power section or older discreet
circuits with mosfets and the likes.

However, my troubleshooting techniques still apply to a broad range of
equipments and I'm not afraid to tackle anything if the need arises.

 

[Mr.T]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:h00lrq$baf$1@news.eternal-september.org...

I don't know why Willaim Watson Michael Dayton-Wright chose those
particular
switches. If you want to damn him, damn him for not installing the caps.

Yep I would, don't you?

As for the power amp... At the time it was designed, there was a lot of
arguing about slewing-induced distortion, TIM, and the like. (There were
tube power amps that suffered from these problems. Dig through your
early-80s JAES issues for an article about one.) The assumption was that,
the wider the open-loop bandwidth, the less likely TIM would be a problem.
So Lux used triple-diffused RF power transistors -- despite the common
knowledge that they could be blown by RF transients. That was the cause in
three cases where the output transistors blew -- not audio transisents.

And how trivial to filter RF from a power amp input. Even cheap amps do it
successfully without affecting the audio range.

MrT.