Corsair II

[Andrew Moore]

FINALLY ordered replacement electrolytic capacitors for the Corsair II - rig has been idle since Jan 1, 2011, when I rebuilt the PTO. Looking forward to getting this rig back on the air.  Then I can find out if using lithium grease on the PTO was a bad idea. Anyone have a lead on a 960 /961 / 962 power supply?  I wouldn't mind finding one to go with it.  Not going to have it ready for this Tuesday's CFO sked but maybe by next week.

--Andrew, NV1B / CFO 963

..

[Andrew Moore]

Corsair II finally back on the air here - rebuilt the PTO on 1/1/2011, and the rig sat idle for nine months, waiting for replacement of electrolytic caps. Finally ordered them and spent the last couple days replacing every one.  Buttoned up the rig and it wouldn't tune, just showed offsets on the display - no PTO signal. Opened it back up and found the broken wire inside the PTO, buttoned it all up again, and it's working beautifully. Can't wait for the first QSO.

I really missed this rig over the past nine months.  I learned about the Corsair II at a friend's place when I got my ticket while in college in 1988 and heard my first CFOs on it - remember listening to them frequently and spending time on lower 40 trying to build speed.  Great memories.

This rig's got soul!  All-time favorite.  One of the best ever made.

[John Zimmerman]

Andrew,

After reading many messages on the Ten Tec archives, I found the Corsair II to be the favorite Ten Tec analog rig.   I hope some day to have one to complement my Omni 6.  There is no doubt that the Corsair II is a classic and a high point in Ten Tec analog design.  This rig is a keeper.

I read some of your messages on the Ten Tec archives as well.  I learned that all signals in the Omni 6 go through the DSP to eliminate phase noise.  So you have one electronic device (DSP) piled on top of another (digital freq synthesis) and the result is that one has to listen to highly processed signals like eating over-processed food.  You mentioned the sound of the Omni 6 bothering you and perhaps this is the reason.  I have gotten used to it but I still love the sound of my Triton IV.   The sound of the ICOM-746 Pro is even worse.  No wonder I find myself turning back to the Triton IV. 

I have a recently purchased TS 820 VFO running my Triton IV now.  It has good linearity and stability.  I now have two backup VFOs for my Triton IV so I don't think I will run out of VFOs in my lifetime. 

Chuck, W5UXH, found out that the semi-breakin on my Omni 6 does not work well if the delay is short but the code is fine for full break-in up to about 50 wpm and then it deteriorates.  That's fast enough for me.   He sent me recordings and I heard it myself. 

Enjoy your "new" Corsair II.

John, K0JVX

---

From: Andrew Moore <andre...@gmail.com>
To: CFO <Chicken-Fat-O...@googlegroups.com>
Sent: Sat, September 3, 2011 12:32:52 AM
Subject: [Chicken Fat Operators-1137] Corsair II

--
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[Andrew Moore]

Yes, I believe you're right on with your description of the DSP on top of freq synthesis on the VI, and figure that's what I was hearing.  Strange thing is I don't think my ears are *that* well tuned into subtle things like that.  But I do know the sense of fatigue was real.  It wasn't horrible; it was just an inability for me to tune in a signal to a comfortable "sweet spot" that I could listen to for a while.  I kept feeling like I had to adjust RIT or filters.  I admit, however, that I never spent enough time on that right to let it grow on me or to truly learn how to dial things in.  It is a fine rig.

I've been listening to the Corsair II a bit today and had a QSO as well - still drifting though.  Maybe my assumption that it  was in need of a PTO rebuild was incorrect, or maybe it doesn't like the lithium grease that I used instead of the magical green Ten-Tec goo.  But it's on both TX and RX so I do believe it's likely that it's PTO related.  Maybe this unit just needs a little more attention on the PTO -- temp or electrical shielding, who knows.

I'm going to work on it, just not sure where to start, but man, this thing is - as you say - a keeper.  Especially now with all that sweat equity I put into it.  While working on it I gained such an appreciation for its aesthetics, its hand-built nature, all the boards separated by function, the interconnects, the visual design & styling, and of course the performance. It does sound so pure and analog, just beautiful.

Hope I can fix the drift.  Suggestions welcome.  I thought about a replacement (DDS) VFO for it, but part of me wants to keep it mechanical and the way the rig was.  I might give in but not yet.  I have had more stability out of Corsair IIs in the past so there must be a solution.

Glad your VI is at least handling 50 WPM well - and Chuck is a good judge too - I agree that's a comfy speed.  Some day I may even get there with 100% proficiency :)

73.

--Andrew, NV1B / CFO 963

..

[Tony W4FOA]

Andrew and John,

I too have the Omni 6+ and absolutely love it.  I guess that explains the fact that I just have no desire to have one of the new “whatever brand it is” radios.  I had a brand new Corsair II which was, and probably still is my favorite, closely followed by the 544 and my Omni 6.  I also have had and loved the Omni C series. The new TT radios really don’t interest me that much, either!

Guess I’m just too much of an “old timer”, hi.

73

Tony, W4FOA
CFO 550

 

 

 

---

[Rod Hotz]

Wrong! You’re an OOT. . . ;-)))))

 

I will have to admit that I still miss my Corsair II except for the burbling PTO as Prose used to call it. Terry, N4TB, tells me the Dolly Parton gang no longer will handle repairs on the OMNI series, which is probably making Al Kahn roll over in his grave.

 

Hope that you and Nan have a good Labor Day weekend over there.

 

 

73,

 

Rod

K5BGB

Licensed June 1955 as KN5BGB

[Andrew Moore]

...

I have a recently purchased TS 820 VFO running my Triton IV now.  It has good linearity and stability.  I now have two backup VFOs for my Triton IV so I don't think I will run out of VFOs in my lifetime. 

...

John - I know you've done extensive work on your Triton IV to eliminate drift -  so before I start trying to isolate the source of my Corsair II's PTO drift, I wonder if you (or anyone else) has any suggestions about possible causes.

I'm making a couple assumptions: 1) the drift is due to temperature (probably a safe assumption), and 2) since the same amount of drift appears to be on both TX and RX, the source is inside the PTO.  It's #2 that I'm not entirely convinced of, since there are shared TX/RX paths elsewhere.  But given the mechanical nature of the PTO, it seems to be a good place to start.

Unfortunately I no longer have a scope here so troubleshooting this will be a little tough.

I'm tempted to add a small quiet, brushless fan to the rig to stabilize temperature, but I'd prefer to find the cause of the problem instead of a workaround.

Thanks,

[D.J.J. Ring, Jr.]

Hello John,

The TS820 VFO on the Triton IV is interesting.  The Triton IV has a nice bright sound and a nice wide bandpass which is wonderful for receiving except under crowded band conditions.

73

DR

David J. Ring, Jr., N1EA
SOWP, VWOA, OOTC, FISTS, CW-Ops, CFO, A1-OP, ex-FOC 1271 ARRL-LM

Chat Skype: djringjr MSN: djringjr@msn.com AIM: N1EA icq: 27380609

Radio-Officers Google Group -- Marine Morse Historic Recordings Page

On Sat, Sep 3, 2011 at 1:22 PM, John Zimmerman <tjl...@att.net> wrote:

[Chuck Broadwell, W5UXH]

In case you Ten Tec guys have not run across the DDS mod from N4YG, check the link below.  On that page, the link to the PDF file instructions might be of interest.  Page 5 of the PDF is the start of a section written by Cap, W0CCA, who has done the mod in several rigs and is very happy with it.  I certainly am happy to not need to chase him around the band anymore. Cap comments:

This set of instructions applies to the Ten Tec Corsair II PTO replacement with a DDS by N4YG. Other
Ten Tec PTO radios will have a similar routine (Omni C, Triton, etc.) but may have glitches or difficulties
not presented by the Corsair II. I have successfully completed the conversion in a Corsair I and Omni
D/Series B with very minor differences. This is intended to be a reversible operation. Once you have the
DDS in and operational, you will not pine for the old PTO, however.

Chuck, W5UXH


N4YG-Corsair-DDS

[joe living]

I have a Ten Tec Omni D and the first Corsair. I have had the Omni D for over 30 years. I have had good luck troubleshooting problems when it breaks down. The only time I sent it to Ten Tec was after a lightning strike!

 

The Corsair arrived last year from E-bay. I opened the box and thought I had bought a bag of cigarette butts. The price was dirt cheap so I put it in the dishwasher and put it through a few cycles except I did not let the dishwasher dry it. For that, I put it out in the Maui sun for a week bringing it in at night. No more cigarette smoke smell. It works fine though I did have to touch up some of the frequency adjustments.

 

Great rigs for QRQ and QSK, but time will take its toll on all of us including our rigs. After doing a number of PTO rebuilds, the DDS mod looks very attractive. Rebuilding the original PTO with the kits Ten Tec provides is like rebuilding a carburetor in the old days. Get a few extra of these rebuild kits. They won't stock them forever. The folks at Ten Tec still have a lot of the parts for these rigs, but you are right, they are not eager to work on them. The biggest potential breakdown is the band switch. The wafers would be very hard to replace.

 

Any CW op looking for a good rig would be wise to check out used Corsair and Omni rigs. They are great buys, but do require someone who can take them apart and fix them. The older power supplies for these rigs have been the main sources of failure for me. A switching supply would be a good replacement for the older Ten Tec analog power supplies.

 

Joe KH6/W3GW

Maui, Hawaii

[Andrew Moore]

Joe, did you REALLY put a complete Corsair II in the dish washer?!  Or just the sheet metal?  If it's the former, you just made my day.

As I go through the process of trying to stabilize my Corsair II's PTO, I agree with you the DDS solution sure looks tempting, as does stocking up on a couple spare rigs.

Your carburetor analogy sounds right on (while PTO may be less complex, with essentially a single circuit instead of several) - mechanical simplicity is great, but like carbs vs. fuel injection, you gain in performance and efficiency, but lose in DIY fixes when it (finally) fails.  And in some cases, the parts are no longer available for even those DIY fixes, as you are pointing out.

As a wise science teacher one said, "Everything in life's a tradeoff."

Must keep reminding myself that the ultimate goal (here anyway) is enjoyment of CW, not the rig that delivers it.  The hard part is that the Corsair II brought so much enjoyment that it's hard to not want to combine the two.

--Andrew, NV1B / CFO 963

..

[Andrew Moore]

On Tue, Sep 6, 2011 at 3:39 PM, joe living <jlivi...@yahoo.com> wrote:

...

The biggest potential breakdown is the band switch. The wafers would be very hard to replace.

...

Not a problem here -- it never moves from 40 meters :)

[Steve Ellington]

Andy:

 

I've had a bunch of old TT rigs over the eons. The Corsairs were more prone to drift than the others even when compared with the Tritons. I never did know why but comparing the schematics of the Corair II and the Omni C I see only one difference in their PTOs and that is the part number of the oscillator transistor. Otherwise every other part is identical (electrically).

 

The Corsair II's PTO osc. xistor is MPS5693 and the Omni C's is MPS6512. I looked at the data sheets for each and didn't see anything obvious however....who knows? I doubt if either of the original are available anyway.

 

One thing you might check or play around with is the "Offset tuning" and "shift" leads to the PTO. These leads feed to a varactor diode across the main oscillator LC network. When you vary the offset tuning on the front panel you are really changing the voltage to that varactor in the PTO which in turn varies the varactor's capacitance thus shifting the PTO frequency. A very slight change in this voltage is all that is needed to cause the PTO fq. to drift, jump or change.

 

Try unhooking those 2 PTO leads and monitor the PTO frequency for a while and note the effect. The PTO covers 5 to 5.5 mHz and you can listen to it on a typical sw receiver or a newer ham rig that has general coverage. I use my IC-7000 as test equipment a lot! The ICOM won't drift and you should be able to tell if the Corsair is drifting by listening to its pto on your other receiver. Just a hank of wire from the antenna laying near the PTO should suffice.

 

Personally of all the older TenTecs, the Corsair series was my least favorite. The Triton and Omni series were single conversion and had very quiet receivers. In the Corsair, they added passband tuning. This required the addition of 2 more IF amps, an oscillator and mixer stage. The extra stages generate a tremendous amount of white noise which can be heard even with no antenna connected. With a narrow xtal filter engaged I found the noise most annoying.

 

TenTec kept this basic design all the up through the Omni 6. Various means were used to mask the white noise. The Corsair II added an audio (BP) filter. The Omni V used a "Tone Control" in an attempt to bypass the hiss to a bearable level. The Omni 6 added audio DSP which was adjustable from a menu and the 6+ expanded the DSP to include more functions but still its main function was to fight that blasted white noise.

 

I bought a new Corsair somewhere around 1985 and tried many ideas in an attempt to reduce that hiss but nothing worked.

The other weakness in pre Omni V rigs was the audio derived AGC which was never quiet fast enough to handle those sudden, strong signals.

 

Changing parts in that PTO is a real bear. Some of the capacitors are NPO, N080, N750 etc. Get a can of circuit freeze spray and a very directive heat gun if you really want to attack that pto and find out whats causing the drift. Actually, I wouldn't bother with it unless it is REALLY drifting fast. The OMNI C was my favorite TT oldie.

 

73 and GL

Steve N4LQ

 

[joe living]

Yes, Andrew, I put the whole thing in the dishwasher except for the speaker. My wife is allergic to cigarette smoke. She said I had to choose between her and my new/used Corsair! I thought about it awhile, considered sending it back to the guy who sold it to me, but decided to put it in the dishwasher. That was almost two years ago and the signal remains very clean (pun intended). I did have to relube the PTO. I mentioned it to one of the guys at Ten Tec in passing. He was not impressed! Oh well, nothing ventured, nothing gained. Of course, I can't recommend this to any one else unless they can afford to destroy the radio. Another recommendation for those brave souls who may consider this approach; do it when the wife is gone for the day!

One other comment. I would have to say that I favor the Omni D over the Corsair. I agree with Steve about the extra stages in the Corsair's IF causing more hiss compared to my Omni D. I keep the Corsairs RF gain at around 10 o'clock to keep the hiss down. If I had to choose between the two, I would take the Omni D over the Corsair.   

Joe KH6/W3GW

[Steve Ellington]

So now we can declare the Corsair II "Dishwasher Safe"!

Hard to believe all those cardboard coil forms and even the speaker survived the moisture.

Maybe someone can test one in the microwave next.

 

Steve N4LQ

--

[Jack]

Joe,

 

That I the best one I’ve heard in some time! If you have a picture of the Corsair, with water running back into your dishwasher, it would make a neat April QST “Up Front” submission. I had to check my calendar when reading your email.

 

Jack

W4SON

CFO # 59

----------------------------------------------------------------------------------------------------------------------------------------------------------

a picture ofFrom: Steve Ellington

Sent: Wednesday, September 07, 2011 9:07 PM

To: chicken-fat-o...@googlegroups.com

Subject: Re: [Chicken Fat Operators-1157] Corsair II

 

[GEORGE, N9EJS]

GOOD one Jack!

George, N9EJS, #861
= = = = = = = = =

On Sep 8, 2:44 am, Jack <jac...@optonline.net> wrote:
> Joe,
>
> That I the best one I’ve heard in some time! If you have a picture of the Corsair, with water running back into your dishwasher, it would make a neat April QST “Up Front” submission. I had to check my calendar when reading your email.
>
> Jack
> W4SON
> CFO # 59

> ---------------------------------------------------------------------------­---------------------------------------------------------------------------­----

> CFO Sked Page:http://www.obriensweb.com/cfosked/cfosked.php'- Hide quoted text -
>
> - Show quoted text -

[Andrew Moore]

For some reason this one got lost in my email... thanks for all the good info.  I will check out the offset tuning and shift leads in the PTO.

I'm going to try disconnecting offset tuning and shift as you mention.  Do these normally have some kind of (non-zero) bias voltage on them, so that if I disconnect them, I no longer have the option of monitoring the drift on the receiver itself?  I assume that "shift" is the per-band offset applied to the PTO...?  I don't have the schematic in front of me at the moment.

I've used the Tritons and the Corsair II quite a bit over the years but never noticed the white noise until it came up recently on the lists. I do know what you mean now that I think about it - I've heard the noise (but never a problem).  That Triton sure was quiet though.

Thanks & 73,

--Andrew

[Steve Ellington]

Andrew

 

The "shift" terminal on the PTO is for the TX offset while the "offset" terminal is for the RX offset. Neither should have any voltage on them when "offset select" switch is in the off position unless something is wired wrong which is unlikely. The voltages will vary when the RX or TX offset are changed but only when "offset select" is engaged.

 

I think that by using a frequency counter or external receiver to monitor the PTO frequency you will find that the PTO is to blame for the drift. I doubt if there is an easy cure other than replacing it with a DDS vfo.

 

As for the white noise. I suppose this just follows the old rule that the more stages, the more noise and subsequently the more effort needed to mask it, I.E. audio filters, tone controls, DSP etc. 

This is why the Triton and Omni series is so much quieter and fatigue free to listen to.

 

I love listening to CW on my direct conversion receiver. One example is the TenTec 1056 any band receiver. It can hear anything that the Corsair can hear but with virtually zero noise. The effect  is as if the ear is wired directly to the ether. 

[John Zimmerman]

Steve,

I like direct conversion receivers too.  I think the Ten Tec Century 21 is a direct conversion and it has a nice sound and is fairly quiet.  I also like super regenerative receivers like the Navy RAK-6 and RAL-6.  They both have audio filters in them and the CW sound is very nice.  I also have a Navy RBA.  I believe it is a TRF radio and I have not had a chance to listen to it yet.  I also enjoy my Triton IV.

I have been listening to my National 240D today. 

Love these old tube sets.

John, K0JVX

---

From: Steve Ellington <n4...@carolina.rr.com>
To: chicken-fat-o...@googlegroups.com
Sent: Tue, September 13, 2011 12:57:10 PM
Subject: Re: [Chicken Fat Operators-1162] Corsair II