Heathkit SB221 Inspection

[357]

NOBODY IN TOWN has 6-32 x 1/4 or anything under 1/2", NOBODY.
I took matters into my own hands and used a bench grinder.

 

[357]

 

[357]

ITS ALIVE!!!

 

[Dmans]

357,
LOOKING GOOD!!

73
David

 

[357]

357,
LOOKING GOOD!!

73
David

thanks! so far so good.
Got the softstart and keyer next. Maybe I can test the tubes

 

[357]

View attachment 32398

 

[357]

I'm worried about the idle current.
90ma on CW 150ma on SSB...?
That ok?

I put the softstart in, it was the hardest of all, I HATE terminal strips.
Tomorrow I'll do the softkey and the Surge Suppressors.
My soldering iron was melting so I wasn't in the greatest of moods tonight.

 

[Dmans]

357,
The SB-220 manual states Plate current in CW mode should be .5 amps and in SSB (Hi Power) "no higher than .33 amps".
Looks like your metered current is .09 in CW and .150 in SSB.
It seems you are safe at the levels you posted. I would imagine as your tubes age, these levels will rise.

73
David

PS
Don't be too bummed about your soldering iron. It appears you have gotten your monies worth out of it. The tip especially!

 

[357]

357,
The SB-220 manual states Plate current in CW mode should be .5 amps and in SSB (Hi Power) "no higher than .33 amps".
Looks like your metered current is .09 in CW and .150 in SSB.
It seems you are safe at the levels you posted. I would imagine as your tubes age, these levels will rise.

73
David

PS
Don't be too bummed about your soldering iron. It appears you have gotten your monies worth out of it. The tip especially!

Thanks for that.

I looked again at the install notes and seen this:

This completes the installation of the RM-220 rectifier and metering board. It will provide you with
protection from diode failure, as well as providing much more accurate meter readings. When you
operate your linear amplifier, you will probably find that the plate voltage reading is much higher than
before. This is not really the case. The voltage is the same as before, but you are now reading the
true voltage. You may notice a slight reduction in the idling plate current of your SB-220/SB-221.
This is because the new board produces 6.8V of bias for the 3-500Z tubes, rather than the 5.1V
provided by the original Heathkit design. This will lower the heat produced by the amplifier during
voice lulls, but will not materially affect the linearity at high power levels.

 

[357]

It doesn't look pretty but its all done and secure.

 

[357]

Thats what I'm talking about!

 

[Unit 75]

Good Job !!

 

[Dmans]

Congrats!

73
David

 

[357]

Nomad will see it

 

[357]

Did a little maintenance on the SB220
Replaced the input disk caps n the heaters and the 6KV cap on the HV input. (forgot to get a picture before I put the cage cover on)

I'd like to do the doorknobs but finding good X7R doorknobs is impossible.
They aren't soft but they are getting up in value.

Amp has performed flawlessly, just a bit of dust so I gave it a clean and lube while I was at it. Input SWR came down a bit and so did the grid a bit...power out unchanged