[apa]

I have a malfunctioning RE101 Space Echo. The direct sound is fine
but the echo output is very low and distorted.

If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head. If I inject
signal into the output electronics I get strong, clean output. I
demagged the heads and the tape path is straight with good contact on
the heads. All the electrolytics in the Rec/Play electronics check
fine with an ESR meter. I subbed in a looped piece of 499 in in case
the tape was bad but the echo output was unchanged. The heads don't
look particularly worn and the output is the same from all three play
heads. So I'm starting to suspect the record head.

Other than the recording function itself, are there any tell tale
signs that a tape head is failing?

Thanks in advance for any help.

Best, Andy

[philicorda[_9_]]

On Thu, 30 Dec 2010 12:34:25 -0800, apa wrote:

I have a malfunctioning RE101 Space Echo. The direct sound is fine but
the echo output is very low and distorted.

If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head. If I inject signal
into the output electronics I get strong, clean output. I demagged the
heads and the tape path is straight with good contact on the heads. All
the electrolytics in the Rec/Play electronics check fine with an ESR
meter. I subbed in a looped piece of 499 in in case the tape was bad
but the echo output was unchanged. The heads don't look particularly
worn and the output is the same from all three play heads. So I'm
starting to suspect the record head.

Did you check the bias oscillator level? My copycat started sounding a
bit weedy and the problem was the valve that generates the bias.
Everything else checked out fine.


Other than the recording function itself, are there any tell tale signs
that a tape head is failing?

Thanks in advance for any help.

Best, Andy

[apa]

On Dec 30, 3:39*pm, philicorda wrote:
On Thu, 30 Dec 2010 12:34:25 -0800, apa wrote:
I have a malfunctioning RE101 Space Echo. *The direct sound is fine but
the echo output is very low and distorted.

If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head. If I inject signal
into the output electronics I get strong, clean output. I demagged the
heads and the tape path is straight with good contact on the heads. All
the electrolytics in the Rec/Play electronics check fine with an ESR
meter. *I subbed in a looped piece of 499 in in case the tape was bad
but the echo output was unchanged. The heads don't look particularly
worn and the output is the same from all three play heads. So I'm
starting to suspect the record head.

Did you check the bias oscillator level? My copycat started sounding a
bit weedy and the problem was the valve that generates the bias.
Everything else checked out fine.



Other than the recording function itself, are there any tell tale signs
that a tape head is failing?

Thanks in advance for any help.

Best, Andy

There's a test point at the bias trap. The service manual says to
adjust the inductor there until there's less than 2.5V RMS (IIRC).
That checked out fine on the Fluke but I'll look it over more closely.
The bias level adjustment on the power supply board is maxed. That's
where it was when I opened it up. The echo response gets worse if I
turn it down.

[Scott Dorsey]

apa wrote:
I have a malfunctioning RE101 Space Echo. The direct sound is fine
but the echo output is very low and distorted.
If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head.

That's good, do you see lots of bias on the record head?

If I inject
signal into the output electronics I get strong, clean output. I
demagged the heads and the tape path is straight with good contact on
the heads.

If you tap the signal pin on the back of the play head with your finger
you get plenty of noise, right?

If you look at the gap in the head with a 50x magnifier, is it nice and
even? Is it wider on one side than the other?

All the electrolytics in the Rec/Play electronics check
fine with an ESR meter. I subbed in a looped piece of 499 in in case
the tape was bad but the echo output was unchanged.

499 will be pretty marginal on this machine since it wants something very
close to a red oxide tape that takes a lot less bias.

The heads don't
look particularly worn and the output is the same from all three play
heads. So I'm starting to suspect the record head.

That would make sense. If you don't have magna-see or some other spray,
you can still record on a loop then put it on a studio tape machine and
play it back to see.

Other than the recording function itself, are there any tell tale
signs that a tape head is failing?

The inductance will drop usually. If you have a bridge you can measure
it and see. Still, heads are cheap enough that you might just want to get
one for substitution purposes.

I'd make really sure you were getting good bias first though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

apa wrote:
There's a test point at the bias trap. The service manual says to
adjust the inductor there until there's less than 2.5V RMS (IIRC).

That's the trap adjustment, to keep the bias from getting into the
record electronics. That's not the adjustment you want.

That checked out fine on the Fluke but I'll look it over more closely.
The bias level adjustment on the power supply board is maxed. That's
where it was when I opened it up. The echo response gets worse if I
turn it down.

If you've got 499 on there, it needs to go around three or four times more
than it can physically go in order to get enough bias for that tape. 499
wants enormously high bias.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[apa]

On Dec 30, 3:59*pm, (Scott Dorsey) wrote:
apa wrote:
I have a malfunctioning RE101 Space Echo. *The direct sound is fine
but the echo output is very low and distorted.
If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head.

That's good, do you see lots of bias on the record head?

If I inject
signal into the output electronics I get strong, clean output. I
demagged the heads and the tape path is straight with good contact on
the heads.

If you tap the signal pin on the back of the play head with your finger
you get plenty of noise, right?



I'll give that a shot.


If you look at the gap in the head with a 50x magnifier, is it nice and
even? *Is it wider on one side than the other?



It looks pretty even.


All the electrolytics in the Rec/Play electronics check
fine with an ESR meter. *I subbed in a looped piece of 499 in in case
the tape was bad but the echo output was unchanged.

499 will be pretty marginal on this machine since it wants something very
close to a red oxide tape that takes a lot less bias.

The heads don't
look particularly worn and the output is the same from all three play
heads. So I'm starting to suspect the record head.

That would make sense. *If you don't have magna-see or some other spray,
you can still record on a loop then put it on a studio tape machine and
play it back to see.


Ah, right!.
And I suppose I could record a bit on the studio deck, make a loop and
then try playback on the echo unit if I disconnect the erase head.



Other than the recording function itself, are there any tell tale
signs that a tape head is failing?

The inductance will drop usually. *If you have a bridge you can measure
it and see. *Still, heads are cheap enough that you might just want to get
one for substitution purposes.


I do have a Sencore inductance meter. Is there a ballpark for a
healthy head?


I'd make really sure you were getting good bias first though.

I'll have another look.

--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."


Thanks as always Scott.

Best, Andy

[Scott Dorsey]

apa wrote:
Ah, right!.
And I suppose I could record a bit on the studio deck, make a loop and
then try playback on the echo unit if I disconnect the erase head.

Right.

Other than the recording function itself, are there any tell tale
signs that a tape head is failing?

The inductance will drop usually. =A0If you have a bridge you can measure
it and see. =A0Still, heads are cheap enough that you might just want to =
get
one for substitution purposes.

I do have a Sencore inductance meter. Is there a ballpark for a
healthy head?

I don't know what the impedance is for those heads, but John French would
know off the top of his head, and he'll know what inductance to expect along
with that. He will also have replacement heads for not too much money.

I don't know where you get replacement loops for those things today, now
that Fidelipac is gone, but there are probably enough surplus broadcast carts
out there that finding some to scavenge should not be a big deal.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On 12/30/2010 4:01 PM, Scott Dorsey wrote:

That's the trap adjustment, to keep the bias from getting into the
record electronics. That's not the adjustment you want.

Except that because he's seeing signal there (better if he
looked at it with a scope to see if it's bias), he probably
has bias, which was my first guess as to what was wrong
based on the description of the problem.



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Mike Rivers]

On 12/30/2010 4:20 PM, apa wrote:

And I suppose I could record a bit on the studio deck, make a loop and
then try playback on the echo unit if I disconnect the erase head.

You're pretty well equipped. That would be a good idea. At
least you could verify the playback. Or you could make a
flux loop - a bunch of turns of wire wrapped around
something like a piece of perforated prototype board, feed
it with a signal generator, put it up against the play head,
and you can verify that the playback electronics and head
are OK.

See:
http://www.manquen.net/audio/docs/Ma...20pictures.htm



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[apa]

On Dec 30, 4:37*pm, Mike Rivers wrote:
On 12/30/2010 4:20 PM, apa wrote:

And I suppose I could record a bit on the studio deck, make a loop and
then try playback on the echo unit if I disconnect the erase head.

You're pretty well equipped. That would be a good idea. At
least you could verify the playback. Or you could make a
flux loop - a bunch of turns of wire wrapped around
something like a piece of perforated prototype board, feed
it with a signal generator, put it up against the play head,
and you can verify that the playback electronics and head
are OK.

See:http://www.manquen.net/audio/docs/Ma...0Testing%20wit....

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com- useful and
interesting audio stuff

The flux loop is an interesting idea. Thanks for the link.

Best, Andy

[William Sommerwerck]

The flux loop is an interesting idea. Thanks for the link.

Just be certain you don't do anything to alter the timeline!

Oh... Wait... Sorry.

[apa]

On Dec 30, 3:59*pm, (Scott Dorsey) wrote:
apa wrote:
I have a malfunctioning RE101 Space Echo. *The direct sound is fine
but the echo output is very low and distorted.
If I trace the signal from the input it looks good on a scope right up
to the last transistor stage before the record head.

That's good, do you see lots of bias on the record head?


I've got 50 Volts there and the waveform looks clean.


That would make sense. *If you don't have magna-see or some other spray,
you can still record on a loop then put it on a studio tape machine and
play it back to see.

I made a loop on the studio deck and disconnected the bias from the
erase head on the echo.
The loop played back fine on all three heads.

I found a place that sells replacement tapes that are supposed to be a
match for the Space Echoes (lubricated and in the right bias range).
I'll give that a go and if it doesn't fix the problem I'll order a new
head.


Thanks to everyone for the help.

Best, Andy