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38-690 Treble/Audio Bandwidth
#1

I recently finished restoring a 37-116 which is a really nice radio. What I noticed is that the treble response when adjusting the treble/bandwidth control is much better than my fully restored 38-690, so much so, that I question something is wrong with the 690. Having nothing to compare it too before, I felt it was fine until now.

I re-aligned the IF in the 690 and was able to balance the peaks while in wide band treble mode on both sides of 470 KHz as per the procedure. This made some difference, but nothing to write home about. The coupling capacitor for the tweeters was changed per Ron's write up and they sound like they are working well.

I also noticed a few things. Obviously the circuits are different in both. 1 vs 2 IF amps, and the treble pots in both radios configured differently as well. So It would be hard to compare the two based on this alone.
In addition, the treble control shafts have a different range of motion. The 37-116 has a full half turn vs only a quarter turn on the 690. This got me thinking maybe there is a mechanical issue with the 690.

My question to the Phorum is should I be expecting better from the 38-690? Does my observation about the treble control's physical range of motion have anything to do with this situation? Or is it simply they are two different radios with different audio reproduction and they are both normal? I'm hoping that those of you familiar with both sets will have an explanation.

Thanks in advance for your comments.

Tony

“People may not remember how fast you did a job, but they will remember how well you did it”


Messages In This Thread
38-690 Treble/Audio Bandwidth - by tbone - 03-09-2021, 06:37 PM
RE: 38-690 Treble/Audio Bandwidth - by rfeenstra - 03-09-2021, 09:43 PM
RE: 38-690 Treble/Audio Bandwidth - by morzh - 03-09-2021, 11:58 PM
RE: 38-690 Treble/Audio Bandwidth - by radiorich - 03-10-2021, 12:52 AM
RE: 38-690 Treble/Audio Bandwidth - by tbone - 03-10-2021, 06:50 AM
RE: 38-690 Treble/Audio Bandwidth - by rfeenstra - 03-10-2021, 02:03 PM
RE: 38-690 Treble/Audio Bandwidth - by rfeenstra - 03-10-2021, 02:18 PM
RE: 38-690 Treble/Audio Bandwidth - by morzh - 03-10-2021, 04:14 PM
RE: 38-690 Treble/Audio Bandwidth - by tbone - 03-10-2021, 07:29 PM
RE: 38-690 Treble/Audio Bandwidth - by rfeenstra - 03-10-2021, 08:38 PM
RE: 38-690 Treble/Audio Bandwidth - by morzh - 03-10-2021, 08:49 PM



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