Hi all.

My Roland E-500 has a problem: after ~5 minutes of being switched on it will
turn itself off and immediately switch back on again. It will then do this
every few minutes, or after a longer period of time, or sometimes not at all
and will work normally. There is nothing happening physically to the
keyboard to trigger a restart and the mains lead is good.

It has an internal switching power supply board and a seperate power
amplifier board with a small relay on it which clicks when the power goes
on, and when the keyboard restarts itself.

I found a discoloured and cracked 220ohm resistor on the power board and
replaced it, even though it was still testing at 200ohms, but this has made
no difference. I've also re-soldered any joints which looked suspect.

One other possible symptom is that the main transformer on the power board
hisses. The sound changes if I push on the transformer itself, or on the
board. There are two large capacitors near the transformer, one of which has
a small bulge on the top, which can be pushed back down easily, but shows no
sign of leaking, nor do any of the other caps.

Any thoughts?

I can put some pictures of the power board on the internet if it would help.
It has big "proper" components on it :-)

Simon.

Den Thu, 25 Jan 2007 09:54:35 +0000 skrev Mungo \"Two Sheds\" Toadfoot:


One other possible symptom is that the main transformer on the power board
hisses. The sound changes if I push on the transformer itself, or on the
board. There are two large capacitors near the transformer, one of which has
a small bulge on the top, which can be pushed back down easily, but shows no
sign of leaking, nor do any of the other caps.

Any thoughts?

New capacitors. The bulge is a sign. If you mesure them with aa ESR meter
you will find a high esr. It cauces all kinds of strange faults in the PSU.

--
Vy73 de OZ1GNN

Christian Treldal wrote:
Den Thu, 25 Jan 2007 09:54:35 +0000 skrev Mungo \"Two Sheds\"
Toadfoot:


One other possible symptom is that the main transformer on the power
board hisses. The sound changes if I push on the transformer itself,
or on the board. There are two large capacitors near the
transformer, one of which has a small bulge on the top, which can be
pushed back down easily, but shows no sign of leaking, nor do any of
the other caps.

Any thoughts?

New capacitors. The bulge is a sign. If you mesure them with aa ESR
meter you will find a high esr. It cauces all kinds of strange faults
in the PSU.

Much appreciated, thank you... and to Mr Plow

I've put some pictures here if you wouldn't mind having a look:
http://www.arcl40.dsl.pipex.com/roland/roland.html

The 1st, 3rd and 4th pictures show the small bulge in the top, and the 5th
and 6th pictures show their position on the board, next to the transformer.

I'll get searching for new ones.

Would it be an idea just to replace all the caps on the board or is that
overkill?

Si

Meat Plow wrote:

Might as well replace all 8 or 9 of them while you're at it. Don't
remember how hard it is to get to the SMPS in your particular
keyboard but if I recall it's not something that I would want to
undertake as other caps fail

Apart from the... oh, 15,000 perhaps, screws holding the back on it's not
too bad to get into the thing - there's remarkably little inside it either,
considering what it can do!

Having said that I'll still replace all the caps I can.

Thanks again,

Si

On Thu, 25 Jan 2007 09:54:35 -0000, "Mungo \"Two Sheds\" Toadfoot"
put finger to keyboard and composed:

Hi all.

My Roland E-500 has a problem: after ~5 minutes of being switched on it will
turn itself off and immediately switch back on again. It will then do this
every few minutes, or after a longer period of time, or sometimes not at all
and will work normally. There is nothing happening physically to the
keyboard to trigger a restart and the mains lead is good.

It has an internal switching power supply board and a seperate power
amplifier board with a small relay on it which clicks when the power goes
on, and when the keyboard restarts itself.

I found a discoloured and cracked 220ohm resistor on the power board and
replaced it, even though it was still testing at 200ohms, but this has made
no difference. I've also re-soldered any joints which looked suspect.

One other possible symptom is that the main transformer on the power board
hisses. The sound changes if I push on the transformer itself, or on the
board. There are two large capacitors near the transformer, one of which has
a small bulge on the top, which can be pushed back down easily, but shows no
sign of leaking, nor do any of the other caps.

Any thoughts?

I can put some pictures of the power board on the internet if it would help.
It has big "proper" components on it :-)

Simon.

I don't think the largest caps are your most likely culprits. Instead
I think that the one near R12 is probably the root cause of your
problems. As a general rule I always check the smaller electrolytics
on the primary side of switchmode PSUs (eg the one near R2) as these
often go high ESR. But as others have advised, change all the caps on
the supply secondary for good measure.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

I don't think the largest caps are your most likely culprits. Instead
I think that the one near R12 is probably the root cause of your
problems. As a general rule I always check the smaller electrolytics
on the primary side of switchmode PSUs (eg the one near R2) as these
often go high ESR. But as others have advised, change all the caps on
the supply secondary for good measure.

- Franc Zabkar

Thanks Franc.

If you have a minute spare I wonder if you would look at the second picture
again and tell me if you can work out what is next to the capacitor you
recommend I replace; the one near R12?

http://www.arcl40.dsl.pipex.com/roland/roland.html

I know it's difficult to make out but the power board is back in the
keyboard now until I can find a source of capacitors, so I can't take more
pictures yet. It looks to me like another capacitor but it's covered in
moulded black plastic with a pinched top. It looks to me like some kind of
sleeving to protect the component from heat, or interference maybe, as it's
located next to the transformer? I will remove the component when I change
the caps but at present I've no real idea what it is!

Any ideas?

Meat Plow wrote:

If you have a minute spare I wonder if you would look at the second
picture again and tell me if you can work out what is next to the
capacitor you recommend I replace; the one near R12?

Maybe an MOV or thermistor? Got a schematic?

Unfortunately not. I wish I did but sites which had Roland schematics were
asked to remove them.

Si

On Sun, 28 Jan 2007 10:37:31 -0000, "Mungo \"Two Sheds\" Toadfoot"
put finger to keyboard and composed:

Franc Zabkar wrote:

I don't think the largest caps are your most likely culprits. Instead
I think that the one near R12 is probably the root cause of your
problems. As a general rule I always check the smaller electrolytics
on the primary side of switchmode PSUs (eg the one near R2) as these
often go high ESR. But as others have advised, change all the caps on
the supply secondary for good measure.

- Franc Zabkar

Thanks Franc.

If you have a minute spare I wonder if you would look at the second picture
again and tell me if you can work out what is next to the capacitor you
recommend I replace; the one near R12?

http://www.arcl40.dsl.pipex.com/roland/roland.html

I know it's difficult to make out but the power board is back in the
keyboard now until I can find a source of capacitors, so I can't take more
pictures yet. It looks to me like another capacitor but it's covered in
moulded black plastic with a pinched top. It looks to me like some kind of
sleeving to protect the component from heat, or interference maybe, as it's
located next to the transformer? I will remove the component when I change
the caps but at present I've no real idea what it is!

Any ideas?

A coil? If so, it will measure close to zero ohms, and there should be
an Lnn circuit reference on the PCB. I'd find out where the + terminal
of the capacitor goes. It will probably go to one of the secondary
outputs at connectors CN1/2/3/4. Actually, upon closer inspection the
capacitor looks to be covered in fixing glue, so it may not be bulging
as I first thought. BTW, when replacing these caps, make sure you use
low ESR, 105 degC types.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

A coil? If so, it will measure close to zero ohms, and there should be
an Lnn circuit reference on the PCB.

Thanks. I'll have a closer look when I start replacing things.

I'd find out where the + terminal
of the capacitor goes. It will probably go to one of the secondary
outputs at connectors CN1/2/3/4. Actually, upon closer inspection the
capacitor looks to be covered in fixing glue, so it may not be bulging
as I first thought. BTW, when replacing these caps, make sure you use
low ESR, 105 degC types.


Ok. There's nothing on the board that *looks* dead at all really; all the
caps look perfect apart from just one of the big ones that has the slight
bulge in the top.

Is it possible that another board is causing the power to shut down and
restart? If so that opens up a whole load of new possibilities! The relay
which clicks when the keyboard is switched on, or resets, is on a seperate
power amplifier board which is fed from the main power board, obviously.

I wish I knew more about this stuff!!

Si