Interesting also that littlediode still shows the BA3122N as being available for purchase. I just contacted them and asked if that was accurate and if so the price for 10 pieces.
Cheers,
James
Cheers,
James
Alonia
Member
In my case, it was by chance that I stumbled across the problem with the IC. I saw the MX-2 on the net for a good price and simply bought it. I thought it would be a simple device to repair, like an MX-1000, M-80, M-4, ... . When I ordered the spare parts, I found the problem with the IC. I read a lot on the net, also about the problem with monolithic transistors.
I organised all the data sheets I could find where something was implemented with the HCA circuit and started making notes. I must have invested more than 100 hours. Currently, the MX-2 is running, but I am still thinking about how I can test this under different conditions.
In my case, it was by chance that I stumbled across the problem with the IC. I saw the MX-2 on the net for a good price and simply bought it. I thought it would be a simple device to repair, like an MX-1000, M-80, M-4, ... . When I ordered the spare parts, I found the problem with the IC. I read a lot on the net, also about the problem with monolithic transistors.
I organised all the data sheets I could find where something was implemented with the HCA circuit and started making notes. I must have invested more than 100 hours. Currently, the MX-2 is running, but I am still thinking about how I can test this under different conditions.
Good work! Did you find a datasheet for the BA3122? I was never able to find one.
Have you tested the amp under full load with a loadbank?
Cheers,
James
Alonia
Member
I don't think it will make any difference if it is fully loaded, as the BA3122N is operated at 7.5V and doesn't have much to do with the load at the end. You mainly load the power transistors.
I don't have a data sheet either. I just downloaded all the service manuals where an HCA circuit was used and compared them.
Replacing monolithic transistors was only the real problem. If 2 transistors are not in one housing, the values drift apart due to different temperatures.
I am thinking of building a test circuit. I still have an original BA3122N.
Later, I can also produce this in some quantity when the circuit is fully developed. This makes the whole thing cheaper for someone who only needs 1 or 2 spare parts.
I do not have any immediate need for the part, but since I do have a MX-1 and an AX-1090 I would be interested in buying a pair as spare parts if you reach the point of producing them in quantity.
I think that is is very good for the owners on these amps that you have taken the time to design the boards.
Please keep us informed as to your progress.
Cheers,
James
I think that is is very good for the owners on these amps that you have taken the time to design the boards.
Please keep us informed as to your progress. Cheers,
James
Alonia
Member
Interesting, you use three 1.5k resistors. If you look at the service manual of the MX-1000, where the HCA circuit is built with components, you will find only 2 resistors with 1.5k.
In addition, the two capacitors that were "built in" parallel to the 1k in the BA3122N are not present in older circuits.
