My first AM station..

[N1ESE]

An Apache would over drive it, even in the "tune" mode.

That's odd, the Chippewa manual states that the amplifier was designed for use with the Apache. 

- JT

[Ed-VA3ES]

Unless I'm mistaken, I thought that the Chippewa was grid driven?   Even if not, and it's grounded-grid, you still can't drive it with 100W of AM.  That's 400W PEP, and too much for any conventional amp.   25W is sufficient, and the Apache will do that in the "tune" Mode.

An Apache would over drive it, even in the "tune" mode.

That's odd, the Chippewa manual states that the amplifier was designed for use with the Apache.   - JT

[Todd, KA1KAQ]

And, I'd insist on being paid in Canadian dollars,  not your  dollarettes! 

HA! And when was the last time you could say that, Ed?? There was a good reason for calling those coins 'Loonies' and 'Toonies'.   

That's odd, the Chippewa manual states that the amplifier was designed for use with the Apache. 

Probably with output padded down somewhat? Johnson actually made a couple of attenuators specifically to allow rigs like the Valiant and others to interface with the Viking Kilowatt.

[N1ESE]

Unless I'm mistaken, I thought that the Chippewa was grid driven?   Even if not, and it's grounded-grid, you still can't drive it with 100W of AM.  That's 400W PEP, and too much for any conventional amp.   25W is sufficient, and the Apache will do that in the "tune" Mode.

The Chippewa has specific control connections on the back for the Apache.  The manual makes it very clear that the Chippewa is designed with the Apache in mind. 

The Chippewa features two grid configurations.  From the manual:

"When the "R" position of the GRID BAND switch is selected, the entire tuned circuit is bypassed and the second or resistive grid current is employed.  The input excitation is delivered to a 170-ohm 80W, non-inductive load resistor.  The voltage developed across this resistive load provides the required driving voltage for Class AB1 operation.  This grid circuit configuration can be used only for Class AB1 linear operation but has the advantage of being capable of using higher power exciters as drivers without the necessity of power reducing networks.  No neutralization or grid tuning is required on any band in Class AB1 linear operation because of the very heavy grid loading provided by the swamping resistor."

- JT

[The Slab Bacon]

Ahha!! this is the same scenario as the Junkston Invader 2000 and Thunderjolt! Blow the power into a built in dummy load and use the obtained voltage across said dummy load to tickle some AB1 grids.

It does a good job of swamping down the grids and keeping the amp stable.  One of these days when I dont have anything better to do, I'm gonna experiment with some mods for my Invader 2000 to convert it to grounded grid / cathode driven and see if I can get a little more snot out of it. As designed, with the I-2000 you cant adjust the loading of the 6146s when you switch into the high power
mode and fire off the PL-175s.
                                                      The Slab Bacon

[Todd, KA1KAQ]

Built-in attenuator. Clever. IIRC, the Chippy is somewhat scarce compared to the Warrior amp? Would've been the crowning piece for that excellent Heath package (Apache, Mohawk, Marauder) offered on ebay last week.

Looking forward to hearing it on the air.

[N1ESE]

IIRC, the Chippy is somewhat scarce compared to the Warrior amp?

From what I've gathered, there were only about 100 made.  I can't find any pictures online of any actually units.  Just plain photos from old Heathkit catalogs.

I'm leaving here in a few minutes to go get it.

- JT

[N1ESE]

Got back home a little while ago and just now finished unloading the Chippewa, big iron, and other assorted goodies I came home with.  Cabinet and transformer for the high voltage supply are sitting on my porch, I need to go to UHaul tomorrow and rent a beefier dolly.  Mine didn't cut it.  The transformer weighs more than the cabinet does!     It isn't an HS-1 matching supply for the Chippy, I was under the impression it was, this thing is a much bigger homebrew supply!

Pics coming up in a little bit.

- JT

[WQ9E]

Hi JT,

Nice find with the Chippewa!  I picked up one last year, also with a very large HB supply.  A couple of Chippewa cautions:

1.  The large tapped resistor on the topside of the chassis is in a position where it is easily damaged, the ham I got mine from had already replaced it after he damaged the original while removing the case.  You can turn the resistor slightly to move the tap side so it is not as likely to suffer damage.

2.  The plate current meter is in the HV lead to the plates and has full plate voltage/current across it.  Keep your fingers away from the meter while operating.  Once in awhile everybody makes a bad design decision and this is definitely one of Heath's bad decisions.

3.  If your power supply was built with 866A or 872 (or any other MV rectifier) be sure and run them filament only for at least 10 minutes to make sure any little mercury blobs in the wrong place get vaporized.  You only need to do this long warm up once (or every time the power supply is moved in such a way that the tubes are tipped, inverted, or greatly shaken).

4.  Your blower will benefit from having a bit of oil added to the oil ports.  Ditto the fan in the Apache.

I like the Chippewa a lot.  Mine is paired with an Apache/Mohawk/SB-10.  I also have a Johnson Pacemaker/T-Bolt setup and the design is pretty similar and the performance seems to be about the same but the KL-1 is certainly much more scarce.

Rodger WQ9E

[W4WSZ]

N1ESE, JT.

I fully agree with Slab Bacon about the Q Multiplier......

If you would like to have one to go with the receiver I shipped you.

I have one FREE for the postage..

Let me know.

73, Bob,W4WSZ

[W4WSZ]

N1ESE,

The Q Multiplier will be mailed tomorrow....enjoy

73,
Bob,W4WSZ

[N1ESE]

As usual, Slab is right.  Definitely hard to tune in AM stations on 75 when crowded.. especially at night.  During the day, the daytime crowd sounds real nice.. even the 3910 guys
 
- JT

[The Slab Bacon]

JT,
    IIRC you were also getting a Q-multiplier with that rx also??
If you did, get it working and install it. It will make a TREMENDOUS improvement to it's selectivity!! Mine with an outboard Q-mult was pretty good to use when things got crowded. You could dial up the best compromise between fidelity and selectivity.

                                                      the Slab Bacon

[N1ESE]

IIRC you were also getting a Q-multiplier with that rx also??                                                      the Slab Bacon

Yup, but it's not here yet. 

- JT

[The Slab Bacon]

As usual, Slab is right.  Definitely hard to tune in AM stations on 75 when crowded.. especially at night.  During the day, the daytime crowd sounds real nice.. even the 3910 guys
 - JT

Good grief JT, don't encourage him!
Mack

Thatz right!! And dont you forgit it!!