UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

FERNSEH · 10th May 2017, 8:41 pm

Hi Oliver,
That's right I don't think the HMV 1804 is all that rare, in fact it could be said the Marconi version far less common.
The big problem is that almost every IF transformer has received attention from the mystery engineer. Until a signal generator is hooked up we don't even know if the vision and sound IFs are the same as the original EMI values.
For safety the EHT transformer can be disconnected when performing adjustments on the signal circuits. The same transformer also supplies the timebase valve heaters and the CRT heater.
Very early production sets had a switch ganged to the brightness control which switched off the mains supply to the EHT transformer thus allowing the set to be operated as a sound only receiver. Evidently the BBC National radio service was at one time radiated from the AP transmitter. Can anyone confirm this?

DFWB.

10th May 2017, 8:41 pm	#40
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: HMV 1804 Television. Hi Oliver, That's right I don't think the HMV 1804 is all that rare, in fact it could be said the Marconi version far less common. The big problem is that almost every IF transformer has received attention from the mystery engineer. Until a signal generator is hooked up we don't even know if the vision and sound IFs are the same as the original EMI values. For safety the EHT transformer can be disconnected when performing adjustments on the signal circuits. The same transformer also supplies the timebase valve heaters and the CRT heater. Very early production sets had a switch ganged to the brightness control which switched off the mains supply to the EHT transformer thus allowing the set to be operated as a sound only receiver. Evidently the BBC National radio service was at one time radiated from the AP transmitter. Can anyone confirm this? DFWB.