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Bush DAC90A
BUSH DAC90A. This popular a.c/d.c mains valve radio was made initially in 1950, to replace the earlier 1946 model, which had employed octal valves. The 90A employs B8 valves, UCH42, UF41, UBC41, UL41, & UY41. Both models are for long & medium wave bands, only. There are many other differences between the 90 and 90A. Earlier 90A's had the same two front knobs as the 90, but later on the 90A employed barrel shaped knobs on the front. There is a "trigger" shaped knob on the lower r.h side of the cabinet (90A) for waveband changeover, whereas on the 90 original, it is on the front r.h side. The tuning knob on the 1946 original was a large knob, placed half way up the r.h side of the cabinet, whereas the 1950's model had it on the front r.h side. I had a repair to carry out recently, on a 90A. The owner had been trying to find a suitable dealer to repair this radio, but was unable to find one, until someone recommended me. The DAC90A was found to be "blowing" fuses, due to the r.f by-pass condenser gone s/c, so I "snipped" it out. Someone in the past had removed all the B8 valves from their sockets, and left them empty. However, a piece of paper was found in the set, illustrating where each valve was located in the chassis. I supplied and fitted replacement valves, but reception was very weak. I then noticed that the m.w frame aerial windings were beginning to fall off their drum. Rather than rewind it, I found that someone had a scrap 90A chassis, c/w good quality frame aerial. I bought the aerial, and installed it as a replacement on this chassis. It worked a treat ! Reception was really good now, even "pulling" in distant stations. There was a problem with the tuning capacitor, it would not travel to max. capacitance, because the vanes were bent out of place. I also noticed that one of the pulleys was not working properly on the dial drive cord, and that it was putting a strain on the capacitor rotor. I lubricated the pulleys, and made sure that the system was under no strain. I noticed that the wax paper condensers were all badly "leaking"., as I tested them on an insulation tester, and most of them were 1 meg ohm or even 0.5 meg, which is not good news !. The fact that this set is to be used on a regular basis, each day, by the owner, and I made sure that the set was up to standard. I installed polypropylene capacitors, so they did not break down ! The rubber insulated wire around the mains dropper resistor has a habit of flaking, so I coated it in heat proof insulation. The loudspeaker diaphragm has a habit of breaking away from the frame, due to the original adhesive "giving-up" its adhesion. I use evo-stik to reseal the joint. I use the original BUSH two-pin mains plug on the prongs on the back of the set - it fully covers the prongs, whereas other standard plugs do not. The last problem that you want is, if someone decides to remove the 2-pin plug from the set, and accidentally touches the prongs, forgetting that the other end of the lead could be still connected to the power socket on the wall. I always install a 1AMP FUSE in the mains plug. The owner was really satisfied with the results !!