curious symptom old Fisher stereo amp, inputs strange - Page 2

On Friday, January 11, 2019 at 9:26:30 AM UTC-5, Tim R wrote:

ch jack) disconnects speakers automatically.  There's no way to have both r
oom sound and headphone sound.  Still it's nice to have this working again.

This is a very common setup.  I have received units with no sound that turn
ed out to be a failure of the headphone jack.  Without the headphones, the  
jack shorts the signal line to allow it to continue to the amp.  If the jac
k does not short, then no sound.  Rare, but I have seen it a number of time
s over the years.

Tim R:

Are there buttons or switches on that Fisher amp  
for selecting pairs of speakers?

:


Yes.
There are two sets of speaker outputs, the A and the B.
There is a little square pushbutton, marked out for A and in for B.  
With the headphone inserted, there is no sound from A whether the button is
 in or out.  I've never put speakers on B so I've not tested that set.  

Apparently you can't use two sets of speakers at the same time, or one set  
plus headphones.  That seems curious to me.  My other stereo amps don't wor
k that way.  But I'm not complaining, this little amp is perfect for what I
 use it for, a portable amp to get sound from a laptop I bring to various p
laces.  

On Sunday, January 13, 2019 at 7:09:40 AM UTC-5, Tim R wrote:

te:

is in or out.  I've never put speakers on B so I've not tested that set.  

t plus headphones.  That seems curious to me.  My other stereo amps don't w
ork that way.  But I'm not complaining, this little amp is perfect for what
 I use it for, a portable amp to get sound from a laptop I bring to various
 places.

To further complicate things, I remember working on some cheaper amps that  
would put the A speakers in series with the B speakers if both A and B were
 selected so as not to kill the outputs with too low impedance.  So if you  
had a pair of speakers on A and nothing on B, pushing the B would kill all  
sound.  Used to get a few nuisance calls over that.

Tim R:

Since there are speaker selectors then the speakers, in theory,  
should not be canceled by plugging in headphones. On my 1990s
era JVC receiver, I have to remember to deselect all speakers  
when listening via headphones, or I'll still be sharing what I'm  
listening to with the wife - or the neighbors...!  And speakers on  
buss A, B, or both can still be driven with it while listening to  
headphones, so I have to remember to select them out.

Sounds like yours has got some serious main board(motherboard to
us PC geeks) issues, or soldering issues.

On Sunday, January 13, 2019 at 3:23:25 PM UTC-5, snipped-for-privacy@gmail.com wrote:


Well, I dunno about that.
Most equipment I've had if the headphone jack was 1/8, it would disconnect speakers, and if 1/4, not.
But looking at this CA-400, I can only select A or B speakers.  I can't choose none.  So it makes sense that the headphone would disconnect them.  Maybe it's working properly.  

Tim R:

My old 1980s Sears one-piece Tuner/Phono/Cassette  
had 1/4" headphone out, and it cancelled the speakers
when I plugged cans into it, just as the 1/8" on my  
later bookshelf CD/Tuner/Aux.

That Fisher though sounds like one of a kind!

wrote:


It is. A very common configuration.

If the switch was a mecanical rotary switch, the inputs would go to the  
separate pins on the switch, and the selected input would then be  
connected to the viper and the tape out, and further through the volume  
and tone controls to the output stage.

So the switch, whether mecanical or electronic, is dead, and you are  
feeding the signal directly into the volume/tone controls.

If you don't need the other inputs, I would just cut my losses and the  
connection to the switch, and just feed into the tape out, obviously  
the tape out is not buffered, otherwise you would be trying to feed  
signal backwards into an amplifier, which would not work.

A HiFi-nut would probably replace the switch with goldplated reed  
relays anyway :-)

Leif

On some receivers/amps, the "Tape Out" RCAs were where you
connected the output FROM the cassette/tape deck - to hear
it back.  Counter-intuitive, and took me time to figger out!  :)

On Monday, May 18, 2015 at 8:21:43 PM UTC-4, snipped-for-privacy@gmail.com wrote:


Okay, this is a Fisher CA-400.

It has 5 sets of L and R RCAs on the back.  They are marked Phono, Tuner, C
D-Aux, REC OUT Tape, P.B. Tape.  The only one that seems to work is REC OUT
.

On the front there are 4 pushbuttons, for Phono, Tuner, CD-Aux, and Tape Mo
nitor.  All the buttons push in and lock, but no indicator lights of any ki
nd appear anywhere.  The power indicator light does come on.  

It says 250 Watts on the back.  It's a compact unit, the sound was not too  
bad out of it, even driving some home entertainment speakers.  It would be  
nice if it worked.  But if repair is more than a parts swap it will be beyo
nd me.  In my youth I held an Amateur Extra Class (NX9L) and I did some pro
jects, but those days are far behind.  

I can't seem to get a print for that unit but from what you wrote I owuld bet you have a 12 volt regulator out.  

If it has mechanical switches, you say the "lock" in, then it does not use that unobtainium IC. It might use some 4066 type CMOS switches but those are easy to get. But the fact there are lights not lighting means likely a supply is missing.  

On Wednesday, May 20, 2015 at 11:12:36 AM UTC-4, snipped-for-privacy@gmail.com wrote:

 bet you have a 12 volt regulator out.  

e that unobtainium IC. It might use some 4066 type CMOS switches but those  
are easy to get. But the fact there are lights not lighting means likely a  
supply is missing.

There are also a couple of weird outlets near the speaker terminals that ap
pear to supply voltage to components.  

I was going to throw this thing away.  But if you think it's safe to use pu
tting the input into the output sockets, maybe it is useful as is.  (I mean
 safe as in not failing when I need it most in public.)  

My memory is not reliable but I think I used it as a home stereo amplifying
 my laptop and feeding a couple of regular stereo speakers.  And when one c
hannel stopped working I moved the inputs over one, not realizing I was usi
ng an output, and it worked again.  

Yes, the perhiperahls ere not stand alone. Some called these rak suystems,  
I called them frack systems for "fake rack". But the amps did have juice. W
hatever of these are left, the perips are usually gone but the amp remaians
, maininly because it was nevr bat on propoerly, overheated ad fried out. F
isher did alot of shitty shit back then. Some units were OK though, for exa
mple my garage stereo is a CA-885. Don't borher looking it upo there is alm
ost zero info on it. It is close to 200 WPC and just doesn't care. In fact  
it puts out over 200 WPC bu I havn't tried to measure it accurately. All I  
know is it ran the lathe off the speaker wires just fine. (JK)

Those outlets are usually aboiut 12 V AC or so. Yuo DO NOT have to use thei
r particular perips, anything that pliugs in the wall wil work as long as y
ou got cables to hook up thre audio signal. You can ru that amop with amnyt
hing, it is just the juk they sold with it is dependent upon that amp for a
 power source. It does not work both ways.  

Bnottom linee, I bet you smack that thing hard on the fround it works. And  
I bet you find bad connections on a three terminal device that says sometin
g like "7812" on it.

snipped-for-privacy@gmail.com wrote:


https://www.samswebsite.com/en/photofact/details/index/id/50794

Paying for the manual would be alright if I was working on it here. But for someone on the web at random, no. Can't do that.  

Thanks anyway. Maybe the OP wants it though.  

Interesting that is an OEM manual they say. Usually they generated their own. Are they like a licensed reseller or something now ? they used to reverse engineer almost everything, but I know that has gotten more difficult by orders of magnitude.  

snipped-for-privacy@gmail.com wrote:



   They ended up with the huge collection of OEM manuals the NRI had,
when that school was shut down by McGraw-Hill. I once asked about
information on a 1938 Philco tombstone radio from NRI, and they mailed
me an original service manual for free, since I had taken a course at
one time.

   Sams only reverse engineered items that sold in excess of 20 thousand
units, but they collected OEM data on everything they could get their
hands on. They also wrote manuals for some company's products that
didn't meet the 20K unit minimum. Those were only available from the
OEMs.

wrote:



Tape out is an output, not an input. I have an older unit. It's for
putting the output to a tape recorder.

On Thursday, May 21, 2015 at 11:05:30 AM UTC-4, Evan Platt wrote:



Evan,
Here is my setup.  My HP laptop feeds an M-Audio Fast Track external sound card/USB interface.  RCA cables out of the M-Audio feed the Tape Out of the Fisher amplifier.  Plenty of loud sound comes out of the speakers.

I have also tried this with the Fast Track feeding an Input on a Pioneer amplifier.  Loud sound comes out of the speakers this way too.

Very clearly, the RCA sockets marked Output on the Fisher are functioning as an input.  Also clearly, the sockets marked Inputs on the Fisher don't do anything.

Something is broken.  Or, maybe outputs always work as inputs and I just never tried, I dunno.    

The tape out jack is essentially a fixed level audio out that comes from th
e switching IC.  If the IC is defective, you are likely backfeeding the IC  
from the output into the amp.  Replace the switching IC.  This is likely to
 be a TC9163 or an LAxxxx (I don't recall the number).

Dan