20-03-2019, 08:55 AM
If you want quick proof of the state of the set you could try any old substitute for the output transformer. A mains transformer witha low voltage secondary in the 3 to 9 volt range (not critical) will work. It may not work well but that's not the point. Just make sure it's physically no smaller than the failed transformer. No need to mount it neatly on the chassis, just hook it up.
Change the output coupling cap. Without looking it up I think there are only 4 waxies altogether so you could Old Sparky's advice and change the lot if you wish.
Use a lamp limiter. This is simply an old fashioned filament bulb in series with the mains. Probably 40W or 60W. It will save the set from damage if there's a problem. Make sure that the chassis is connected to mains neutral and use an RCD. Don't rely on the set's on/off switch. Always unplug before doing any work on the set.
If you're lucky the bulb will only glow dimly, the heaters will light up and you'll hear something from the speaker. Measure the grid voltage on the UL41. Ideally it should be zero but some +ve voltage is allowable. Don't know how much is regarded as acceptable these days but if it's more than half a volt I'd be worried. Valve might be OK as it could be the pin 4 problem mentioned above.
Change the output coupling cap. Without looking it up I think there are only 4 waxies altogether so you could Old Sparky's advice and change the lot if you wish.
Use a lamp limiter. This is simply an old fashioned filament bulb in series with the mains. Probably 40W or 60W. It will save the set from damage if there's a problem. Make sure that the chassis is connected to mains neutral and use an RCD. Don't rely on the set's on/off switch. Always unplug before doing any work on the set.
If you're lucky the bulb will only glow dimly, the heaters will light up and you'll hear something from the speaker. Measure the grid voltage on the UL41. Ideally it should be zero but some +ve voltage is allowable. Don't know how much is regarded as acceptable these days but if it's more than half a volt I'd be worried. Valve might be OK as it could be the pin 4 problem mentioned above.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
