Peter Larsen wrote:
The danish ReVox importer made worse damage to my A77 in 1974 when
fitting a 15 ips capstan shaft than what you see on these pictures,
unfortunately it was 1999 before I understood just what it was that was
wrong with the transport and why its 15 kHz stability was poor ....
capstan not at 90 degrees to the tape transport plane .... :-(

I hope you sent them a letter of complaint 15 years after the fact. The
motor kit comes with a bag of shim washers and you're supposed to shim
the motor straight specifically to prevent this. Sounds like somebody was
not reading the manual.
--scott


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

On Sun, 03 Oct 2004 13:01:33 +0200, Peter Larsen
wrote:

--------8---------------
The danish ReVox importer made worse damage to my A77 in 1974 when
fitting a 15 ips capstan shaft than what you see on these pictures,
unfortunately it was 1999 before I understood just what it was that was
wrong with the transport and why its 15 kHz stability was poor ....
capstan not at 90 degrees to the tape transport plane .... :-(


Kind regards

Peter Larsen

-- For a (very) so-la-la reproduction of a 15 ips tape, I have a
coressponding capstan which I can change on my Revox B77 Dolby. But,
the tape transport is quite disturbed, the pressure at the capstan
seems increased, yes the capstan is not at 90 deg., and the tape is
not touching that righthand tape guide (that one with synthetic ruby
washers). The HighSpeed Revox A and B77 models, PR99 etc. had their
entire capstan motors mounted tilted in comparison to the 3 1/4 -- 7
1/2 models. The bolt holes at the mounting plate are offest a little.
If this isn't bothering, the playback electronics still made for the
tape speed of 7 1/2 is... And I'd never record with such a capstan
mounted to this machine The result would be quite poor for an Revox

Edi Zubovic, Crikvenica, Croatia

On Sun, 03 Oct 2004 13:01:33 +0200, Peter Larsen
wrote:

--------8---------------
The danish ReVox importer made worse damage to my A77 in 1974 when
fitting a 15 ips capstan shaft than what you see on these pictures,
unfortunately it was 1999 before I understood just what it was that was
wrong with the transport and why its 15 kHz stability was poor ....
capstan not at 90 degrees to the tape transport plane .... :-(


Kind regards

Peter Larsen

-- For a (very) so-la-la reproduction of a 15 ips tape, I have a
coressponding capstan which I can change on my Revox B77 Dolby. But,
the tape transport is quite disturbed, the pressure at the capstan
seems increased, yes the capstan is not at 90 deg., and the tape is
not touching that righthand tape guide (that one with synthetic ruby
washers). The HighSpeed Revox A and B77 models, PR99 etc. had their
entire capstan motors mounted tilted in comparison to the 3 1/4 -- 7
1/2 models. The bolt holes at the mounting plate are offest a little.
If this isn't bothering, the playback electronics still made for the
tape speed of 7 1/2 is... And I'd never record with such a capstan
mounted to this machine The result would be quite poor for an Revox

Edi Zubovic, Crikvenica, Croatia

Edi Zubovic wrote:

washers). The HighSpeed Revox A and B77 models, PR99 etc. had their
entire capstan motors mounted tilted in comparison to the 3 1/4 -- 7
1/2 models.

The tilt is sideways, i.e. in the longitudinal direction of the tape. I
discovered it because a tape that had gotten a wee bit too much silicone
oil in cleaning traveled sideways.

The guy who drilled the new hole for the larger capstan must have done
it freehand. And he knew ... I wondered then why the rubber roller arm
had been obviously bent and replaced it with a new one, thinking no more
of it. I discussed it with some people back then, and nobody came up
with the idea that the rubber roller arm might have been bent so as to
get the roller parallel with the tilted capstan.

The bolt holes at the mounting plate are offest a little.
If this isn't bothering, the playback electronics still made for the
tape speed of 7 1/2 is...

Not anymore, not since 1977, the so called Radio & Television
modifications (x) have all been implemented and playback electronics
have been properly matched to the actual heads.

(x) swedish magazine that had a series of articles about how to fix all
that ails a ReVox A77 ex works.

And I'd never record with such a capstan
mounted to this machine

Nor would I. But the machine was - and is - not a bad machine, but it is
a baaad machine to play marginal backcoated tapes on.

The result would be quite poor for an Revox

Hmm ... yes, I had abandoned any thought of making another analog tape
recording by the time I found the problem, the ampex problem hit me real
hard - if only I had used more Fuji tapes ..... they sounded better, but
I was worried they would not last. Eventually they do run in to
problems, just like the 368 the appear to be a clone of, but way less
than ampex, and in fact also less than Agfa ... at least guesstimated on
the tapes I own.

I got me a G36 as a supplementary machine a couple of years ago, but the
mains power safety relay cut out when I connected it to grounded preamp
..... I wonder if all it needs is to be left powered up for the caps to
reform ... but I don't feel well about leaving a known imperfect mains
powered contraption powered up.

Edi Zubovic, Crikvenica, Croatia


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Edi Zubovic wrote:

washers). The HighSpeed Revox A and B77 models, PR99 etc. had their
entire capstan motors mounted tilted in comparison to the 3 1/4 -- 7
1/2 models.

The tilt is sideways, i.e. in the longitudinal direction of the tape. I
discovered it because a tape that had gotten a wee bit too much silicone
oil in cleaning traveled sideways.

The guy who drilled the new hole for the larger capstan must have done
it freehand. And he knew ... I wondered then why the rubber roller arm
had been obviously bent and replaced it with a new one, thinking no more
of it. I discussed it with some people back then, and nobody came up
with the idea that the rubber roller arm might have been bent so as to
get the roller parallel with the tilted capstan.

The bolt holes at the mounting plate are offest a little.
If this isn't bothering, the playback electronics still made for the
tape speed of 7 1/2 is...

Not anymore, not since 1977, the so called Radio & Television
modifications (x) have all been implemented and playback electronics
have been properly matched to the actual heads.

(x) swedish magazine that had a series of articles about how to fix all
that ails a ReVox A77 ex works.

And I'd never record with such a capstan
mounted to this machine

Nor would I. But the machine was - and is - not a bad machine, but it is
a baaad machine to play marginal backcoated tapes on.

The result would be quite poor for an Revox

Hmm ... yes, I had abandoned any thought of making another analog tape
recording by the time I found the problem, the ampex problem hit me real
hard - if only I had used more Fuji tapes ..... they sounded better, but
I was worried they would not last. Eventually they do run in to
problems, just like the 368 the appear to be a clone of, but way less
than ampex, and in fact also less than Agfa ... at least guesstimated on
the tapes I own.

I got me a G36 as a supplementary machine a couple of years ago, but the
mains power safety relay cut out when I connected it to grounded preamp
..... I wonder if all it needs is to be left powered up for the caps to
reform ... but I don't feel well about leaving a known imperfect mains
powered contraption powered up.

Edi Zubovic, Crikvenica, Croatia


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Scott Dorsey wrote:

Peter Larsen wrote:

The danish ReVox importer made worse damage to my A77 in 1974 when
fitting a 15 ips capstan shaft than what you see on these pictures,
unfortunately it was 1999 before I understood just what it was that was
wrong with the transport and why its 15 kHz stability was poor ....
capstan not at 90 degrees to the tape transport plane .... :-(

I hope you sent them a letter of complaint 15 years after the fact. The
motor kit comes with a bag of shim washers and you're supposed to shim
the motor straight specifically to prevent this. Sounds like somebody was
not reading the manual.

Somebody was indeed very incompetent. I tried looking the importer up,
they appear to be out of business. Reminds me ... there are still tapes
that need digitizing.

--scott


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Scott Dorsey wrote:

Peter Larsen wrote:

The danish ReVox importer made worse damage to my A77 in 1974 when
fitting a 15 ips capstan shaft than what you see on these pictures,
unfortunately it was 1999 before I understood just what it was that was
wrong with the transport and why its 15 kHz stability was poor ....
capstan not at 90 degrees to the tape transport plane .... :-(

I hope you sent them a letter of complaint 15 years after the fact. The
motor kit comes with a bag of shim washers and you're supposed to shim
the motor straight specifically to prevent this. Sounds like somebody was
not reading the manual.

Somebody was indeed very incompetent. I tried looking the importer up,
they appear to be out of business. Reminds me ... there are still tapes
that need digitizing.

--scott


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

On Mon, 04 Oct 2004 07:32:25 +0200, Peter Larsen
wrote:

--------------8----------------------
Not anymore, not since 1977, the so called Radio & Television
modifications (x) have all been implemented and playback electronics
have been properly matched to the actual heads.

(x) swedish magazine that had a series of articles about how to fix all
that ails a ReVox A77 ex works.
Oh, so then
And I'd never record with such a capstan
mounted to this machine

Nor would I. But the machine was - and is - not a bad machine, but it is
a baaad machine to play marginal backcoated tapes on.

The result would be quite poor for an Revox

Hmm ... yes, I had abandoned any thought of making another analog tape
recording by the time I found the problem, the ampex problem hit me real
hard - if only I had used more Fuji tapes ..... they sounded better, but
I was worried they would not last. Eventually they do run in to
problems, just like the 368 the appear to be a clone of, but way less
than ampex, and in fact also less than Agfa ... at least guesstimated on
the tapes I own.-
- I'll try to find some more of BASF remnants -- namely LGR 50 MK1
pancakes. I still have some 5 of them fresh in nylon bags. They're 30
cm but go fine with Revox and this broadcast tape has indeed been a
cake literally; excellent and very forgiving about levels, it soft
saturates prior to clipping. -- It goes fine with a Revox and it
doesn't feed itself with heads like broadcast Agfas used to do... but
Ampex (no Quantegy yet; old stock) 407, which are still obtainable to
me here, are also quite fair with Revox.
I got me a G36 as a supplementary machine a couple of years ago, but the
mains power safety relay cut out when I connected it to grounded preamp
.... I wonder if all it needs is to be left powered up for the caps to
reform ... but I don't feel well about leaving a known imperfect mains
powered contraption powered up.
If such a machine is to be powered up after decades, it is best done
with an autotransformer I think. I had a bit of luck when I tried to
start the Revox after a really long time. Its transformer has been
shortcircuited for a while until the power capacitors formed... not a
pretty picture (and smell). Everything went fine at the end though...
but in your case, when the safety relay responded, I think there must
have been a difference in earth potential and this is something asking
for 1:1 transformers or similar isolation to be 100% sure... Revox are
I think nulled; they have only two-prong power plugs and no other
ground.



Kind regards

Peter Larsen

Edi Zubovic, Crikvenica, Croatia

On Mon, 04 Oct 2004 07:32:25 +0200, Peter Larsen
wrote:

--------------8----------------------
Not anymore, not since 1977, the so called Radio & Television
modifications (x) have all been implemented and playback electronics
have been properly matched to the actual heads.

(x) swedish magazine that had a series of articles about how to fix all
that ails a ReVox A77 ex works.
Oh, so then
And I'd never record with such a capstan
mounted to this machine

Nor would I. But the machine was - and is - not a bad machine, but it is
a baaad machine to play marginal backcoated tapes on.

The result would be quite poor for an Revox

Hmm ... yes, I had abandoned any thought of making another analog tape
recording by the time I found the problem, the ampex problem hit me real
hard - if only I had used more Fuji tapes ..... they sounded better, but
I was worried they would not last. Eventually they do run in to
problems, just like the 368 the appear to be a clone of, but way less
than ampex, and in fact also less than Agfa ... at least guesstimated on
the tapes I own.-
- I'll try to find some more of BASF remnants -- namely LGR 50 MK1
pancakes. I still have some 5 of them fresh in nylon bags. They're 30
cm but go fine with Revox and this broadcast tape has indeed been a
cake literally; excellent and very forgiving about levels, it soft
saturates prior to clipping. -- It goes fine with a Revox and it
doesn't feed itself with heads like broadcast Agfas used to do... but
Ampex (no Quantegy yet; old stock) 407, which are still obtainable to
me here, are also quite fair with Revox.
I got me a G36 as a supplementary machine a couple of years ago, but the
mains power safety relay cut out when I connected it to grounded preamp
.... I wonder if all it needs is to be left powered up for the caps to
reform ... but I don't feel well about leaving a known imperfect mains
powered contraption powered up.
If such a machine is to be powered up after decades, it is best done
with an autotransformer I think. I had a bit of luck when I tried to
start the Revox after a really long time. Its transformer has been
shortcircuited for a while until the power capacitors formed... not a
pretty picture (and smell). Everything went fine at the end though...
but in your case, when the safety relay responded, I think there must
have been a difference in earth potential and this is something asking
for 1:1 transformers or similar isolation to be 100% sure... Revox are
I think nulled; they have only two-prong power plugs and no other
ground.



Kind regards

Peter Larsen

Edi Zubovic, Crikvenica, Croatia

Edi Zubovic wrote:

[ lotsa great stuff omitted]

I got me a G36 as a supplementary machine a couple of years ago,
but the mains power safety relay cut out when I connected it
to grounded preamp ... I wonder if all it needs is to be left
powered up for the caps to reform ... but I don't feel well
about leaving a known imperfect mains powered contraption
powered up.

If such a machine is to be powered up after decades,
it is best done with an autotransformer I think.

Such a contraption is inching its way into my wishlist.

I had a bit of luck when I tried to start the Revox
after a really long time.

Unused items should occasionally be left powered up for an extented
period of time, i.e. multiple days.

Its transformer has been shortcircuited for a while until
the power capacitors formed... not a pretty picture (and smell).
Everything went fine at the end though... but in your case, when
the safety relay responded,

Leak to ground relay .... checks the diff between outgoing amperage and
return.

I think there must have been a difference in earth potential
and this is something asking for 1:1 transformers

I have a pair of those, but they are sitting in a plastic box with one
side's winding in series between left and right, with a source
resistance in the 1 to 2 kOhm range they form an excellent VLF mono
combiner and they have occasionally done wonders to problematic
recordings back in the analog age.

or similar isolation to be 100% sure... Revox are I think nulled;
they have only two-prong power plugs and no other ground.

Arne E. Jensens hypothesis was that what ails it is leak current in a
coupling cap in the signal path .... in which case perhaps it really is
only about leaving it powered up for a week instead of only a day. It is
a hybrid btw. - it has been a langue lab machine and has since had the
valve playback electronics replaced, probably with a board that I know
was designed by someone who replaced all signal electronics in their
A700's, 553x is socketed ....

As for the grounding ... we run two pronged here in Denmark, but
grounding is an unavoidable property of an antenna system that is common
to all apartments in a building.

Edi Zubovic, Crikvenica, Croatia


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Edi Zubovic wrote:

[ lotsa great stuff omitted]

I got me a G36 as a supplementary machine a couple of years ago,
but the mains power safety relay cut out when I connected it
to grounded preamp ... I wonder if all it needs is to be left
powered up for the caps to reform ... but I don't feel well
about leaving a known imperfect mains powered contraption
powered up.

If such a machine is to be powered up after decades,
it is best done with an autotransformer I think.

Such a contraption is inching its way into my wishlist.

I had a bit of luck when I tried to start the Revox
after a really long time.

Unused items should occasionally be left powered up for an extented
period of time, i.e. multiple days.

Its transformer has been shortcircuited for a while until
the power capacitors formed... not a pretty picture (and smell).
Everything went fine at the end though... but in your case, when
the safety relay responded,

Leak to ground relay .... checks the diff between outgoing amperage and
return.

I think there must have been a difference in earth potential
and this is something asking for 1:1 transformers

I have a pair of those, but they are sitting in a plastic box with one
side's winding in series between left and right, with a source
resistance in the 1 to 2 kOhm range they form an excellent VLF mono
combiner and they have occasionally done wonders to problematic
recordings back in the analog age.

or similar isolation to be 100% sure... Revox are I think nulled;
they have only two-prong power plugs and no other ground.

Arne E. Jensens hypothesis was that what ails it is leak current in a
coupling cap in the signal path .... in which case perhaps it really is
only about leaving it powered up for a week instead of only a day. It is
a hybrid btw. - it has been a langue lab machine and has since had the
valve playback electronics replaced, probably with a board that I know
was designed by someone who replaced all signal electronics in their
A700's, 553x is socketed ....

As for the grounding ... we run two pronged here in Denmark, but
grounding is an unavoidable property of an antenna system that is common
to all apartments in a building.

Edi Zubovic, Crikvenica, Croatia


Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************

Peter Larsen wrote:
Edi Zubovic wrote:

[ lotsa great stuff omitted]

I got me a G36 as a supplementary machine a couple of years ago,
but the mains power safety relay cut out when I connected it
to grounded preamp ... I wonder if all it needs is to be left
powered up for the caps to reform ... but I don't feel well
about leaving a known imperfect mains powered contraption
powered up.

If such a machine is to be powered up after decades,
it is best done with an autotransformer I think.

Such a contraption is inching its way into my wishlist.

It is worth having. In the meantime, a lamp board with a number of 60W
bulbs in parallel with switches will allow you to provide a voltage drop
to an appliance and allow you to bring up up slowly over the course of a
few hourse.

My personal feeling about cap reforming is that if capacitors have deformed
in storage, they should really be replaced anyway and bringing the gear up
slowly just helps you avoid replacing something that should be replaced. But
I realize this is a religious issue.

All of the A77 machines I have used had some amount of ground leakage, and
I don't honestly know why. But I would look at the primary of the power
transformer and look for filtering there that might be leaking, or for
leakage through the transformer.
--scott

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

Peter Larsen wrote:
Edi Zubovic wrote:

[ lotsa great stuff omitted]

I got me a G36 as a supplementary machine a couple of years ago,
but the mains power safety relay cut out when I connected it
to grounded preamp ... I wonder if all it needs is to be left
powered up for the caps to reform ... but I don't feel well
about leaving a known imperfect mains powered contraption
powered up.

If such a machine is to be powered up after decades,
it is best done with an autotransformer I think.

Such a contraption is inching its way into my wishlist.

It is worth having. In the meantime, a lamp board with a number of 60W
bulbs in parallel with switches will allow you to provide a voltage drop
to an appliance and allow you to bring up up slowly over the course of a
few hourse.

My personal feeling about cap reforming is that if capacitors have deformed
in storage, they should really be replaced anyway and bringing the gear up
slowly just helps you avoid replacing something that should be replaced. But
I realize this is a religious issue.

All of the A77 machines I have used had some amount of ground leakage, and
I don't honestly know why. But I would look at the primary of the power
transformer and look for filtering there that might be leaking, or for
leakage through the transformer.
--scott

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

Scott Dorsey wrote:

If such a machine is to be powered up after decades,
it is best done with an autotransformer I think.

Such a contraption is inching its way into my wishlist.

It is worth having. In the meantime, a lamp board with a
number of 60W bulbs in parallel with switches ....

Hmmm .... we run 230 volts over here, I think I'll look into getting the
trafo - it is simpler, thanks.



Kind regards

Peter Larsen

--
*******************************************
* My site is at: http://www.muyiovatki.dk *
*******************************************