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.
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
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?
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:Thank you for adding the part numbers to the post.
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 >>>
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.
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.
John Keiser wrote:
==================
This old oscilloscope was given to me and I am attempting to restore as** But have no test gear and no experience ?
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.** 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.
This old oscilloscope was given to me and I am attempting to restore asthe PS outputs 150V, +/-12, +5 vdc. Do they *all* drop 50%? All rise 15% no load? If so, that suggests a bad transformer or perhaps a bridge rectifier lost a leg. a scope would help with diagnosing the rectifier. Actually don't even need a scope for
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.
the PS outputs 150V, +/-12, +5 VDC. Do they *all* drop 50%? All rise 15% no load? If so, that suggests a bad transformer or perhaps a bridge rectifier lost a leg. a scope would help with diagnosing the rectifier. Actually don't even need a scope forthe BR. DMM will work. Looks like everything else in the PS can be troubleshot with a DMM & ESR meter for finding bad caps.
BTW IC u1212 is a TA7179 (not 7199)but it is a dual track regulator. Interesting that they use the sense lines.
Via email he said that there is 40 volts of ripple at C1213.
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.
On 11/14/2021 2:20 PM, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore asWith the excellent advice and encouragement of Mr. Terrell I believe the problems are caused by a defective regulator IC [TA7179P].
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.
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.
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 asWith the excellent advice and encouragement of Mr. Terrell I believe the
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.
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
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.
On 11/14/2021 2:20 PM, John Keiser wrote:
This old oscilloscope was given to me and I am attempting to restore asWith the excellent advice and encouragement of Mr. Terrell I believe the problems are caused by a defective regulator IC [TA7179P].
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.
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.
I'd be inclined to just do an easy work around. Two 12V (7812/7912) ICs can do all of that with almost no rewiring, particularly if you don't need the supplies to be adjustable. The two ICs will even mount on the heatsinks in place of those tworegulator transistors.
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.
Ali Express delivered on a TA71170P IC yesterday.
Nicely packed from Tajikistan.
| Sysop: | Keyop |
|---|---|
| Location: | Huddersfield, West Yorkshire, UK |
| Users: | 293 |
| Nodes: | 16 (2 / 14) |
| Uptime: | 219:59:30 |
| Calls: | 6,622 |
| Calls today: | 4 |
| Files: | 12,171 |
| Messages: | 5,317,887 |