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From: William R. Walsh on 2 Apr 2010 20:34
Hello all...

I was all of bored and inspired by reports of these stereo receivers going
up in sparks and smoke from time to time to see what was inside this stereo
receiver and how well it was put together. I think they're actually a decent
piece of equipment as long as they're not abused or the specifications
violated. The following web page is the result:

http://greyghost.mooo.com/rx4109takeapart/

This also applies to the Insignia NS-R2000 sold by Best Buy, possibly other
receivers produced by Sherwood with other names on them, and the RX-4105
model.

While not strictly related to the repair of electronics, maybe it would help
someone in such an effort. I'd greatly appreciate *constructive* comments,
suggestions and clarifications...especially for the section on the audio
amplifier, where I have only the most rudimentary understanding of what is
going on.

Does anyone have the Sherwood RX-4109 service manual kicking around? I'd
gladly pay for one and/or provide a valid e-mail address to which it could
be sent. (Sherwood hasn't responded to me in two days, and I have reason to
believe that none of the e-mail addresses on their site really work. I
haven't broken down and called them. Yet.)

William


From: Mark Zacharias on 3 Apr 2010 07:05
"William R. Walsh" <newsgroups1(a)idontwantjunqueemail.walshcomptech.com>
wrote in message news:xtWdnVYJ292EECvWnZ2dnUVZ_rmdnZ2d(a)mchsi.com...
> Hello all...
>
> I was all of bored and inspired by reports of these stereo receivers going
> up in sparks and smoke from time to time to see what was inside this
> stereo
> receiver and how well it was put together. I think they're actually a
> decent
> piece of equipment as long as they're not abused or the specifications
> violated. The following web page is the result:
>
> http://greyghost.mooo.com/rx4109takeapart/
>
> This also applies to the Insignia NS-R2000 sold by Best Buy, possibly
> other
> receivers produced by Sherwood with other names on them, and the RX-4105
> model.
>
> While not strictly related to the repair of electronics, maybe it would
> help
> someone in such an effort. I'd greatly appreciate *constructive* comments,
> suggestions and clarifications...especially for the section on the audio
> amplifier, where I have only the most rudimentary understanding of what is
> going on.
>
> Does anyone have the Sherwood RX-4109 service manual kicking around? I'd
> gladly pay for one and/or provide a valid e-mail address to which it could
> be sent. (Sherwood hasn't responded to me in two days, and I have reason
> to
> believe that none of the e-mail addresses on their site really work. I
> haven't broken down and called them. Yet.)
>
> William
>
>

I've seen several models that have a similar look inside. Denon uses the
same chinese vendor and has for years. I've seen it on lower end Pioneers -
not their high-end mind you. They are mostly OK to service if you have the
service literature; frequently they will have a "special" bias transistor,
like a 2SC3964 or a 2SD947. Not the type of thing one normally stocks unless
maybe you do a lot of audio, like I do.

Most use the infamous Denon .22 ohm small emitter resistors, 4 per channel.
Some later ones have gone to a more traditional .47 version, still
paralleled 2+2 on each channel.
I will literally order the .22 versions 50 at a time, since they are only
..15 ea from Denon, and I go through so many of them. You have to replace all
4 if the channel blows, even if one or two check "good". They'll come back
to bite you.

The mid-fi Denon and cheap Pioneer versions generally use the 2SB1560 and
2SD2390. Higher powered models often use the 2SB1647 and 2SD2560.

Mark Z.

From: Engineer on 4 Apr 2010 12:21
On Apr 2, 8:34 pm, "William R. Walsh"
<newsgrou...(a)idontwantjunqueemail.walshcomptech.com> wrote:
> Hello all...
>
> I was all of bored and inspired by reports of these stereo receivers going
> up in sparks and smoke from time to time to see what was inside this stereo
> receiver and how well it was put together. I think they're actually a decent
> piece of equipment as long as they're not abused or the specifications
> violated. The following web page is the result:
>
> http://greyghost.mooo.com/rx4109takeapart/
>
> This also applies to the Insignia NS-R2000 sold by Best Buy, possibly other
> receivers produced by Sherwood with other names on them, and the RX-4105
> model.
>
> While not strictly related to the repair of electronics, maybe it would help
> someone in such an effort. I'd greatly appreciate *constructive* comments,
> suggestions and clarifications...especially for the section on the audio
> amplifier, where I have only the most rudimentary understanding of what is
> going on.
>
> Does anyone have the Sherwood RX-4109 service manual kicking around? I'd
> gladly pay for one and/or provide a valid e-mail address to which it could
> be sent. (Sherwood hasn't responded to me in two days, and I have reason to
> believe that none of the e-mail addresses on their site really work. I
> haven't broken down and called them. Yet.)
>
> William

Great write-up, William, thanks. For my sins, I play with earlier all-
analog stereo receivers (1970's and 1980's Sansui, Pioneer, etc.) I
can't seem to resists the low cost - even free sometimes! But they all
sound very good. Anyway, trying to give them up and stick to tubes!
If people want straight stereo from CD and FM radio, I recommend this
pure vintage route if you have the tech skills to check them out.
Cheers,
Roger
PS. I had a Sherwood S7100A in the 1970's - bought new!
From: William R. Walsh on 4 Apr 2010 15:50
Hi!

> I've seen several models that have a similar look inside. Denon uses the
> same chinese vendor and has for years.

Sherwood claims on their web site that they manufacture a large quantity of
stereo receivers for other people. I don't know that it's true, but I have
no reason to believe they'd lie about it. Therefore my guess is that they
control the factory where these things are put together.

> I've seen it on lower end Pioneers - not their high-end mind you.

I wonder if that's changed in recent times. I don't work on a lot of audio
equipment, but I did go and look at some of the owner's manuals from
Pioneer's site--even some of their ELITE receivers show a strong similarity
to the Sherwood designs.

> They are mostly OK to service if you have the service literature;
frequently they
> will have a "special" bias transistor, like a 2SC3964 or a 2SD947.

I'm trying to get the service literature, either through a download or for
purchase. I'd like to have it, if for no other reason than to say that I do.

William


From: William R. Walsh on 4 Apr 2010 16:22
Hi!

> Great write-up, William, thanks.

You are welcome, and thank you for taking the time to read it.

> For my sins, I play with earlier all-analog stereo receivers (1970's and
1980's
> Sansui, Pioneer, etc.) I can't seem to resists the low cost - even free
sometimes!
> But they all sound very good.

For the most part I haven't been impressed with modern stereo receivers and
these home theater "things" that seem to be all over the place. I didn't
really feel that a lot of them had good enough construction internally to
meet what the specifications printed in the book said. One case that stands
out was where a friend of mine decided to dump his old Pioneer (mid 70s)
receiver for a brand new Harman/Kardon unit in the early 2000s. After
comparing the two, I talked him out of it and gave the Pioneer a good
cleaning. It desperately needed one (controls and internals), after which it
was fine again.

These (RX-4105, 4109 and the clones) actually seem like pretty decent
receivers to me. If they a little more thought put into the cooling for the
power transistors, I think they'd be even better.

I like the old gear too. I guess you could say it has character--and
oftentimes, more interesting visual design than the stuff of today. I have
an old basic Sansui receiver in beautiful condition that was given to me.
I'm not sure of the model # or specifics, but it plays well and its only
problem is a fidgety blinking lamp behind the "signal strength" display. I
haven't dared to take it apart just because it's in such nice shape, nor do
I know what its power ratings are. I'd say not much (there are no vent
openings in the case, other than at the rear) yet it still works very well
in the rec room.

When I was young, I got to partying with my dad's Pioneer SX-5 receiver and
burned out some part of the power supply for the front panel controls! It
still played from external inputs, although the tuner quit, the display
showed only incorrect symbols and most of the front panel buttons didn't
work properly. He opted to have it fixed, and the repair shop that worked on
it (can't recall who it was now) said that the failed part was a common
problem. They not only replaced it but also claimed to have tried to give
the part better cooling. That was in the early 90s.

I always wondered what they did, yet I never bothered to crack the cover
until around Christmas 2009 when that receiver decided to play holiday music
at full volume regardless of what the volume dial was set to. I did manage
to fix it, and at the same time, I found the repair--a small transistor
toward the front of the unit had very clearly been replaced. The shop that
had worked on it ran extension wires from the circuit board to the
replacement transistor, which they mounted to the same heatsink as the power
transistors.

> Anyway, trying to give them up and stick to tubes!

My only piece of tube-type hi-fi equipment is a Knight/Allied Radio stereo
amplifier and tuner pair. Both date from 1959. I don't make any fancy claims
for these pieces, although I really do think there is a noticeable
difference in the sound this puts out as compared to solid state gear. I
don't use the tuner as much, because it doesn't receive FM stereo (it would
receive stereo broadcasts with one channel coming from AM and the other from
FM, and it has an output for an external multiplex decoder). So I'm using an
analog tuned Kenwood AM/FM Stereo tuner that I'm very happy with when I want
to listen to the radio there. The speakers are some tall, late model Sansui
units (don't recall the model number for those either).

http://greyghost.mooo.com/knight/ has pictures of amp and tuner from the
night I brought them home. I went over the amplifier looking for serious
problems when I bought it, but I probably need to do more as one of the EL84
tubes seems to be going into a mild runaway state after a while. Some of
those old wax capacitors probably aren't too good...

I have other tube-type audio equipment, nearly all of those pieces are table
radios. Most wouldn't qualify as "high fidelity" outside of the two Zenith
radios that make the "high fidelity" claim on their cabinets. That stuff is
here:

http://greyghost.mooo.com/radiocollection/

So that's probably more than you cared to know, but there it is.

William


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