My shielding attempts made no difference. I also unbolted the transformer so I could move it around slightly (as much as the leads would allow). That had no effect. I think my next step will be to re
Hi Gary, Thanks for the offer! I may take you up on that pending the outcome of my next round of work. I'm going to replace all the cracked capacitors - found a couple more, one of them on the power
Just noticed this C21 Digital on eBay: http://www.ebay.com/itm/Working-made-in-USA-DIGITAL-Ten-Tec-Century-21-with-a-keying-issue-/232358014086?hash=item36199dec86:g:dzkAAOSwAPVZMaJ3 "Although there
Hi Chris, The hum is present in the speaker, just not so noticeable because it is much less sensitive and much further from my ear. I suspect the speaker is less responsive to frequencies below 120Hz
Thanks Byron. Grounding to PS ground had no effect. I don't see a 4.7 Ohm resistor anywhere... are we talking a resistor on the audio board? Here is the schematic for the audio board: https://drive.g
You may be right Stuart, it may just be a characteristic of the radio. Several people have said that now. I have no other C21 to compare it to, but it sounds excessive to me. I will keep at it for a
I figured out the 4.7 Ohm resistor and 240 uF cap. You must have been looking at the Century 22 schematic. It uses the same LM380 as the Century 21, BUT it has additional filtering on the 12V feeding
Just when you thought this thread was done... some interesting new information! It seems that Ten-Tec started adding in additional shielding for the transformer at some point. Mine does not have the
Thanks Carter. I tried some shielding using some thin steel I had, but I want to replicate the shield that Ten-Tec used. They must have done that for a reason! It turns out that my C21 digital is a v
I'm learning a lot about shielding... tons of good resources on the Net. This article was particularly useful: http://www.ets-lindgren.com/pdf/emctd_1293_weibler.pdf The fact that Ten-Tec used alumin
I agree Carter. Here is another thought... perhaps its a heat-sink, and not a shield? That would explain the use of aluminum. Now that I think of it, when I removed the transformer there was a square
Very good info, thank you! Check out this neat article from 73 Magazine, Dec. 1977: https://archive.org/stream/73-magazine-1977-12/12_December_1977#page/n29/mode/2up There is the man himself, and a p
Hi Mike, You can use either the ACC1 or the regular key jack. The output of an external keyer looks just like a straight key to the radio. I'd probably use the key jack since the required cable is ju
Hi Curt, I didn't mess with the bridge rectifier. When I removed the transformer from the chassis, the noise went away. I've made a shield out of steel for the transformer, but have not yet had time
I know, I've been in contact with him. =) I'm planning to have a QSO with him soon. And yes, I will be using my C21 for that QSO! -Josh WA7FPV _______________________________________________ TenTec m
Huge thanks to Ed, W3NR, for sending this to me! It is a hand written letter to 'Tom' (not sure who this is) from Ten-Tec dated Feb 13, 1978. "I also have a hand written how-to on adding a pre-amp to
No need to resort to Wayback machine... searchable archive of this list is here: http://lists.contesting.com/archives//html/TenTec/ This info is included at the bottom of every email that is sent out
You mean like this page here? https://www.tentec.com/?page_id=143 "The service@tentec.com email is monitored Monday through Wednesday. At this time we are unable to offer extensive telephone or email
Hi Paul, You are in luck. I posted high quality scans of the entire manual here: https://drive.google.com/drive/folders/0B_pjAwEfeYcdYmRaTUhRTnN6SFU?usp=sharing Here is a file where I put the two pag
Incidentally, I recently talked to Dick Frey. He lives in Oregon. I'm going to have a QSO with him, and I'm going to use my C21 Digital! =) -Josh WU7H Seattle, WA ____________________________________