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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old Yesterday, 7:12 pm   #21
FERNSEH
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Default Re: Sharp TRP801

The +12volt supply for the IF amplifiers and tuner is derived from the line output transformer. Because the line output stage doesn't work the power supplier has been connected direct to the IF board. All the transistors are PNP types and the circuits are of the "upside down" type, that is, the supply rail is positive and the transistor collectors are connected to near ground potential.
The vision IF amplifier doesn't work but at least the sound IF amplifier does and is delivering almost 4 volts P - P of audio across the detector load resistor.
The sound intermediate frequency has been determined to be 14Mhz and this will be the frequency for both TV standards. The AVC is efficient, maintaining a constant voltage across the load resistor irrespective of signal levels.

DFWB.
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Old Yesterday, 8:37 pm   #22
Heatercathodeshort
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Default Re: Sharp TRP801

That is a very interesting TV David. At a quick glance it has an English Emerson look about it, very American.
We never thought transistors would fail but I suppose 60 years on we can forgive them. There can't be many transistor portables of this era that have survived.
When they went wrong they were just dropped in the garbage. That is the problem with small items. Hope you get it sorted. John.
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Old Today, 12:43 pm   #23
FERNSEH
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Default Re: Sharp TRP801

Hi John,
It's likely an NTSC version was made for the American and Japanese markets.
The attachment shows the additional tuning and damping components added across the primaries of the vision IF transformers.

DFWB.
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Old Today, 4:55 pm   #24
Welsh Anorak
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Default Re: Sharp TRP801

Some very careful soldering there to avoid track bridging.
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Old Today, 5:32 pm   #25
FERNSEH
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Default Re: Sharp TRP801

"Some very careful soldering there to avoid track bridging."

Hi Glyn,
All the soldering must have been done by hand rather than by an automated flow system. Wouldn't have been very pleasant working conditions.

DFWB.
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