Car radio repair

[Engineer]

I would really appreciate the group's advice in a field not
familiar to me.

I picked up a car radio at a garage sale last week (for
US$2.00 so it doesn't owe me much!)

It's a 1982 (+/-) model AIMOR brand, out of an Audi or VW,
model # CX-15D.

It will end up as a workshop radio. I have it working on
the bench off an 11.6 volt, 1 amp, home-brew P/S (pulls just
over 0.3 Amps in radio mode.) The AM/FM works perfectly but
the cassette exhibits a strange behaviour - it plays, but
continuously track reverses every second, anywhere on the
tape!

I have only sprayed inside the drive with switch cleaner, to
no effect.

My thoughts so far are as follows:
1. There is too much mechanical drag on the cassette (dirt,
perhaps) so it thinks it must reverse (the cassette itself
is OK.).
2. At 11.6 volts (it's designed for about 13.6 volts, of
course), the motor(s) pull too much current and a current
sensor indicates end of tape.

Any ideas how to fix?

BTW, I can't yet see how the drive comes out of the chassis
for service. I've taken off the escutcheon and front
mounting plate but I still don't see an obvious drive
removal path - it's all very tightly assembled indeed!

All replies welcomed.

Cheers,

Roger
--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"

 

[Dave D]

"Engineer" <LandRJones@sprint.ca> wrote in message
news:3F22EB26.9F7B7AB6@sprint.ca...

I would really appreciate the group's advice in a field not
familiar to me.

I picked up a car radio at a garage sale last week (for
US$2.00 so it doesn't owe me much!)

It's a 1982 (+/-) model AIMOR brand, out of an Audi or VW,
model # CX-15D.

It will end up as a workshop radio. I have it working on
the bench off an 11.6 volt, 1 amp, home-brew P/S (pulls just
over 0.3 Amps in radio mode.) The AM/FM works perfectly but
the cassette exhibits a strange behaviour - it plays, but
continuously track reverses every second, anywhere on the
tape!

I have only sprayed inside the drive with switch cleaner, to
no effect.

My thoughts so far are as follows:
1. There is too much mechanical drag on the cassette (dirt,
perhaps) so it thinks it must reverse (the cassette itself
is OK.).
2. At 11.6 volts (it's designed for about 13.6 volts, of
course), the motor(s) pull too much current and a current
sensor indicates end of tape.

Any ideas how to fix?

That could be a simple case of too little available current from the PSU. It
could also be a bad end of tape sensor or associated components. Have you
tried running it off a car battery?

Dave

 

[Jeff]

1982? Belt drive? That would do it.
Not a Mfg or model I have seen, most Audi/VW here
were Blaupunkt or Panasonic.
Jeff

"Engineer" <LandRJones@sprint.ca> wrote in message
news:3F22EB26.9F7B7AB6@sprint.ca...

I would really appreciate the group's advice in a field not
familiar to me.

I picked up a car radio at a garage sale last week (for
US$2.00 so it doesn't owe me much!)

It's a 1982 (+/-) model AIMOR brand, out of an Audi or VW,
model # CX-15D.

It will end up as a workshop radio. I have it working on
the bench off an 11.6 volt, 1 amp, home-brew P/S (pulls just
over 0.3 Amps in radio mode.) The AM/FM works perfectly but
the cassette exhibits a strange behaviour - it plays, but
continuously track reverses every second, anywhere on the
tape!

I have only sprayed inside the drive with switch cleaner, to
no effect.

My thoughts so far are as follows:
1. There is too much mechanical drag on the cassette (dirt,
perhaps) so it thinks it must reverse (the cassette itself
is OK.).
2. At 11.6 volts (it's designed for about 13.6 volts, of
course), the motor(s) pull too much current and a current
sensor indicates end of tape.

Any ideas how to fix?

BTW, I can't yet see how the drive comes out of the chassis
for service. I've taken off the escutcheon and front
mounting plate but I still don't see an obvious drive
removal path - it's all very tightly assembled indeed!

All replies welcomed.

Cheers,

Roger
--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"

 

[Engineer]

Engineer wrote:

(snip)

It's a 1982 (+/-) model AIMOR brand, out of an Audi or VW,
model # CX-15D.

(snip)

I have it working on
the bench off an 11.6 volt, 1 amp, home-brew P/S (pulls just
over 0.3 Amps in radio mode.) The AM/FM works perfectly but
the cassette exhibits a strange behaviour - it plays, but
continuously track reverses every second, anywhere on the
tape!

I have only sprayed inside the drive with switch cleaner, to
no effect.

My thoughts so far are as follows:
1. There is too much mechanical drag on the cassette (dirt,
perhaps) so it thinks it must reverse (the cassette itself
is OK.).
2. At 11.6 volts (it's designed for about 13.6 volts, of
course), the motor(s) pull too much current and a current
sensor indicates end of tape.

It turns out that #2 is NOT the problem - see below.

Any ideas how to fix?


That could be a simple case of too little available current from the PSU. It
could also be a bad end of tape sensor or associated components. Have you
tried running it off a car battery?

Dave

Good point, the capability of the P/S had crossed my mind
but it still delivers at least 11.5 volts on cassette play.
I have a 14 VDC "several amp" industrial quality supply on
my bathroom radio (another recycled car radio, from a 1980
Honda Accord), so I'll try that.

Just tried this, at a regulated 13.6 volts. No change,
still does the alternating cassette reverse, so it's not the
P/S. Have figure out where to go from here...? I still
can't figure out if the cassette drive can be removed from
the chassis - I can't see any screws to remove (two at the
back on inside brass posts are not the primary cassette
drive mount.)

Not sure about any "end of tape sensor" - what is it? I
thought the unit sensed increased motor current as the deck
stalled.

Cheers,

Roger

--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"

 

[Dave D]

"Engineer" <LandRJones@sprint.ca> wrote in message
news:3F23710C.F5296269@sprint.ca...

Not sure about any "end of tape sensor" - what is it? I
thought the unit sensed increased motor current as the deck
stalled.

On cheaper decks it's usually a mechanical affair, a plastic tongue over
which the tape runs. When the tape pulls tight it depresses the tongue,
shutting off the mechanism. Some designs use a clever link from one of the
spools (usually the take up spool) which triggers when it stops.

On better systems, a revolving disc driven from the take up spool has either
magnetic or optically reflective strips which as they rotate cause the
sensor to alternate between an on and off condition, sending continuous
pulses to the auto stop circuit.

When the wheel stops, the sensor stays either on or off, so the pulses stop
and the auto stop or auto reverse is triggered.

There are variations on these systems, hopefully you'll be able to spot the
right bits.

Dave

 

[Engineer]

Engineer wrote:

... can't figure out if the cassette drive can be removed from
the chassis - I can't see any screws to remove (two at the
back on inside brass posts are not the primary cassette
drive mount.)

Yes they are, just figured it out! Remove 4 screws (two of
the above on the posts) and it just lifts out on a short
multi-wire umbilical. The mechanical forensics continues...
BTW, power ground is via the chassis screws, so you have to
bond the separated chassis with a wire to run the cassette
drive out of the radio proper.

Cheers,

Roger

--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"

 

[Engineer]

Engineer wrote:

Engineer wrote:

... can't figure out if the cassette drive can be removed from
the chassis - I can't see any screws to remove (two at the
back on inside brass posts are not the primary cassette
drive mount.)

Yes they are, just figured it out! Remove 4 screws (two of
the above on the posts) and it just lifts out on a short
multi-wire umbilical. The mechanical forensics continues...
BTW, power ground is via the chassis screws, so you have to
bond the separated chassis with a wire to run the cassette
drive out of the radio proper.

Fixed! Cleaned belt, cleaned gears... cassette deck plays
outside chassis! Now just have to clean capstan pinch
wheels (dirty brown tape debris on the rubber) and
reassemble.

Thanks for all replies.

Cheers,

Roger

--
Roger Jones, P.Eng.
Thornhill, Ontario,
Canada.

"Friends don't let friends vote Liberal"

 

[Dave D]

"Engineer" <LandRJones@sprint.ca> wrote in message
news:3F273AC4.BE5C1371@sprint.ca...

Engineer wrote:

Engineer wrote:

... can't figure out if the cassette drive can be removed from
the chassis - I can't see any screws to remove (two at the
back on inside brass posts are not the primary cassette
drive mount.)

Yes they are, just figured it out! Remove 4 screws (two of
the above on the posts) and it just lifts out on a short
multi-wire umbilical. The mechanical forensics continues...
BTW, power ground is via the chassis screws, so you have to
bond the separated chassis with a wire to run the cassette
drive out of the radio proper.

Fixed! Cleaned belt, cleaned gears... cassette deck plays
outside chassis! Now just have to clean capstan pinch
wheels (dirty brown tape debris on the rubber) and
reassemble.

Thanks for all replies.

Cheers,

Roger

Congratulations and well done Roger!

Dave