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HEATHKIT SB-200 Info required Please.

You're right, I'm not sure why I was talking grid current dip on a grounded grid design.

But if the tubes are not neutral, one side of the dip will be steeper or sharper than the other, but shouldn't max out still happen at the plate current dip?

No. It might but probably not. Some are close.
 
Well I know of a tv shop that still works with tv tubes and stuff. Perhaps i can call tomorrow and see if they have the capabilities of checking them. Wish i owned a TV-7D/U tube tester. Well if they are the tubes Pretty sure the price on a new set is not too bad for the money.:pop:
 
I've used the cheapies listed on ebay with no problems.

There are a lot of horror stories about Asian 572Bs. I must be lucky.
 
Yes Ive heard horror stories about those Over seas tubes from some of the ham forums. But eBay has a pretty good selection going on now so will have to wait and see . Definitely going to check with the TV shop first. They should have the provisions to do so I hope. But i will find out hopefully today. :pop:
 
Another question Iv removed the top lid by removing the 2 side screws. Underneath is that aluminum sheet that covers the tubes. Ive removed all the screws except the few towards the front. How can I access these screws. Seems like they are tucked underneath part of the upper front housing strip that holds the 2 screws for the top hinged cover. I could just bend it to remove the tubes but is there another way in there? I promise to discharge the caps and tubes prior. Thanks........
 
well looks like my buddy is going to have to buy a set of tubes. Seems like no one has a tub tester for the Sb200. Thanks to you all that responded to this thread. Best regards and wishes with a happy 4th of July.............(y)
 
sb-200 if i remember correctly had 811a/572b in them. If you had a tube checker that will do 812 tubes it should work as the 812 are a low output version of the 811.

Rich
 
Ive searched hi and Low here in the city and surrounding cities and friends To no avail. Ive tried tube amp repair shops as well. I figured the matched set of Cetron T160l are the originals and has to be at least 35 years of age. Still looks clean no foggy appearance just the round mirror circle that appears on the bottom side of the tubes. You would think after 35 years tubes could loose half its output. :headbang
 
I've got a feeling those Cetron tubes are not the original tubes. I don't think 'Cetron' was around when that amplifier was in production. (Not that it matters a lot, they are replacements for a 572B tube.)
Something that your friend will want to keep in mind, or anyone with an SB-200, or any amplifier that uses 572 tubes in a horizontal position! All brands of 572's do not have the same relation between the pins and the internal structure of the tube elements. That means even if the tube sockets are mounted correctly, if the elements in the tube are positioned so that the filaments/grid structure isn't "vertical" (not "flat", length/width dimensions), they will short out when they get hot and 'sag'. The rectangularly shaped filament/grid structure/assembly has to stand on it's 'side', not flat. Wish I could remember the 'brand' that did that, but can't. That's one reason why you don't see many 572's used laying down, sort of.
- 'Doc
 

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