Greetings,
I have a Marantz 1090 on my bench. A friend had bought it on eBay a few weeks back and discovered it had multiple problems when he went to use it. Audible distortion from the left channel. Horrid scratchiness when sliders and pots were adjusted, among others. He brought it to me and asked if I thought it could be salvaged. Aside from the performance issues, the overall appearance was good, if not excellent. I said yes, absolutely. Hindsight, that may have been a bit premature. The previous owner/tech had made some "modifications". it took me quite a while (and some help from leestereo) to discover them and reverse. The unit began to perform quite nicely. On my suggestion, the unit looked to be in good physical shape and knowing of Leestereo's "how to", I encouraged my friend to spend the money and have me recap it. The recap was uneventful. Bias came in nicely and the unit sounded pleasing to the ear. He took it home, sent me a "it sounds beautiful..." text and about a week or so later, the Ringwraiths found it. He said one day it was playing wonderfully and the next it sounded like a portal to hell. I have it on my bench now. I did some poking and prodding with my distortion analyzer & Oscope. The THD distortion numbers were high, .3+%. Then suddenly... my dbt began to indicate a pulsating current draw, like a heart beat! I shut it down immediately. I made several attempts at determining what configuration would manifest the issue, but every time I powered it up, the surge would start up again and I shut it down quickly. Off the cuff, it reminds me of a bad output transistor, that has shorted. The oscillation however, is not something I have encountered previously. As always, any insight past experience with similar, etc. is greatly appreciated.
Kind regards,
Steve
I have a Marantz 1090 on my bench. A friend had bought it on eBay a few weeks back and discovered it had multiple problems when he went to use it. Audible distortion from the left channel. Horrid scratchiness when sliders and pots were adjusted, among others. He brought it to me and asked if I thought it could be salvaged. Aside from the performance issues, the overall appearance was good, if not excellent. I said yes, absolutely. Hindsight, that may have been a bit premature. The previous owner/tech had made some "modifications". it took me quite a while (and some help from leestereo) to discover them and reverse. The unit began to perform quite nicely. On my suggestion, the unit looked to be in good physical shape and knowing of Leestereo's "how to", I encouraged my friend to spend the money and have me recap it. The recap was uneventful. Bias came in nicely and the unit sounded pleasing to the ear. He took it home, sent me a "it sounds beautiful..." text and about a week or so later, the Ringwraiths found it. He said one day it was playing wonderfully and the next it sounded like a portal to hell. I have it on my bench now. I did some poking and prodding with my distortion analyzer & Oscope. The THD distortion numbers were high, .3+%. Then suddenly... my dbt began to indicate a pulsating current draw, like a heart beat! I shut it down immediately. I made several attempts at determining what configuration would manifest the issue, but every time I powered it up, the surge would start up again and I shut it down quickly. Off the cuff, it reminds me of a bad output transistor, that has shorted. The oscillation however, is not something I have encountered previously. As always, any insight past experience with similar, etc. is greatly appreciated.
Kind regards,
Steve
