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1. [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Mon, 29 May 2017 09:34:07 -0700; Greetings Ten-Tec List, I just recently bought my first Ten-Tec rig - a Century 21/ Digital. I really like the radio and I'm having a lot of fun with it! The one fault I've found with it is a loud hu; /archives//html/TenTec/2017-05/msg00136.html (7,601 bytes)
2. [TenTec] Century 21 audio hum (score: 1): Author: Curt Benjamin via TenTec <tentec@xxxxxxxxxxxxxx>; Date: Mon, 29 May 2017 23:19:42 +0000 (UTC); Josh, direct conversion receivers such as the one in the C21 are inherently susceptible to AC hum from the power supply since all the system gain comes from the AF stages. The 23 VDC is only used in; /archives//html/TenTec/2017-05/msg00137.html (7,261 bytes)
3. Re: [TenTec] Century 21 audio hum (score: 1): Author: Dukes HiFi <dukeshifi@xxxxxxxxxxx>; Date: Mon, 29 May 2017 21:54:20 -0500; "Have you checked the health of the bridge rectifier? I wonder if a partially blown diode assembly could be the culprit. Not likely. Diodes have two failure modes, open and shorted. If they get leaky; /archives//html/TenTec/2017-05/msg00139.html (9,639 bytes)
4. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Mon, 29 May 2017 20:49:27 -0700; Hi Gary, I attempted to measure the audio output on the scope. I measured it both on the internal supply and on external. This is with the volume pot turned all the way down so all you hear is the hu; /archives//html/TenTec/2017-05/msg00140.html (8,904 bytes)
5. Re: [TenTec] Century 21 audio hum (score: 1): Author: Dukes HiFi <dukeshifi@xxxxxxxxxxx>; Date: Mon, 29 May 2017 23:45:42 -0500; Thats not a lot of ripple thats for sure. The fact that the volume pot does not reduce the hum clearly proves that the direct conversion design of this receiver is not your root cause. of hum. The fa; /archives//html/TenTec/2017-05/msg00141.html (11,272 bytes)
6. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Mon, 29 May 2017 22:12:58 -0700; Hi Gary, Yes, I hardly need to turn the volume up at all when listening to normal signals. There was something in the Ten-Tec manual about an 'attenuation network' for the phones to suppress noise. I; /archives//html/TenTec/2017-05/msg00142.html (7,927 bytes)
7. Re: [TenTec] Century 21 audio hum (score: 1): Author: Dukes HiFi <dukeshifi@xxxxxxxxxxx>; Date: Tue, 30 May 2017 08:14:43 -0500; I think you will find that result very much to your liking. 73 and enjoy that classic! Gary _______________________________________________ TenTec mailing list TenTec@xxxxxxxxxxxxxx http://lists.cont; /archives//html/TenTec/2017-05/msg00143.html (8,694 bytes)
8. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 12:35:05 -0700; Hi Dan, The manual says I should be using 8 Ohm headphones, which is what I am using. I tried the swamping resistor that Gary suggested. 220 Ohms knocked the hum down to where I almost can't hear it; /archives//html/TenTec/2017-05/msg00147.html (8,811 bytes)
9. Re: [TenTec] Century 21 audio hum (score: 1): Author: Stuart Rohre <Rohre@xxxxxxxxxxxxxxxx>; Date: Tue, 30 May 2017 15:42:19 -0500; But if one diode in a bridge rectifier opens up, you have a off balance power supply DC bus. Stuart Rohre K5KVH _______________________________________________ TenTec mailing list TenTec@xxxxxxxxxxxx; /archives//html/TenTec/2017-05/msg00148.html (8,164 bytes)
10. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 13:55:09 -0700; Stuart, Aside from pulling the bridge rectifier out and testing each diode, is there a way to tell if one of the diodes is open? I'm trying to visualize what having one open diode would do... wouldn'; /archives//html/TenTec/2017-05/msg00149.html (8,846 bytes)
11. Re: [TenTec] Century 21 audio hum (score: 1): Author: Carl Moreschi <n4py3@xxxxxxxxxxxxx>; Date: Tue, 30 May 2017 16:57:51 -0400; I don't think 8 ohm headphones were correct. I think much higher impedance phones forces you to turn the volume up and drown out the hum. Direct conversion receivers are susceptible to a hum because; /archives//html/TenTec/2017-05/msg00150.html (10,128 bytes)
12. Re: [TenTec] Century 21 audio hum (score: 1): Author: Howie WA3MCK <wa3mck@xxxxxxxxx>; Date: Tue, 30 May 2017 17:03:14 -0400; Hi Jim, I don't have any noticeable hum on my C21. I however the swamping resistor is a good idea. If I may ask - how and where did you install it? Howie WA3MCK ______________________________________; /archives//html/TenTec/2017-05/msg00151.html (10,776 bytes)
13. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 14:09:11 -0700; Thanks Carl. I think you are right about the headphones - the 'swamping resistor' is achieving the same thing, but I might look for a higher impedance set. Only other set I have are 32 Ohm, and that; /archives//html/TenTec/2017-05/msg00152.html (9,919 bytes)
14. Re: [TenTec] Century 21 audio hum (score: 1): Author: Stuart Rohre <Rohre@xxxxxxxxxxxxxxxx>; Date: Tue, 30 May 2017 16:11:43 -0500; Do you have diode test function on your DMM? if so, you can inspect each diode in a bridge in circuit, or at worst take off one lead from Plus (+) bus. Silicon diodes will show 600 mv across each one; /archives//html/TenTec/2017-05/msg00153.html (9,440 bytes)
15. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 14:34:15 -0700; Hi Howie, I opened up the plug on my phones (housing unscrews on this one, other plugs might not), unsoldered the wire that was connected to the 'tip' terminal, and put the resistor between that tip; /archives//html/TenTec/2017-05/msg00155.html (9,292 bytes)
16. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 14:49:25 -0700; Hi Stuart, I know that I can test the diodes, but getting the power board out for testing is a lot of work. I would definitely do it if I suspected the bridge rectifier, which is why I asked about sy; /archives//html/TenTec/2017-05/msg00156.html (10,158 bytes)
17. Re: [TenTec] Century 21 audio hum (score: 1): Author: Howie WA3MCK <wa3mck@xxxxxxxxx>; Date: Tue, 30 May 2017 17:54:25 -0400; Josh, Thank you for the info on the swamping resistor placement and installation. I have an analog C21. Bought it in the late 90's, had it on the air for a few years, sold it to Joe N2CX, he had it f; /archives//html/TenTec/2017-05/msg00157.html (10,661 bytes)
18. Re: [TenTec] Century 21 audio hum (score: 1): Author: Josh Gibbs <gibbsjj@xxxxxxxxx>; Date: Tue, 30 May 2017 15:05:21 -0700; Sounds like its time for a PTO clean and re-lube! I've been reading about that procedure. Seems that usually the PTO parts are fine and you just need to clean out the old grease and get some fresh gr; /archives//html/TenTec/2017-05/msg00159.html (10,583 bytes)
19. Re: [TenTec] Century 21 audio hum (score: 1): Author: Howie WA3MCK <wa3mck@xxxxxxxxx>; Date: Tue, 30 May 2017 18:15:25 -0400; Tri-Flow? What is that Josh? I'm familiar with the flush/clean procedure. I have been told that 90W cup grease or bicycle chain lubricant is the way to go. What say you? _____________________________; /archives//html/TenTec/2017-05/msg00160.html (11,577 bytes)
20. Re: [TenTec] Century 21 audio hum (score: 1): Author: Greg S via TenTec <tentec@xxxxxxxxxxxxxx>; Date: Tue, 30 May 2017 22:27:15 +0000 (UTC); Subject: Re: [TenTec] Century 21 audio hum To: "Discussion of Ten-Tec Equipment" <tentec@xxxxxxxxxxxxxx>, "Josh Gibbs" <Gibbsjj@xxxxxxxxx> Date: Tuesday, May 30, 2017, 6:15 PM Tri-Flow? What is that; /archives//html/TenTec/2017-05/msg00161.html (11,809 bytes)

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