Repaired a Technics SU C2000 control amplifier, which is just a preamp. An
LED displays that it is in this VBO mode.
The SU C1000 has a battery back for this, but no battery pack in the C2000
unless it is somehow hidden in the faux (poids for your bucks) heavy metal
sub frame. No monster caps either , so what is this all about ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in message
...

Repaired a Technics SU C2000 control amplifier, which is just a preamp. An
LED displays that it is in this VBO mode.
The SU C1000 has a battery back for this, but no battery pack in the C2000
unless it is somehow hidden in the faux (poids for your bucks) heavy metal
sub frame. No monster caps either , so what is this all about ?


Just as a guess, flash memory?

David.

David Looser wrote in message
...
"N_Cook" wrote in message
...

Repaired a Technics SU C2000 control amplifier, which is just a preamp.
An
LED displays that it is in this VBO mode.
The SU C1000 has a battery back for this, but no battery pack in the
C2000
unless it is somehow hidden in the faux (poids for your bucks) heavy
metal
sub frame. No monster caps either , so what is this all about ?


Just as a guess, flash memory?

David.



From the C1000 repair and user manual you press a button to opt for battery
operation for no mains hum/ fridge spikes etc presumably (if/after the
battery is charged off
the mains) or opt for mains power to the preamp. So I assumed the same with
the C2000 but no battery or battery switch or anywhere obvious a missing
battery could be/have been connected/located.
If it was not for Technics make and going by the heavy lump of metal, for no
functional purpose, I would have said it was a con.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in message
...


From the C1000 repair and user manual you press a button to opt for
battery
operation for no mains hum/ fridge spikes etc presumably

Shades of the 1920s and 30s, when battery operation was preferred by some
"audiophiles" of the day (because "mains sets hum"). But I thought that
attitude had died out decades ago, apparently not.

(if/after the
battery is charged off
the mains) or opt for mains power to the preamp. So I assumed the same
with
the C2000 but no battery or battery switch or anywhere obvious a missing
battery could be/have been connected/located.

I had assumed before that the battery was to back-up settings, hence my
comment about flash memory. If the VBO is intended to run the pre-amp, but
there is no battery, and no mains supply, I can only guess that in VBO mode
the pre-amp is entirely passive.

If it was not for Technics make and going by the heavy lump of metal, for
no
functional purpose, I would have said it was a con.


I'm not sure that just because it has a well-known name on the front you can
necessarily assume that it's not.

David.

N_Cook wrote:
If it was not for Technics make and going by the heavy lump of metal, for no
functional purpose, I would have said it was a con.


It's a very clean power supply, virtually as good as a battery as
regards supply noise.

Technics have this used all over the place, from pre-amplifiers to CD,
DVD and Blueray players.

More info here
http://www.diyaudio.com/forums/showthread/t-118458.html


--
Adrian C

"Adrian C" wrote in message
...
N_Cook wrote:
If it was not for Technics make and going by the heavy lump of metal, for
no
functional purpose, I would have said it was a con.


It's a very clean power supply, virtually as good as a battery as regards
supply noise.

Technics have this used all over the place, from pre-amplifiers to CD, DVD
and Blueray players.

More info here
http://www.diyaudio.com/forums/showthread/t-118458.html


Ah!... we're back in bull**** territory again :-(

David.

David Looser wrote:


Ah!... we're back in bull**** territory again :-(


:-)

The next topic is "VC-4 Amplifier System" - found plastered on the front
of my Technics tuner.

--
Adrian C

Adrian C wrote in message
...
N_Cook wrote:
If it was not for Technics make and going by the heavy lump of metal,
for no
functional purpose, I would have said it was a con.


It's a very clean power supply, virtually as good as a battery as
regards supply noise.

Technics have this used all over the place, from pre-amplifiers to CD,
DVD and Blueray players.

More info here
http://www.diyaudio.com/forums/showthread/t-118458.html


--
Adrian C

Looks like a regular linear ps to me except for the transformer being about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N_Cook wrote:

Looks like a regular linear ps to me except for the transformer being about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.

I was wrong in calling it a "very clean power supply". I should have
said "it has the effect of a very clean power supply"....

Have a look around the preamp section. As from the link I gave (from
google), it's not a regulator but an "active filter".

Quote "tracks input voltage as changed by variations in line voltage and
load, and takes out some AC. That may be useful under some special
circumstances. In the tube days, this was done using a large choke,
that's in a way what this circuit simulates."

FWIW I tried a patent search. Got nothing.

--
Adrian C

Adrian C wrote in message
...
N_Cook wrote:

Looks like a regular linear ps to me except for the transformer being
about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.

I was wrong in calling it a "very clean power supply". I should have
said "it has the effect of a very clean power supply"....

Have a look around the preamp section. As from the link I gave (from
google), it's not a regulator but an "active filter".

Quote "tracks input voltage as changed by variations in line voltage and
load, and takes out some AC. That may be useful under some special
circumstances. In the tube days, this was done using a large choke,
that's in a way what this circuit simulates."

FWIW I tried a patent search. Got nothing.

--
Adrian C

There are 2SD2037 and 2SB1357 ,probably as pass transistors downstream of
the 18V regulators, using some of the headroom to drop to +/- slightly lower
rails and a load of little electros, which doesn't strike me as particularly
groundbreaking, let alone simulating a battery.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"Adrian C" wrote in message
...
N_Cook wrote:

Looks like a regular linear ps to me except for the transformer being
about
4 times the size necessary for a preamp and relays - more superfluous
weight.
Pair of 3300uF caps , 78M18,79M18, 5V reg , no chokes, no mu-metal or
anything noticeably odd but, at least, no gold plating.

Doesn't sound anything special. 78M18 and 79M18 are bog-standard regulator
chips.

I was wrong in calling it a "very clean power supply". I should have said
"it has the effect of a very clean power supply"....

Have a look around the preamp section. As from the link I gave (from
google), it's not a regulator but an "active filter".

Quote "tracks input voltage as changed by variations in line voltage and
load, and takes out some AC. That may be useful under some special
circumstances. In the tube days, this was done using a large choke, that's
in a way what this circuit simulates."

Active filters in power supplies are common when low ripple is required but
voltage stabilisation is not required. At it's simplest it's just an emitter
follower with the base fed from the input via a resistor and decoupled to
ground by a large capacitor. If the current loading is high a compound
transistor (darlington pair) might be used. Again nothing special there,
they've been used for years (thermionic version were in use before the
invention of the transistor).

FWIW I tried a patent search. Got nothing.

Not original enough to be patentable.

David.