AM503B current amplifier questions.


 

Picked up an AM503B on our favorite source. It does not work, how strange is that.

There seems to be vary limited info on this unit, i.e. no schematics even for money.

The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.

Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.

Has anyone on this group ever worked on one of these? Any ideas?

Best regards,
Tom


stefan_trethan
 

I've recently repaired one.

Hakan has scanned the schematics for the AM503A, which is different but useful:
<http://hakanh.com/dl/kits.htm>

The manual for the AM503B without schematic can be downloaded any
place on the internet or Tek, it says this but no more:

550–594 Error occurred during internal automatic adjustment. Repeated
errors in the range 550–594
indicate the Amplifier needs repair.

The manual (with schematic) for the old AM503 is also readily
available but less useful since it is so different.


I would proceed in the following steps:
Remove the probe - is the DC offset still there?
Remove the output amplifier IC. The big one with the funny compression
socket held by two bolts. The DC offset should definitely be gone?

Check voltage at the input to the amplifier IC (pin 27 of the ceramic
attenuator hybrid goes through a choke right over to the IC).
Check voltage at pin 3 of the hybrid (input).

If there is voltage on pin 27 but none at pin 3 you almost certainly
have the same fault I had and the protection didoe (dual schottky
SOT23) on the hybrid is leaking.


ST








On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
<TekScopes@yahoogroups.com> wrote:
Picked up an AM503B on our favorite source. It does not work, how strange is that.

There seems to be vary limited info on this unit, i.e. no schematics even for money.

The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.

Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.

Has anyone on this group ever worked on one of these? Any ideas?

Best regards,
Tom









------------------------------------
Posted by: tmiller11147@verizon.net
------------------------------------


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

Yahoo Groups Links



Gary Robert Bosworth
 

TMiller:

That is a very popular piece of test instrument. There must be dozens of
group members who will be able to help you. I have a manual, but I do not
have any time to scan it for you. Someone must have a PDF already prepared.
'
Gary


On Wed, Nov 4, 2015 at 1:02 PM, tmiller11147@verizon.net [TekScopes] <
TekScopes@yahoogroups.com> wrote:



Picked up an AM503B on our favorite source. It does not work, how strange
is that.

There seems to be vary limited info on this unit, i.e. no schematics even
for money.

The scope output is hung positive at 0.4 volts and there is a fault code
of 592 and it is flashing.

Looking at the old 503 amplifier shows that there is +3 volts on pin A and
-3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to
power the probe. The internal supplies seem to be good as far as I can
tell. But without a schematic I am shooting in the dark.

Has anyone on this group ever worked on one of these? Any ideas?

Best regards,
Tom




[Non-text portions of this message have been removed]




--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247


[Non-text portions of this message have been removed]


 

Hi,


I have one that starts working after a minute or two



Jerry Massengale

-----Original Message-----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes] <TekScopes@yahoogroups.com>
To: TekScopes <TekScopes@yahoogroups.com>
Sent: Wed, Nov 4, 2015 6:35 pm
Subject: Re: [TekScopes] AM503B current amplifier questions.






I've recently repaired one.

Hakan has scanned the schematics for the AM503A, which is different but useful:
<http://hakanh.com/dl/kits.htm>;

The manual for the AM503B without schematic can be downloaded any
place on the internet or Tek, it says this but no more:

550–594 Error occurred during internal automatic adjustment. Repeated
errors in the range 550–594
indicate the Amplifier needs repair.

The manual (with schematic) for the old AM503 is also readily
available but less useful since it is so different.

I would proceed in the following steps:
Remove the probe - is the DC offset still there?
Remove the output amplifier IC. The big one with the funny compression
socket held by two bolts. The DC offset should definitely be gone?

Check voltage at the input to the amplifier IC (pin 27 of the ceramic
attenuator hybrid goes through a choke right over to the IC).
Check voltage at pin 3 of the hybrid (input).

If there is voltage on pin 27 but none at pin 3 you almost certainly
have the same fault I had and the protection didoe (dual schottky
SOT23) on the hybrid is leaking.

ST

On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
<TekScopes@yahoogroups.com> wrote:
Picked up an AM503B on our favorite source. It does not work, how strange is that.

There seems to be vary limited info on this unit, i.e. no schematics even for money.

The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.

Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.

Has anyone on this group ever worked on one of these? Any ideas?

Best regards,
Tom





[Non-text portions of this message have been removed]



------------------------------------
Posted by: tmiller11147@verizon.net
------------------------------------


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

Yahoo Groups Links









[Non-text portions of this message have been removed]


Richard R. Pope
 

TMiller,
I have an AM503 that I would like to trade for a digital counter
for either a TM-50x or TM-500x
Thanks,

--
Richard R. Pope
President
Reedsburg Area Model Railroad Club, RAMRC
1230 19th Street #5
Reedsburg, WI 53959
608-768-7448
mechanic_2@charter.net


On 11/4/2015 8:08 PM, Gary Robert Bosworth grbosworth@gmail.com
[TekScopes] wrote:

TMiller:

That is a very popular piece of test instrument. There must be dozens of
group members who will be able to help you. I have a manual, but I do not
have any time to scan it for you. Someone must have a PDF already
prepared.
'
Gary

On Wed, Nov 4, 2015 at 1:02 PM, tmiller11147@verizon.net [TekScopes] <
TekScopes@yahoogroups.com> wrote:



Picked up an AM503B on our favorite source. It does not work, how
strange
is that.

There seems to be vary limited info on this unit, i.e. no schematics
even
for money.

The scope output is hung positive at 0.4 volts and there is a fault code
of 592 and it is flashing.


 

About the time the AM503B (I am referring to the B model only) came out Tek stopped including schematics in their manuals. They became Instruction Manuals rather than Service Manuals. There was nothing that might be of use to a service technician - no theory of operation, no schematics, no parts lists (mechanical or electronic), no calibration procedure, etc. This was one manifestation that Tek's days were numbered. Another one of the TM500 instruments that suffered the same fate was the TVC501 Time-Interval to Voltage Converter.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Wednesday, November 04, 2015 6:09 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] AM503B current amplifier questions.

TMiller:

That is a very popular piece of test instrument. There must be dozens of group members who will be able to help you. I have a manual, but I do not have any time to scan it for you. Someone must have a PDF already prepared.
'
Gary


On Wed, Nov 4, 2015 at 1:02 PM, tmiller11147@verizon.net [TekScopes] < TekScopes@yahoogroups.com> wrote:



Picked up an AM503B on our favorite source. It does not work, how
strange is that.

There seems to be vary limited info on this unit, i.e. no schematics
even for money.

The scope output is hung positive at 0.4 volts and there is a fault
code of 592 and it is flashing.

Looking at the old 503 amplifier shows that there is +3 volts on pin A
and
-3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems
to power the probe. The internal supplies seem to be good as far as I
can tell. But without a schematic I am shooting in the dark.

Has anyone on this group ever worked on one of these? Any ideas?

Best regards,
Tom




[Non-text portions of this message have been removed]




--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247






------------------------------------
Posted by: Gary Robert Bosworth <grbosworth@gmail.com>
------------------------------------


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

Yahoo Groups Links


 

Removed the probe - still stuck at +0.4 DC.

Removed the output IC and output is 0.0 V.

The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.

I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?

Thank you for your help.

Tom

Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.

----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Wednesday, November 04, 2015 7:35 PM
Subject: Re: [TekScopes] AM503B current amplifier questions.



I've recently repaired one.

Hakan has scanned the schematics for the AM503A, which is different but useful:
<http://hakanh.com/dl/kits.htm>

The manual for the AM503B without schematic can be downloaded any
place on the internet or Tek, it says this but no more:

550–594 Error occurred during internal automatic adjustment. Repeated
errors in the range 550–594
indicate the Amplifier needs repair.

The manual (with schematic) for the old AM503 is also readily
available but less useful since it is so different.

I would proceed in the following steps:
Remove the probe - is the DC offset still there?
Remove the output amplifier IC. The big one with the funny compression
socket held by two bolts. The DC offset should definitely be gone?

Check voltage at the input to the amplifier IC (pin 27 of the ceramic
attenuator hybrid goes through a choke right over to the IC).
Check voltage at pin 3 of the hybrid (input).

If there is voltage on pin 27 but none at pin 3 you almost certainly
have the same fault I had and the protection didoe (dual schottky
SOT23) on the hybrid is leaking.

ST

On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
<TekScopes@yahoogroups.com> wrote:
> Picked up an AM503B on our favorite source. It does not work, how strange is that.
>
> There seems to be vary limited info on this unit, i.e. no schematics even for money.
>
> The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
>
> Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
>
> Has anyone on this group ever worked on one of these? Any ideas?
>
> Best regards,
> Tom
>
>
>
>
>
>
>
>
>
> ------------------------------------
> Posted by: tmiller11147@verizon.net
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>




[Non-text portions of this message have been removed]


 

Thanks Gary. We'll see what pops up.

Regards

----- Original Message -----
From: Gary Robert Bosworth grbosworth@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Wednesday, November 04, 2015 9:08 PM
Subject: Re: [TekScopes] AM503B current amplifier questions.



TMiller:

That is a very popular piece of test instrument. There must be dozens of
group members who will be able to help you. I have a manual, but I do not
have any time to scan it for you. Someone must have a PDF already prepared.
'
Gary

On Wed, Nov 4, 2015 at 1:02 PM, tmiller11147@verizon.net [TekScopes] <
TekScopes@yahoogroups.com> wrote:

>
>
> Picked up an AM503B on our favorite source. It does not work, how strange
> is that.
>
> There seems to be vary limited info on this unit, i.e. no schematics even
> for money.
>
> The scope output is hung positive at 0.4 volts and there is a fault code
> of 592 and it is flashing.
>
> Looking at the old 503 amplifier shows that there is +3 volts on pin A and
> -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to
> power the probe. The internal supplies seem to be good as far as I can
> tell. But without a schematic I am shooting in the dark.
>
> Has anyone on this group ever worked on one of these? Any ideas?
>
> Best regards,
> Tom
>
>
>
>
>
>
>
>

--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247


 

Didn't they pass the whole line off to Tegam? They then dropped everything. Also, no help even for paid service.

----- Original Message -----
From: 'Dennis Tillman' dennis@ridesoft.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Wednesday, November 04, 2015 11:18 PM
Subject: RE: [TekScopes] AM503B current amplifier questions.



About the time the AM503B (I am referring to the B model only) came out Tek stopped including schematics in their manuals. They became Instruction Manuals rather than Service Manuals. There was nothing that might be of use to a service technician - no theory of operation, no schematics, no parts lists (mechanical or electronic), no calibration procedure, etc. This was one manifestation that Tek's days were numbered. Another one of the TM500 instruments that suffered the same fate was the TVC501 Time-Interval to Voltage Converter.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Wednesday, November 04, 2015 6:09 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] AM503B current amplifier questions.

TMiller:

That is a very popular piece of test instrument. There must be dozens of group members who will be able to help you. I have a manual, but I do not have any time to scan it for you. Someone must have a PDF already prepared.
'
Gary

On Wed, Nov 4, 2015 at 1:02 PM, tmiller11147@verizon.net [TekScopes] < TekScopes@yahoogroups.com> wrote:

>
>
> Picked up an AM503B on our favorite source. It does not work, how
> strange is that.
>
> There seems to be vary limited info on this unit, i.e. no schematics
> even for money.
>
> The scope output is hung positive at 0.4 volts and there is a fault
> code of 592 and it is flashing.
>
> Looking at the old 503 amplifier shows that there is +3 volts on pin A
> and
> -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems
> to power the probe. The internal supplies seem to be good as far as I
> can tell. But without a schematic I am shooting in the dark.
>
> Has anyone on this group ever worked on one of these? Any ideas?
>
> Best regards,
> Tom
>
>
>
>
>
>
>
>

--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247



------------------------------------
Posted by: Gary Robert Bosworth <grbosworth@gmail.com>
------------------------------------

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

Yahoo Groups Links


stefan_trethan
 

If the input to the IC is zero, and the output not, would that not
indicate the IC is bad? Does it have an offset input?

On mine the output 27 of the att. was definitely not zero, so it isn't
the same fault.

You don't have access to a second to swap the IC, right?

I don't know about the 3V but can measure if you instruct where.

ST

On Thu, Nov 5, 2015 at 7:21 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
Removed the probe - still stuck at +0.4 DC.

Removed the output IC and output is 0.0 V.

The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.

I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?

Thank you for your help.

Tom

Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.







----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Wednesday, November 04, 2015 7:35 PM
Subject: Re: [TekScopes] AM503B current amplifier questions.



I've recently repaired one.

Hakan has scanned the schematics for the AM503A, which is different but useful:
<http://hakanh.com/dl/kits.htm>

The manual for the AM503B without schematic can be downloaded any
place on the internet or Tek, it says this but no more:

550–594 Error occurred during internal automatic adjustment. Repeated
errors in the range 550–594
indicate the Amplifier needs repair.

The manual (with schematic) for the old AM503 is also readily
available but less useful since it is so different.

I would proceed in the following steps:
Remove the probe - is the DC offset still there?
Remove the output amplifier IC. The big one with the funny compression
socket held by two bolts. The DC offset should definitely be gone?

Check voltage at the input to the amplifier IC (pin 27 of the ceramic
attenuator hybrid goes through a choke right over to the IC).
Check voltage at pin 3 of the hybrid (input).

If there is voltage on pin 27 but none at pin 3 you almost certainly
have the same fault I had and the protection didoe (dual schottky
SOT23) on the hybrid is leaking.

ST

On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
<TekScopes@yahoogroups.com> wrote:
> Picked up an AM503B on our favorite source. It does not work, how strange is that.
>
> There seems to be vary limited info on this unit, i.e. no schematics even for money.
>
> The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
>
> Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
>
> Has anyone on this group ever worked on one of these? Any ideas?
>
> Best regards,
> Tom
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: tmiller11147@verizon.net
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>








------------------------------------
Posted by: "Tom Miller" <tmiller11147@verizon.net>
------------------------------------


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

Yahoo Groups Links



 

On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.
It's a bit hard to see the pin labels.

I don't have a second unit, at least not yet. I tend to agree it is looking pretty bad for the IC.

----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Thursday, November 05, 2015 1:38 AM
Subject: Re: [TekScopes] AM503B current amplifier questions.



If the input to the IC is zero, and the output not, would that not
indicate the IC is bad? Does it have an offset input?

On mine the output 27 of the att. was definitely not zero, so it isn't
the same fault.

You don't have access to a second to swap the IC, right?

I don't know about the 3V but can measure if you instruct where.

ST

On Thu, Nov 5, 2015 at 7:21 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
> Removed the probe - still stuck at +0.4 DC.
>
> Removed the output IC and output is 0.0 V.
>
> The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.
>
> I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?
>
> Thank you for your help.
>
> Tom
>
> Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.
>
>
>
>
>
>
>
> ----- Original Message -----
> From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> To: TekScopes
> Sent: Wednesday, November 04, 2015 7:35 PM
> Subject: Re: [TekScopes] AM503B current amplifier questions.
>
>
>
> I've recently repaired one.
>
> Hakan has scanned the schematics for the AM503A, which is different but useful:
> <http://hakanh.com/dl/kits.htm>
>
> The manual for the AM503B without schematic can be downloaded any
> place on the internet or Tek, it says this but no more:
>
> 550–594 Error occurred during internal automatic adjustment. Repeated
> errors in the range 550–594
> indicate the Amplifier needs repair.
>
> The manual (with schematic) for the old AM503 is also readily
> available but less useful since it is so different.
>
> I would proceed in the following steps:
> Remove the probe - is the DC offset still there?
> Remove the output amplifier IC. The big one with the funny compression
> socket held by two bolts. The DC offset should definitely be gone?
>
> Check voltage at the input to the amplifier IC (pin 27 of the ceramic
> attenuator hybrid goes through a choke right over to the IC).
> Check voltage at pin 3 of the hybrid (input).
>
> If there is voltage on pin 27 but none at pin 3 you almost certainly
> have the same fault I had and the protection didoe (dual schottky
> SOT23) on the hybrid is leaking.
>
> ST
>
> On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
> <TekScopes@yahoogroups.com> wrote:
> > Picked up an AM503B on our favorite source. It does not work, how strange is that.
> >
> > There seems to be vary limited info on this unit, i.e. no schematics even for money.
> >
> > The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
> >
> > Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
> >
> > Has anyone on this group ever worked on one of these? Any ideas?
> >
> > Best regards,
> > Tom
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> > Posted by: tmiller11147@verizon.net
> > ------------------------------------
> >
> >
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: "Tom Miller" <tmiller11147@verizon.net>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>




[Non-text portions of this message have been removed]


stefan_trethan
 

I get -0.581V on A and 0,579V on B with the probe disconnected.

ST

On Thu, Nov 5, 2015 at 8:01 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.
It's a bit hard to see the pin labels.

I don't have a second unit, at least not yet. I tend to agree it is looking pretty bad for the IC.

----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Thursday, November 05, 2015 1:38 AM
Subject: Re: [TekScopes] AM503B current amplifier questions.



If the input to the IC is zero, and the output not, would that not
indicate the IC is bad? Does it have an offset input?

On mine the output 27 of the att. was definitely not zero, so it isn't
the same fault.

You don't have access to a second to swap the IC, right?

I don't know about the 3V but can measure if you instruct where.

ST

On Thu, Nov 5, 2015 at 7:21 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
> Removed the probe - still stuck at +0.4 DC.
>
> Removed the output IC and output is 0.0 V.
>
> The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.
>
> I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?
>
> Thank you for your help.
>
> Tom
>
> Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.
>
>
>
>
>
>
>
> ----- Original Message -----
> From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> To: TekScopes
> Sent: Wednesday, November 04, 2015 7:35 PM
> Subject: Re: [TekScopes] AM503B current amplifier questions.
>
>
>
> I've recently repaired one.
>
> Hakan has scanned the schematics for the AM503A, which is different but useful:
> <http://hakanh.com/dl/kits.htm>
>
> The manual for the AM503B without schematic can be downloaded any
> place on the internet or Tek, it says this but no more:
>
> 550–594 Error occurred during internal automatic adjustment. Repeated
> errors in the range 550–594
> indicate the Amplifier needs repair.
>
> The manual (with schematic) for the old AM503 is also readily
> available but less useful since it is so different.
>
> I would proceed in the following steps:
> Remove the probe - is the DC offset still there?
> Remove the output amplifier IC. The big one with the funny compression
> socket held by two bolts. The DC offset should definitely be gone?
>
> Check voltage at the input to the amplifier IC (pin 27 of the ceramic
> attenuator hybrid goes through a choke right over to the IC).
> Check voltage at pin 3 of the hybrid (input).
>
> If there is voltage on pin 27 but none at pin 3 you almost certainly
> have the same fault I had and the protection didoe (dual schottky
> SOT23) on the hybrid is leaking.
>
> ST
>
> On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
> <TekScopes@yahoogroups.com> wrote:
> > Picked up an AM503B on our favorite source. It does not work, how strange is that.
> >
> > There seems to be vary limited info on this unit, i.e. no schematics even for money.
> >
> > The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
> >
> > Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
> >
> > Has anyone on this group ever worked on one of these? Any ideas?
> >
> > Best regards,
> > Tom
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> > Posted by: tmiller11147@verizon.net
> > ------------------------------------
> >
> >
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
>
>
>
>
>
>
>
> ------------------------------------
> Posted by: "Tom Miller" <tmiller11147@verizon.net>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>




[Non-text portions of this message have been removed]



------------------------------------
Posted by: "Tom Miller" <tmiller11147@verizon.net>
------------------------------------


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

Yahoo Groups Links



 

Ok, then I am chasing a rabbit hole with that one. The probe hall sensor must work over a wide range.

Thanks for the help Stefan.

----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Thursday, November 05, 2015 2:52 AM
Subject: Re: [TekScopes] AM503B current amplifier questions.



I get -0.581V on A and 0,579V on B with the probe disconnected.

ST

On Thu, Nov 5, 2015 at 8:01 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
> On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.
> It's a bit hard to see the pin labels.
>
> I don't have a second unit, at least not yet. I tend to agree it is looking pretty bad for the IC.
>
> ----- Original Message -----
> From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> To: TekScopes
> Sent: Thursday, November 05, 2015 1:38 AM
> Subject: Re: [TekScopes] AM503B current amplifier questions.
>
>
>
> If the input to the IC is zero, and the output not, would that not
> indicate the IC is bad? Does it have an offset input?
>
> On mine the output 27 of the att. was definitely not zero, so it isn't
> the same fault.
>
> You don't have access to a second to swap the IC, right?
>
> I don't know about the 3V but can measure if you instruct where.
>
> ST
>
> On Thu, Nov 5, 2015 at 7:21 AM, 'Tom Miller' tmiller11147@verizon.net
> [TekScopes] <TekScopes@yahoogroups.com> wrote:
> > Removed the probe - still stuck at +0.4 DC.
> >
> > Removed the output IC and output is 0.0 V.
> >
> > The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.
> >
> > I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?
> >
> > Thank you for your help.
> >
> > Tom
> >
> > Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.
> >
> >
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> > To: TekScopes
> > Sent: Wednesday, November 04, 2015 7:35 PM
> > Subject: Re: [TekScopes] AM503B current amplifier questions.
> >
> >
> >
> > I've recently repaired one.
> >
> > Hakan has scanned the schematics for the AM503A, which is different but useful:
> > <http://hakanh.com/dl/kits.htm>
> >
> > The manual for the AM503B without schematic can be downloaded any
> > place on the internet or Tek, it says this but no more:
> >
> > 550–594 Error occurred during internal automatic adjustment. Repeated
> > errors in the range 550–594
> > indicate the Amplifier needs repair.
> >
> > The manual (with schematic) for the old AM503 is also readily
> > available but less useful since it is so different.
> >
> > I would proceed in the following steps:
> > Remove the probe - is the DC offset still there?
> > Remove the output amplifier IC. The big one with the funny compression
> > socket held by two bolts. The DC offset should definitely be gone?
> >
> > Check voltage at the input to the amplifier IC (pin 27 of the ceramic
> > attenuator hybrid goes through a choke right over to the IC).
> > Check voltage at pin 3 of the hybrid (input).
> >
> > If there is voltage on pin 27 but none at pin 3 you almost certainly
> > have the same fault I had and the protection didoe (dual schottky
> > SOT23) on the hybrid is leaking.
> >
> > ST
> >
> > On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
> > <TekScopes@yahoogroups.com> wrote:
> > > Picked up an AM503B on our favorite source. It does not work, how strange is that.
> > >
> > > There seems to be vary limited info on this unit, i.e. no schematics even for money.
> > >
> > > The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
> > >
> > > Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
> > >
> > > Has anyone on this group ever worked on one of these? Any ideas?
> > >
> > > Best regards,
> > > Tom
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> > >
> > > ------------------------------------
> > > Posted by: tmiller11147@verizon.net
> > > ------------------------------------
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo Groups Links
> > >
> > >
> > >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> > Posted by: "Tom Miller" <tmiller11147@verizon.net>
> > ------------------------------------
> >
> >
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: "Tom Miller" <tmiller11147@verizon.net>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>




[Non-text portions of this message have been removed]


stefan_trethan
 

I see there's DC offset and DC level going into the amplifier IC.
Is there any AC signal going through at all?
Let me know if you need any other voltages.

ST

On Thu, Nov 5, 2015 at 9:03 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
Ok, then I am chasing a rabbit hole with that one. The probe hall sensor must work over a wide range.

Thanks for the help Stefan.


----- Original Message -----
From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
To: TekScopes
Sent: Thursday, November 05, 2015 2:52 AM
Subject: Re: [TekScopes] AM503B current amplifier questions.



I get -0.581V on A and 0,579V on B with the probe disconnected.

ST

On Thu, Nov 5, 2015 at 8:01 AM, 'Tom Miller' tmiller11147@verizon.net
[TekScopes] <TekScopes@yahoogroups.com> wrote:
> On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.
> It's a bit hard to see the pin labels.
>
> I don't have a second unit, at least not yet. I tend to agree it is looking pretty bad for the IC.
>
> ----- Original Message -----
> From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> To: TekScopes
> Sent: Thursday, November 05, 2015 1:38 AM
> Subject: Re: [TekScopes] AM503B current amplifier questions.
>
>
>
> If the input to the IC is zero, and the output not, would that not
> indicate the IC is bad? Does it have an offset input?
>
> On mine the output 27 of the att. was definitely not zero, so it isn't
> the same fault.
>
> You don't have access to a second to swap the IC, right?
>
> I don't know about the 3V but can measure if you instruct where.
>
> ST
>
> On Thu, Nov 5, 2015 at 7:21 AM, 'Tom Miller' tmiller11147@verizon.net
> [TekScopes] <TekScopes@yahoogroups.com> wrote:
> > Removed the probe - still stuck at +0.4 DC.
> >
> > Removed the output IC and output is 0.0 V.
> >
> > The pin27 connection goes to pin 4 of the IC is 0 volts as is the input on pin 6. I am not clear on the pins you gave other than I follow pin 27 through a choke then into the IC.
> >
> > I still have not figured out how this unit makes the +/- 3 volts as used in the 503A. In the 503A there are two TO92 regulators feeding the Hall sensor. On the 503B, I only measure +/- 0.58 volts. Is that right?
> >
> > Thank you for your help.
> >
> > Tom
> >
> > Oh, one other thing - I replaced the NVRAM memory battery as it was dead. This is a 1.5 volt silver cell. On the 503A it calls for executing routine 99 to restore the NVRAM. The 503B only goes to 53 for the service functions.
> >
> >
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: Stefan Trethan stefan_trethan@gmx.at [TekScopes]
> > To: TekScopes
> > Sent: Wednesday, November 04, 2015 7:35 PM
> > Subject: Re: [TekScopes] AM503B current amplifier questions.
> >
> >
> >
> > I've recently repaired one.
> >
> > Hakan has scanned the schematics for the AM503A, which is different but useful:
> > <http://hakanh.com/dl/kits.htm>
> >
> > The manual for the AM503B without schematic can be downloaded any
> > place on the internet or Tek, it says this but no more:
> >
> > 550–594 Error occurred during internal automatic adjustment. Repeated
> > errors in the range 550–594
> > indicate the Amplifier needs repair.
> >
> > The manual (with schematic) for the old AM503 is also readily
> > available but less useful since it is so different.
> >
> > I would proceed in the following steps:
> > Remove the probe - is the DC offset still there?
> > Remove the output amplifier IC. The big one with the funny compression
> > socket held by two bolts. The DC offset should definitely be gone?
> >
> > Check voltage at the input to the amplifier IC (pin 27 of the ceramic
> > attenuator hybrid goes through a choke right over to the IC).
> > Check voltage at pin 3 of the hybrid (input).
> >
> > If there is voltage on pin 27 but none at pin 3 you almost certainly
> > have the same fault I had and the protection didoe (dual schottky
> > SOT23) on the hybrid is leaking.
> >
> > ST
> >
> > On Wed, Nov 4, 2015 at 10:02 PM, tmiller11147@verizon.net [TekScopes]
> > <TekScopes@yahoogroups.com> wrote:
> > > Picked up an AM503B on our favorite source. It does not work, how strange is that.
> > >
> > > There seems to be vary limited info on this unit, i.e. no schematics even for money.
> > >
> > > The scope output is hung positive at 0.4 volts and there is a fault code of 592 and it is flashing.
> > >
> > > Looking at the old 503 amplifier shows that there is +3 volts on pin A and -3 volts on pin D. On this unit, I get about +/- 0.5 volts. This seems to power the probe. The internal supplies seem to be good as far as I can tell. But without a schematic I am shooting in the dark.
> > >
> > > Has anyone on this group ever worked on one of these? Any ideas?
> > >
> > > Best regards,
> > > Tom
> > >
> > >
> > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> > >
> > > ------------------------------------
> > > Posted by: tmiller11147@verizon.net
> > > ------------------------------------
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo Groups Links
> > >
> > >
> > >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> > ------------------------------------
> > Posted by: "Tom Miller" <tmiller11147@verizon.net>
> > ------------------------------------
> >
> >
> > ------------------------------------
> >
> > Yahoo Groups Links
> >
> >
> >
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
> Posted by: "Tom Miller" <tmiller11147@verizon.net>
> ------------------------------------
>
>
> ------------------------------------
>
> Yahoo Groups Links
>
>
>








------------------------------------
Posted by: "Tom Miller" <tmiller11147@verizon.net>
------------------------------------


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

Yahoo Groups Links



 

The operating range of the hall sensor is pretty limited. The force
coil is used to null out the magnetic flux detected by the hall sensor
so it operates close to zero. This has two benefits; the core is kept
out of saturation and the hall effect sensor operates where it is most
linear.

On Thu, 05 Nov 2015 03:03:46 -0500, you wrote:

Ok, then I am chasing a rabbit hole with that one. The probe hall sensor must work over a wide range.

Thanks for the help Stefan.


stefan_trethan
 

I think he meant the bias voltage.

ST

On Thu, Nov 5, 2015 at 12:56 PM, David davidwhess@gmail.com
[TekScopes] <TekScopes@yahoogroups.com> wrote:
The operating range of the hall sensor is pretty limited. The force
coil is used to null out the magnetic flux detected by the hall sensor
so it operates close to zero. This has two benefits; the core is kept
out of saturation and the hall effect sensor operates where it is most
linear.

On Thu, 05 Nov 2015 03:03:46 -0500, you wrote:

Ok, then I am chasing a rabbit hole with that one. The probe hall sensor must work over a wide range.

Thanks for the help Stefan.

------------------------------------
Posted by: David <davidwhess@gmail.com>
------------------------------------


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

Yahoo Groups Links



Albert Otten
 

The supply voltage is between A and D, not between A and B. (Typo?).
Note that the probe AM6302, which was designed for +/- 3 V, is still suitable for the AM503B. Then it's hard to believe that the measured voltages are normal. The sensitivity of the Hall sensor is proportional to the Hall current (and voltage). Going back from +/- 3 V to +/- 0.5 V would reduce the sensitivity by a factor 6.

Albert


---In TekScopes@yahoogroups.com, <stefan_trethan@...> wrote :

I get -0.581V on A and 0,579V on B with the probe disconnected.

ST

On Thu, Nov 5, 2015 at 8:01 AM, 'Tom Miller' tmiller11147@... mailto:tmiller11147@...
[TekScopes] <TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com> wrote:
> On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.


stefan_trethan
 

Yes, A and D, sorry.
Perhaps the voltage is lower with the probe disconnected?
The amp is fully functional, I just performance tested it the other
day together with that other amp I fixed.

ST

On Thu, Nov 5, 2015 at 1:10 PM, aodiversen@concepts.nl [TekScopes]
<TekScopes@yahoogroups.com> wrote:
The supply voltage is between A and D, not between A and B. (Typo?).
Note that the probe AM6302, which was designed for +/- 3 V, is still suitable for the AM503B. Then it's hard to believe that the measured voltages are normal. The sensitivity of the Hall sensor is proportional to the Hall current (and voltage). Going back from +/- 3 V to +/- 0.5 V would reduce the sensitivity by a factor 6.

Albert


---In TekScopes@yahoogroups.com, <stefan_trethan@...> wrote :

I get -0.581V on A and 0,579V on B with the probe disconnected.

ST

On Thu, Nov 5, 2015 at 8:01 AM, 'Tom Miller' tmiller11147@... mailto:tmiller11147@...
[TekScopes] <TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com> wrote:
> On the probe connector, pin A should be -3.0 volts and pin D should be +3 volts. At least that is what the 503A shows.




[Non-text portions of this message have been removed]



------------------------------------
Posted by: aodiversen@concepts.nl
------------------------------------


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

Yahoo Groups Links



Albert Otten
 

Could the supply voltages at connector A and D be floating w.r.t. ground? Did you also measure between A and D?
Albert



---In TekScopes@yahoogroups.com, <stefan_trethan@...> wrote :

Yes, A and D, sorry.
Perhaps the voltage is lower with the probe disconnected?
The amp is fully functional, I just performance tested it the other
day together with that other amp I fixed.

ST


stefan_trethan
 

Will do tomorrow.

ST

On Thu, Nov 5, 2015 at 7:49 PM, aodiversen@concepts.nl [TekScopes]
<TekScopes@yahoogroups.com> wrote:
Could the supply voltages at connector A and D be floating w.r.t. ground? Did you also measure between A and D?
Albert