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thanatoid 09-08-2010 11:15 PM

Phono preamp in old receiver problem
 
Hi gang,

I have an old Sharp AM/FM receiver with an 8-track player. Made
in Japan ca. 1975 or something. It had a BSR turntable which was
broken. I removed the seized turntable, cleaned the whole unit,
sprayed all the pots, replaced the three little 6V bulbs behind
the black/green tuner window, and it is fabulous. It's built
like a tank and weighs a ton. The pots feel like military grade
stuff. The function switches are simply unbelievable. The front
panel is white (OK, bone now) with black controls, the box is
all wood with the then-standard "vinyl wood veneer".

I have a spare turntable which works perfectly. I intended to
connect it to the phono preamp of this receiver. I did, but I am
not getting sound. I am getting low-frequency pink noise, but no
audio signal. What is even stranger is that I hear one of the
channels "pop" when I dis/connect ONE of the two RCA audio
cables going into the phono preamp of the receiver. I tested all
the cables after extending them, and they are OK (see below).

I tried connecting the turntable signal to the line input, and
it DOES work. Of course, the signal is VERY low, but you CAN
hear the LP playing with the volume full up. So either I DID
somehow **** up the audio cable assembly (it tests OK though!)
or the phono preamp is partially or totally NG, in which case
there is probably nothing that can be done.

The line inputs can be used for a CD/DVD player, the receiver
works as a 4-speaker unit or 2 main/2 remote speakers, and it
sounds great. AM and line in are loud as hell, FM volume is
about 30% of that, but still usable.

Does anyone have any idea what I should do first? I want to
determine exactly /what/ in the chain from the *turntable audio
cables/cable extensions/original RCA plugs and cable/circuit
board* is NG.

(The phonograph audio cables were only long enough to reach the
bottom of the turntable, which was 3 inches above the main
circuit board, now they have to reach to the back and out of the
unit, so I had to add about 8 inches of cable - but I tested the
cables, both channels, live /and/ ground, and I made NO mistakes
- everything was connected/soldered correctly.

If the phono preamp is dead, it's dead. The unit is still a
/great/ AM (and decent FM) receiver and line-in amplifier,
handles TWO sets of stereo speakers, and it will outlast all of
us. I have yet to find an 8-track cartridge, but the mechanism
and all the belts seem fine. Plus I don't think anyone needs an
8-track deck, while /quite/ a few people might enjoy having a
receiver with a phono preamp. Unless the phono preamp IS dead,
of course. But maybe someone can help me determine if it
actually IS dead...

I /tried/ to make this short, really!

Any advice will be greatly appreciated.

(NB: I also posted this to several audio groups - had to post
this separately since eternal sept will not allow me to
crosspost to this group, possibly since it has no hierarchy in
the group name.)


--
Any mental activity is easy if it need not be subjected to
reality.

n0i 09-08-2010 11:51 PM

Re: Phono preamp in old receiver problem
 
On 9/8/2010 7:15 PM, thanatoid wrote:
> Hi gang,
>
> I have an old Sharp AM/FM receiver with an 8-track player. Made
> in Japan ca. 1975 or something. It had a BSR turntable which was
> broken. I removed the seized turntable, cleaned the whole unit,
> sprayed all the pots, replaced the three little 6V bulbs behind
> the black/green tuner window, and it is fabulous. It's built
> like a tank and weighs a ton. The pots feel like military grade
> stuff. The function switches are simply unbelievable. The front
> panel is white (OK, bone now) with black controls, the box is
> all wood with the then-standard "vinyl wood veneer".
>
> I have a spare turntable which works perfectly. I intended to
> connect it to the phono preamp of this receiver. I did, but I am
> not getting sound. I am getting low-frequency pink noise, but no
> audio signal. What is even stranger is that I hear one of the
> channels "pop" when I dis/connect ONE of the two RCA audio
> cables going into the phono preamp of the receiver. I tested all
> the cables after extending them, and they are OK (see below).
>
> I tried connecting the turntable signal to the line input, and
> it DOES work. Of course, the signal is VERY low, but you CAN
> hear the LP playing with the volume full up. So either I DID
> somehow **** up the audio cable assembly (it tests OK though!)
> or the phono preamp is partially or totally NG, in which case
> there is probably nothing that can be done.
>
> The line inputs can be used for a CD/DVD player, the receiver
> works as a 4-speaker unit or 2 main/2 remote speakers, and it
> sounds great. AM and line in are loud as hell, FM volume is
> about 30% of that, but still usable.
>
> Does anyone have any idea what I should do first? I want to
> determine exactly /what/ in the chain from the *turntable audio
> cables/cable extensions/original RCA plugs and cable/circuit
> board* is NG.
>
> (The phonograph audio cables were only long enough to reach the
> bottom of the turntable, which was 3 inches above the main
> circuit board, now they have to reach to the back and out of the
> unit, so I had to add about 8 inches of cable - but I tested the
> cables, both channels, live /and/ ground, and I made NO mistakes
> - everything was connected/soldered correctly.
>
> If the phono preamp is dead, it's dead. The unit is still a
> /great/ AM (and decent FM) receiver and line-in amplifier,
> handles TWO sets of stereo speakers, and it will outlast all of
> us. I have yet to find an 8-track cartridge, but the mechanism
> and all the belts seem fine. Plus I don't think anyone needs an
> 8-track deck, while /quite/ a few people might enjoy having a
> receiver with a phono preamp. Unless the phono preamp IS dead,
> of course. But maybe someone can help me determine if it
> actually IS dead...
>
> I /tried/ to make this short, really!
>
> Any advice will be greatly appreciated.
>
> (NB: I also posted this to several audio groups - had to post
> this separately since eternal sept will not allow me to
> crosspost to this group, possibly since it has no hierarchy in
> the group name.)
>
>


Have you checked for bad solder connections? The older an amp gets the
worse the connections can be. heat/expansion/cool/contraction...

Also, what exactly was wrong with the old BSR TT?

n0i


PeeCee 09-09-2010 01:42 AM

Re: Phono preamp in old receiver problem
 

"philo" <philo@privacy.net> wrote in message
news:0vqdnRadkY5RvhXRnZ2dnUVZ_vKdnZ2d@ntd.net...
>
> "thanatoid" <waiting@the.exit.invalid> wrote in message
> news:Xns9DEDB9C364E63thanexit@81.169.183.62...
>> Hi gang,
>>
>> I have an old Sharp AM/FM receiver with an 8-track player. Made
>> in Japan ca. 1975 or something. It had a BSR turntable which was
>> broken. I removed the seized turntable, cleaned the whole unit,
>> sprayed all the pots, replaced the three little 6V bulbs behind
>> the black/green tuner window, and it is fabulous. It's built
>> like a tank and weighs a ton. The pots feel like military grade
>> stuff. The function switches are simply unbelievable. The front
>> panel is white (OK, bone now) with black controls, the box is
>> all wood with the then-standard "vinyl wood veneer".
>>
>> I have a spare turntable which works perfectly. I intended to
>> connect it to the phono preamp of this receiver. I did, but I am
>> not getting sound. I am getting low-frequency pink noise, but no
>> audio signal. What is even stranger is that I hear one of the
>> channels "pop" when I dis/connect ONE of the two RCA audio
>> cables going into the phono preamp of the receiver. I tested all
>> the cables after extending them, and they are OK (see below).
>>
>> I tried connecting the turntable signal to the line input, and
>> it DOES work. Of course, the signal is VERY low, but you CAN
>> hear the LP playing with the volume full up. So either I DID
>> somehow **** up the audio cable assembly (it tests OK though!)
>> or the phono preamp is partially or totally NG, in which case
>> there is probably nothing that can be done.
>>
>> The line inputs can be used for a CD/DVD player, the receiver
>> works as a 4-speaker unit or 2 main/2 remote speakers, and it
>> sounds great. AM and line in are loud as hell, FM volume is
>> about 30% of that, but still usable.
>>
>> Does anyone have any idea what I should do first? I want to
>> determine exactly /what/ in the chain from the *turntable audio
>> cables/cable extensions/original RCA plugs and cable/circuit
>> board* is NG.
>>
>> (The phonograph audio cables were only long enough to reach the
>> bottom of the turntable, which was 3 inches above the main
>> circuit board, now they have to reach to the back and out of the
>> unit, so I had to add about 8 inches of cable - but I tested the
>> cables, both channels, live /and/ ground, and I made NO mistakes
>> - everything was connected/soldered correctly.
>>
>> If the phono preamp is dead, it's dead. The unit is still a
>> /great/ AM (and decent FM) receiver and line-in amplifier,
>> handles TWO sets of stereo speakers, and it will outlast all of
>> us. I have yet to find an 8-track cartridge, but the mechanism
>> and all the belts seem fine. Plus I don't think anyone needs an
>> 8-track deck, while /quite/ a few people might enjoy having a
>> receiver with a phono preamp. Unless the phono preamp IS dead,
>> of course. But maybe someone can help me determine if it
>> actually IS dead...
>>
>> I /tried/ to make this short, really!
>>
>> Any advice will be greatly appreciated.
>>
>> (NB: I also posted this to several audio groups - had to post
>> this separately since eternal sept will not allow me to
>> crosspost to this group, possibly since it has no hierarchy in
>> the group name.)
>>
>>
>>

>
> If you do not have an audio signal generator to test the pre-amp...
> you can just put a wire to the input
> and touch it...
> if the pre-amp is working you should get a loud buzz or hum
>



Reminds me of the classic request to have a look at a
radio/gramophone/whatever thats 'probably only got a broken wire' !!!!
(notes carefully polished valves with all the markings buffed off and forced
into the wrong sockets)

Best I ever had was a TT that wouldn't work because the owner wanted to add
a CD player input so he cut the 'red' wire to the TT 'because it was the
most logical'
(he was a teacher after all and 'knew' about these things)
He was not best pleased when he discovered he'd cut the 12v DC to the TT and
in the process cooked the regulated power supply on the PCB because he did
it with the power on.
:-)
P.


philo 09-09-2010 06:22 AM

Re: Phono preamp in old receiver problem
 
On 09/08/2010 08:42 PM, PeeCee wrote:
>
> "philo" <philo@privacy.net> wrote in message
> news:0vqdnRadkY5RvhXRnZ2dnUVZ_vKdnZ2d@ntd.net...
>>
>> "thanatoid" <waiting@the.exit.invalid> wrote in message
>> news:Xns9DEDB9C364E63thanexit@81.169.183.62...
>>> Hi gang,
>>>
>>>


<snip>
d/ to make this short, really!
>>>
>>> Any advice will be greatly appreciated.
>>>
>>> (NB: I also posted this to several audio groups - had to post
>>> this separately since eternal sept will not allow me to
>>> crosspost to this group, possibly since it has no hierarchy in
>>> the group name.)
>>>
>>>
>>>

>>
>> If you do not have an audio signal generator to test the pre-amp...
>> you can just put a wire to the input
>> and touch it...
>> if the pre-amp is working you should get a loud buzz or hum
>>

>
>
> Reminds me of the classic request to have a look at a
> radio/gramophone/whatever thats 'probably only got a broken wire' !!!!
> (notes carefully polished valves with all the markings buffed off and
> forced into the wrong sockets)
>
> Best I ever had was a TT that wouldn't work because the owner wanted to
> add a CD player input so he cut the 'red' wire to the TT 'because it was
> the most logical'
> (he was a teacher after all and 'knew' about these things)
> He was not best pleased when he discovered he'd cut the 12v DC to the TT
> and in the process cooked the regulated power supply on the PCB because
> he did it with the power on.
> :-)
> P.



I must have at least 16 vacuum tube radios in my house...

The other day I moved one and wow was it dusty back there!

NotMe 09-09-2010 02:44 PM

Re: Phono preamp in old receiver problem
 

"thanatoid" <waiting@the.exit.invalid> wrote in message
news:Xns9DEDB9C364E63thanexit@81.169.183.62...
> Hi gang,
>
> I have an old Sharp AM/FM receiver with an 8-track player. Made
> in Japan ca. 1975 or something. It had a BSR turntable which was
> broken. I removed the seized turntable, cleaned the whole unit,
> sprayed all the pots, replaced the three little 6V bulbs behind
> the black/green tuner window, and it is fabulous. It's built
> like a tank and weighs a ton. The pots feel like military grade
> stuff. The function switches are simply unbelievable. The front
> panel is white (OK, bone now) with black controls, the box is
> all wood with the then-standard "vinyl wood veneer".
>
> I have a spare turntable which works perfectly. I intended to
> connect it to the phono preamp of this receiver. I did, but I am
> not getting sound. I am getting low-frequency pink noise, but no
> audio signal. What is even stranger is that I hear one of the
> channels "pop" when I dis/connect ONE of the two RCA audio
> cables going into the phono preamp of the receiver. I tested all
> the cables after extending them, and they are OK (see below).
>
> I tried connecting the turntable signal to the line input, and
> it DOES work. Of course, the signal is VERY low, but you CAN
> hear the LP playing with the volume full up. So either I DID
> somehow **** up the audio cable assembly (it tests OK though!)
> or the phono preamp is partially or totally NG, in which case
> there is probably nothing that can be done.
>
> The line inputs can be used for a CD/DVD player, the receiver
> works as a 4-speaker unit or 2 main/2 remote speakers, and it
> sounds great. AM and line in are loud as hell, FM volume is
> about 30% of that, but still usable.
>
> Does anyone have any idea what I should do first? I want to
> determine exactly /what/ in the chain from the *turntable audio
> cables/cable extensions/original RCA plugs and cable/circuit
> board* is NG.
>
> (The phonograph audio cables were only long enough to reach the
> bottom of the turntable, which was 3 inches above the main
> circuit board, now they have to reach to the back and out of the
> unit, so I had to add about 8 inches of cable - but I tested the
> cables, both channels, live /and/ ground, and I made NO mistakes
> - everything was connected/soldered correctly.
>
> If the phono preamp is dead, it's dead. The unit is still a
> /great/ AM (and decent FM) receiver and line-in amplifier,
> handles TWO sets of stereo speakers, and it will outlast all of
> us. I have yet to find an 8-track cartridge, but the mechanism
> and all the belts seem fine. Plus I don't think anyone needs an
> 8-track deck, while /quite/ a few people might enjoy having a
> receiver with a phono preamp. Unless the phono preamp IS dead,
> of course. But maybe someone can help me determine if it
> actually IS dead...
>
> I /tried/ to make this short, really!
>
> Any advice will be greatly appreciated.
>
> (NB: I also posted this to several audio groups - had to post
> this separately since eternal sept will not allow me to
> crosspost to this group, possibly since it has no hierarchy in
> the group name.)
>
>


Been decades since I did any audio work on that sort of hardware. My SWAG
would be an impedance problem. Perhaps an audio transformer on the input?



hwf 09-09-2010 02:58 PM

Re: Phono preamp in old receiver problem
 
thanatoid wrote:
> Hi gang,
>

Not yet...

> I have an old Sharp AM/FM receiver with an 8-track player. Made
> in Japan ca. 1975 or something. It had a BSR turntable which was
> broken. I removed the seized turntable,


You shoulda stopped right there. If youda fix'd that you woulda had the
right turntable for the rest of the system.

SHAME ON YOU.

--
www.skepticalscience.com|www.youtube.com/officialpeta
cageprisoners.com|www.snuhwolf.9f.com|www.eyeonpalin.org
_____ ____ ____ __ /\_/\ __ _ ______ _____
/ __/ |/ / / / / // // . . \\ \ |\ | / __ \ \ \ __\
_\ \/ / /_/ / _ / \ / \ \| \| \ \_\ \ \__\ _\
/___/_/|_/\____/_//_/ \_@_/ \__|\__|\____/\____\_\



BinaryBillThe Sailor@Sea++.com 09-09-2010 03:22 PM

Re: Phono preamp in old receiver problem
 
On Thu, 9 Sep 2010 09:44:17 -0500, "NotMe" <me@privacy.net> wrote:

>
>"thanatoid" <waiting@the.exit.invalid> wrote in message
>news:Xns9DEDB9C364E63thanexit@81.169.183.62...
>> Hi gang,
>>
>> I have an old Sharp AM/FM receiver with an 8-track player. Made
>> in Japan ca. 1975 or something. It had a BSR turntable which was
>> broken. I removed the seized turntable, cleaned the whole unit,
>> sprayed all the pots, replaced the three little 6V bulbs behind
>> the black/green tuner window, and it is fabulous. It's built
>> like a tank and weighs a ton. The pots feel like military grade
>> stuff. The function switches are simply unbelievable. The front
>> panel is white (OK, bone now) with black controls, the box is
>> all wood with the then-standard "vinyl wood veneer".
>>
>> I have a spare turntable which works perfectly. I intended to
>> connect it to the phono preamp of this receiver. I did, but I am
>> not getting sound. I am getting low-frequency pink noise, but no
>> audio signal. What is even stranger is that I hear one of the
>> channels "pop" when I dis/connect ONE of the two RCA audio
>> cables going into the phono preamp of the receiver. I tested all
>> the cables after extending them, and they are OK (see below).
>>
>> I tried connecting the turntable signal to the line input, and
>> it DOES work. Of course, the signal is VERY low, but you CAN
>> hear the LP playing with the volume full up. So either I DID
>> somehow **** up the audio cable assembly (it tests OK though!)
>> or the phono preamp is partially or totally NG, in which case
>> there is probably nothing that can be done.
>>
>> The line inputs can be used for a CD/DVD player, the receiver
>> works as a 4-speaker unit or 2 main/2 remote speakers, and it
>> sounds great. AM and line in are loud as hell, FM volume is
>> about 30% of that, but still usable.
>>
>> Does anyone have any idea what I should do first? I want to
>> determine exactly /what/ in the chain from the *turntable audio
>> cables/cable extensions/original RCA plugs and cable/circuit
>> board* is NG.
>>
>> (The phonograph audio cables were only long enough to reach the
>> bottom of the turntable, which was 3 inches above the main
>> circuit board, now they have to reach to the back and out of the
>> unit, so I had to add about 8 inches of cable - but I tested the
>> cables, both channels, live /and/ ground, and I made NO mistakes
>> - everything was connected/soldered correctly.
>>
>> If the phono preamp is dead, it's dead. The unit is still a
>> /great/ AM (and decent FM) receiver and line-in amplifier,
>> handles TWO sets of stereo speakers, and it will outlast all of
>> us. I have yet to find an 8-track cartridge, but the mechanism
>> and all the belts seem fine. Plus I don't think anyone needs an
>> 8-track deck, while /quite/ a few people might enjoy having a
>> receiver with a phono preamp. Unless the phono preamp IS dead,
>> of course. But maybe someone can help me determine if it
>> actually IS dead...
>>
>> I /tried/ to make this short, really!
>>
>> Any advice will be greatly appreciated.
>>
>> (NB: I also posted this to several audio groups - had to post
>> this separately since eternal sept will not allow me to
>> crosspost to this group, possibly since it has no hierarchy in
>> the group name.)
>>
>>

>
>Been decades since I did any audio work on that sort of hardware. My SWAG
>would be an impedance problem. Perhaps an audio transformer on the input?
>


Why not start with the really easy and basic stuff that even a
non-tech can check. Their may be corrosion on the little slide on
connetors for the wires where they attach to the phono cartridge after
sitting for so many years. Unplug each one and then simply plug it
back on the pin it came off of.

It could also be a bum phono cartridge. easy enough to check for a
buzz when yu touch those connections. If they cause a loud buzz or hum
when you touch them, but there is no sound when you touch the needle,
the cartidge is bad.

You could also try plugging the turntable into the regular line in to
see iof there is ANY output. It will sound tinny, but it will tell you
if the turntable, cartridge, and wires are all intact.


joevan 09-09-2010 03:39 PM

Re: Phono preamp in old receiver problem
 
On Thu, 09 Sep 2010 11:22:25 -0400, BinaryBillThe Sailor@Sea++.com
wrote:

>On Thu, 9 Sep 2010 09:44:17 -0500, "NotMe" <me@privacy.net> wrote:
>
>>
>>"thanatoid" <waiting@the.exit.invalid> wrote in message
>>news:Xns9DEDB9C364E63thanexit@81.169.183.62...
>>> Hi gang,
>>>
>>> I have an old Sharp AM/FM receiver with an 8-track player. Made
>>> in Japan ca. 1975 or something. It had a BSR turntable which was
>>> broken. I removed the seized turntable, cleaned the whole unit,
>>> sprayed all the pots, replaced the three little 6V bulbs behind
>>> the black/green tuner window, and it is fabulous. It's built
>>> like a tank and weighs a ton. The pots feel like military grade
>>> stuff. The function switches are simply unbelievable. The front
>>> panel is white (OK, bone now) with black controls, the box is
>>> all wood with the then-standard "vinyl wood veneer".
>>>
>>> I have a spare turntable which works perfectly. I intended to
>>> connect it to the phono preamp of this receiver. I did, but I am
>>> not getting sound. I am getting low-frequency pink noise, but no
>>> audio signal. What is even stranger is that I hear one of the
>>> channels "pop" when I dis/connect ONE of the two RCA audio
>>> cables going into the phono preamp of the receiver. I tested all
>>> the cables after extending them, and they are OK (see below).
>>>
>>> I tried connecting the turntable signal to the line input, and
>>> it DOES work. Of course, the signal is VERY low, but you CAN
>>> hear the LP playing with the volume full up. So either I DID
>>> somehow **** up the audio cable assembly (it tests OK though!)
>>> or the phono preamp is partially or totally NG, in which case
>>> there is probably nothing that can be done.
>>>
>>> The line inputs can be used for a CD/DVD player, the receiver
>>> works as a 4-speaker unit or 2 main/2 remote speakers, and it
>>> sounds great. AM and line in are loud as hell, FM volume is
>>> about 30% of that, but still usable.
>>>
>>> Does anyone have any idea what I should do first? I want to
>>> determine exactly /what/ in the chain from the *turntable audio
>>> cables/cable extensions/original RCA plugs and cable/circuit
>>> board* is NG.
>>>
>>> (The phonograph audio cables were only long enough to reach the
>>> bottom of the turntable, which was 3 inches above the main
>>> circuit board, now they have to reach to the back and out of the
>>> unit, so I had to add about 8 inches of cable - but I tested the
>>> cables, both channels, live /and/ ground, and I made NO mistakes
>>> - everything was connected/soldered correctly.
>>>
>>> If the phono preamp is dead, it's dead. The unit is still a
>>> /great/ AM (and decent FM) receiver and line-in amplifier,
>>> handles TWO sets of stereo speakers, and it will outlast all of
>>> us. I have yet to find an 8-track cartridge, but the mechanism
>>> and all the belts seem fine. Plus I don't think anyone needs an
>>> 8-track deck, while /quite/ a few people might enjoy having a
>>> receiver with a phono preamp. Unless the phono preamp IS dead,
>>> of course. But maybe someone can help me determine if it
>>> actually IS dead...
>>>
>>> I /tried/ to make this short, really!
>>>
>>> Any advice will be greatly appreciated.
>>>
>>> (NB: I also posted this to several audio groups - had to post
>>> this separately since eternal sept will not allow me to
>>> crosspost to this group, possibly since it has no hierarchy in
>>> the group name.)
>>>
>>>

>>
>>Been decades since I did any audio work on that sort of hardware. My SWAG
>>would be an impedance problem. Perhaps an audio transformer on the input?
>>

>
>Why not start with the really easy and basic stuff that even a
>non-tech can check. Their may be corrosion on the little slide on
>connetors for the wires where they attach to the phono cartridge after
>sitting for so many years. Unplug each one and then simply plug it
>back on the pin it came off of.
>
>It could also be a bum phono cartridge. easy enough to check for a
>buzz when yu touch those connections. If they cause a loud buzz or hum
>when you touch them, but there is no sound when you touch the needle,
>the cartidge is bad.
>
>You could also try plugging the turntable into the regular line in to
>see iof there is ANY output. It will sound tinny, but it will tell you
>if the turntable, cartridge, and wires are all intact.

How about some industrial contact cleaner on all connections.

thanatoid 09-09-2010 03:46 PM

Re: Phono preamp in old receiver problem
 
n0i <thunderstruck_n0i@live> wrote in
news:45a3d$4c8820d3$4a533956$8524@FUSE.NET:

> Have you checked for bad solder connections? The older an
> amp gets the
> worse the connections can be.
> heat/expansion/cool/contraction...
>
> Also, what exactly was wrong with the old BSR TT?


Thanks for your reply. Everything else works, all solder
connections appear good, AND the BSR turntable HAD sound -
please *see below* for the full (REALLY full, sorry) answer
incl. your BSR q. reply:

-- Update (very long, I apologize!) --

First of all, many thanks to all who replied. It is very much
appreciated.

Now for the /bad/ part.

Something one person mentioned in his reply made me remember a
rather *crucial* detail which I had forgotten (I am not
completely senile yet, but I have been /incredibly/ busy for the
last few weeks, and my brain is running out of RAM).

It is this: BEFORE I removed the BSR turntable, I DID check to
see whether there was AUDIO SIGNAL coming from it. There was,
loud and clear - when I touched the stylus, it sounded like an
earthquake. Very little "system noise", too.

The turntable itself was "seized" - after I have (with some
violence) managed to take it apart, I saw that the 2 main cog
wheels of the belt-less motor were practically frozen together
at a bizarre angle and would NOT budge. I have NO idea how that
happened - and the 4" screwdriver shaft, 2 children's plastic
letters with magnets, and assorted bits of 30+ year old food I
found inside the receiver could NOT have had anything to do with
it, either, since the BSR motor was fairly well enclosed within
the /incredibly/ complicated mechanical design (a changer).

Now that I have remembered this, it is obvious I screwed
something up. I have never seen a ceramic cartridge, but I am
99.99% positive that BOTH the BSR and the Sony (ca. 1990)
turntable carts are magnetic. So, since I have no signal but
weird pink noise, I must have screwed up the cables. Or do you
think I may have destroyed the preamp?

(This may be a good moment to mention that I am using the term
"phono preamp" in a generic sense. I always thought a phono
preamp might be/would be a small enclosed piece of electronics,
but in this receiver, it appears to be a part of the main
circuit board - the two original (and now extended) cables from
the BSR turntable stylus/arm are soldered right onto the circuit
board, and go who-knows-where - presumably, into components
which make up this receiver's "phone preamp" section.)

(THIS may /also/ be a good moment to mention that while I have
had some disastrous luck with simple things and astoundingly
good luck with complicated things, I am NOT a technician, and do
not own an oscilloscope - I check connections with two gator
clips connected to a 1.5V battery with a flashlight bulb, and
after over 30 years of "considering it", I finally bought a five
dollar "voltmeter" which /appears/ to work - I found out a cheap
110V/22V AC/DC adapter outputs 25VDC when set to 12V output
[when the input voltage is set to 110V] and 12.5VDC from its 9V
setting [when the input voltage is set to 110V (it is 110V
here)]. The Sony turntable (originally a component of a system,
with a tiny power connector which plugs into the back of the
main system unit and where I found out 12VDC is output) is
running on a supposedly "regulated" fancy Radio Shack AC/DC
adapter which puts out 11.8V DC. (When I reverse the polarity,
the turntable spins backwards.)

If anyone has read this far, please accept my deep thanks for
your patience. I can't write more concisely - I realize it's an
illness.

Anyway - the question now is WHAT did I do to mess things up?
Since I consider the receiver largely indestructible, I do not
think I have *destroyed* anything, not to mention the voltages
involved are totally minuscule and it being a solid state unit -
as the front panel proudly states ;-) - there is little danger
of blowing it up. Plus everything else works.

My plan is as follows:

1. Cut the original "BSR cartridge/turntable to the main circuit
board" cables, strip ends.
2. Attach gator clips to them and connect to the Sony turntable
output cable.
3. Hopefully, hear sound. Extend cables again, making SURE I
don't screw up this time.

If I hear no sound, I will connect the 4 very thin cables from
the original BSR cartridge (I saved the cart assembly and cables
before I saw the turntable was connected to the circuit board
with 2 standard cables with RCA plugs) to the cut cables leading
to the circuit board and see if I hear anything. If I do, I will
post for more advice.

But for now, my question is:

If after doing all this, I still get the /same/ pink noise (NOT
hum - strange, huh?) and get NO audio, WHAT do I do?

Thank you /very much/ for your patience, and my apologies for
having forgotten a crucial part of the puzzle. Further help will
be greatly appreciated. If anyone wants to see pix of the 2
cartridges or the circuit board where the phono audio cables are
soldered into it, I can post them to photobucket or something,
OR a binary group if you have binaries access.

The replies are different in every one of the 5 groups, so I
will post this followup to each group separately. I don't really
understand how crossposting works, since I never do it, and
eternal september /may/ be "funny" about crossposting to boot.


--
Any mental activity is easy if it need not be subjected to
reality.

thanatoid 09-09-2010 03:46 PM

Re: Phono preamp in old receiver problem
 
"philo" <philo@privacy.net> wrote in
news:0vqdnRadkY5RvhXRnZ2dnUVZ_vKdnZ2d@ntd.net:

<snip>

> If you do not have an audio signal generator to test the
> pre-amp... you can just put a wire to the input
> and touch it...
> if the pre-amp is working you should get a loud buzz or hum


Thanks for the reply... I can't find the pre-amp (see below).

-- Update (very long, I apologize!) --

First of all, many thanks to all who replied. It is very much
appreciated.

Now for the /bad/ part.

Something one person mentioned in his reply made me remember a
rather *crucial* detail which I had forgotten (I am not
completely senile yet, but I have been /incredibly/ busy for the
last few weeks, and my brain is running out of RAM).

It is this: BEFORE I removed the BSR turntable, I DID check to
see whether there was AUDIO SIGNAL coming from it. There was,
loud and clear - when I touched the stylus, it sounded like an
earthquake. Very little "system noise", too.

The turntable itself was "seized" - after I have (with some
violence) managed to take it apart, I saw that the 2 main cog
wheels of the belt-less motor were practically frozen together
at a bizarre angle and would NOT budge. I have NO idea how that
happened - and the 4" screwdriver shaft, 2 children's plastic
letters with magnets, and assorted bits of 30+ year old food I
found inside the receiver could NOT have had anything to do with
it, either, since the BSR motor was fairly well enclosed within
the /incredibly/ complicated mechanical design (a changer).

Now that I have remembered this, it is obvious I screwed
something up. I have never seen a ceramic cartridge, but I am
99.99% positive that BOTH the BSR and the Sony (ca. 1990)
turntable carts are magnetic. So, since I have no signal but
weird pink noise, I must have screwed up the cables. Or do you
think I may have destroyed the preamp?

(This may be a good moment to mention that I am using the term
"phono preamp" in a generic sense. I always thought a phono
preamp might be/would be a small enclosed piece of electronics,
but in this receiver, it appears to be a part of the main
circuit board - the two original (and now extended) cables from
the BSR turntable stylus/arm are soldered right onto the circuit
board, and go who-knows-where - presumably, into components
which make up this receiver's "phone preamp" section.)

(THIS may /also/ be a good moment to mention that while I have
had some disastrous luck with simple things and astoundingly
good luck with complicated things, I am NOT a technician, and do
not own an oscilloscope - I check connections with two gator
clips connected to a 1.5V battery with a flashlight bulb, and
after over 30 years of "considering it", I finally bought a five
dollar "voltmeter" which /appears/ to work - I found out a cheap
110V/22V AC/DC adapter outputs 25VDC when set to 12V output
[when the input voltage is set to 110V] and 12.5VDC from its 9V
setting [when the input voltage is set to 110V (it is 110V
here)]. The Sony turntable (originally a component of a system,
with a tiny power connector which plugs into the back of the
main system unit and where I found out 12VDC is output) is
running on a supposedly "regulated" fancy Radio Shack AC/DC
adapter which puts out 11.8V DC. (When I reverse the polarity,
the turntable spins backwards.)

If anyone has read this far, please accept my deep thanks for
your patience. I can't write more concisely - I realize it's an
illness.

Anyway - the question now is WHAT did I do to mess things up?
Since I consider the receiver largely indestructible, I do not
think I have *destroyed* anything, not to mention the voltages
involved are totally minuscule and it being a solid state unit -
as the front panel proudly states ;-) - there is little danger
of blowing it up. Plus everything else works.

My plan is as follows:

1. Cut the original "BSR cartridge/turntable to the main circuit
board" cables, strip ends.
2. Attach gator clips to them and connect to the Sony turntable
output cable.
3. Hopefully, hear sound. Extend cables again, making SURE I
don't screw up this time.

If I hear no sound, I will connect the 4 very thin cables from
the original BSR cartridge (I saved the cart assembly and cables
before I saw the turntable was connected to the circuit board
with 2 standard cables with RCA plugs) to the cut cables leading
to the circuit board and see if I hear anything. If I do, I will
post for more advice.

But for now, my question is:

If after doing all this, I still get the /same/ pink noise (NOT
hum - strange, huh?) and get NO audio, WHAT do I do?

Thank you /very much/ for your patience, and my apologies for
having forgotten a crucial part of the puzzle. Further help will
be greatly appreciated. If anyone wants to see pix of the 2
cartridges or the circuit board where the phono audio cables are
soldered into it, I can post them to photobucket or something,
OR a binary group if you have binaries access.

The replies are different in every one of the 5 groups, so I
will post this followup to each group separately. I don't really
understand how crossposting works, since I never do it, and
eternal september /may/ be "funny" about crossposting to boot.


--
Any mental activity is easy if it need not be subjected to
reality.


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