Help with Sony SLV-N750 VCR

[G B]

Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it apart
and "shot-gun" replaced the nine capacitors in the general area of the power
supply with capacitors of the same value. It now will power up and even
play a tape BUT when it is powered down (in standby) the display blinks on
and off. It seems the power supply is cycling on and off. Any idea what
would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)

 

[Mark Zacharias]

"G B" <geeberry@frontiernet.net> wrote in message
news:09bel.135782$3_4.112933@newsfe10.iad...

Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it apart
and "shot-gun" replaced the nine capacitors in the general area of the
power supply with capacitors of the same value. It now will power up and
even play a tape BUT when it is powered down (in standby) the display
blinks on and off. It seems the power supply is cycling on and off. Any
idea what would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)

Maybe just need to set the clock?

Mark Z.

 

[b]

On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:

Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it apart
and "shot-gun" replaced the nine capacitors in the general area of the power
supply with capacitors of the same value. It now will power up and even
play a tape BUT when it is powered down (in standby) the display blinks on
and off. It seems the power supply is cycling on and off. Any idea what
would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)

with weak or pulsing displays there's usually some relatively high
value caps (2200uF) on the line to the panel need changing.

 

[Arfa Daily]

"Mark Zacharias" <mark_zacharias@labolgcbs.net> wrote in message
news:Z7iel.18575$Ws1.6999@nlpi064.nbdc.sbc.com...

"G B" <geeberry@frontiernet.net> wrote in message
news:09bel.135782$3_4.112933@newsfe10.iad...
Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it apart
and "shot-gun" replaced the nine capacitors in the general area of the
power supply with capacitors of the same value. It now will power up
and even play a tape BUT when it is powered down (in standby) the
display blinks on and off. It seems the power supply is cycling on and
off. Any idea what would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)



Maybe just need to set the clock?

Mark Z.

My first thought, too ...

Arfa

 

[G B]

Thanks for the reply...

This VCR will automatically set the clock, so no blinking --:-- forever,
when it works correctly. The problem is, even if you set the clock, when
the unit is put in STANDBY mode. The power supply appears to be unable to
keep its standby power stable. The VCR will reset itself. (again and again
and again) That means if the clock was set while in the powered on state,
when it shuts down, the
clock is reset. Problem is, I have no idea how this VCR power supply keeps
its
standy power working. I assume it shuts down the regular switcher but has
some sort of regulator that provides enough to keep system memory and
bootstrap working. Any other ideas?

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:u6uel.27692$HW6.11889@newsfe25.ams2...

"Mark Zacharias" <mark_zacharias@labolgcbs.net> wrote in message
news:Z7iel.18575$Ws1.6999@nlpi064.nbdc.sbc.com...
"G B" <geeberry@frontiernet.net> wrote in message
news:09bel.135782$3_4.112933@newsfe10.iad...
Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it
apart and "shot-gun" replaced the nine capacitors in the general area of
the power supply with capacitors of the same value. It now will power
up and even play a tape BUT when it is powered down (in standby) the
display blinks on and off. It seems the power supply is cycling on and
off. Any idea what would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)



Maybe just need to set the clock?

Mark Z.

My first thought, too ...

Arfa

 

[G B]

The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then goes
blank and starts again. Also every time the display blinks, the carriage
motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?

"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...

On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it apart
and "shot-gun" replaced the nine capacitors in the general area of the
power
supply with capacitors of the same value. It now will power up and even
play a tape BUT when it is powered down (in standby) the display blinks
on
and off. It seems the power supply is cycling on and off. Any idea what
would cause this? Any help is appreciated...

Greg (gberry--AT--frontiernet--dot--net)

with weak or pulsing displays there's usually some relatively high
value caps (2200uF) on the line to the panel need changing.

 

[Arfa Daily]

"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of the
power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display blinks
on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...

"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...

The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then goes
blank and starts again. Also every time the display blinks, the carriage
motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?

Have you replaced any electros in the front end or were they all secondary
side ? This sort of odd behaviour in switchers can be symptomatic of small
caps - often only from 1 to 47uF in value - situated around the oscillator /
control IC having gone high ESR. You will often find them located close to
some other component or heatsink, which runs hot. Do you have an ESR meter ?
Just as an aside, it makes a thread and the replies much easier to follow if
you bottom-post rather than top.

Arfa

 

[G B]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:wZ8fl.7570$1s3.6110@newsfe14.ams2...

"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of the
power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display
blinks on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...


"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...
The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then
goes blank and starts again. Also every time the display blinks, the
carriage motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?


Have you replaced any electros in the front end or were they all secondary
side ? This sort of odd behaviour in switchers can be symptomatic of small
caps - often only from 1 to 47uF in value - situated around the oscillator
/ control IC having gone high ESR. You will often find them located close
to some other component or heatsink, which runs hot. Do you have an ESR
meter ? Just as an aside, it makes a thread and the replies much easier to
follow if you bottom-post rather than top.

Arfa

I replaced 9 caps all in the area of the switcher, or at least where I think
the switcher is. I replaced the large regulation cap (82uF @ 200V) and I
replaced a small (4.7uF@50V) on what I would consider the primary side.
(prior to the large transformer). I replaced all the electorlytics: 10uF,
100uF, 330uF, 470uF, and 1000uF values on what I think is the secondary. Do
you know if the switcher provides the boot-strap voltage in standby mode?
Or do they have another regulator somewhere off the line regulation
circuitr? I have also what appears to be a hot-spot on the circuit board
around QIP107, RIP110, QIP108, ZDIP05, and DIP109. It doesn't feel warm to
the touch after it has been running for a while.. so the hot-spot is a bit
of a mystery. I don't have an ESR meter here. I guess I could probe the
removed components at work... of course I don't know what the ESR of the
original caps. I thought I could use a DMM to get an indication, but it
must be marginal enough I can't tell which one is the bad actor.

As for the posting at the top vs bottom... thank Outlook for always starting
at the top rather than the bottom of the post

 

[Mark Zacharias]

"G B" <geeberry@frontiernet.net> wrote in message
news:y4Jfl.48235$8a4.39372@newsfe08.iad...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:wZ8fl.7570$1s3.6110@newsfe14.ams2...
"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display
and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of the
power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display
blinks on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...


"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...
The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then
goes blank and starts again. Also every time the display blinks, the
carriage motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?


Have you replaced any electros in the front end or were they all
secondary side ? This sort of odd behaviour in switchers can be
symptomatic of small caps - often only from 1 to 47uF in value - situated
around the oscillator / control IC having gone high ESR. You will often
find them located close to some other component or heatsink, which runs
hot. Do you have an ESR meter ? Just as an aside, it makes a thread and
the replies much easier to follow if you bottom-post rather than top.


Arfa



I replaced 9 caps all in the area of the switcher, or at least where I
think the switcher is. I replaced the large regulation cap (82uF @ 200V)
and I replaced a small (4.7uF@50V) on what I would consider the primary
side. (prior to the large transformer). I replaced all the
electorlytics: 10uF, 100uF, 330uF, 470uF, and 1000uF values on what I
think is the secondary. Do you know if the switcher provides the
boot-strap voltage in standby mode? Or do they have another regulator
somewhere off the line regulation circuitr? I have also what appears to
be a hot-spot on the circuit board around QIP107, RIP110, QIP108, ZDIP05,
and DIP109. It doesn't feel warm to the touch after it has been running
for a while.. so the hot-spot is a bit of a mystery. I don't have an ESR
meter here. I guess I could probe the removed components at work... of
course I don't know what the ESR of the original caps. I thought I could
use a DMM to get an indication, but it must be marginal enough I can't
tell which one is the bad actor.

As for the posting at the top vs bottom... thank Outlook for always
starting at the top rather than the bottom of the post

Likely scenario:
The hot spot on the board was caused by the over-voltage at that point,
caused by the bad caps. You replaced the caps - now the voltage there is
normal. This presumes the zener diode, which is what got hot, did not just
short.

Mark Z.

 

[Arfa Daily]

"G B" <geeberry@frontiernet.net> wrote in message
news:y4Jfl.48235$8a4.39372@newsfe08.iad...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:wZ8fl.7570$1s3.6110@newsfe14.ams2...
"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display
and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of the
power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display
blinks on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...


"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...
The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then
goes blank and starts again. Also every time the display blinks, the
carriage motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?


Have you replaced any electros in the front end or were they all
secondary side ? This sort of odd behaviour in switchers can be
symptomatic of small caps - often only from 1 to 47uF in value - situated
around the oscillator / control IC having gone high ESR. You will often
find them located close to some other component or heatsink, which runs
hot. Do you have an ESR meter ? Just as an aside, it makes a thread and
the replies much easier to follow if you bottom-post rather than top.


Arfa



I replaced 9 caps all in the area of the switcher, or at least where I
think the switcher is. I replaced the large regulation cap (82uF @ 200V)
and I replaced a small (4.7uF@50V) on what I would consider the primary
side. (prior to the large transformer). I replaced all the
electorlytics: 10uF, 100uF, 330uF, 470uF, and 1000uF values on what I
think is the secondary. Do you know if the switcher provides the
boot-strap voltage in standby mode? Or do they have another regulator
somewhere off the line regulation circuitr? I have also what appears to
be a hot-spot on the circuit board around QIP107, RIP110, QIP108, ZDIP05,
and DIP109. It doesn't feel warm to the touch after it has been running
for a while.. so the hot-spot is a bit of a mystery. I don't have an ESR
meter here. I guess I could probe the removed components at work... of
course I don't know what the ESR of the original caps. I thought I could
use a DMM to get an indication, but it must be marginal enough I can't
tell which one is the bad actor.

As for the posting at the top vs bottom... thank Outlook for always
starting at the top rather than the bottom of the post

Yeah, that's a problem with it. Nobody gets too upset on here, but on some
groups they get *really* arsey if you do it. Top posting can sometimes
confuse a thread, especially when specific questions are being answered, and
the majority are posting one way, and someone is posting the other ...

As to your question, I would expect that the standby supplies for the system
control micro are derived from the switcher, but I couldn't say for sure.
It's been a while since I did any work on any VCRs, Sony included. Knowing
what the ESRs of the original caps should be is not really an absolute. As I
have commented a number of times with regard to using ESR meters, a lot of
it is intuition, with the meter just acting as a backup. In general, the
smaller the value of the cap, the higher its ESR will read on a meter. The
small ones, such as your 4.7uF, should not read higher than a few ohms. 47uF
up to say 220uF should not be higher than a couple of ohms. Above this
capacitance value, ESRs will generally be in decimals of an ohm, and a
factor of 10 lower than that for the 'big' values of 2200uF and up. In
general, the higher the voltage working, the lower the range of ESR values
that would be 'normal' for any particular cap. Usually, if a cap has reached
a point where it is causing trouble in a switcher, its ESR value will have
gone off with the fairies, and be easily spotted as the bad one.
Interestingly, its capacitance value will often read near enough correct on
a C - meter.

What your remaining problem is, I really don't know without looking at a
schematic for the power supply, but one thing I would say is that it seems
odd that you have managed to cure the primary problem with replacing
whichever cap it was amongst the ones that you changed, and then been left
with this slightly 'odd' problem. A faulty cap is a good call for the
original problem, and was almost certainly the correct diagnosis, but it is
very rare, when this is the case, for there to be any other issues. If it
were me, I think that as a first move, I would go over all my work again
very carefully, making sure that I had got the right values in the right
places (for that you would need a schematic), and that I had not
accidentally put any in backwards (easily done :-\ ). Also, make sure that
the replacement types are 'suitable' i.e. the correct or very close value,
similar voltage working, low ESR type. They should also be 105 degree or
better types for future reliability. Also, I would not trust any caps that
you have had lying around in a drawer for years, or any radial leaded types
as being suitable.

Stating the obvious maybe, but also be sure that your soldering is all good.
If it's not something which you do all day, it is easy to get a poor joint
on a component, without realising it ...

Arfa

 

[G B]

"Mark Zacharias" <mark_zacharias@labolgcbs.net> wrote in message
news:VlOfl.3120$%54.1662@nlpi070.nbdc.sbc.com...

"G B" <geeberry@frontiernet.net> wrote in message
news:y4Jfl.48235$8a4.39372@newsfe08.iad...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:wZ8fl.7570$1s3.6110@newsfe14.ams2...
"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display
and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of
the power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display
blinks on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...


"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...
The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then
goes blank and starts again. Also every time the display blinks, the
carriage motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?


Have you replaced any electros in the front end or were they all
secondary side ? This sort of odd behaviour in switchers can be
symptomatic of small caps - often only from 1 to 47uF in value -
situated around the oscillator / control IC having gone high ESR. You
will often find them located close to some other component or heatsink,
which runs hot. Do you have an ESR meter ? Just as an aside, it makes a
thread and the replies much easier to follow if you bottom-post rather
than top.

Arfa



I replaced 9 caps all in the area of the switcher, or at least where I
think the switcher is. I replaced the large regulation cap (82uF @ 200V)
and I replaced a small (4.7uF@50V) on what I would consider the primary
side. (prior to the large transformer). I replaced all the
electorlytics: 10uF, 100uF, 330uF, 470uF, and 1000uF values on what I
think is the secondary. Do you know if the switcher provides the
boot-strap voltage in standby mode? Or do they have another regulator
somewhere off the line regulation circuitr? I have also what appears to
be a hot-spot on the circuit board around QIP107, RIP110, QIP108, ZDIP05,
and DIP109. It doesn't feel warm to the touch after it has been running
for a while.. so the hot-spot is a bit of a mystery. I don't have an ESR
meter here. I guess I could probe the removed components at work... of
course I don't know what the ESR of the original caps. I thought I could
use a DMM to get an indication, but it must be marginal enough I can't
tell which one is the bad actor.

As for the posting at the top vs bottom... thank Outlook for always
starting at the top rather than the bottom of the post



Likely scenario:
The hot spot on the board was caused by the over-voltage at that point,
caused by the bad caps. You replaced the caps - now the voltage there is
normal. This presumes the zener diode, which is what got hot, did not just
short.

Mark Z.
That was at least part of the theory.. I was thinking this might be the

circuit that was used to regulate ~150VDC down to a standby voltage. I need
to trace the circuits to see if I can figure it out. If it is the problem,
I have no idea what to replace it with. I doubt I can see the numbers on
the diode, but
I will yank it all back apart to see if I can determine what it is. Any
idea what the standby voltage in these VCR's is?
Greg

 

[G B]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:ZQOfl.207$875.77@newsfe21.ams2...

"G B" <geeberry@frontiernet.net> wrote in message
news:y4Jfl.48235$8a4.39372@newsfe08.iad...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:wZ8fl.7570$1s3.6110@newsfe14.ams2...
"b" <reverend_rogers@yahoo.com> wrote in message
news:d28c65b1-42f1-4dbd-8447-b1907cf101dc@r41g2000prr.googlegroups.com...
On 23 ene, 04:51, "G B" <geebe...@frontiernet.net> wrote:
Hi,

I have a Sony SLVN750. It failed such that it had no time display
and
would no longer power up when pressing the power switch. I tore it
apart
and "shot-gun" replaced the nine capacitors in the general area of
the power
supply with capacitors of the same value. It now will power up and
even
play a tape BUT when it is powered down (in standby) the display
blinks on
and off. It seems the power supply is cycling on and off. Any idea
what
would cause this? Any help is appreciated...


"G B" <geeberry@frontiernet.net> wrote in message
news:8T4fl.29$np4.6@newsfe15.iad...
The display isn't flashing per say...

The display goes blank after the supply apepars to shut itself down. It
returns after say 500 msecs.. then stays on for about a second.. then
goes blank and starts again. Also every time the display blinks, the
carriage motor appears to go through its position check...
I did replace the all the "big" electrolytic caps.. the largest were a
couple of 1000uF... I suspect that section of the circuit is working
properly.. I think there must be a standby power section of the circuit
which is toast... any ideas?


Have you replaced any electros in the front end or were they all
secondary side ? This sort of odd behaviour in switchers can be
symptomatic of small caps - often only from 1 to 47uF in value -
situated around the oscillator / control IC having gone high ESR. You
will often find them located close to some other component or heatsink,
which runs hot. Do you have an ESR meter ? Just as an aside, it makes a
thread and the replies much easier to follow if you bottom-post rather
than top.

Arfa



I replaced 9 caps all in the area of the switcher, or at least where I
think the switcher is. I replaced the large regulation cap (82uF @ 200V)
and I replaced a small (4.7uF@50V) on what I would consider the primary
side. (prior to the large transformer). I replaced all the
electorlytics: 10uF, 100uF, 330uF, 470uF, and 1000uF values on what I
think is the secondary. Do you know if the switcher provides the
boot-strap voltage in standby mode? Or do they have another regulator
somewhere off the line regulation circuitr? I have also what appears to
be a hot-spot on the circuit board around QIP107, RIP110, QIP108, ZDIP05,
and DIP109. It doesn't feel warm to the touch after it has been running
for a while.. so the hot-spot is a bit of a mystery. I don't have an ESR
meter here. I guess I could probe the removed components at work... of
course I don't know what the ESR of the original caps. I thought I could
use a DMM to get an indication, but it must be marginal enough I can't
tell which one is the bad actor.

As for the posting at the top vs bottom... thank Outlook for always
starting at the top rather than the bottom of the post


Yeah, that's a problem with it. Nobody gets too upset on here, but on some
groups they get *really* arsey if you do it. Top posting can sometimes
confuse a thread, especially when specific questions are being answered,
and the majority are posting one way, and someone is posting the other ...

As to your question, I would expect that the standby supplies for the
system control micro are derived from the switcher, but I couldn't say for
sure. It's been a while since I did any work on any VCRs, Sony included.
Knowing what the ESRs of the original caps should be is not really an
absolute. As I have commented a number of times with regard to using ESR
meters, a lot of it is intuition, with the meter just acting as a backup.
In general, the smaller the value of the cap, the higher its ESR will read
on a meter. The small ones, such as your 4.7uF, should not read higher
than a few ohms. 47uF up to say 220uF should not be higher than a couple
of ohms. Above this capacitance value, ESRs will generally be in decimals
of an ohm, and a factor of 10 lower than that for the 'big' values of
2200uF and up. In general, the higher the voltage working, the lower the
range of ESR values that would be 'normal' for any particular cap.
Usually, if a cap has reached a point where it is causing trouble in a
switcher, its ESR value will have gone off with the fairies, and be easily
spotted as the bad one. Interestingly, its capacitance value will often
read near enough correct on a C - meter.

What your remaining problem is, I really don't know without looking at a
schematic for the power supply, but one thing I would say is that it seems
odd that you have managed to cure the primary problem with replacing
whichever cap it was amongst the ones that you changed, and then been left
with this slightly 'odd' problem. A faulty cap is a good call for the
original problem, and was almost certainly the correct diagnosis, but it
is very rare, when this is the case, for there to be any other issues. If
it were me, I think that as a first move, I would go over all my work
again very carefully, making sure that I had got the right values in the
right places (for that you would need a schematic), and that I had not
accidentally put any in backwards (easily done :-\ ). Also, make sure that
the replacement types are 'suitable' i.e. the correct or very close value,
similar voltage working, low ESR type. They should also be 105 degree or
better types for future reliability. Also, I would not trust any caps that
you have had lying around in a drawer for years, or any radial leaded
types as being suitable.

Stating the obvious maybe, but also be sure that your soldering is all
good. If it's not something which you do all day, it is easy to get a poor
joint on a component, without realising it ...

Arfa

I'm going to tear it apart again. I will check the cap's polarity, but I am

not expecting I messed that up. I did draw a diagram before removing the
original capacitors so I think I have the right capacitors in the right
holes. I did substitute one value, I think a 100uF for an 82uF. I tried to
buy duplicate values so worse case I can try a 2nd version of the
replacement capacitor. I will reflow all the solder too... I'm pretty good
at seeing a bad joint, but I've been bitten by that before too.

Thanks for all your help... This would be so much easier if we just had a
schematic or a similar schematic to get an idea from

-Greg

 

[Arfa Daily]

Yeah, that's a problem with it. Nobody gets too upset on here, but on
some groups they get *really* arsey if you do it. Top posting can
sometimes confuse a thread, especially when specific questions are being
answered, and the majority are posting one way, and someone is posting
the other ...

As to your question, I would expect that the standby supplies for the
system control micro are derived from the switcher, but I couldn't say
for sure. It's been a while since I did any work on any VCRs, Sony
included. Knowing what the ESRs of the original caps should be is not
really an absolute. As I have commented a number of times with regard to
using ESR meters, a lot of it is intuition, with the meter just acting as
a backup. In general, the smaller the value of the cap, the higher its
ESR will read on a meter. The small ones, such as your 4.7uF, should not
read higher than a few ohms. 47uF up to say 220uF should not be higher
than a couple of ohms. Above this capacitance value, ESRs will generally
be in decimals of an ohm, and a factor of 10 lower than that for the
'big' values of 2200uF and up. In general, the higher the voltage
working, the lower the range of ESR values that would be 'normal' for any
particular cap. Usually, if a cap has reached a point where it is causing
trouble in a switcher, its ESR value will have gone off with the fairies,
and be easily spotted as the bad one. Interestingly, its capacitance
value will often read near enough correct on a C - meter.

What your remaining problem is, I really don't know without looking at a
schematic for the power supply, but one thing I would say is that it
seems odd that you have managed to cure the primary problem with
replacing whichever cap it was amongst the ones that you changed, and
then been left with this slightly 'odd' problem. A faulty cap is a good
call for the original problem, and was almost certainly the correct
diagnosis, but it is very rare, when this is the case, for there to be
any other issues. If it were me, I think that as a first move, I would go
over all my work again very carefully, making sure that I had got the
right values in the right places (for that you would need a schematic),
and that I had not accidentally put any in backwards (easily done :-\ ).
Also, make sure that the replacement types are 'suitable' i.e. the
correct or very close value, similar voltage working, low ESR type. They
should also be 105 degree or better types for future reliability. Also, I
would not trust any caps that you have had lying around in a drawer for
years, or any radial leaded types as being suitable.

Stating the obvious maybe, but also be sure that your soldering is all
good. If it's not something which you do all day, it is easy to get a
poor joint on a component, without realising it ...

Arfa

I'm going to tear it apart again. I will check the cap's polarity, but I
am not expecting I messed that up. I did draw a diagram before removing
the original capacitors so I think I have the right capacitors in the
right holes. I did substitute one value, I think a 100uF for an 82uF. I
tried to buy duplicate values so worse case I can try a 2nd version of the
replacement capacitor. I will reflow all the solder too... I'm pretty
good at seeing a bad joint, but I've been bitten by that before too.

Thanks for all your help... This would be so much easier if we just had a
schematic or a similar schematic to get an idea from

-Greg

100uF subbed for 82uF will not be a problem.

Arfa