Restoration of an Ekco B86. - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 30th Jan 2006, 2:48 am

Just before Christmas I completed the restoration of an Ekco B86 battery table radio. Thanks to the employment of a double pentode output valve this radio receiver can offer performance approaching that of a mains radio.
The set was found in poor condition.The chassis was rusty and all the valves were missing.
The first task was to remove all the components from the chassis derust it and paint it in Ford dove grey.
The original Mazda valve line-up was, TP25 frequency changer, VP215 IF amplifier, L21DD leaky grid detector and AVC diode. The output valve was a QP240. Two Mazda valves were found, a TP25 and a QP240. A Marconi W21 was chosen as the replacement for the VP215 and for the L21DD a Mullard TDD2A was pressed into service.
The set was easy enough to get going but I did have problems lining up the bandpass front end. The B86 operates with a low IF frequency of 130Kc/s so a selective front end is required to overcome image interference.
A clever feature of this radio is the amplified AVC system. The triode section of the L21DD acts as a leaky grid detector and the IF component present at the anode is rectified by one of the diodes. The arrangement works well.
For the power supply I use a mains transformer removed from an old video recorder. The filament winding of the display device supplies 35 volts and this added to the output from other windings will produce the required 120 volts HT when a voltage doubler is employed. Other secondary windings are used to supply grid bias and the 2volt filament supply. An LM317 regulator takes care of the latter.

So although I'm having no success with the Decca CTV25 here one restoration project that really was worthwhile.

DFWB.

FERNSEH · 30th Jan 2006, 11:46 am

The Ekco B86 battery table set.

DFWB

Hunts smoothing bomb · 30th Jan 2006, 1:48 pm

Well done

Looks like a very nice set, I didn't realise they did a battery version with this cabinet,
Don't give up on the CTV25 though,

Best regards
Lee

jay_oldstuff · 30th Jan 2006, 8:35 pm

wow i'm impressed that looks lovely
those old VCR transformers realy come in usefull a coupple of my battery sets have powerpacks made from them.
any chance of a chassis pic
Keep up the good work

Jay

FERNSEH · 2nd Feb 2006, 11:42 pm

Here are a couple of pictures of the chassis.

DFWB.

30th Jan 2006, 2:48 am	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Restoration of an Ekco B86. Just before Christmas I completed the restoration of an Ekco B86 battery table radio. Thanks to the employment of a double pentode output valve this radio receiver can offer performance approaching that of a mains radio. The set was found in poor condition.The chassis was rusty and all the valves were missing. The first task was to remove all the components from the chassis derust it and paint it in Ford dove grey. The original Mazda valve line-up was, TP25 frequency changer, VP215 IF amplifier, L21DD leaky grid detector and AVC diode. The output valve was a QP240. Two Mazda valves were found, a TP25 and a QP240. A Marconi W21 was chosen as the replacement for the VP215 and for the L21DD a Mullard TDD2A was pressed into service. The set was easy enough to get going but I did have problems lining up the bandpass front end. The B86 operates with a low IF frequency of 130Kc/s so a selective front end is required to overcome image interference. A clever feature of this radio is the amplified AVC system. The triode section of the L21DD acts as a leaky grid detector and the IF component present at the anode is rectified by one of the diodes. The arrangement works well. For the power supply I use a mains transformer removed from an old video recorder. The filament winding of the display device supplies 35 volts and this added to the output from other windings will produce the required 120 volts HT when a voltage doubler is employed. Other secondary windings are used to supply grid bias and the 2volt filament supply. An LM317 regulator takes care of the latter. So although I'm having no success with the Decca CTV25 here one restoration project that really was worthwhile. DFWB.

30th Jan 2006, 11:46 am	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Restoration of an Ekco B86. The Ekco B86 battery table set. DFWB Attached Thumbnails

30th Jan 2006, 1:48 pm	#3
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: Restoration of an Ekco B86. Well done Looks like a very nice set, I didn't realise they did a battery version with this cabinet, Don't give up on the CTV25 though, Best regards Lee __________________ Lee

30th Jan 2006, 8:35 pm	#4
jay_oldstuff Octode Join Date: Jan 2005 Location: Hyde, Greater Manchester, UK. Posts: 1,074	Re: Restoration of an Ekco B86. wow i'm impressed that looks lovely those old VCR transformers realy come in usefull a coupple of my battery sets have powerpacks made from them. any chance of a chassis pic Keep up the good work Jay

2nd Feb 2006, 11:42 pm	#5
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Restoration of an Ekco B86. Here are a couple of pictures of the chassis. DFWB. Attached Thumbnails