Anyone happen to know if this full wave bridge rectifier is a silicon-diode bridge?
It seems way too small to be 4 selenium diodes, however the age of the unit puts it kinda "on the line".
I ask because I want to replace as little as possible in this old girl. I'm already into the power supply because of leaky "safety caps' on the primary side, making the chassis all "tingly". Of course, upon opening said can of worms, I found a can cap that farts when you tap on it.
These hand-wired tuned circuits freak me out. Having worked on many an old (and new) FM Transmitter, one of the guys I work with dubbed FM "F*&king Magic", and I wholeheartedly agree. I have no desire to jab at this girl unnecessarily with a soldering iron.
I assume I should just drop the $4 and replace the little tin box with a modern bridge rectifier...
Thx
art
It seems way too small to be 4 selenium diodes, however the age of the unit puts it kinda "on the line".
I ask because I want to replace as little as possible in this old girl. I'm already into the power supply because of leaky "safety caps' on the primary side, making the chassis all "tingly". Of course, upon opening said can of worms, I found a can cap that farts when you tap on it.
These hand-wired tuned circuits freak me out. Having worked on many an old (and new) FM Transmitter, one of the guys I work with dubbed FM "F*&king Magic", and I wholeheartedly agree. I have no desire to jab at this girl unnecessarily with a soldering iron.
I assume I should just drop the $4 and replace the little tin box with a modern bridge rectifier...
Thx
art
I have a 350 (not B) tuner sitting in my warehouse. I looked at the schematic and it shows a 6X4 tube for the power rectifier. It also shows two diode quads in the multiplex circuit. They are 1N294's which are "gold bonded germanium diodes". If that is the case in your tuner, don't mess with them.
I got the tuner and a 272 amplifier at as yard sale several years ago. THe amplifier rocks, but I never tried the tuner.
I got the tuner and a 272 amplifier at as yard sale several years ago. THe amplifier rocks, but I never tried the tuner.
Found it!
The "B" schematic clearly shows a Monolithic bridge rectifier 'module', and the innards of the tuner reveal a little metal box with the typical "AC / AC / + / - " stamps on its four terminals.
I just wandered over to hhscott.com, dug a little, and found out that, yes, the 6X4 rectifier tube was indeed replaced in the "B" and "C" units with....
...a selenium bridge rectifier.
So, I guess we can call this one answered!
(FWIW, the Scott 350 B is an excellent tuner, in less crowded FM environments. The sensitivity is quite good, but there are many more signals in the 88-108 MHz band than there were in 1963/4. It has a tough time choosing between adjacent signals, especially when you want the weaker of the two. It does, however, sound great once it's tuned to a strong carrier free from adjacent or co-channel interference.)
The "B" schematic clearly shows a Monolithic bridge rectifier 'module', and the innards of the tuner reveal a little metal box with the typical "AC / AC / + / - " stamps on its four terminals.
I just wandered over to hhscott.com, dug a little, and found out that, yes, the 6X4 rectifier tube was indeed replaced in the "B" and "C" units with....
...a selenium bridge rectifier.
So, I guess we can call this one answered!
(FWIW, the Scott 350 B is an excellent tuner, in less crowded FM environments. The sensitivity is quite good, but there are many more signals in the 88-108 MHz band than there were in 1963/4. It has a tough time choosing between adjacent signals, especially when you want the weaker of the two. It does, however, sound great once it's tuned to a strong carrier free from adjacent or co-channel interference.)
Here in south Florida there is at least one signal on every FM frequency. Many are pirates running very dirty transmitters. I use a solid state Technics tuner and it often can't deal with the intermodulation and adjacent channel crud.
I work for Motorola designing two way FM radios. Yes that term was commonly used to describe the operation of the early radios like the HT-220. None of the young guys have ever heard it though. Think the tuner is trick. Those early radios all used tiny hand wound RF coils at 450 MHz. It's all SMD now.
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