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Dynaco FM-5 Stereo Light On All Of The Time

74.75.221.118
Posted on September 28, 2009 at 15:47:36
jsheitert
 The stereo indicator lamp on my Dynaco FM-5 stays on all of the time, even if a station is not tuned in. The tuner still has the original lamps and has not been modified. Does anyone have any idea what could be causing this?

RE: Dynaco FM-5 Stereo Light On All Of The Time, posted on November 13, 2009 at 09:44:59
sheitert
 I checked the voltage at the IC V+ pin and it is just below 12 V. Also checked the voltage at Q60 and it is 13.6 V. There is a 100 ohm resistor between Q60 and the IC V+ pin. Installed the new IC and the stereo light still stays on. I should have described the problem better the first time. The stereo light stays on MOST of the time. There are some points(2 or 3) as you tune across the dial where the light goes out, but it is on most of the time. And it is on even if a station is not tuned. In addition, it stays on when you push the panel switch to "Mono". Any other ideas?

RE: Dynaco FM-5 Stereo Light On All Of The Time, posted on September 28, 2009 at 16:38:09
Bill Thomas
Industry Professional

Posts: 1330
Location: Southern USA
Joined: January 3, 2004
 IC51 is most likely the culprit. It is an MC1307P and can be replaced with an NTE 722. Make SURE you check the regulated Voltages from the Power Supply. If the IC had too much Voltage applied due to a non-working regulator in the Power Supply, the new IC will also blow.

Hope this helps.

Bill

RE: Dynaco FM-5 Stereo Light On All Of The Time, posted on October 4, 2009 at 06:51:59
sheitert
 Thanks, Bill. I will give this a try. I noticed, after submitting my question, that I am only getting mono sound which makes sense if the multiplex chip is bad.

RE: Dynaco FM-5 Stereo Light On All Of The Time, posted on November 20, 2009 at 12:19:04
jsheitert
 I checked the voltage at the IC V+ pin and it is just below 12 V. Also checked the voltage at Q60 and it is 13.6 V. There is a 100 ohm resistor between Q60 and the IC V+ pin. Installed the new IC and the stereo light still stays on. I should have described the problem better the first time. The stereo light stays on MOST of the time. There are some points(2 or 3) as you tune across the dial where the light goes out, but it is on most of the time. And it is on even if a station is not tuned. In addition, it stays on when you push the panel switch to "Mono".

Update: When I first turn on the tuner, if a station is not tuned the stereo light does not turn on. When I tune to a station the tuned and stereo lights turn on. When I change stations the tuned light goes out then turns on again as it should when a reach a station. The stereo light stays on during this process. It is almost like it "latches" but will not "unlatch" when it should.

Anyone have any other ideas? Thanks.

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