Well its taken some time for the penny to drop that there was a fault in the heater chain caused by an ageing Thermistor which of course you can't buy but I found a couple of do-fors on Ebay; the heater chain consist of 5 heater, two 5v pilot lights and a couple of thermistors. I didn't realise at first that all heaters were not created equal 3 are 12v the af stage is 19v and the rectifier is 35v so with the two 5v bulbs that gives 100v and my transformer gives 110 volts. This is where resistor r21 and thermistor r19 comes in the votage across them should be around 10vac but it was 30-40v as the thermistor no longer dropped low enough to pass 190ma.....! changing r19 and replacing a broken thermistor fixed all that and the voltage and current became correct.
This wasn't the end of the problems as the audio sounded rough, this turned out to be to to corrosion and the coil was sticking, fortunately I had a spare one in my junk box once it was changed it sounded loud and good as new. Attaching a centre fed doublet to the set I was able to pick up shortwave broadcast from Arabia and China.
So what next you ask? well I have picked up an old Yaesu FT101e for not very much but... the pa coils are fried and the receiver is a bit deaf, with the cost of new valves more than what I paid for the rig plus all the problems with matching a 100+ watts to an antenna I feel a qrp FT101 coming on; watch this space.
A final note
I sold the Eddystone on eBay for around £50, imagine my surprise when I found this. Yes it is the same radio scratch for scratch but it has been polished well....!
Have one to sell? Sell it yourself
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Eddystone Radio Type S870 Receiver Tuner Shortwave Valve S-870 Birmingham Green
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1 comment:
Randomly found your blog...just got hold of a nice Eddystsone 870A - main problem was a replaced dial glass with no markings !. made up a replica but in black - best I could do with acetate sheet and a printer..and recently sorted an FT101E. Restored about 25 HF statiosn in the last few years. Cheers, Steve G3ZPS. www.g3zps.com
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