Heathkit Chippewa amplifier

[AE7IX]

Hi All
I just acquired a Heathkit Chippewa amplifier from a good friend who had passed recently, this amp has not been fired up for nearly 20 years so this will be a fun project to bring this old beauty back on line.
Here are a couple of pictures of the unit and the power supply, I will post more as I clean it up and bring it online.

[AE7IX]

Ok, got it up and running today, ran just the filaments for about an hour then  turned on the high voltage and keyed it with no drive in SSB mode and adjusted the idling plate current with the bias adjustment to 180 mA per the instructions and let it make heat like that for a couple of hours.
The tubes do have the blue glow so they are a little gassy, 1 is a little brighter blue than the other.
I put it in line and tuned up on 3.915 and  slowly started bringing the power up over about an hour, 60 watts drive gives me about 1000 out, so far so good.
Here's a few more pictures with the cover off while I was bringing the tubes up.

[KE7TRP]

Jim, So glad you got the beast up and running!   1k is pretty good. 

I guess you got the 220 volt line run and installed? 

I really like that power supply he built.  Looks like a bud case.  I will be on tonight so I can hear this thing!

Clark

[AE7IX]

More pics of the input circuit

[KE7TRP]

Jim, The Amp sounded awesome on the air. Its very clean and has a loud voice.  If you ever got into running AM, That is the amp to do it. We need to make an AM night. You can run that amp at 300 watts AM all night and the only thing that's burned up is your electric bill

After looking at the recent photos, Its clear that the block of resistors is the input pad.  This seems to be in line all the time on this KW-1.  Even if you choose the tuned input.  I followed the pad output right to the mica cap, then to the ceramic feed through and then over to a choke and to the grids of the 4-400s.

This would mean that you can run 100 watts into the amp without issue.  I think you are not seeing Grid drive on the meter at 50 to 60 watts as there is not enough drive to show Grid.  On my Tbolt you really have to drive it to see any grid.

On my Johnson thunderbolt, You can choose "tuned" inputs or "RES" for resistive.  In the RES position you can run 60 watts or so input without any trouble but on the Tuned input mode, You do NOT have the pad inline. So Max drive is 10 to 15 watts PEP.   I ran this with 10 watts in and got full power 1000 watts out.  You better make sure your exciter is clean with that kind of gain!

I wonder about making a modification to the Tbolt so the Pad is always inline like the KW1.  I will have to look over the schematic when I have time. 

C

[N9DIX]

I was wondering did you find and of the filter caps in the power supply bad or leaking? I have an SB220 with a pair of 3-500z that haven't been on the air for at least 18 years. I was thinking in using a rheostat to the line voltage up once I had just filaments lit for a while like you did. It will probably be a few more months till I get the shack finish above the barn and hand an antenna. Last time I ran it I could get a full 1000 watts key down. I use to run RTTY with it with the output turned down some but it held a constant 750 watts.

Glad you got it running. I've heard via the grapevine that Heathkit will be coming back to producing kits, when I don't know but they do have a website up with some info. Hope they do.

73's Jim

[KE7TRP]

Hi Jim. Thanks for posting.

I have owned several SB220's and I use one everyday.  I never had a capacitor failure in any of them.  I would just turn the Amp on and key it up in the CW/Tune position with no drive. This will put a low current on the tubes. If you don't hear any noises, The amp is good to go.  You can leave it keyed up for a while to de-gas the tubes this way. 

The 3-500s are instant on so you don't need to warm I up after this. Just turn it on and key instantly.  In fact, This is how I operate mine while working DX. I pretune the band, tune and load for the band I want to use by a chart, Flip it on, Make the contact and flip it off.

C

[N9DIX]

Thanks C, I still don't have the shack finished so I'm not on the air yet. That's good to know about the caps and yes I'll have 220 available when I do get things going. I will have the case opened first and blow the cow-webs out and clean up the dust. Also will check the caps for any leaking. I was just worried that since it hasn't had any power applied for the past 18-20 years that the caps might of dried out. I'll let you know when I do get it running. Thanks again.
73's Jim