[Phil]

Hello
I was in touch with a Welding Service center today , have been having a
problem with a Lincoln Precision 185 TIG welding machine , seems the Encoder
for the amperage control has decided to go Nuts , man says there $50.00 PC
board will cost me $ 980.50 , I thought he was kidding at first and he said
no he wasn't , the thing really will cost that much , I have mostly used
Miller over the years and have had pretty good luck with there units , I
live fairly close to Cleveland and a lady called me several years ago and
wondered why I didn't patronize my local Lincoln Co. , if see calls me again
I'll have a reason to tell her I prefer BLUE , I think this Lincoln 185 cost
just a little more than the PC Board and it's just over three years old.
Phil

[Jon Elson]

Phil wrote:
Hello
I was in touch with a Welding Service center today , have been having a
problem with a Lincoln Precision 185 TIG welding machine , seems the Encoder
for the amperage control has decided to go Nuts , man says there $50.00 PC
board will cost me $ 980.50 , I thought he was kidding at first and he said
no he wasn't , the thing really will cost that much , I have mostly used
Miller over the years and have had pretty good luck with there units , I
live fairly close to Cleveland and a lady called me several years ago and
wondered why I didn't patronize my local Lincoln Co. , if see calls me again
I'll have a reason to tell her I prefer BLUE , I think this Lincoln 185 cost
just a little more than the PC Board and it's just over three years old.
You might check around, especially on the net, there might be
somebody that will repair it rather than replace. When PC
boards get that expensive, it is very likely somebody who knows
the system can fix it much cheaper. It is unfortunate that
Lincoln doesn't give out circuit diagrams of their boards, only
the machine wiring. I had a bad capacitor in my post-flow
timer, and it cost me a tank of gas before I realized what it
was doing. It was easy enough to trace that back to the bad
component in my case.

Jon

[Jim Wilkins]

On Sep 24, 10:31 pm, "Phil" wrote:
Hello
I was in touch with a Welding Service center today , have been having a
problem with a Lincoln Precision 185 TIG welding machine , seems the Encoder
for the amperage control has decided to go Nuts , man says there $50.00 PC
board will cost me $ 980.50 ,...
Phil

When my Square Wave 175's amperage control failed the repairman told
me to wiggle a few main board connectors first, and that fixed it.

Jim Wilkins

[Jim Stewart]

Phil wrote:
Hello
I was in touch with a Welding Service center today , have been having a
problem with a Lincoln Precision 185 TIG welding machine , seems the Encoder
for the amperage control has decided to go Nuts , man says there $50.00 PC
board will cost me $ 980.50 , I thought he was kidding at first and he said
no he wasn't , the thing really will cost that much , I have mostly used
Miller over the years and have had pretty good luck with there units , I
live fairly close to Cleveland and a lady called me several years ago and
wondered why I didn't patronize my local Lincoln Co. , if see calls me again
I'll have a reason to tell her I prefer BLUE , I think this Lincoln 185 cost
just a little more than the PC Board and it's just over three years old.

I've taken some guff from the local welding
shops about my decision to buy a Thermal-Arc
TIG, mostly along the lines of "you can't get
service for that thing and we can fix a Miller/
Lincoln.

I feel better now.

[Ignoramus30458]

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

[Pete C.]

Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

[Ignoramus30458]

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

[Pete C.]

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there it
is indicated as a device that looks like a pot, has three connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical rotary
encoder that is quite standard, available from Digi-Key, and could be
upgraded to a more reliable optical version for a few dollars more if he
can find a 5 volt supply for the optical version.

[Ignoramus30458]

On Tue, 25 Sep 2007 13:45:39 -0500, Pete C. wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there it
is indicated as a device that looks like a pot, has three connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical rotary
encoder that is quite standard, available from Digi-Key, and could be
upgraded to a more reliable optical version for a few dollars more if he
can find a 5 volt supply for the optical version.

That makes sense, but how does the OP know that it is malfunctioning?

i

[Pete C.]

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:45:39 -0500, Pete C. wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there it
is indicated as a device that looks like a pot, has three connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical rotary
encoder that is quite standard, available from Digi-Key, and could be
upgraded to a more reliable optical version for a few dollars more if he
can find a 5 volt supply for the optical version.

That makes sense, but how does the OP know that it is malfunctioning?

i

The report was that the amperage set point made wild jumps when trying
to adjust, i.e. dirty mechanical encoder contact bounce. I expect either
of us could repair the machine at minimal cost in a minimal time.
Unfortunately you aren't very likely to find someone with component
level troubleshooting expertise at a welding supply shop.

[Ignoramus30458]

On Tue, 25 Sep 2007 14:02:55 -0500, Pete C. wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:45:39 -0500, Pete C. wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there it
is indicated as a device that looks like a pot, has three connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical rotary
encoder that is quite standard, available from Digi-Key, and could be
upgraded to a more reliable optical version for a few dollars more if he
can find a 5 volt supply for the optical version.

That makes sense, but how does the OP know that it is malfunctioning?

i

The report was that the amperage set point made wild jumps when trying
to adjust, i.e. dirty mechanical encoder contact bounce. I expect either
of us could repair the machine at minimal cost in a minimal time.
Unfortunately you aren't very likely to find someone with component
level troubleshooting expertise at a welding supply shop.

I agree, then. I would definitely try to check out the encoder before
starting on the path of $950 part swapping.

i

[RichD]

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

[Pete C.]

RichD wrote:

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

Not sure whether my 250 is new style or old, it's about 1995 vintage. I
should add the thermal fan control on mine since in home shop use it
would hardly ever come on and would reduce dust ingestion substantially.

[Pete C.]

RLM wrote:

On Tue, 25 Sep 2007 14:02:55 -0500, Pete C. wrote:

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:45:39 -0500, Pete C. wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C. wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it? Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in any of
these machines beyond a microcontroller chip and perhaps a PAL chip.
Most of the components should be readily available from Digi-Key. I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there it
is indicated as a device that looks like a pot, has three connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical rotary
encoder that is quite standard, available from Digi-Key, and could be
upgraded to a more reliable optical version for a few dollars more if he
can find a 5 volt supply for the optical version.

That makes sense, but how does the OP know that it is malfunctioning?

i

The report was that the amperage set point made wild jumps when trying
to adjust, i.e. dirty mechanical encoder contact bounce. I expect either
of us could repair the machine at minimal cost in a minimal time.
Unfortunately you aren't very likely to find someone with component
level troubleshooting expertise at a welding supply shop.

You may well find someone with the ability to troubleshoot and
repair things at the component level but the management know that the
customer will complain about the cost of troubleshooting time and the
labor to replace the inexpensive component parts. The warranty will be
limited, if any, and if the failure of the one component has stressed
another component and it fails in a short time the manager eats the
warranty.
The customer looses faith in the dealer because, in his opinion, it
wasn't fixed the first time right. These are the hardest customers to
win back.

Replacing a board (card) insures the manufacturers warranty and the
manufacturer will reimburse the dealer and recall the faulty part to find
the problem and improve future models or may offer a recall on the part if
it shows chronic failure rates and possibly replace it free.

The OP should ask if perhaps there is a recall in effect that may have been
over looked. Poor management tend to pigeon hole information that they don't
understand. I've known service managers that couldn't put lead in a
mechanical pencil or were amazed that it was even possible.

There are those issues as well unfortunately...

[Ignoramus30458]

On Tue, 25 Sep 2007 15:14:49 -0500, Pete C. wrote:
RichD wrote:

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

Not sure whether my 250 is new style or old, it's about 1995 vintage. I
should add the thermal fan control on mine since in home shop use it
would hardly ever come on and would reduce dust ingestion substantially.

Do you know, though, which points to monitor for temperature?

i

[Pete C.]

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 15:14:49 -0500, Pete C. wrote:
RichD wrote:

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

Not sure whether my 250 is new style or old, it's about 1995 vintage. I
should add the thermal fan control on mine since in home shop use it
would hardly ever come on and would reduce dust ingestion substantially.

Do you know, though, which points to monitor for temperature?

i

I'm sure looking in the manual for the newer version that has that
feature would tell me.

[Phil]

Thanks , I appreciate all the interest in the Lincoln 185 TIG problem , 30
yrs. of HAM radio and Airplanes , I have seen a little of everything , yes
it is the $ 2.00 mechanical encoder that is giving the problem , I work part
time for a Co. that makes precision SS parts , retired several years ago
from full time aircraft welding and the little part time works well for me ,
if the welder was owned by myself I would have pulled the PC board out a
long time ago and either replaced it with a higher quality mech. encoder or
as one post mentioned , just find the 5 v. and use an optical , Co.is under
FDA and ISO and owner is pretty touchy about everything , welder is about 4
months out of warranty and looks like Lincoln will try to give us a little
break , I guess the price of the PC Board came to mind because I wonder what
some poor guy out in the field that is clueless on the electrical thing
would do if he had the same problem , a local welder repair shop said that
he could get the board and install it in our shop , Lincoln said that he is
not on there list , got to take the thing 60 miles and two trips , looks
like the small guy always gets kicked in the ass .
"Pete C." wrote in message
...
RLM wrote:

On Tue, 25 Sep 2007 14:02:55 -0500, Pete C. wrote:

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:45:39 -0500, Pete C.
wrote:
Ignoramus30458 wrote:

On Tue, 25 Sep 2007 13:36:16 -0500, Pete C.
wrote:
Ignoramus30458 wrote:

Can you clarify just what is wrong? What kind of encoder is it?
Can
you replace it with a generic part?

i

I expect that there are few to no custom electronic components in
any of
these machines beyond a microcontroller chip and perhaps a PAL
chip.
Most of the components should be readily available from Digi-Key.
I
expect the encoder in question is about $10 from Digi-Key.

When I hear "encoder", I do feel like it is probably generic. What
kind of isolation testing has the OP done so far? What makes him or
his dealer conclude that it is an encoder?

i

I found a previous thread discussing this a few months ago. In there
it
is indicated as a device that looks like a pot, has three
connections to
the PCB and continuous rotation. I suspect it's a $5 mechanical
rotary
encoder that is quite standard, available from Digi-Key, and could
be
upgraded to a more reliable optical version for a few dollars more
if he
can find a 5 volt supply for the optical version.

That makes sense, but how does the OP know that it is malfunctioning?

i

The report was that the amperage set point made wild jumps when trying
to adjust, i.e. dirty mechanical encoder contact bounce. I expect
either
of us could repair the machine at minimal cost in a minimal time.
Unfortunately you aren't very likely to find someone with component
level troubleshooting expertise at a welding supply shop.

You may well find someone with the ability to troubleshoot and
repair things at the component level but the management know that the
customer will complain about the cost of troubleshooting time and the
labor to replace the inexpensive component parts. The warranty will be
limited, if any, and if the failure of the one component has stressed
another component and it fails in a short time the manager eats the
warranty.
The customer looses faith in the dealer because, in his opinion, it
wasn't fixed the first time right. These are the hardest customers to
win back.

Replacing a board (card) insures the manufacturers warranty and the
manufacturer will reimburse the dealer and recall the faulty part to find
the problem and improve future models or may offer a recall on the part
if
it shows chronic failure rates and possibly replace it free.

The OP should ask if perhaps there is a recall in effect that may have
been
over looked. Poor management tend to pigeon hole information that they
don't
understand. I've known service managers that couldn't put lead in a
mechanical pencil or were amazed that it was even possible.

There are those issues as well unfortunately...

[Pete C.]

Phil wrote:

Thanks , I appreciate all the interest in the Lincoln 185 TIG problem , 30
yrs. of HAM radio and Airplanes , I have seen a little of everything , yes
it is the $ 2.00 mechanical encoder that is giving the problem , I work part
time for a Co. that makes precision SS parts , retired several years ago
from full time aircraft welding and the little part time works well for me ,
if the welder was owned by myself I would have pulled the PC board out a
long time ago and either replaced it with a higher quality mech. encoder or
as one post mentioned , just find the 5 v. and use an optical , Co.is under
FDA and ISO and owner is pretty touchy about everything , welder is about 4
months out of warranty and looks like Lincoln will try to give us a little
break , I guess the price of the PC Board came to mind because I wonder what
some poor guy out in the field that is clueless on the electrical thing
would do if he had the same problem , a local welder repair shop said that
he could get the board and install it in our shop , Lincoln said that he is
not on there list , got to take the thing 60 miles and two trips , looks
like the small guy always gets kicked in the ass .

Ah, the joys of administratium, it saves companies so much money and
improves quality... hysterical laughter

[Ignoramus30458]

They are too cheap not to buy a good welder, but reluctant to let
their guy to try to take a stap at fixing it properly... I am going to
watch for a liquidation auction of that company...

i

[Too_Many_Tools]

On Sep 24, 9:31 pm, "Phil" wrote:
Hello
I was in touch with a Welding Service center today , have been having a
problem with a Lincoln Precision 185 TIG welding machine , seems the Encoder
for the amperage control has decided to go Nuts , man says there $50.00 PC
board will cost me $ 980.50 , I thought he was kidding at first and he said
no he wasn't , the thing really will cost that much , I have mostly used
Miller over the years and have had pretty good luck with there units , I
live fairly close to Cleveland and a lady called me several years ago and
wondered why I didn't patronize my local Lincoln Co. , if see calls me again
I'll have a reason to tell her I prefer BLUE , I think this Lincoln 185 cost
just a little more than the PC Board and it's just over three years old.
Phil

You really need to check the comparable prices from Miller...you will
see similar prices.

The welding industry really needs some competition.

I hope Thermal-Arc does well.

TMT

[RichD]

I know what you mean about the dirt sucked into it. Wow!
What a cleanup job that was.
Well, it happens I was taking a 2 year "Machine Technology" course
at the local college that also has a welding tech course.
Guess what ALL stick/tig the machines are?
With permission, I opened up an idle machine, since these are
relatively new to see what the new guts look like and what the fan
control is as I had heard that you could have bought a kit to add
the fan control. The manuals they had also had the diagrams, so
I came away with the info and did some shopping. It's fairly easy
to do. Add a relay (120V fan on/off) and 2 NC temp sensors.
One goes on the big tryristor heatsink and the other gets buryed
in the transformer coils (lots of gaps to jamb it into).
Tracing out the wiring is the hard part.
I love that quiet now.
RichD

On Sep 25, 4:14 pm, "Pete C." wrote:
RichD wrote:

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

Not sure whether my 250 is new style or old, it's about 1995 vintage. I
should add the thermal fan control on mine since in home shop use it
would hardly ever come on and would reduce dust ingestion substantially.

[Ignoramus30458]

On Tue, 25 Sep 2007 18:00:13 -0700, RichD wrote:
I know what you mean about the dirt sucked into it. Wow!
What a cleanup job that was.
Well, it happens I was taking a 2 year "Machine Technology" course
at the local college that also has a welding tech course.
Guess what ALL stick/tig the machines are?
With permission, I opened up an idle machine, since these are
relatively new to see what the new guts look like and what the fan
control is as I had heard that you could have bought a kit to add
the fan control. The manuals they had also had the diagrams, so
I came away with the info and did some shopping. It's fairly easy
to do. Add a relay (120V fan on/off) and 2 NC temp sensors.

NC???

i

One goes on the big tryristor heatsink and the other gets buryed
in the transformer coils (lots of gaps to jamb it into).
Tracing out the wiring is the hard part.
I love that quiet now.
RichD

On Sep 25, 4:14 pm, "Pete C." wrote:
RichD wrote:

I repaired my Miller Synrowave 250 the second time it broke.
I have the early production one (old style board). The output
just goes ON at some fixed setting. Panel control or foot peddle
does nothing.
The schem. did come with it. Turns out they used a now obsolete
op-amp that was prone to fail. No pin for pin modern replacement.
I cross wired a new op-amp type in to check it out, and all was well.
Ebay turned up plenty of the old type. Swapped it out and.. Viola!
I put the thermal fan control mod in it while it was open.
RichD, Atlanta

Not sure whether my 250 is new style or old, it's about 1995 vintage. I
should add the thermal fan control on mine since in home shop use it
would hardly ever come on and would reduce dust ingestion substantially.

[Louis Ohland]

Ignoramus30458 wrote:
to do. Add a relay (120V fan on/off) and 2 NC temp sensors.

NC???

Normally closed

[Pete C.]

Ignoramus30458 wrote:

On Tue, 25 Sep 2007 18:00:13 -0700, RichD wrote:
I know what you mean about the dirt sucked into it. Wow!
What a cleanup job that was.
Well, it happens I was taking a 2 year "Machine Technology" course
at the local college that also has a welding tech course.
Guess what ALL stick/tig the machines are?
With permission, I opened up an idle machine, since these are
relatively new to see what the new guts look like and what the fan
control is as I had heard that you could have bought a kit to add
the fan control. The manuals they had also had the diagrams, so
I came away with the info and did some shopping. It's fairly easy
to do. Add a relay (120V fan on/off) and 2 NC temp sensors.

NC???

Failsafe perhaps? Broken wire turns the fan on? Haven't looked at the
manual yet.

[Ignoramus30458]

On Tue, 25 Sep 2007 20:33:11 -0500, Louis Ohland wrote:
Ignoramus30458 wrote:
to do. Add a relay (120V fan on/off) and 2 NC temp sensors.

NC???

Normally closed

Would they not need to be normally open? Parallel?

i

[RichD]

Yes, they are NC, normally closed. When you turn the machine on, you
will see the fan kick a few turns as the relay has to kick in to hold
the fan off until a temp sensor opens. In series is the only way it
will work in this case. Safer anyway.
ACRelaytemp sensetemp senseAC
The sensors are, for transformer, PEPI ModelVA #48W+080f (80 deg C).
For heat sink, a Thermodisc type L125 C (257 F). 2 screw type.
Relay is similar type to others in the case and coil is 24VAC.
RichD