Rescued this Bush DAC90 from being “Up-cycled”, sale in a dog charity shop, via a heads up from the great Brad Swift. This set was released a year or so after WW2, around 1946.It´s production ran for 4 years or so, when it was replaced with a very very similar set using the newly developed B8A valve set. This was known as the DAC90A
The DAC90 uses the Octal base valves, 5 in all. In my opinion it is a nicer wireless, but that is only because I like the larger Octal base valves. This set had not been touched, original mains lead and 2 pin connector. Lots of lovely thick dust on the chassis which is always a good sign.
Quite a struggle getting the knobs off and the chassis out. If these sets spent their days in a damp environment, the screws can be hard to undo. Carefully injecting a few drops of penetrating fluid is always a good move. The antenna assembly is bolted to the side to the case, with a screw hiding under the tuning knob. This would not move, not wanting to put too much pressure on the case. So, the 3 wires to the antenna had to be unscrewed, just makes testing the set more awkward. At least with the DAC90, the speaker of part of the chassis unlike the DAC90A whether the speaker is fixed to the case.
The set was powered up, low voltage with current limiting for 20 mins. Eventually at full power, we had lots of crackles, but no hum. That was a good sign and showed that the mains reservoir electrolytic may be good and the CL33 output valve didn’t have heater to cathode shorts. Armed with a handful of 0.047uF capdensors, .0047uF, couple of .01uFs etc.. The old wax Hunts caps were snipped out and replaced. They all have become very leaky. The dropper resistor had to have it’s wiring replaced and this had all crumbled away with the heat. The dial lamp diffuser was dark yellow having been exposed to years of Capstan Full Strengths. All cleaned up, along with the bulb which had an inch of dust. I lubricated the tuning mechanism and then ping… The tuning wire went loose. My heart sank. Luckily, it had not broken, just slipped off the drum on the tuning capacitor. The problem was that the rubber bushes securing the tuning capacitor had turned to mush, allowing it to sit at a wrong angle. Had to fabricoddle up some new suspension.
A quick clean of the inside of the case and using some detergent, removed 75 years of smoke. A full clean up of the chassis will be one on the next rainy day. I just wanted to see how the set responded to it’s TLC. Powered all up and a rough trim of the I.F stages and she worked very well. Looks like the set has all the original valves.
After the case was cleaned, my hands looked as if I had been for a fake tanning session, ready for BBC Breakfast news. Rubbed wax into the case and buffed it up, which made it look quite respectable. I thought I would finish it off with a bit of furniture spray polish. That was a horrid finish. Never had that before. Then, after a few minutes, I realized I was using a can of fly spray. Take it from me, don’t use it on Bakelite.
So 75 year old wireless gets to live for another 75 years.
