The MIVAR chassis series TV705 / TV708 is the last MIVAR tv chassis with tubes, and last model with hand wired chassis parts and last model series of MIVAR tv with wooden cabinet for B/W screen series.
It's divided in sections providing Signal processing with full discretes components, synch separation even with discrete components and FRAME deflection with output transformer and a completely hand wired Line deflection + EHT stages on the right side.
Power supply is located on the left side of the chassis which is a heavy steel basis.
The chassis is entirely developed by MIVAR and around PHILIPS semiconductors and it's not a crappy copy from another cheap crap around recognizeable even in that era.
Tubes used:
- PY88
- PL504
- PCL805
- The EHT Output is realized with a selenium rectifier.
The EHT selenium rectifier which is a Specially designed selenium rectifiers were once widely used as EHT rectifiers in television sets and photocopiers. A layer of selenium was applied to a sheet of soft iron foil, and thousands of tiny discs (typically 2mm diameter) were punched out of this and assembled as "stacks" inside c
eramic tubes. Rectifiers capable of supplying tens of
thousands of volts could be made this way. Their internal resistance was
extremely high, but most EHT applications only required a few hundred
microamps at most, so this was not normally an issue. With the
development of inexpensive high voltage silicon rectifiers, this
technology has fallen into disuse.A selenium rectifier is a type of metal rectifier, invented in 1933. They were used to replace vacuum tube rectifiers in power supplies for electronic equipment, and in high current battery charger applications.
The photoelectric and rectifying properties of selenium were observed by C. E. Fitts around 1886 but practical rectifier devices were not manufactured routinely until the 1930s. Compared with the earlier copper oxide rectifier, the selenium cell could withstand higher voltage but at a lower current capacity per unit area.
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