i love these little radio shack cassette decks so when i saw this one at the thrift store i knew i
had to get it even though it's filthy and when i tried it out with a tape it would not play or
fast forward or rewind so you'll probably need new belts but the price sticker on it is $6.99
but they had the 25 off sale on it so the total i paid including tax was $5.59 so for
five dollars in change i got myself a cassette player and hopefully we can get it working
this model was introduced in 1989 along with its big brother the auto reverse
version with dolby which was twice the price but here it is the realistic scp-31 for $49.95
available october 30th 1988 ideal for tight spaces they say it's a low-cost way to add cassette
capability to your existing stereo system or use in your office or dorm room where space is tight
metal and chrome or normal bias selector and then in 1991 they added another deck to that range of
compact cassette decks the one that records which i've featured in a video years ago the sct-86
so that was the complete range of these mini cassette decks from radio shack the scp-32
auto reverse play-only deck scp-31 low-cost playback deck and sct-86
recorder player on a budget the scp-32 auto reverse deck last appeared in the 1997 catalog
while the scp-31 playback deck continued until 2000 and the sct-86 recording deck lasted for one
more year until 2001 and then it was replaced with the rca sct-510 which i've also done a video about
like i said this thing is filthy these buttons are not supposed to look like that that's just
a lot of dirt in the little grooves in the buttons and on the bottom it looks
like somebody had this thing duct taped down to a counter somewhere unfortunately they ripped off
the part of the sticker that would tell us when it was made but sometime in the early 1990s this
was after they changed the brand from realistic to optimus but otherwise it's the same thing
so it's just the standard piano key button playback only deck it does have soft eject
which is nice and a switch to select normal and chrome or metal playback equalization although
it does not have dolby noise reduction and on the back the only thing besides the sticker
is just the audio output and the power cord and yes it was made in china the specifications for
the scp-31 aren't particularly impressive as you would expect from such an inexpensive deck
but at least the wow and flutter is a reasonable 0.15 percent
there's the mechanism it does have a stereo playback head
and it's your typical tanashin style mechanism it looks like it's seen quite
a bit of use because that pinch roller is looking rather glazed but otherwise
nothing really out of the ordinary i have it plugged in when i press play you can see
nothing's moving neither the takeup reel or the capstan same thing with fast forward and rewind
but when i engage any of the modes and hold my ear up to it i cannot hear the motor so instead
of possibly just being bad belts we may have a bad motor or some other kind of fault with this deck
just as i suspected it's a typical tanashin mechanism looks like it was genuine tanashin
judging by this part number stamped on it and the belts are fine those belts seem to be perfectly
fine the motor is a mabuchi eg-530ad 12 volt dc 2400 rpm counter clockwise a very typical
cassette deck motor and judging by that stamp in the cover it is a genuine mabuchi motor
here's the circuit board it has the power transformer bridge rectifier and a filter
capacitor and then all these electronics looks like most of it is in that shielded box to reduce
hum and interference from getting into the audio
so very simple circuit layout and very simple mechanism
i think this could simply have a bad power transformer because here i have
120 volts ac coming into the primary and on the secondary absolutely nothing
and you may be wondering did the power transformer burn out because we have a shorted rectifier
and i don't think so because if i measure the secondary it's measuring about 13 ohms
which sounds about right for the secondary of a power transformer so it's not a dead short
the markings on the transformer don't indicate the output voltage but i'm
guessing 12 volts ac considering that the motor is 12 volts dc it
does have a center tapped secondary but you can see that center tap is not used for anything
so what i'm going to do is just remove this built-in power transformer in this power cord
and install this it's a 12 volt ac power adapter 300 milliamps should be perfectly fine
for a cassette player it doesn't need that much current to run it has one of
these connectors on it but i can just cut that off and wire it in directly
this cheapo desoldering iron made quick work of removing the power transformer and thankfully
it wasn't too difficult to remove the old power cord from the strain relief so i can reuse that
here is the output of that 12 volt ac wall wart
fed through the original strain relief and stuffed into the holes of the secondary of the original
transformer and yes i did remember to snake it through the hole in the cover
and there it is soldered into place it's ac so polarity doesn't matter
so that's my modification to get this hopefully working again just remove the original dead power
transformer and wire in an external 12 volt ac power supply going through the original strain
relief onto the circuit board where the output of the original secondary of the transformer was
so i have it plugged in we should have approximately 12 volts ac coming out of it here
and 14.6 volts ac now the question is what is coming out of the rectifier
of this power supply on the board so we should be able to take
any ground on the circuit and measure it here and we have 19 volts coming out of it
i don't know that may be a little bit high but we'll see yeah i measured 16 volts going
into that 12 volt motor so i'm going to have to remove this and put in a 9 volt ac power supply
i replaced it with a 9 volt ac power transformer taken from a hayes modem
and now i have a much more reasonable 12.8 volts coming out of the rectifier
and when i engage play and measure the voltage on the motor itself
11.3 a little bit low compared to the 12 volts it's rated for but it should be perfectly fine
and there you can see the motor is spinning just fine with original belts
and i don't hear it whining or groaning or anything so the motor seems to be perfectly fine
if we look inside our take-up reel is spinning so
there's fast forward and there's rewind which kicks off the auto stop just like it should
so looks like the only thing wrong with this was that power transformer
now that i know that it's basically working i clean the heads
or head in this case because it's a playback only deck and capstan and pinch roller i've
shown that before in other videos so i didn't feel the need to show it again
to check the speed of the motor in this deck i'm going to use a little bit different of
a method than i usually do instead of using a special program on my computer
i have the line output of this deck connected to an audio amplifier in this case it just happens
to be another cassette recorder which i can monitor the input of through its built-in speaker
and i have my tablet running a frequency counter program so i'll engage the recording
monitor mode on this deck so we can hear what's coming through its input then i'll
take my test tape which has a three kilohertz tone on it stick it in this deck press play
and i don't think i need to do any adjustment
because that's pretty damn close to three kilohertz and it doesn't
even sound like it has a lot of wow and flutter
"if you're looking for the ultimate in stereo sound you've found it here's how it works
instruments and vocals are placed in their proper staging locations stereo imaging is improved
and a larger more true to life sound field is created the music takes on a new spatial quality
tone bursts resonant lows sizzling highs and dramatic passages
seem to float in mid-air and you are center stage right in the middle of the performance... listen"
"we will now pause for several seconds of fine music"
so there is the repaired five dollar radio shack cassette deck
i still need to do a more thorough cleaning to remove this dirt from these grooves
but it doesn't look too bad and the only sign of something being different is that instead of
the original ac power cord it now has this thinner wire going to the power adapter from a hayes modem
i think what contributed to the demise of that original power transformer is that you may have
noticed there is no power switch on this tape deck as long as it's plugged in that built-in
power supply is putting out 12 volts dc and as you saw from the duct tape residue on the bottom i'm
thinking this was probably permanently installed somewhere so it was probably plugged in and had
that power transformer powered on for many many years until it eventually just burned out so it's
a good idea if you have any kind of audio device like i know many turntables are the same way
where as long as it's plugged in there's a power supply built into it that's powered on you should
unplug those or at least put them into a switched outlet and turn them off when they're not in use
so while the tape heads are obsessing over their thousand dollar nakamichi
dragons i just had fun fixing up this cheap little radio shack cassette player
that probably would have been thrown out if i hadn't rescued it and repaired it
"i am a talking telephone and you could use me for your own make the wire sing or
groan and tell a tale of woe any distance you can yell and tell a man to go to...
well, most any place you wish him with the talking telephone"