50s Japanese am/fm tube dual speaker radio

[bob91343]

I never saw a screw base NE-51 so you may have to do some surgery to replace it. You can temporarily parallel a good neon lamp to see if that's the problem. Old neon lamps do go bad from gas leaks.

I'm an engineer also but get excited about everything from DC to maybe 30 MHz. I also repair musical and stereo gear and have an impressive lab. I just acquired an HP 3456A DVM but it doesn't work so I'm negotiating with the seller. I also used to own a stereo repair shop. And I have a ham ticket.

You can use the sweep gen for education but frankly I never found one useful for FM alignment. Better to use an FM generator. You can use the DVM to check the forward drop of the diodes; it should run in the vicinity of a quarter of a volt (as opposed to silicon, about two thirds of a volt). Reverse leakage can be a problem though and your meter won't measure that unless it's drastically leaky.

[maxhifi]

Originally Posted by bob91343

I never saw a screw base NE-51 so you may have to do some surgery to replace it. You can temporarily parallel a good neon lamp to see if that's the problem. Old neon lamps do go bad from gas leaks.

I'm an engineer also but get excited about everything from DC to maybe 30 MHz. I also repair musical and stereo gear and have an impressive lab. I just acquired an HP 3456A DVM but it doesn't work so I'm negotiating with the seller. I also used to own a stereo repair shop. And I have a ham ticket.

You can use the sweep gen for education but frankly I never found one useful for FM alignment. Better to use an FM generator. You can use the DVM to check the forward drop of the diodes; it should run in the vicinity of a quarter of a volt (as opposed to silicon, about two thirds of a volt). Reverse leakage can be a problem though and your meter won't measure that unless it's drastically leaky.

Hm I need to get my hands on an fm generator. The diodes have a 0.37V drop according to my meter and nothing in the other direction but as you said not entirely useful. The neon lamp has a metric looking threaded base, not the usual type. I have an amateur radio license too but never actually used it. I would not
Call my "shop" impressive, more like a room in the basement with a work bench and a bunch of obsolete test equipment, but it gets me by.