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Post by paraglide on Jul 10, 2023 19:24:38 GMT 12
Hi, does anyone have the CCT for a Philco 1662 (as below). I have this model but some resistors are totally destroyed due to overheating so need replacing plus over items. www.vintageradio.co.nz/model/philco/1662. Thanks |
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Post by Richard on Jul 11, 2023 13:52:25 GMT 12
Looking on Steves website, I see a model 1661, which is probably a similar schematic, if not the same?  otherwise you could draw out the circuit and work out the part values. or post the circuit here and someone could give you an idea of what they should be? |
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Post by Peter Walsham on Jul 11, 2023 14:23:08 GMT 12
The 1661 is a 6 valve set, while the 1662 is a 7 valve set. I'm guessing that the 1662 either has a RF stage or an extra audio stage (to compensate for the reduction of gain in the Bass/Treble control circuit. However, I think I'd almost put money on the power supplies of the two models being very similar. If the 1662 has a Push-Pull output stage, then they'd most probably have a different power supply arrangement.
Paraglide: Where in the circuit are the burnt out resistors?
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Post by paraglide on Jul 12, 2023 20:23:16 GMT 12
Hi Peter, Thanks for the response. It is definitely different to the 1661 however it may help. The resistor is on the plate cct of the 6AT6 - I will do a drawing to try and work out over the weekend - maybe something close to the 270k. Cheers
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Post by Peter Walsham on Jul 12, 2023 22:13:12 GMT 12
A 270k Ohm resistor is certainly OK for the plate of a 6AT6, however I am very surprised to hear that this is one resistor that has burnt out - as it would only dissipate a little under 1/4 of a watt even if the plate end of it was shorted to chassis - but you never know. Radios have a habit of throwing unexpected curve balls at times.
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Post by Philconut on Jul 24, 2023 9:19:57 GMT 12
They certainly do. I recently repaired a Philco 401. I had it operating on the bench for some hours before returning it to its owner. Her rang me the next day to say that it had stopped after only an hour. There were 3 faults! The OPT primary was open circuit, the ECH42 emission had collapsed and the oscillator plate resistor had upped its value by 20 times!
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