Pioneer SX-1000 motorboats on the AM Band

[Jeffhs]

Originally Posted by vortalexfan

Hello everyone, recently my Pioneer SX-1000 TD has started randomly Motorboating (it sounds like a helicopter taking off or a Tommy Gun being fired) when its on the AM Band when the Bass and Treble controls maxed out, but when the controls are turned down to the "Flat" position (both tone controls set to the middle position) the motorboating stops and the receiver works fine then.

I've looked over the service information and I don't see anything obvious that could cause the issue (I was expecting to see an equalizer board like in my Pioneer SX-737, but all I see is a Control Amp board).

I was thinking perhaps maybe a bad electrolytic cap or two in the control amp board but I'm not sure which ones to check as there are over 10 of them on that board.

Also as a side note, when the receiver starts motorboating, if you switch modes to like the FM Band, Phono mode, tape mode, etc., the motorboating continues to go on in all of the different modes unless you turn down the bass and treble controls or if you turn off the receiver and switch it to one of the other modes besides AM and then turn it back on and then it won't do it anymore.
Also if you just have it on FM/FM Stereo or any other mode to start with and not AM and you have the tone controls maxed out then it won't motorboat at all, it only does it in AM mode.

Any ideas as to what might be causing my problem and where I might check to try and resolve the issue?

Thanks for your help.

If your Pioneer receiver is motorboating on all functions, I would suggest changing the filter caps in the power supply, as they could be going bad. However, since you say the noise can still be heard on all modes unless the receiver is turned off and back on again, and then the receiver works normally until it is switched off and back on once again, I'm not at all sure where the trouble may be.

BTW, if this only occurs on the AM band, not FM, FM/MPX or any other mode, I would suggest simply using the receiver on FM only and as an amplifier for your turntable and/or CD player (using the receiver's "aux" position on its function selector). I don't know what is on AM radio in your area (I live near Cleveland), although if it is anything at all like the Cleveland area, most of the stations are all talk, sports and other such programming, with almost all music programming being on FM. Your region of Indiana gets AM and FM radio stations from the Chicago area where, again, most if not all local AM stations have switched to talk and sports programming. (At night, after dark, I can hear most of the 50kW AM stations in Chicago, where I have in fact noticed most programming has been switched from music to talk; one of my favorite Chicago AM stations was WMAQ-AM 670, before that station switched to sports talk several years ago after NBC sold its radio stations, of which WMAQ-AM was one; the former WMAQ-FM was another.)

As I said, unless you have one or more favorite AM stations you would like to hear on your Pioneer receiver, I would just use the FM tuner for music and the AUX position of the function switch if you have a turntable and/or CD player in your hi-fi system. I use this type of setup (along with a connection to my cable TV service so I can get easy-listening music, which this area's radio stations no longer have anything to do with--long story and OT) with my own bookshelf stereo and don't miss AM radio at all. In fact, as far as I am concerned, all the AM stations in my area could disappear tomorrow and I wouldn't miss them in the least.