Kikusui COS6100M Oscilloscope...

J

John Keiser

Guest
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.
 
P

Phil Allison

Guest
terrell....@gmail.com wrote:
=======================
Via email he said that there is 40 volts of ripple at C1213.

** As measured with a DMM on AC volts ?
Means the p-p value is about 150V .

That cap is open cct.
Would explain a great deal of no sweep.


...... Phil
 
J

John Keiser

Guest
On 11/14/2021 2:20 PM, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby.  I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good.  My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.

With the excellent advice and encouragement of Mr. Terrell I believe the
problems are caused by a defective regulator IC [TA7179P].
The part is long obsolete but before brewing a work around [same IC
fails in arcade games and Roland devices] I will wait for a Chinese IC
marketed as a replacement. [Fraud for $2? Maybe.]
I will report back with the result next year.
 
T

three_jeeps

Guest
On Thursday, November 18, 2021 at 2:02:39 PM UTC-5, John Keiser wrote:
On 11/14/2021 2:20 PM, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.
With the excellent advice and encouragement of Mr. Terrell I believe the
problems are caused by a defective regulator IC [TA7179P].
The part is long obsolete but before brewing a work around [same IC
fails in arcade games and Roland devices] I will wait for a Chinese IC
marketed as a replacement. [Fraud for $2? Maybe.]
I will report back with the result next year.

There are a number of online cross reference resources that you might want to look into.
Here are a few:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjHsujbhKX0AhUIq3IEHfckALwQFnoECAQQAQ&url=https%3A%2F%2Fwww.digchip.com%2Fdatasheets%2Fcross_reference.php&usg=AOvVaw0ElL3bUTnek3Be3bwIbWpD

Which turns up this:
https://www.digchip.com/datasheets/cross_reference.php
(different pkg, similar characteristics)

Another site:
https://www.sourceresearch.com/cross-reference.cfm
lists some alternatives, but no indication of how compatible they are, e.g. form factor, electrical, thermal, etc.
Alternatives include: MC1468L SG4501J ECG921

I remember the Mot part - used it back in the day. It seemed to be used a lot. Of course, you would want to compare datasheets to ensure compatibility in your situation.

Way back, there used to be a pub ICMaster that (from my perspective) had a pretty good CR section. I don\'t think they are around anymore or what the equivalent is now days.

Good luck
J
 
J

John Keiser

Guest
On 11/19/2021 8:36 AM, three_jeeps wrote:
On Thursday, November 18, 2021 at 2:02:39 PM UTC-5, John Keiser wrote:
On 11/14/2021 2:20 PM, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.
With the excellent advice and encouragement of Mr. Terrell I believe the
problems are caused by a defective regulator IC [TA7179P].
The part is long obsolete but before brewing a work around [same IC
fails in arcade games and Roland devices] I will wait for a Chinese IC
marketed as a replacement. [Fraud for $2? Maybe.]
I will report back with the result next year.

There are a number of online cross reference resources that you might want to look into.
Here are a few:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjHsujbhKX0AhUIq3IEHfckALwQFnoECAQQAQ&url=https%3A%2F%2Fwww.digchip.com%2Fdatasheets%2Fcross_reference.php&usg=AOvVaw0ElL3bUTnek3Be3bwIbWpD

Which turns up this:
https://www.digchip.com/datasheets/cross_reference.php
(different pkg, similar characteristics)

Another site:
https://www.sourceresearch.com/cross-reference.cfm
lists some alternatives, but no indication of how compatible they are, e.g. form factor, electrical, thermal, etc.
Alternatives include: MC1468L SG4501J ECG921

I remember the Mot part - used it back in the day. It seemed to be used a lot. Of course, you would want to compare datasheets to ensure compatibility in your situation.

Way back, there used to be a pub ICMaster that (from my perspective) had a pretty good CR section. I don\'t think they are around anymore or what the equivalent is now days.

Good luck
J

I was aware of the Motorola IC.
SG4501 looks promising as well.
Alibaba indicates that my TA7179P has shipped so it may arrive many
weeks sooner than previously anticipated.
Good to have alternatives.
Thank you.
 
L

legg

Guest
On Fri, 19 Nov 2021 13:12:13 -1000, John Keiser <johnkeiser@juno.com>
wrote:

<snip>
There are a number of online cross reference resources that you might want to look into.
Here are a few:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjHsujbhKX0AhUIq3IEHfckALwQFnoECAQQAQ&url=https%3A%2F%2Fwww.digchip.com%2Fdatasheets%2Fcross_reference.php&usg=AOvVaw0ElL3bUTnek3Be3bwIbWpD

Which turns up this:
https://www.digchip.com/datasheets/cross_reference.php
(different pkg, similar characteristics)

Another site:
https://www.sourceresearch.com/cross-reference.cfm
lists some alternatives, but no indication of how compatible they are, e.g. form factor, electrical, thermal, etc.
Alternatives include: MC1468L SG4501J ECG921

I remember the Mot part - used it back in the day. It seemed to be used a lot. Of course, you would want to compare datasheets to ensure compatibility in your situation.

Way back, there used to be a pub ICMaster that (from my perspective) had a pretty good CR section. I don\'t think they are around anymore or what the equivalent is now days.

Good luck
J




I was aware of the Motorola IC.
SG4501 looks promising as well.
Alibaba indicates that my TA7179P has shipped so it may arrive many
weeks sooner than previously anticipated.
Good to have alternatives.
Thank you.

I can do an MC1468L, if you get stuck.

Datecode 8006 ;-)

RL
 
M

Michael Terrell

Guest
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.

It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
 
M

Michael Terrell

Guest
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.

It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
 
M

Michael Terrell

Guest
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.

It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
 
M

Michael Terrell

Guest
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.

It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
 
J

John Keiser

Guest
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?
 
J

John Keiser

Guest
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?
 
J

John Keiser

Guest
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF
Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?
 
M

Michael Terrell

Guest
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
 
M

Michael Terrell

Guest
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
 
M

Michael Terrell

Guest
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
 
J

John Keiser

Guest
On 11/15/2021 10:08 AM, Michael Terrell wrote:
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
That was my thinking as well, especially since the PS is divided into 3
discrete circuits.
The line side is steady at 120V.
The voltage adjustment plug is set correctly.
I reflowed the transformer connections but no joy.
 
J

John Keiser

Guest
On 11/15/2021 10:08 AM, Michael Terrell wrote:
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
That was my thinking as well, especially since the PS is divided into 3
discrete circuits.
The line side is steady at 120V.
The voltage adjustment plug is set correctly.
I reflowed the transformer connections but no joy.
 
J

John Keiser

Guest
On 11/15/2021 10:08 AM, Michael Terrell wrote:
On Monday, November 15, 2021 at 10:39:57 AM UTC-5, John Keiser wrote:
On 11/14/2021 9:39 PM, Michael Terrell wrote:
On Sunday, November 14, 2021 at 7:20:46 PM UTC-5, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.
The screen does display a green blob that can be moved with positioning
controls but no trace.
I suspect the transformer based power supply.
https://imgur.com/FzOaOgp
Visually the caps look good. My ESR meter says they are OK.
No burnt components.
I disconnected all the boards feeding off the PS.
TP readings are 15% high.
[I had not expected the readings to be high with the regulation.]
When I plug in 2 of the boards, the TP readings drop to 50% low.
Since the TP voltages drop when either of several boards are plugged in
- and I assume that multiple boards would not likely fail - I surmise
that something in the PS is unable to handle the expected current.
The power transistors Q1211, Q1212, Q1215, Q1216 Q 1218, Q1219 easily
unplug and seem to test OK out of circuit.
There are 2 ICs U1212 and U 1211 that seem to be part of the regulation
but I don\'t know how to test these.
Am I on the right track?
What should I do next?
Thank you for any advice.


It would have helped to have the part numbers.
U1211 is a upc4558, a gumdrop dual Op Amp. One half is used for the + 5VDC rail. The other half is in the + 55 VDC rail.
U1212 is a TA7199P, which is a dual, tracking voltage regulator. that provide the + and - 12VDC rails.

Do you have a working scope to troubleshoot with? Have you tested the bridge rectifiers? Which volatge are you measuring?

Manual at: http://bama.edebris.com/download/kikusui/cos6100/COS6100_E.PDF

Thank you for adding the part numbers to the post.
I do not have a scope.
I am measuring the +150, +55, +21, +12, +5 and -12 rails.

How would you proceed without a scope?

Are they all changing about the same percentage? That would indicate a problem with the transformer or line wiring.
That was my thinking as well, especially since the PS is divided into 3
discrete circuits.
The line side is steady at 120V.
The voltage adjustment plug is set correctly.
I reflowed the transformer connections but no joy.
 
P

Phil Allison

Guest
John Keiser wrote:
==================
This old oscilloscope was given to me and I am attempting to restore as
a pandemic hobby. I am aware of the HV dangers and take precautions.

** But have no test gear and no experience ?

The screen does display a green blob that can be moved with positioning
controls but no trace.

** Tells me there is little wrong.
Do you have vertical response to an input signal?

> I suspect the transformer based power supply.

** Why ??

Do you know how to even use this scope ?

4/5 channel, 100MHz.
It sure ain\'t no basic model.


...... Phil
 

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