Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels (as
indicated on the meters) are lower in playback than record. IOW, if I record
a cassette with the levels reading around 0, the tape will play back with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give the
general idea. I also cannot remember if this was the way things were going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have inadvertently
moved while repairing? or perhaps it needs some adjustment in another area?

Thanks

I would suggest to demagnetize and clean the heads before going
farther. Also, use a tape cassette that is not very old. After these
cassettes are a number of years old, the permability of the magnetic
coating may deteriate with age.

When these decks are calibrated, a proper test reference tape is used
to align the playback first. Then for the record section we use a know
standard type fresh high quality recording tape, and an audio
generator to reference the response of the machine. There is a test
reference tape for dolby, and one for no dolby. There are also test
reference tapes for metal, and ones for the different types of oxide
tapes.

For properly setting up an audio tape machine you will need a scope,
audio generator, reference standards tape, a high quality recording
tape if each type that the machine is supposed to use, and a VU meter.
The service manual should have the details of how to set the machine
up.

There is the combination of the capston speed, tape tension, azmuth,
head height, head postion, guide adjustments, pinch roller pressure,
and then the adjusting pots for the EQ's, levels, and Bias settings to
be set up. This is just to mention a few things that can effect the
performance of your audio tape machine.

In the lower cost machines they average out many of the adjustments,
for the different types of tapes to be used.

If the sound is not distorted, or is not out of ballance, and it is
uniform, I would just do a head cleaning and demagnetization. I would
not venture in to the alignment of the unit, unless I was prepared to
go all the way with proper servicing, and the proper checks. You can
probably find a head demagnetizer at most audio HiFi stores. Radio
Shack used to sell them. You can use some rubbing alcohol and a soft
tissue to clean the heads.

Most of the non factory authorized shops may have some type of test
reference tape and an audio generator, and do a simplified alignment
with the scope. This is not going to be a truely accurate alignment.

Considering the age and the value of your machine, is this all worth
it. Also, the performance of the machine may not be very stable unless
it is a very expensive unit, and there are no parts inside that have
become off specs from age.

Before doing any adjustments, it is very important that the
electronics, and the mechanics of the machine are working as best as
possible to specifications. If not, and you start to make adjustments,
the situation can be made worse.

Jerry G.
========


"tempus fugit" wrote in message ...
Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels (as
indicated on the meters) are lower in playback than record. IOW, if I record
a cassette with the levels reading around 0, the tape will play back with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give the
general idea. I also cannot remember if this was the way things were going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have inadvertently
moved while repairing? or perhaps it needs some adjustment in another area?

Thanks

ouch

Thanks for the info Jerry. I have demagnetized and cleaned the heads a few
times (this was the first thing I did when the left channel was weak), so
unless the heads are worn (which is altogether possible) I don't think
that's the issue.

Everything is fairly well balanced now, so maybe I'll just leave it be. As
you pointed out, the deck is quite old, and was only a few hundred bucks
when I got it, so it's not like it's a high end deck. I just thought if the
calibration process (or some of it) wasn't too involved, I'd see what I
could do.


"Jerry Greenberg" wrote in message
m...
I would suggest to demagnetize and clean the heads before going
farther. Also, use a tape cassette that is not very old. After these
cassettes are a number of years old, the permability of the magnetic
coating may deteriate with age.

When these decks are calibrated, a proper test reference tape is used
to align the playback first. Then for the record section we use a know
standard type fresh high quality recording tape, and an audio
generator to reference the response of the machine. There is a test
reference tape for dolby, and one for no dolby. There are also test
reference tapes for metal, and ones for the different types of oxide
tapes.

For properly setting up an audio tape machine you will need a scope,
audio generator, reference standards tape, a high quality recording
tape if each type that the machine is supposed to use, and a VU meter.
The service manual should have the details of how to set the machine
up.

There is the combination of the capston speed, tape tension, azmuth,
head height, head postion, guide adjustments, pinch roller pressure,
and then the adjusting pots for the EQ's, levels, and Bias settings to
be set up. This is just to mention a few things that can effect the
performance of your audio tape machine.

In the lower cost machines they average out many of the adjustments,
for the different types of tapes to be used.

If the sound is not distorted, or is not out of ballance, and it is
uniform, I would just do a head cleaning and demagnetization. I would
not venture in to the alignment of the unit, unless I was prepared to
go all the way with proper servicing, and the proper checks. You can
probably find a head demagnetizer at most audio HiFi stores. Radio
Shack used to sell them. You can use some rubbing alcohol and a soft
tissue to clean the heads.

Most of the non factory authorized shops may have some type of test
reference tape and an audio generator, and do a simplified alignment
with the scope. This is not going to be a truely accurate alignment.

Considering the age and the value of your machine, is this all worth
it. Also, the performance of the machine may not be very stable unless
it is a very expensive unit, and there are no parts inside that have
become off specs from age.

Before doing any adjustments, it is very important that the
electronics, and the mechanics of the machine are working as best as
possible to specifications. If not, and you start to make adjustments,
the situation can be made worse.

Jerry G.
========


"tempus fugit" wrote in message
...
Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it
apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels
(as
indicated on the meters) are lower in playback than record. IOW, if I
record
a cassette with the levels reading around 0, the tape will play back
with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been
a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give
the
general idea. I also cannot remember if this was the way things were
going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to
be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have
inadvertently
moved while repairing? or perhaps it needs some adjustment in another
area?

Thanks

"tempus fugit" wrote in message ...
Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels (as
indicated on the meters) are lower in playback than record. IOW, if I record
a cassette with the levels reading around 0, the tape will play back with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give the
general idea. I also cannot remember if this was the way things were going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have inadvertently
moved while repairing? or perhaps it needs some adjustment in another area?

Thanks

I sympathise with all the above, but when all's said and done we are
talking about a 20 year old machine using a format which is rapidly
growing obsolete. there must come a point at which one asks: is this
worth spending time and money on?
Second hand markets are full of cassette decks, even hi-spec ones,
going for ridiculously low prices (seeing as CD-R has occupied the
mainstream for home recording.)

Rather than spend time on your present machine which will possibly
need a schematic and test equipment to rectify completely, it may be
simpler to get a decent , tested, quality 3 head machine from a
reputable dealer if you really want a good spec cassette machine.
Ben

Thanks Ben.
Rather than spend time on your present machine which will possibly
need a schematic and test equipment to rectify completely, it may be
simpler to get a decent , tested, quality 3 head machine from a
reputable dealer if you really want a good spec cassette machine.


Ya, I know that, but I hate to throw something away that I might be able to
fix (it's a little "problem" I have). Also, if I can do it, it would be cool
to learn how, especially in light of your above comment - if I screw
something up irreparably, I can always pick up a used cheapie (hell, I've
pulled decks out of the garbage that were working fine), and I have another
one lying around anyway.



"b" wrote in message
om...
"tempus fugit" wrote in message
...
Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it
apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels
(as
indicated on the meters) are lower in playback than record. IOW, if I
record
a cassette with the levels reading around 0, the tape will play back
with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been
a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give
the
general idea. I also cannot remember if this was the way things were
going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to
be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have
inadvertently
moved while repairing? or perhaps it needs some adjustment in another
area?

Thanks

I sympathise with all the above, but when all's said and done we are
talking about a 20 year old machine using a format which is rapidly
growing obsolete. there must come a point at which one asks: is this
worth spending time and money on?
Second hand markets are full of cassette decks, even hi-spec ones,
going for ridiculously low prices (seeing as CD-R has occupied the
mainstream for home recording.)

Rather than spend time on your present machine which will possibly
need a schematic and test equipment to rectify completely, it may be
simpler to get a decent , tested, quality 3 head machine from a
reputable dealer if you really want a good spec cassette machine.
Ben


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On Sat, 23 Oct 2004 10:17:57 -0400, "tempus fugit"
wrote:

Hey all;

I've got a Technics tape deck (RS-B18) that is about 20 years old. I had
some problems with intermittent channels (rec and play) and took it apart to
see what I could do. I found a cold solder joint in the signal path and
resoldered it, which (so far, anyway) has fixed the problem.

However, there are a few things I'm wondering about. First, the levels (as
indicated on the meters) are lower in playback than record. IOW, if I record
a cassette with the levels reading around 0, the tape will play back with
the levels at, say -3 or so. It also varies depending on how the noise
reduction and bias is set:

1. No Dolby, CrO2 - levels are pretty much the same
2. Dolby B, Cr02 - levels slightly lower on playback
3. dbx, Cr02 - levels considerably (3 - 6 db) lower on playback
4. any or no noise reduction, Metal - no playback at all (this has been a
problem since I got the deck)

I can post more combinations if need be, but I hope that this will give the
general idea. I also cannot remember if this was the way things were going
before the repair (I think it was though).
Are these type of discrepencies normal, or can/should I adjust things to
equal them out?

I also noticed that the playback was a little dull after the repair (to be
honest, I hadn't used the deck in quite a while, so it may be the way it
always sounded). Would this be a bias setting that I may have inadvertently
moved while repairing? or perhaps it needs some adjustment in another area?

Thanks


It's perfectly normal for you to lose a bit of gain. Meters are far
from exact and you are dealing with an analog process.
Tape formulations are such that they are simply not 100% capable of
capturing all the signal that you give them.
That's why you run a test recording before the real thing on any
type/batch of tape you're going to use.
Also has alot to do with the type of metering you're using too.
Some decks use A weighted some B or even C.
Some use a average weight combination etc...
(Peak, Average and mixed are the 3 basic flavors tho' there are dozens
of variations.)
In fact it's desireable to stay a bit under 0 with most tapes,
especially Chrome and Metal, both of which distort easily with
oversaturation.
As for DBX, it's designed to under record about -3 to -10 dbs to allow
for greater headroom on high or sudden peaks/surges.
There wer attempts in the late70's early 80's to design cassette decks
that would test tone tapes and set the optimum level.
One was the Luxman KXP-102, I had one of these and they produced the
most accurate, clean mids and lows capable out of cassette tapes.
It would run a test tone in three basic ranges(low, mids and highs)
and read the results repeating the tones until the optimumlevel had
been achieved in each zone.
This allowed it to tweak bias and noise reduction until you got the
perfect recording with each tape.(It was less than perfect in
capturing the very highs but was a great deck for instrumental jass
and blues etc...)
Just run a test on whatever type of tape you're using adjusting the
gain untill you get the desired level that gives you highest sound
level without oversaturation.(Think you'll find that you'll be setting
the gain around 7 or so and depending on your type of meters the
signal will show to be around +2 to +4 during record and bang on 0 on
playback.