[YamahaDX] Does Anyone Have Photos Of DX7 Battery Section of Motherboard?

[[e-mail] [YamahaDX]]

I am in need of some REAL CLOSE UPs of the front and back of the DX7 MK1 to show the traces and so forth around the battery area. There may be a short or short trace I'm missing. I replaced 1 battery with success in 1 DX7 but the other one is being VERY stubborn. Everything else works on it except keeping internal patches. Annoying as hell. Wish it had more than 1 channel to transmit on - use it as a controller. I've tried 3 times to get it going. I may have toasted some trace but some of them do not show up like others. For instance, the positive on the back has a 3 sided square embedded without trace lines. Then, it has some square box-like thing at the end with little circuit like thingies. I thought I could short cut it and go directly to the end square instead of going around the 3 sided trace.

The negative has a trace strip that leads down to a diode but insists on being in on the fun and I can't do a shortcut down there on the front side also.

Funny (NOT!) that it worked almost like that on the first one but the 2nd DX7 is complaining. The schematics don't help much, even though I can locate D4 and the Ram chips, it doesn't give much info to the novice about the battery. Unless I need to learn Latin. :)

Any help would be appreciated. I have scoured the 'Net and found many batteries but not such fine detail.

Tracy

[Tracy Barber [e-mail] [YamahaDX]]

BTW,

I tested the battery and it was 3.x V by itself. New battery, I would have to assume. After the soldering, I checked the solder points (solder hills - oops!) and the told me the reading was 2.9 V, our favorite number. This was before putting the board back into the DX7. Then, hooking it back up it tells me 4.5 / 4.6 V again. You nasty mutha! could this mean a bad RAM chip or something that gets activated with the power on? Makes no sense to me.

I should've included that info in the first message. Sorry.

Tracy


--------------------------------------------
On Tue, 6/19/18, ***@yahoo.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Tuesday, June 19, 2018, 9:49 PM


 









I am in need of some REAL CLOSE UPs of
the front and back of the DX7 MK1 to show the traces and so
forth around the battery area. There may be a short or short
trace I'm missing. I replaced 1 battery with success in
1 DX7 but the other one is being VERY stubborn.  Everything
else works on it except keeping internal patches.  Annoying
as hell.  Wish it had more than 1 channel to transmit on -
use it as a controller.  I've tried 3 times to get it
going.  I may have toasted some trace but some of them do
not show up like others.  For instance, the positive on the
back has a 3 sided square embedded without trace lines. 
Then, it has some square box-like thing at the end with
little circuit like thingies.  I thought I could short cut
it and go directly to the end square instead of going around
the 3 sided trace.

The
negative has a trace strip that leads down to a diode but
insists on being in on the fun and I can't do a shortcut
down there on the front side also.

Funny (NOT!) that it worked almost like that on
the first one but the 2nd DX7 is complaining.  The
schematics don't help much, even though I can locate D4
and the Ram chips, it doesn't give much info to the
novice about the battery.  Unless I need to learn Latin. 
:)

Any help would be
appreciated.  I have scoured the 'Net and found many
batteries but not such fine detail.

Tracy











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[Brian [e-mail] [YamahaDX]]

I think someone said that might mean a you have a shorted diode and you’re reading the 5v line.


From: Tracy Barber ***@yahoo.com [YamahaDX]
Sent: Wednesday, 20 June 2018 12:09 PM
To: ***@yahoogroups.com
Subject: Re: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section ofMotherboard?

BTW,

I tested the battery and it was 3.x V by itself. New battery, I would have to assume. After the soldering, I checked the solder points (solder hills - oops!) and the told me the reading was 2.9 V, our favorite number. This was before putting the board back into the DX7. Then, hooking it back up it tells me 4.5 / 4.6 V again. You nasty mutha! could this mean a bad RAM chip or something that gets activated with the power on? Makes no sense to me.

I should've included that info in the first message. Sorry.

Tracy


--------------------------------------------
On Tue, 6/19/18, ***@yahoo.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Tuesday, June 19, 2018, 9:49 PM


 









I am in need of some REAL CLOSE UPs of
the front and back of the DX7 MK1 to show the traces and so
forth around the battery area. There may be a short or short
trace I'm missing. I replaced 1 battery with success in
1 DX7 but the other one is being VERY stubborn.  Everything
else works on it except keeping internal patches.  Annoying
as hell.  Wish it had more than 1 channel to transmit on -
use it as a controller.  I've tried 3 times to get it
going.  I may have toasted some trace but some of them do
not show up like others.  For instance, the positive on the
back has a 3 sided square embedded without trace lines. 
Then, it has some square box-like thing at the end with
little circuit like thingies.  I thought I could short cut
it and go directly to the end square instead of going around
the 3 sided trace.

The
negative has a trace strip that leads down to a diode but
insists on being in on the fun and I can't do a shortcut
down there on the front side also.

Funny (NOT!) that it worked almost like that on
the first one but the 2nd DX7 is complaining.  The
schematics don't help much, even though I can locate D4
and the Ram chips, it doesn't give much info to the
novice about the battery.  Unless I need to learn Latin. 
:)

Any help would be
appreciated.  I have scoured the 'Net and found many
batteries but not such fine detail.

Tracy











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------------------------------------
Posted by: Tracy Barber <***@yahoo.com>
------------------------------------


------------------------------------

Yahoo Groups Links

[[e-mail] [YamahaDX]]

Do you have a volt meter or multi-meter, Tracy?

With the power off, the static RAM chips should be being powered from your 3V battery via a diode, D4, so there should be a small voltage drop across it, if it's working properly.

A healthy diode will have a voltage drop of about 0.3V to 0.6V, depending on the material it's made from. 0.6V is most likely. If you see zero volts, from one terminal to the other, the diode has melted into a conductive blob.

The voltage drop would be positive when measured with the "+" (red) lead of the meter on the anode, and the "-" (black) lead on the cathode, but you could measure both ways, to make sure.

The idea of the diode is to supply a small current to the static RAM, whether or not there's a 5V supply. If there is a 5V supply (the DX7 is turned on), that powers the static RAM. If there isn't, the supply is meant to come from the 3V battery, via the diode.

However, if the diode has melted into a conductive blob, it conducts both ways, so 5V is applied to the battery, whenever the DX7 is turned on... which is probably not good for the battery. That could also happen if the contacts for the diode have been bridged by solder while changing the battery - assuming it's close to the battery socket.

If the diode has failed by going open circuit (which can happen too), the static RAM wouldn't be fed from the 3V battery, and nothing would get remembered with the power off, so it seems safe to assume that's not the case.

- Andy

[[e-mail] [YamahaDX]]

Oops - I thought I'd said this, but apparently, not.

The cathode of a diode is normally marked by a stripe.

The anode end will be connected to the positive terminal of the 3V battery socket.

- Andy

[[e-mail] [YamahaDX]]

Okay, I missed the part where you said it's not retaining patches, Tracy.

I'm not clear on what you said about wiring the battery. Could you post some pictures of that area?

The positive terminal of the battery should lead to the anode of D4, not the negative terminal. Are you sure you've wired it in correctly?

The negative terminal of the battery should connect to ground, which is fairly easy to spot, normally - ground traces normally cover quite a lot of area. Also, they're connected to the negative pin of several large capacitors.

A meter that can show continuity, and read voltage, should be all you need - i.e. one costing just a few dollars, or currency of your choice; nothing fancy.

I would measure the voltage across the battery while in circuit, preferably with and without being powered up. I'd also measure the voltage drop across D4, and/or the voltage at the cathode (stripe end, probably) of D4, from ground, in both cases. That should be enough to work out what's going on.

If the 3V battery was wired in backwards, it's possible it wouldn't do any harm - the diode D4 would protect the static RAM chips from it; they just wouldn't remember. It might damage the circuit that tries to read its voltage, but then again, it might not. Since the software that does that isn't meant to read a negative voltage, it may just give a wrong answer.

- Andy

[[e-mail] [YamahaDX]]

My DX7 MK1 had a problem with patches becoming corrupted when powered off. It turned out it wasn't the battery, but the Zener diode ZD1 on the power supply board had failed. This diode is used to ensure the RAM is prevented from being written with bad data as the power turns off.


I'm not saying this is definitely what you have, but it's another possible thing to check.


Ant.

[[e-mail] [YamahaDX]]

A couple of things... if you get a REAL copy of the service manual the PCB layout is easy to read. It is included in color so there is no guessing. There is an infamous jumper on the bottom of the board. I think this was a production requirement of some sort, so as someone said check the continuity from the battery + pad to the diode and then the diode to the SRAM Vcc. The SRAM needs to be of a particular type, so beware of incorrect chips in the sockets.

The 4.5v thing on the FUNCTION CONTROL Battery Check is a common problem but I don't know the solution and have not investigated it myself yet. Too busy discovering bugs in the velocity firmware (that are loosely associated with the low velocity MIDI Out).

[Tracy Barber [e-mail] [YamahaDX]]

Hmmm... I hear ya...

Looking at it, D4 "looks" fine. I checked it for volts and can't remember what they were. This is where I'm leading. Some other diode / thingie near the battery acting up. Booked for later thought. Thanks.

Tracy


--------------------------------------------
On Wed, 6/20/18, Brian ***@gmail.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: RE: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section ofMotherboard?
To: "***@yahoogroups.com" <***@yahoogroups.com>
Date: Wednesday, June 20, 2018, 1:22 AM


 









 I think someone said that might
mean a you have a shorted diode and you’re reading the 5v
line.

[Tracy Barber [e-mail] [YamahaDX]]

Very good response. Now to digest it. Take my time with it and open 'er up and look at it again. This I should be able to do from the top of the mommy board, yes?

I have a Fluke 87V MM. Checks the battery levels fine, so there's juice in the meter.

Food for thought for later. Have to do an evening extravaganza tonight and tomorrow night so it may take me 3 days to get 'er done.

Thanks!

Tracy



--------------------------------------------
On Wed, 6/20/18, ***@ntlworld.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: Re: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Wednesday, June 20, 2018, 1:55 AM


 









Do you have a volt meter or multi-meter, Tracy?

With the power off, the static
RAM chips should be being powered from your 3V battery via a
diode, D4, so there should be a small voltage drop across
it, if it's working properly.

A healthy diode will have a voltage drop of
about 0.3V to 0.6V, depending on the material it's made
from.  0.6V is most likely.  If you see zero volts, from
one terminal to the other, the diode has melted into a
conductive blob.

The
voltage drop would be positive when measured with the
"+" (red) lead of the meter on the anode, and the
"-" (black) lead on the cathode, but you could
measure both ways, to make sure.

The idea of the diode is to supply a small
current to the static RAM, whether or not there's a 5V
supply.  If there is a 5V supply (the DX7 is turned on),
that powers the static RAM.  If there isn't, the supply
is meant to come from the 3V battery, via the diode.

However, if the diode has
melted into a conductive blob, it conducts both ways, so 5V
is applied to the battery, whenever the DX7 is turned on...
which is probably not good for the battery.  That could
also happen if the contacts for the diode have been bridged
by solder while changing the battery - assuming it's
close to the battery socket.

If the diode has failed by going open circuit
(which can happen too), the static RAM wouldn't be fed
from the 3V battery, and nothing would get remembered with
the power off, so it seems safe to assume that's not the
case.

- Andy









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[Tracy Barber [e-mail] [YamahaDX]]

That's info I was looking for with a photo. Perfect. Pieces coming together now. I know there's a diode hooked to the negative side, but I'll find the positive side thingie.

Tracy


--------------------------------------------
On Wed, 6/20/18, ***@ntlworld.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: Re: [YamahaDX] Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Wednesday, June 20, 2018, 2:00 AM


 









Oops - I thought I'd said this, but apparently,
not.

The cathode of a diode
is normally marked by a stripe.

The anode end will be connected to the positive
terminal of the 3V battery socket.

[Tracy Barber [e-mail] [YamahaDX]]

I didn't take into consideration that the battery holder I'm soldering in may have the wires backwards! All I need to do is look at the working one for that answer. I bought 3 of these holders from the same place and 2 of them work well. 1 is in a Korg DDD-5 drum machine and the other in a DX7 Mk1 and they are both singing.

My eye for these things is not up to snuff yet, but I am learning - slowly. Some good teaching here on Yahoo with this and other projects. I'll put all of your post together and look them over in order.

Worst case, I'll post photos here of the soldering demon's work. No doubt there's a faux pas somewhere that I'm not privy to. I'll get it!

Tracy




--------------------------------------------
On Wed, 6/20/18, ***@ntlworld.com [YamahaDX] <***@yahoogroups.com> wrote:

Subject: [YamahaDX] Re: Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Wednesday, June 20, 2018, 2:46 AM


 









Okay, I missed the part where you said it's not
retaining patches, Tracy.

I'm not clear on what you said about wiring
the battery.  Could you post some pictures of that area?

The positive terminal of the
battery should lead to the anode of D4, not the negative
terminal.  Are you sure you've wired it in
correctly?

The negative
terminal of the battery should connect to ground, which is
fairly easy to spot, normally - ground traces normally cover
quite a lot of area.  Also, they're connected to the
negative pin of several large capacitors.

A meter that can show
continuity, and read voltage, should be all you need - i.e.
one costing just a few dollars, or currency of your choice;
nothing fancy.

I would
measure the voltage across the battery while in circuit,
preferably with and without being powered up.  I'd also
measure the voltage drop across D4, and/or the voltage at
the cathode (stripe end, probably) of D4, from ground, in
both cases.  That should be enough to work out what's
going on.

If the 3V battery
was wired in backwards, it's possible it wouldn't do
any harm - the diode D4 would protect the static RAM chips
from it; they just wouldn't remember.  It might damage
the circuit that tries to read its voltage, but then again,
it might not.  Since the software that does that isn't
meant to read a negative voltage, it may just give a wrong
answer.

- Andy

[Tracy Barber [e-mail] [YamahaDX]]

OK, I can read the board and schematic for that devil. I'll take a peek and see if it's toast. Good hint.

Yeah, everything else is working, including the diagnostics - up to 8 of 11.. Weird DX7 version or something.

Tracy


--------------------------------------------
On Wed, 6/20/18, ***@goffart.co.uk [YamahaDX] <***@yahoogroups.com> wrote:

Subject: [YamahaDX] Re: Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Wednesday, June 20, 2018, 4:28 AM


 









My DX7 MK1 had a problem with patches
becoming corrupted when powered off. It turned out it
wasn't the battery, but the Zener diode ZD1 on the power
supply board had failed. This diode is used to ensure the
RAM is prevented from being written with bad data as the
power turns off.
I'm not saying this is
definitely what you have, but it's another possible
thing to check.
Ant.

[Tracy Barber [e-mail] [YamahaDX]]

Yeah, I have the B/W multi-copied version. Impossible to see. The schematics are weird because the chips aren't in contiguous places like they are on the mommy board. I can find stuff, but the battery and traces therein are elusive. Thanks!

Funny (NOT!) that I saw something about the speed of MIDI when perusing documents. If I remember (brain is fuzzy) where I saw anything like that, I'll give a shout. I have a few places to look, in mind. This was something I was lacking when writing editors for the Korg DW6000 and Sequential Prophet 6000. Got them to work on an IBM PC (yoiks!) but had no timing mechanism for faster PCs. That was the only weak point of the editors back in the DOS daze... should've got an Assembler routine somewhere.

Tracy


--------------------------------------------
On Wed, 6/20/18, ***@jps.net [YamahaDX] <***@yahoogroups.com> wrote:

Subject: [YamahaDX] Re: Does Anyone Have Photos Of DX7 Battery Section of Motherboard?
To: ***@yahoogroups.com
Date: Wednesday, June 20, 2018, 12:06 PM


 









A couple of things... if you get a REAL copy of the
service manual the PCB layout is easy to read.  It is
included in color so there is no guessing.  There is an
infamous jumper on the bottom of the board. I think this was
a production requirement of some sort, so as someone said
check the continuity from the battery + pad to the diode and
then the diode to the SRAM Vcc.  The SRAM needs to be of a
particular type, so beware of incorrect chips in the
sockets.

The 4.5v thing on
the FUNCTION CONTROL Battery Check is a common problem but I
don't know the solution and have not investigated it
myself yet.  Too busy discovering bugs in the velocity
firmware (that are loosely associated with the low velocity
MIDI Out).