I had replaced the old 8-pin 2A3's with new 4-pin 2A3's for AI Second Audio mono blocks. And I have checked several components as recommended.
After the work, I found that the sound from the left block is noticeably weaker than the right, and I had to turn the balance nob to 10 o'clock direction to listen properly.
Here is what I have done.
1. Replace the tube socket from Octal to UX4
2. Replace 2A3 tubes with new ones
3. Change the rectifiers as recommended
4. Replace the electrolytic condensers for the heater.
During the work I have checked the electric characteristics of each step to make sure it is the same or within range, described in the First Audio schematics (which is the only reference I could get.)
When I faced the issue, I have exchanged all 2A3's of each monoblock and found the result the same. So I can guess I have issues on the left channel block.
I want any recommendation on what I need to check further or replace to fix the problem.
Thanks a lot.
After the work, I found that the sound from the left block is noticeably weaker than the right, and I had to turn the balance nob to 10 o'clock direction to listen properly.
Here is what I have done.
1. Replace the tube socket from Octal to UX4
2. Replace 2A3 tubes with new ones
3. Change the rectifiers as recommended
4. Replace the electrolytic condensers for the heater.
During the work I have checked the electric characteristics of each step to make sure it is the same or within range, described in the First Audio schematics (which is the only reference I could get.)
When I faced the issue, I have exchanged all 2A3's of each monoblock and found the result the same. So I can guess I have issues on the left channel block.
I want any recommendation on what I need to check further or replace to fix the problem.
Thanks a lot.
Attachments
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Try to check all operating point's voltage.
I attached some hand drawn schematics.
Are you sure, that all tube filament "lighted" properly?
I attached some hand drawn schematics.
Are you sure, that all tube filament "lighted" properly?
Attachments
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Thanks for the help
Yes, I am sure all the filaments of the tube are properly lighted.
And as I have described in the post,
1) I have exchanged 4 x ECC82's between two mono blocks. Found the result is same.
2) Next, also exchanged 4 x 2A3's, the sound difference remains same.
Anyway, it is my first time to see the Second Audio Circuit diagram.
I appreciate it.
From the diagram, 2 x ECC88 and 2 x PCC88 are described, and I think those were changed to 4 x ECC82 in Second Audio V.3.
The reference document from Borderpatrol in 2005 shows the tube difference by Second Audio version.
It seems that differently from V.1 and V.2, 2nd Audio V3 seems to have used ECC82 instead of ECC88. When I bought the 2nd Audio, it was shipped with ECC82's and that is how I guess my 2nd A is V.3.
I am attaching the printout from Borderpatrol website in 2005.
Yes, I am sure all the filaments of the tube are properly lighted.
And as I have described in the post,
1) I have exchanged 4 x ECC82's between two mono blocks. Found the result is same.
2) Next, also exchanged 4 x 2A3's, the sound difference remains same.
Anyway, it is my first time to see the Second Audio Circuit diagram.
I appreciate it.
From the diagram, 2 x ECC88 and 2 x PCC88 are described, and I think those were changed to 4 x ECC82 in Second Audio V.3.
The reference document from Borderpatrol in 2005 shows the tube difference by Second Audio version.
It seems that differently from V.1 and V.2, 2nd Audio V3 seems to have used ECC82 instead of ECC88. When I bought the 2nd Audio, it was shipped with ECC82's and that is how I guess my 2nd A is V.3.
I am attaching the printout from Borderpatrol website in 2005.
Attachments
The power section not changed, so 2A3 voltage points must be similar, than in schematic.
If it's OK, try to measure the AC voltage on 220k grid leak resistors if input feeds for example 0.5V 1kHz tone.
If it's OK, try to measure the AC voltage on 220k grid leak resistors if input feeds for example 0.5V 1kHz tone.
mike4kim,
6B4G filament is 6.3V @ 1A. Other than the different filament and Octal pinout, it is essentially a 2A3.
6A3 filament is 6.3V @ 1A. Other than the different filament, it is essentially a 2A3.
2A3 filament is 2.5V @ 2.5A. Other than the different filament and 4 pins, it is essentially a 6B4G (and other than the filament, it is essentially a 6A3).
The power supply schematic for the filaments supplies 6.3V @ 1A.
That same power supply, can not supply the required 2.5V @ 2.5A to a 2A3, you will get maximum smoke, or at least the power transformer will die early from the excess heat, and perhaps the diodes too.
With those facts in mind, what tube types did you previously use in the amp,
Versus what tubes did you end up using?
Check that first, before spending more time troubleshooting.
6B4G filament is 6.3V @ 1A. Other than the different filament and Octal pinout, it is essentially a 2A3.
6A3 filament is 6.3V @ 1A. Other than the different filament, it is essentially a 2A3.
2A3 filament is 2.5V @ 2.5A. Other than the different filament and 4 pins, it is essentially a 6B4G (and other than the filament, it is essentially a 6A3).
The power supply schematic for the filaments supplies 6.3V @ 1A.
That same power supply, can not supply the required 2.5V @ 2.5A to a 2A3, you will get maximum smoke, or at least the power transformer will die early from the excess heat, and perhaps the diodes too.
With those facts in mind, what tube types did you previously use in the amp,
Versus what tubes did you end up using?
Check that first, before spending more time troubleshooting.
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The Tubes on AI Second Audio
Hi,
Thanks for the quick reply.
The tubes on AI Second Audio unit were Shuguang 8-pin based 2A3, which I was told was produced during late 80's and early 90's.
The new 2A3 tubes are Shuguang 4-pin based 2A3.
Shuguang says the electrical characteristics of both tubes are the same, and replaceable.
Other than the difference in sound strength between two monoblocks, I do not have any problem yet.
Based on the information above, including schematics, I will work with my technician. and I will get back with the result.
Thanks for the help and information.
Hi,
Thanks for the quick reply.
The tubes on AI Second Audio unit were Shuguang 8-pin based 2A3, which I was told was produced during late 80's and early 90's.
The new 2A3 tubes are Shuguang 4-pin based 2A3.
Shuguang says the electrical characteristics of both tubes are the same, and replaceable.
Other than the difference in sound strength between two monoblocks, I do not have any problem yet.
Based on the information above, including schematics, I will work with my technician. and I will get back with the result.
Thanks for the help and information.
An Octal based 2A3 would have a 2.5V 2.5A filament. And that is not an original 2A3, it is a modern day change due to some marketing scheme.
Perhaps it had a 6.3V 1A filament (a 6B4G, with a marking that said "2A3").
A 6.3V 1A power supply would have quite a time running a 2.5V 2.5A filament.
The schematic shows 6.3VDC.
It is still a mystery, which is right?
A bogus schematic?
A Pseudo 2A3?
Perhaps it had a 6.3V 1A filament (a 6B4G, with a marking that said "2A3").
A 6.3V 1A power supply would have quite a time running a 2.5V 2.5A filament.
The schematic shows 6.3VDC.
It is still a mystery, which is right?
A bogus schematic?
A Pseudo 2A3?
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"It is still a mystery, which is right?"
As you can see in post #3, AI made -at least- three version.
I attached one version's schematics.
Other versions would be differents.
As you can see in post #3, AI made -at least- three version.
I attached one version's schematics.
Other versions would be differents.
Three versions of AI 2nd Audio
I acknowledged there are three versions and mine belong to V.3, since it has ECC82 tubes installed.
I briefly discussed with my technician on the difference and its implication.
He is quite happy with V.1 schematics as at least he has a very good reference document to start with. Much better than the First Audio schematics he used to refer to.
I am sure your sharing gave us a much better chance. Thanks
I acknowledged there are three versions and mine belong to V.3, since it has ECC82 tubes installed.
I briefly discussed with my technician on the difference and its implication.
He is quite happy with V.1 schematics as at least he has a very good reference document to start with. Much better than the First Audio schematics he used to refer to.
I am sure your sharing gave us a much better chance. Thanks
New 2A3 from Shuguang
I think I understand the discussion on filament voltage and ampere.
I just checked the tube seller site which shows the 2A3 specification and you are right. It has 2.5V, 2.5A filament.
I will check with my technician whether he changed the power supply to the filament.
I think I understand the discussion on filament voltage and ampere.
I just checked the tube seller site which shows the 2A3 specification and you are right. It has 2.5V, 2.5A filament.
I will check with my technician whether he changed the power supply to the filament.
There are a nicely renovated "The Second".
[SOLD] Audio Innovations Second Audio monos. - Sold Items - HiFi WigWam
[SOLD] Audio Innovations Second Audio monos. - Sold Items - HiFi WigWam