July 21, 2009 at 6:14 am #1423
Ed Stone
Forum Participant

Not good news I fear regarding the transformer in the Rogers set – I think it may have a partially-shorted secondary as suspected. I left the set running for a couple of hours and the transformer reached a temperature around 64C – a bit on the hot side – and was very slowly still creeping-up. It ran cooler when I fed it 105v from a variac. The set was still working ok, but I decided to switch off and only assign the set to ‘light duties’ – max an hour on or so – or fork out $50 or so for a new transformer, use a ‘bucking’ transformer, high-wattage series resistor or use the ‘dual zener trick’ in the primary.

I did some slight re-furbishing of the cabinet – limited to toning-in some scuffs and scratches with a touch-up pen and then a quick polish. Also installed a scrap of cloth over inside of the speaker aperture grill.

Next job wil be making the missing escutcheons for behind the tuning and volume control knobs (if you look carefully on the photos below you can see four small holes that these used to be screwed into). In the meantime, I have been working on drafting some tuning dial artwork – I used a signal genny/DFM and marked out the dial at 100kHz or 50kHz intervals onto a piece of paper placed behind the tuning knob. I did not align the set at all before I did this and it looks pretty good for broadcast band coverage as it is, tuning from 500kHz to 1700kHz.

In use, I have noticed that the set has some heterodynes present when tuning-in stations – maybe due to the RF, IF and detector tubes being un-metalized types. (these should be 6A7S, 88S (or78S) and 6B7S types). I may try wrapping some aluminum foil around the tubes that are in there to see if it makes a difference. If it is not this causing the problem I will try aligning it and then adding some additional by-passing.

Ed

Download DSC00154 [1024×768].JPG. (Caution: This file may not be virus scanned.)

Download DSC00156 [1024×768].JPG. (Caution: This file may not be virus scanned.)

Download Rogers Dial Draft 1.jpg. (Caution: This file may not be virus scanned.)