UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Toshiba Portable TV (C-1480B)

Clydeuk · 27th Oct 2015, 11:53 pm

Bear in mind a lot of the low voltage supplies are derived from the LOPTx so these will read low resistance to chassis. The important one to check is the HT (B+)connection and the connection to the output transistor, check from collector to chassis, if this reads a short the transformer is probably dud (assuming the transistor is ok as you mentioned).

If there's no short, do you get any voltage at the collector? Normally you won't be able to measure this as when working it's high frequency spikes and a meter will object, if you get steady HT however there is no line drive.

Without the line output stage running there will be no sound as the supplies are missing.

27th Oct 2015, 11:53 pm	#4
Clydeuk Hexode Join Date: Mar 2012 Location: Liverpool, Merseyside, UK. Posts: 453	Re: Toshiba Portable TV (C-1480B) Bear in mind a lot of the low voltage supplies are derived from the LOPTx so these will read low resistance to chassis. The important one to check is the HT (B+)connection and the connection to the output transistor, check from collector to chassis, if this reads a short the transformer is probably dud (assuming the transistor is ok as you mentioned). If there's no short, do you get any voltage at the collector? Normally you won't be able to measure this as when working it's high frequency spikes and a meter will object, if you get steady HT however there is no line drive. Without the line output stage running there will be no sound as the supplies are missing.