Why did manufacturers use 5 volt heater rectifiers? - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

julie_m · 18th Feb 2018, 1:20 am

Couldn't you just use an EM84 in a 300mA TV heater chain, with a shunt resistor to make up the current difference?

Herald1360 · 18th Feb 2018, 3:16 pm

WOT

?!

Put an extra resistor in a telly?

julie_m · 18th Feb 2018, 11:19 pm

They would make fewer of the PM84, though, seeing as not all TVs would be fitted with one; so you'd expect them to be sold more expensively than an EM84 (found in almost every tape recorder), and probably by more than the cost of a resistor.

turretslug · 18th Feb 2018, 11:29 pm

Perhaps there was also a worry that, on switch on, the 0.2A heater of the E-eye would be proportionately harder hit as its shunt would be ohmic? Also, a bit more assemblage involved with a resistor, who knows what calculations go on with OEM quantities, T + M, favoured valve-maker deals? It might all seem arcane- but so does the 35Y4/35Z5 thing with a bulb across part of the heater to save on resistors, this time with the opposing attraction that the rectifier goes phut a little quicker when the inevitably short-lived bulb fails....

18th Feb 2018, 1:20 am	#21
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Why did manufacturers use 5 volt heater rectifiers? Couldn't you just use an EM84 in a 300mA TV heater chain, with a shunt resistor to make up the current difference? __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

18th Feb 2018, 3:16 pm	#22
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Why did manufacturers use 5 volt heater rectifiers? WOT?! Put an extra resistor in a telly? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

18th Feb 2018, 11:19 pm	#23
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Why did manufacturers use 5 volt heater rectifiers? They would make fewer of the PM84, though, seeing as not all TVs would be fitted with one; so you'd expect them to be sold more expensively than an EM84 (found in almost every tape recorder), and probably by more than the cost of a resistor. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

18th Feb 2018, 11:29 pm	#24
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,395	Re: Why did manufacturers use 5 volt heater rectifiers? Perhaps there was also a worry that, on switch on, the 0.2A heater of the E-eye would be proportionately harder hit as its shunt would be ohmic? Also, a bit more assemblage involved with a resistor, who knows what calculations go on with OEM quantities, T + M, favoured valve-maker deals? It might all seem arcane- but so does the 35Y4/35Z5 thing with a bulb across part of the heater to save on resistors, this time with the opposing attraction that the rectifier goes phut a little quicker when the inevitably short-lived bulb fails....