The KB ER15 is an AC/DC version of the ER10 radio, the cabinets look identical.
The Trader service sheet 1058 covers the KB models DR15 ER15 FR15 GR15, they are basically the same chassis but there are some minor differences in the circuits which are explained in the Trader sheet.
I bought this radio from a person on Gumtree, it looked in good condition from the photos, and it was very kindly collected by Terry whilst he was travelling in the Midlands area.
On close inspection it became obvious that 3 of the knobs were not original, shaft extensions had been added and bakelite knobs had been fitted. Once the chassis was removed I could see that a lot of repairs had been done in the past.
Some of the valves in the set were not the original ones, V2 which should be a 12K7GT had been substituted with a W76 which appears to be a direct equivalent, if not a little taller. V3 should have been a 12Q7GT but a 12SQ7 had been fitted in its place and the socket wiring had been altered to allow for the fact that this has no top cap is not pin equivalent to the 12Q7GT. The Rectifier valve should be a 35Z4GT and in its place was a U75. The heater chain current is controlled by a D15 barretta.
Some capacitors had been previously changed with a variety of styles of capacitor. There were grey RS caps and Mullard pink & mustard caps and another white plastic cap, all looking like they were from the mid to late 50's.
I checked these for leakage, and where they were in the more critical parts of the circuit I decided to replace them with new, I left the Mullard caps in place.
I disconnected the wiring from the Smoothing caps and connected them one at a time to my electrolytic capacitor reformer, the reformer showed full scale deflection at more than 5ma leakage and stayed there even after an hour or so for all 4 capacitors, so these were changed for new. As they were all under the chassis I did not make a very neat job of this, but it is functional and safe. I removed one of the capacitor mounting clips and in its place fitted a strong solder tag, all 4 electrolytic capacitors were then arranged around this tag and connected to their respective wires.
By now the radio was ready to test, so I switched it on via a lamp limiter. After a long time the HT started to slowly rise, and eventually the radio slowly started to work.
One of the strangest things I found on the chassis was the dial lamps holders and wiring had been completely removed including the associated lamp shunts. These had been replaced with a piece of wire. I removed the wire and checked the heater current at full mains voltage and it was only 130mA. My normal mains is only about 235v so this could partially account for the low current.
I remembered I had a very tatty old Philco B2850 radio in my shed and this might have some lamp holders.
Not only did it have lamp holders it also had similar valves. I removed them so I could replace the incorrect valves. The rectifier was changed back to a 35Z4GT and also the correct 12Q7GT was fitted. This required moving the heater and anode connections and fitting a clip to the screened grid cable and taking the wire, which was still just long enough, up through a convenient hole in the chassis to the top cap of the 12Q7GT.
I found two 3.5v 150mA bulbs and as I did not have a 680 ohm resistor of sufficient power for the lamp shunt I used a 5 watt 470 ohm, this gave just enough voltage to light the 2 pilot lamps. I had no suitable thermister to use on the lamp shunt so left this out.
I rechecked the heater current and it had dropped slightly to around 120mA but the radio was still working well even though it did take a long time to warm up.
From my point of view this completed the electrical restoration.
All that was required to do now was smarten up the cabinet a little. I found some long reach KB knobs of the correct type and fitted these with out the shaft extensions. The finish on the cabinet was cleaned and dried then given a wipe over with furniture rejuvenate oil..
Mike
The Trader service sheet 1058 covers the KB models DR15 ER15 FR15 GR15, they are basically the same chassis but there are some minor differences in the circuits which are explained in the Trader sheet.
I bought this radio from a person on Gumtree, it looked in good condition from the photos, and it was very kindly collected by Terry whilst he was travelling in the Midlands area.
On close inspection it became obvious that 3 of the knobs were not original, shaft extensions had been added and bakelite knobs had been fitted. Once the chassis was removed I could see that a lot of repairs had been done in the past.
Some of the valves in the set were not the original ones, V2 which should be a 12K7GT had been substituted with a W76 which appears to be a direct equivalent, if not a little taller. V3 should have been a 12Q7GT but a 12SQ7 had been fitted in its place and the socket wiring had been altered to allow for the fact that this has no top cap is not pin equivalent to the 12Q7GT. The Rectifier valve should be a 35Z4GT and in its place was a U75. The heater chain current is controlled by a D15 barretta.
Some capacitors had been previously changed with a variety of styles of capacitor. There were grey RS caps and Mullard pink & mustard caps and another white plastic cap, all looking like they were from the mid to late 50's.
I checked these for leakage, and where they were in the more critical parts of the circuit I decided to replace them with new, I left the Mullard caps in place.
I disconnected the wiring from the Smoothing caps and connected them one at a time to my electrolytic capacitor reformer, the reformer showed full scale deflection at more than 5ma leakage and stayed there even after an hour or so for all 4 capacitors, so these were changed for new. As they were all under the chassis I did not make a very neat job of this, but it is functional and safe. I removed one of the capacitor mounting clips and in its place fitted a strong solder tag, all 4 electrolytic capacitors were then arranged around this tag and connected to their respective wires.
By now the radio was ready to test, so I switched it on via a lamp limiter. After a long time the HT started to slowly rise, and eventually the radio slowly started to work.
One of the strangest things I found on the chassis was the dial lamps holders and wiring had been completely removed including the associated lamp shunts. These had been replaced with a piece of wire. I removed the wire and checked the heater current at full mains voltage and it was only 130mA. My normal mains is only about 235v so this could partially account for the low current.
I remembered I had a very tatty old Philco B2850 radio in my shed and this might have some lamp holders.
Not only did it have lamp holders it also had similar valves. I removed them so I could replace the incorrect valves. The rectifier was changed back to a 35Z4GT and also the correct 12Q7GT was fitted. This required moving the heater and anode connections and fitting a clip to the screened grid cable and taking the wire, which was still just long enough, up through a convenient hole in the chassis to the top cap of the 12Q7GT.
I found two 3.5v 150mA bulbs and as I did not have a 680 ohm resistor of sufficient power for the lamp shunt I used a 5 watt 470 ohm, this gave just enough voltage to light the 2 pilot lamps. I had no suitable thermister to use on the lamp shunt so left this out.
I rechecked the heater current and it had dropped slightly to around 120mA but the radio was still working well even though it did take a long time to warm up.
From my point of view this completed the electrical restoration.
All that was required to do now was smarten up the cabinet a little. I found some long reach KB knobs of the correct type and fitted these with out the shaft extensions. The finish on the cabinet was cleaned and dried then given a wipe over with furniture rejuvenate oil..
Mike
