"N Cook" wrote in message
...
N Cook wrote in message
...
Had been in a loft for years
Original Mullard EL84 tested good gain,no leakage, and all else checked
out.
On powering there was amp hiss and crackle on turning the worn out vol
control.
But stroking the stylus with fingertip produced nothing.
I did not think to feed an external signal into the tape input and now it
is
back apart.
Wiring between pu and vol control is fine.
Putting the output of either pu LP or 45 to a scope and touching either
stylus produces absolutely no signal at 2mV per division.

Make of rotatable pu looks like
Fulfi (Googling produces nothing)
, Made in England, number TC8S , and TC8C and TC8RS for the stylii.
Does it need an excitation voltage ? its only connected to the valve grid
via 1M vol pot.

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




Let this be a lesson to anyone in the UK -
DO NOT store Rochelle crystal cartridges in lofts or sheds.
The crystal must be hygroscopic.
After removing the copper rivits (used flute section of small end mill to
avoid the rotating rivet problem with drilling out rivets in plastic) and
separating the 2 main parts, the problem was obvious.
I just managed to move the parts apart enough to photograph before the
active part fell to bits, lightly probing with a pin it was the
consistency
of dusty paste.
(1 mm graph paper)
http://home.graffiti.net/diverse:gra...et/ful-fi1.jpg
Left section is the cover, slid sideways, and the R section, on a nylon
nut
for focus, is inverted, part of the "crystal" with angled ground strip
that
touches the central pu pin (common to the other pu) to the outside, along
with the signal pin for that pick up.
The other pickup , not seen yet, but will be the same state, is under the
central view.
The brown part is the rubbery material that engages with the crystals and
stylus shafts.
Plenty of copper carbonate corrosion inside.

The remaining parts of the yoke, styli etc
http://home.graffiti.net/diverse:gra...et/ful-fi2.jpg

Anyone reckon I can rob the crystal from a piezo ceramic pickup to fudge a
functional and "as original" repair?
I assume piezo-ceramic is not prone to this problem over 40 years.


As I recall, ceramic cartridges do not have anything like as much output as
a genuine crystal type. Why not just replace the whole cartridge with an
SX5H or whatever ? I seem to think that Dansettes were fitted with a
comparitively 'modern' type such as this, anyway.

Arfa

On Tue, 20 Nov 2007 12:42:49 GMT, "Arfa Daily"
wrote:



Anyone reckon I can rob the crystal from a piezo ceramic pickup to fudge a
functional and "as original" repair?
I assume piezo-ceramic is not prone to this problem over 40 years.


As I recall, ceramic cartridges do not have anything like as much output as
a genuine crystal type. Why not just replace the whole cartridge with an
SX5H or whatever ? I seem to think that Dansettes were fitted with a
comparitively 'modern' type such as this, anyway.


ISTR that cheap record players that just had a single valve output
stage and no pre-amplifier used a "High-output" cartridge. (Is that
what the H in SX5H means ?) a standard output cartridge would be very
quiet and a ceramic quieter still.

Also FWIR that output valve would typically be a UL84 or similar (not
as a rule EL84), with 100ma (80v) heaters fed off a tap on the shaded
pole turntable motor, to save the cost of a filament transformer.

The crystal cartridges didn't need any excitation voltage.

DG

"Derek Geldard" wrote in message
...
On Tue, 20 Nov 2007 12:42:49 GMT, "Arfa Daily"
wrote:



Anyone reckon I can rob the crystal from a piezo ceramic pickup to fudge
a
functional and "as original" repair?
I assume piezo-ceramic is not prone to this problem over 40 years.


As I recall, ceramic cartridges do not have anything like as much output
as
a genuine crystal type. Why not just replace the whole cartridge with an
SX5H or whatever ? I seem to think that Dansettes were fitted with a
comparitively 'modern' type such as this, anyway.


ISTR that cheap record players that just had a single valve output
stage and no pre-amplifier used a "High-output" cartridge. (Is that
what the H in SX5H means ?) a standard output cartridge would be very
quiet and a ceramic quieter still.

Also FWIR that output valve would typically be a UL84 or similar (not
as a rule EL84), with 100ma (80v) heaters fed off a tap on the shaded
pole turntable motor, to save the cost of a filament transformer.

The crystal cartridges didn't need any excitation voltage.

DG


Yes Derek, that's it exactly. I did one just last week that used a UL84 and
UY85 reccy, fed just as you say, by a tap on the motor winding. I seem to
recall that those crystal cartridges had an output approaching 2v p-p, and
obviously, with a very high impedance in the order of megs, which matched
nicely for level and Z, directly to the grid circuit of the UL84. Ceramic
cartridges, on the other hand, only have an output of 200 mV or so I think,
at an impedance of around 50 - 100k. I think that you are right that the "H"
is for high. The BSR SC5H is a high output ceramic, so I guess it's "S" for
stereo, "X" for xtal, "C" for ceramic, and "H" for high.

It's all going back a bit to my apprentice years now, but I have a dim
recollection of later units that were fitted with a ceramic cartridge, using
something like a UCL84 which contained a triode as well as the output
pentode, and that the triode was pressed into service as a preamp.

Arfa

Arfa Daily wrote in message
...

"Derek Geldard" wrote in message
...
On Tue, 20 Nov 2007 12:42:49 GMT, "Arfa Daily"
wrote:



Anyone reckon I can rob the crystal from a piezo ceramic pickup to
fudge
a
functional and "as original" repair?
I assume piezo-ceramic is not prone to this problem over 40 years.


As I recall, ceramic cartridges do not have anything like as much output
as
a genuine crystal type. Why not just replace the whole cartridge with an
SX5H or whatever ? I seem to think that Dansettes were fitted with a
comparitively 'modern' type such as this, anyway.


ISTR that cheap record players that just had a single valve output
stage and no pre-amplifier used a "High-output" cartridge. (Is that
what the H in SX5H means ?) a standard output cartridge would be very
quiet and a ceramic quieter still.

Also FWIR that output valve would typically be a UL84 or similar (not
as a rule EL84), with 100ma (80v) heaters fed off a tap on the shaded
pole turntable motor, to save the cost of a filament transformer.

The crystal cartridges didn't need any excitation voltage.

DG


Yes Derek, that's it exactly. I did one just last week that used a UL84
and
UY85 reccy, fed just as you say, by a tap on the motor winding. I seem to
recall that those crystal cartridges had an output approaching 2v p-p, and
obviously, with a very high impedance in the order of megs, which matched
nicely for level and Z, directly to the grid circuit of the UL84. Ceramic
cartridges, on the other hand, only have an output of 200 mV or so I
think,
at an impedance of around 50 - 100k. I think that you are right that the
"H"
is for high. The BSR SC5H is a high output ceramic, so I guess it's "S"
for
stereo, "X" for xtal, "C" for ceramic, and "H" for high.

It's all going back a bit to my apprentice years now, but I have a dim
recollection of later units that were fitted with a ceramic cartridge,
using
something like a UCL84 which contained a triode as well as the output
pentode, and that the triode was pressed into service as a preamp.

Arfa



The circuit is minimalism, as in the Newnes 1959 guide for Dansette Major de
Luxe.
A triple cap can, 2 other axial caps, 2 Rs, rectifier , 2 pots, EL84, mains
and o/p transformer.
I took another Sonotone apart. I had not lost a silver spring from the other
one, only one active element is used so 2 wires only.
I will try lashups as series and parallel trying to determine which gives
most signal/ most f range.

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

I decided to take a skew view before wiring in

http://home.graffiti.net/diverse:gra...et/ful-fi4.jpg
2 rings of green silicone rubber sleeving to take silvered wires before dabs
of gummy glue.
One black rubber pad chamfered to rest in the top cover, yellow-white rubber
pad cut down , orginal brown rubbery moulding that enclosed both original
rochelle crystals and extensions to both stylii saddles.
The saphire of the original remounted ( coded yellow and green) stylus is
just visible to the top and right of the brown section, through a gap in the
white plastic casing.
The original small plastic stylus saddle went quite neatly through the hole
for the original rochelle.
The now unused second brass screw mount for the other stylus and its
corresponding saddle rest flat, on the brown section, is visible on the
lower edge.
Decided to wire in only one active element of the Sonotone and also to have
more space to play with ditch the 78 option and just use 2 of the original 3
pins and plates to the outside. It is very critical on signal generation on
how much the rubber supports are compressed, I may cut the thickness down a
bit if the sound is ropey.
It would probably be possible, in space terms, to separate the 2 sonotone
and mount one either side and retain double stylus, rotating function.


--
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
...
I decided to take a skew view before wiring in

http://home.graffiti.net/diverse:gra...et/ful-fi4.jpg
2 rings of green silicone rubber sleeving to take silvered wires before
dabs
of gummy glue.
One black rubber pad chamfered to rest in the top cover, yellow-white
rubber
pad cut down , orginal brown rubbery moulding that enclosed both original
rochelle crystals and extensions to both stylii saddles.
The saphire of the original remounted ( coded yellow and green) stylus is
just visible to the top and right of the brown section, through a gap in
the
white plastic casing.
The original small plastic stylus saddle went quite neatly through the
hole
for the original rochelle.
The now unused second brass screw mount for the other stylus and its
corresponding saddle rest flat, on the brown section, is visible on the
lower edge.
Decided to wire in only one active element of the Sonotone and also to
have
more space to play with ditch the 78 option and just use 2 of the original
3
pins and plates to the outside. It is very critical on signal generation
on
how much the rubber supports are compressed, I may cut the thickness down
a
bit if the sound is ropey.
It would probably be possible, in space terms, to separate the 2 sonotone
and mount one either side and retain double stylus, rotating function.



I wish I could make enough money in the repair business, to have time to
'play' like this ... !! d;~}

Arfa

Arfa Daily wrote in message
...

"N Cook" wrote in message
...
I decided to take a skew view before wiring in

http://home.graffiti.net/diverse:gra...et/ful-fi4.jpg
2 rings of green silicone rubber sleeving to take silvered wires before
dabs
of gummy glue.
One black rubber pad chamfered to rest in the top cover, yellow-white
rubber
pad cut down , orginal brown rubbery moulding that enclosed both
original
rochelle crystals and extensions to both stylii saddles.
The saphire of the original remounted ( coded yellow and green) stylus
is
just visible to the top and right of the brown section, through a gap in
the
white plastic casing.
The original small plastic stylus saddle went quite neatly through the
hole
for the original rochelle.
The now unused second brass screw mount for the other stylus and its
corresponding saddle rest flat, on the brown section, is visible on the
lower edge.
Decided to wire in only one active element of the Sonotone and also to
have
more space to play with ditch the 78 option and just use 2 of the
original
3
pins and plates to the outside. It is very critical on signal
generation
on
how much the rubber supports are compressed, I may cut the thickness
down
a
bit if the sound is ropey.
It would probably be possible, in space terms, to separate the 2
sonotone
and mount one either side and retain double stylus, rotating function.



I wish I could make enough money in the repair business, to have time to
'play' like this ... !! d;~}

Arfa



Googling for what a Rochellle crystal should look like I found someone else
has gone down this route
http://www3.sympatico.ca/belanger.er.../cartridge.htm
completely different internals

--
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
...
I decided to take a skew view before wiring in

http://home.graffiti.net/diverse:gra...et/ful-fi4.jpg
2 rings of green silicone rubber sleeving to take silvered wires before
dabs
of gummy glue.
One black rubber pad chamfered to rest in the top cover, yellow-white
rubber
pad cut down , orginal brown rubbery moulding that enclosed both original
rochelle crystals and extensions to both stylii saddles.
The saphire of the original remounted ( coded yellow and green) stylus is
just visible to the top and right of the brown section, through a gap in
the
white plastic casing.
The original small plastic stylus saddle went quite neatly through the
hole
for the original rochelle.
The now unused second brass screw mount for the other stylus and its
corresponding saddle rest flat, on the brown section, is visible on the
lower edge.
Decided to wire in only one active element of the Sonotone and also to
have
more space to play with ditch the 78 option and just use 2 of the original
3
pins and plates to the outside. It is very critical on signal generation
on
how much the rubber supports are compressed, I may cut the thickness down
a
bit if the sound is ropey.
It would probably be possible, in space terms, to separate the 2 sonotone
and mount one either side and retain double stylus, rotating function.


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



Got back to this back-burner job today.
I had to abandon putting piezo element in the original cartridge housing,
not enough output.
Sliding a cable tie lightly over the stylus gave about 100mV , wheras doing
the same over a complete piezo, ie vibration not having to go through a load
of brownish rubber gave about 2V pk-pk output with the cable tie.
Adabted the yoke to be able to slide in piezo pick-up ,retains the little
78/LP flag , and can rotate but no second stylus, and is shrouded in the arm
so nothing shows in normal use.

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