05-01-2018, 09:01 PM
(This post was last modified: 05-01-2018, 09:07 PM by Geordie McBoyne.)
The Cameo SC70 is a worker. Only problems experience were around the frequency changer stage. The local oscillator was dead on both wavebands, 'scope was connected to the tuning capacitor, nothing. Tried another TP25, still no results. The oscillator coils checked out OK. Decided to give the wavechange switch a squirt of switch cleaner, that did the trick. Now the set is a good performer and gives full coverage across the medium waveband, 530Khz to 1600Khz. LW is OK. In terms of sensitivity the Cameo is as good as the Pye 65A and 69A battery receivers but audio quality and power output is nowhere as good as the Pye sets. The Cameo employs a single PEN45 output pentode whereas the Pye 65/69A have a push-pull output stage using the Mazda QP25 double pentode.
The Cameo operates from a 90 volt HT battery and according to the data for the PEN45 valve the power output is only 195mW. 400mW when the HT is 120V.
https://frank.pocnet.net/sheets/146/p/PEN25.pdfV.
The QP25 double pentode will deliver 450mW from a 90 volt HT supply. Almost 1 watt @ 120V.
https://frank.pocnet.net/sheets/146/q/QP25.pdf
Geordie McBoyne.
The Cameo operates from a 90 volt HT battery and according to the data for the PEN45 valve the power output is only 195mW. 400mW when the HT is 120V.
https://frank.pocnet.net/sheets/146/p/PEN25.pdfV.
The QP25 double pentode will deliver 450mW from a 90 volt HT supply. Almost 1 watt @ 120V.
https://frank.pocnet.net/sheets/146/q/QP25.pdf
Geordie McBoyne.
