have someone the manual (with schematics) of such machine? I have some problem with input selector and volume controls
Try contacting ARC directly, they should be able to provide it to you possibly even as a pdf by email..
Hi Zeferino,
Can't help you with the schematics but i'm also a CA-50 owner.
Very fine amplifier! Have you tried some tube rolling for finetuning te sound or still the sovteks and svetlana's ?
I would appreciate a copy/scan of the schematic from you when you have it...very helpful in case there is a problem. So far not with my amp. After 6 years still the first set of tubes in it! (and they still measure OK)...
greetings,
Sander
Can't help you with the schematics but i'm also a CA-50 owner.
Very fine amplifier! Have you tried some tube rolling for finetuning te sound or still the sovteks and svetlana's ?
I would appreciate a copy/scan of the schematic from you when you have it...very helpful in case there is a problem. So far not with my amp. After 6 years still the first set of tubes in it! (and they still measure OK)...
greetings,
Sander
Audio Research CA 50 - help with a repair?
Hi:
Is anyone here familiar with the Audio Research CA50 integrated amplifier?
One of the output tubes shorted out and took out a 100 ohm 2 watt screen resistor. This was easy to replace.
There is still something else wrong with the unit. With all tubes out of the unit, will not power up blowing the main fuse.
Thanks,
Derek
Hi:
Is anyone here familiar with the Audio Research CA50 integrated amplifier?
One of the output tubes shorted out and took out a 100 ohm 2 watt screen resistor. This was easy to replace.
There is still something else wrong with the unit. With all tubes out of the unit, will not power up blowing the main fuse.
Thanks,
Derek
Sounds like one problem, caused another problem.
And, on many amplifiers, if you remove the output tubes, the B+ rises, and sometimes takes out electrolytic caps that are not rated for the increased B+.
Do some deep digging and investigation, before powering up the amplifier again.
And, on many amplifiers, if you remove the output tubes, the B+ rises, and sometimes takes out electrolytic caps that are not rated for the increased B+.
Do some deep digging and investigation, before powering up the amplifier again.
Last edited:
Thanks 6A3sUMMER. The B+ rail is regulated by a FET. Should be fine with the tubes out. It's a bit challenging to debug since it blows fuses however.
auric,
1. Suppose the FET regulator shorted.
What then?
2. The output tubes cathodes are returned through the DCR of the output transformer secondary.
There does not appear to be any way to check the individual cathode currents of the output tubes.
There does not appear to be any way to adjust the balance of the output tube currents (use extremely well matched output tubes).
The output tubes seem to be fixed grid bias, or adjustable fixed grid bias.
3. If I had such an amplifier, I would first fix it, and then modify it to have 4 individual self bias resistors with 4 individual bypass caps, for all 4 output tubes (2L and 2R).
Yes, it would have a little less output power, but it might last a lot longer that way (and not require extremely well matched output tubes in order to get top performance).
1. Suppose the FET regulator shorted.
What then?
2. The output tubes cathodes are returned through the DCR of the output transformer secondary.
There does not appear to be any way to check the individual cathode currents of the output tubes.
There does not appear to be any way to adjust the balance of the output tube currents (use extremely well matched output tubes).
The output tubes seem to be fixed grid bias, or adjustable fixed grid bias.
3. If I had such an amplifier, I would first fix it, and then modify it to have 4 individual self bias resistors with 4 individual bypass caps, for all 4 output tubes (2L and 2R).
Yes, it would have a little less output power, but it might last a lot longer that way (and not require extremely well matched output tubes in order to get top performance).
Last edited:
Time to invest in extremely well matched tubes.
Then find all the problems Before they arrive, and then you will be able to complete the repair, using the new tubes (use some regular tubes to get the problems worked out; do not possibly ruin the expensive/unobtanium ones).
Then find all the problems Before they arrive, and then you will be able to complete the repair, using the new tubes (use some regular tubes to get the problems worked out; do not possibly ruin the expensive/unobtanium ones).
Whatever you call it, there is high voltage *before* the FET. On a cap. Which may not like the unloaded voltage. (Although it should.)
You can power-up with a large *incandescent* lamp in series with the wall power. In concept, you then cut-out parts of the power system until the lamp goes out; or cut back to the power switch then add-back bit by bit until the lamp goes bright. In practice, this is liable to dangerous shock so is not for the timid or the careless.