Some AC-DC tube radios were wired so that the chassis was connected to one side of the power plug when turned on, and to the other side of the power plug when turned off. One side of the plug connected to the power switch. The other side of the power switch was connected to the chassis. The heater series string was connected from the chassis to the other side of the plug.
I recapped and rewired one of these to run safely and cooly off a 12 VAC 1A wall-wart supply.
I rewired the small-signal tubes (12BE6, 12BA6, 12AT6/12AV6 or 12SA7, 12SK7, 12SQ7) with their 12 V heaters in parallel across the 12 VAC. I used three silicon rectifiers to triple the 12 VAC to 36 VDC for B+ for these tubes. The gain is lower, but they work fine. I removed the rectifier tube (35W4 or 35Z5) entirely.
I relpaced the audio output tube (50C5 or 50B5 or 50L6) and output transformer with a LM384 running from 12 VDC (halfwave-rectified 12 VAC). I used a resistive divider at the LM384 input to reduce the gain to the unity voltage gain exhibited by the audio output tube and transformer. I reused the output transformer primary as a filter choke for the 36 VDC supply filter.
@David Ashton: "(Andy Capp was a working-class British layabout forever shirking work, drinking beer and chatting up barmaids, and a cigarette hanging out of his mouth). He had a long suffering wife called Flo who had cleaning jobs to bring in a bit of money."
Andy resides at gocomics.com. Here's today's story:
Edit: The picture doesn't show on my PC, but I don't know if it's our net-nanny software or not.
@kfield: You mean you were pouring it directly down your gullet, bypassing your lips entirely?
Hey -- I'm not gauch -- my mom brough tme up propper -- I know which color drinking straws and which paper umbrellas go with each type of cocktail -- and when it comes to a formal dinner in which white, red, and dessert wines are served with each course, I know that you use the drinking straws starting from the outside -- LOL
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Are the design challenges the same as with embedded systems, but with a little developer- and IT-skills added in? What do engineers need to know? Rick Merritt talks with two experts about the tools and best options for designing IoT devices in 2016. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.