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SCORE!!! Near Mint SB 220

AK321

AK321

Active Member
Oct 31, 2014
112
73
38
Murray KY.
Scored this beauty from a local SK estate. Can't wait to get it up and running. Cables are the only thing holding me back. Got a nice 2KW tuner to go with it.
 

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It has been sitting for a year or more. I plan on putting in all the Harbach mods eventually. I will have to let it idle for a day or more to avoid a possible tube flashover in case the seals leak. They probably don't but I don't want to take any chances. I have an Ampkeyer that I bought from the Heathkit Shop (Mike Bryce is a great guy to work with, BTW) and it is a keying interface to use until I put the mods in. It looks like the amp has had new HV caps installed already.
 
I have the TL922 myself, very close to the same. Have the soft key installed. I see Harbach has the caps in stock again. Might have to get the kit soon.
Rich
 
AK321 said:
It has been sitting for a year or more. I plan on putting in all the Harbach mods eventually. I will have to let it idle for a day or more to avoid a possible tube flashover in case the seals leak. They probably don't but I don't want to take any chances. I have an Ampkeyer that I bought from the Heathkit Shop (Mike Bryce is a great guy to work with, BTW) and it is a keying interface to use until I put the mods in. It looks like the amp has had new HV caps installed already.
Click to expand...

Idling will not getter the tubes. They don't get hot enough. I suggest that you bring the HV up slowly and then apply a steady carrier with low drive. Slowly increase drive until the tube plates start to show a little color. Operate it like this for 15 or 20 minutes before normal operation. Carefully watch the meters for signs of arcing.
 
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Nice score for sure. I re-capped mine a few months ago with a Harbach snap-in cap kit.

What brand tubes are in it and what's the added toggle switch on the front panel for?


yMbNsFI.jpg
 
I'm installing new caps as well, along with new metering board. It's a standby switch. It has the original Eimac 3-500Zs.
 
I got it fired up and meter is showing 1250v on CW and 1600 in SSB mode, so it's low on hv. It's definitely got some issues, so caps are getting replaced. Definitely going to put a soft start board in it, and perhaps new vacuum relays.
 
If the voltage is that low...I would suggest a New Diode/Bias/Metering board also and a new higher output fan motor...Those fans are notorious for not pushing enough air after they get some age which leads to solder melting out of the tubes pins.

http://harbachelectronics.com/product-category/heathkit-sb220-sb221/

New caps board
New Rectifier/Bias Board
Soft Start module (optional but recommended) Helps to protect the new power supply parts
Soft keying (is a must)
New fan Motor and blade assembly
When she is all done, the old girl will be a workhorse ready for many years of service.
All the Best
Gary
 
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