[TowerTalk] Running 3-500Z in the horizontal position

[Bert]

Thanks to all who shared their experience re. 3-500Z.

Running the amp upside down works for me.

Bert VE3NR





On 2020-10-09 14:43, Chucks Laptop wrote:
> Anecdotally, I made the mistake while I was posted in Laos in 1969 - 
> 1971, of turning my SB220 on its side to trouble shoot a problem. I 
> soon discovered that wasn't a good idea. I noticed something wrong 
> very quickly and shut it off, fortunately before damage to the 
> filament transformer windings. Both tubes were damaged by the sagging 
> filament syndrome. It's one thing to be offshore and quite another to 
> be in CONUS. No internet, e-mail, just snail mail, or Amateur Radio. 
> APO Services were there, but took lots of time.
>
> I fired up my spare SB-200 and was back on the air. Several of the US 
> Hams offered to send me the tubes, but in the end I got them from 
> Henry Radio. I didn't know about the caveat of running the 3-500 tubes 
> while on their sides. When the replacement tubes arrived, and were 
> installed, the SB-220 fired up and worked. I got lucky. The bias 
> circuit survived despite my best efforts to destroy it. It was pure 
> luck that I didn't repeat the same mistake. I still didn't know that 
> operating the tubes on their sides was a no-no. As I recall, there was 
> nothing in the Heathkit Manual that mentioned this.  Perhaps Eimac had 
> a bulletin, but being out of the US made some resources unavailable.
>
> That complete station followed me to the Ivory Coast and operated 
> without further problems. Great old amplifier, and remarkably, still 
> is in many stations!
>
> 73
>
> Chuck, W6AJW
>
>
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