Heathkit SB 220 intro. What it is in for & things to think about when working with HV amplifier.

[@boxingday11]

Have two of these ladies, that I still use, thanks for your upload.👍🏻🕊

[@andydelle4509]

Early in my career, early, 1980s, I worked on full power UHF TV transmitters. Try 19kv at 13 amps! The rule was not to worry about the high voltage. Just don't let yourself to become grounded. After numerous HV accident investigations it was learned that it's not the HV contact that gets you. It's the ground! Where is your other hand? Where are your feet? What type of shoes are you wearing? What is the floor surface?

[@theradioroom726]

19,000 volts! that could make for a very bad day. Thank you for also bringing up the concerns on the ground. Awareness of where you are and what you are doing is very important. I try to make sure I think out every move when working on HV. (Of course 19kv would involve a lot more consideration. Just getting close, not even touching the HV while grounded would be a bad day.) Thank you for adding these things to remember. The questions you ask are ones everybody should consider before working on HV. Let me go over this particular situation in regards to your questions to consider. My other hand is not in my pocket where it normally is when working on live or unverified HV, as I was holding the phone for recording. I am wearing safety toe and electrical hazard work boots (required by my regular everyday job). In this case, the floor is carpet over concrete slab. Thank you for sharing, input from those with much experience helps everyone in gaining knowledge.

[@DPMaintenance]

I just got one of these it is very good condition with documents including original bill of sale and documents on all the mods and new parts installed in 1996 and new tubes in 2000. I just got it home yesterday and have not turned it on yet still researching it is my first amplifier. It has a small red toggle switch on the front I think this might be a standby switch and a big toggle switch added to the back top left not sure what that is for yet. Might have a few questions for you at some point not in a hurry to put it on the air yet need a tuner. Looks like it has had all the mods and new parts installed based on the sales receipts I have that came with it.

[@michaelgermino626]

Nice video. Where can I find that schematic you had up on your screen. I just acquired a SB-220.

[@theradioroom726]

I cannot remember exactly where I found it. Here is a link to a good one that I just found. www.manualslib.com/manual/465938/Heath-Heathkit-Sb-220.html?page=2#manual Also you may want a manual if you do not already have one. Here is a link www.manualslib.com/manual/903246/Heathkit-Sb-220.html Thanks for watching!

[@tramdr]

I am working on an Ameritron AL-82 and one of the things that vexes me is that it also has a bank of 8 450v HV caps, but according to the manual, the amp runs at 3800V resting, 3300 keydown. I don't get it. The cap banks rating of 8 x 450 = 3600v and that would be max with no safety margin right? I really don't get this.

[@theradioroom726]

Apologies for the delayed reply. I wanted to take the time and take a look at a schematic for the AL-82. Took a bit to find the time to sit down with it. Yes Ameritron is running the filter bank on the edge. This is common in many capacitor banks I have noticed for many types of power supply filters. Perhaps comes down to not wanting to spend more for higher voltage caps in production costs when 450v "will do". As far as the no load voltage listed in the specifications of the manual of 3800v, this is for absolutely no load on the power supply. When in circuit there is some load. Further, when in operation, the nominal voltage is 3600v not to exceed 3700v. The manual contains a warning to not alter the power supply to exceed 3700v. I suspect that is because they are already pushing things a bit with the filter caps and that also gives a bit of overhead on the 3-500 tubes with 4000v max plate voltage. That is still pushing it in my opinion. I prefer some overhead instead of running on the edge and trusting the resistors to prevent a cascade failure of the caps. There are available replacement capacitor banks for the AL-82 that use 500v caps that would provide 300-400v overhead..... and a little more peace of mind. Thanks for watching!

[@itsonlyme9938]

Are eimac 3-500 tubes still being made ?

[@theradioroom726]

From what I understand Eimac has not made 3-500 tubes for a while or any other glass tubes. There are 3-500 tubes available new from various sellers and manufacturers. I believe RF Parts, Amperex and Taylor still produce them. Thank you for watching!