DAC90a Number Three.

[Joe]

I've finally started to have a look at my latest DAC90.

           

The wiring is in a bit of a state

   

I took the chassis out and noticed that the voltage selector was on 210V. The dropper seemed OK so I put that up to 250V. I then changed the AF coupler and, after checking none of the balding wires were touching, gave it some juice. Nothing seemed to be happening but I then saw faint glows through the muck on the valves. I also saw the the lamp limiter was getting un-healthily bright. I then remembered that I hadn't snipped the filter. This looked like it had already spewed it's guts at some stage and after chopping its wire it played quite happily.

I tested the grid on the UL41 and found about quarter of a volt. I've hitherto used my DMM for that but the battery is flat. I didn't use my valve voltmeter as I wasn't sure as to the safety of using this on a live chassis. It was interesting to note how connecting the AVO caused a drop in volume and my little 2000 ohm/volt one an even greater one.

Call it silly anthropomorphism if you like (but remember I'm a Moderator with the power to ban people ) but in my experience Bush sets just WANT to work whereas quite a few others seem to be happy in their slumbers and will fight to continue their retirement.

The extra sockets on the back weren't connected to anything. The speaker leads have been extended but it must have been done some time ago as they've had time to go crispy.

   

The main interest in this one will be repairing the case and I was pleased to find that it hadn't been glued but stuck up with parcel tape so doing a better job will be more straight-forward.

- Joe

[Bushbaby]

Hi Joe,
Looks like you've made a good start and I'm sure that you will be able to fix the case. What are the waxies like? I have found that they are mostly out of spec and need replacing straight off.

Best of Luck

Rob

[Joe]

I've only changed one so far and, surprisingly, it wasn't too bad. They will get changed as even if they test OK now they may play up when they get warm or in the near future - I've left them alone before and ended up changing them a few weeks later.

I've done a bit of cleaning so far so can see better what's what.

- Joe

[Yorkie]

You're right about the filter cap on the top of the chassis Joe - it looks done to a crisp! Not worth replacing unless you want to preserve originality as it makes no appreciable difference in or out. The top two sections of the dropper look as though they've had a hard life, perhaps through drawing excess current. The wiring is in the usual state, and I wonder how many restorers who cut their teeth on the DAC90A as many seem to do, realise the dangers of decayed wiring on the dial light bulbs, which is quite close to the speaker frame and mesh grille. Some may think what's the big deal - it's just two 3.5V bulbs in series, but given that the mains connector is reversible and the set works with it either way round, if the chassis live, and decayed wiring on the dial light leads comes into contact with the speaker frame or expanded metal grille, it could have tragic consequences. True, it may seem an unlikely possibilty, but the risk is there to be seen.

I've always wondered - even back in the less safety conscious days of the late 1940s - how Bush got away with that shocking (pun intended!) two-pin reversible mains connector, but then many radios of that era which were wired directly to the switch on the voluime control simply had a tight knot tied in the flimsy twin core mains lead as a means of cable restraint. It was an era when many electrical items were pluged into two-pin connectors which in turn were plugged into light bulb sockets - sometimes a 'Y' shaped twin connector, allowing the light to function as well as whatever was connected to it - an electric iron, radio, fire - whatever! But then as pre-teen kids in that era, we used to walk into Boots Chemists and buy all the chemicals to make our own fireworks and no-one bothered us. How times change.

I think that Ray at Worthing, who refurbishes and sells DAC90As always removes the mains connector and directly wires the mains lead to the mains switch so that when he sells the radio it conforms to current requirments, as well as fitting a small transformer to power the dial light bulbs. The two pin connector has a very poor cable restraint arrangment, as witnessed by most of them showing the two conductors with the outer sheath and the two conductors unrestrained, as in Joe's example (which doesn't actually look like the usual right angled Bush 2-pin connector unless there were two designs).

Best of luck with the restoration Joe, in particular the cabinet.

[Aerodyne]

Hi Joe
It looks as though your set has spent some years in the home of a chain-smoker - lots of nicotine-like staining. It should come up a treat.
The wrong setting of the mains voltage was probably done to persuade the local oscillator to function. You may well find that valve and the rectifier and output valves to be low emission. I like the little Bush sets, though. Keep us informed on your progress.
Tony

[Joe]

I've done a bit more this morning.

When I was dusting the worst of the muck off the aerial coil started to fall off the former so first thing was to put some shellac on that.

I then washed the case and have done the re-wiring. The photo shows the light-box half cleaned to show the contrast.

       

For once I think I'll give the old caps the benefit of the doubt for a while, I've no plans on selling this set so if it goes wrong in the future it won't be a problem.

For the same reason it can keep it's deadly mains connector - if I were selling it I'd either hard-wire the flex or fit an IEC connector. I suppose the detachable things do have the advantage of making sure that it can't be jammed tight to a wall so it will always get some ventilation.

I too had noticed how dark the top bit of the dropper is and had expected it to be o/c and then somebody had re-set the voltage selector to by-pass the damaged bit.

More after dinner.

- Joe

[Retired]

Hi,

Good luck with this restoration Joe; I'm interested in the case restoration rather than the electrics which end up hidden from view. You've now washed it's face so how are you going to tackle the cabinet?

To me sets in such poor condition are just wonderful giving many happy hours of tinkering. Thanks for sharing Joe.

Kind regards, Col.

[Andrewausfa]

Indeed, as Col says, lots of hours of tinkering and fun.

I've not had or worked on a DAC90 but would certainly like to at some stage. I've had some sets in just as smokey condition and I used to take hours delicately working away with cotton buds. After reading how some people stick whole chassis in the dish-washer I've now taken a more robust approach and spray the whole lot with foaming cleaner and scrub with a toothbrush.

Good luck Joe.

Andrew

[Joe]

I'd been thinking about sneaking this into my mate's dish-washer but that would finish off the waxies for sure. I'd also be worried about moisture lingering in the IFTs and causing damage. As Col says, that's out of sight anyway so I never feel it's worth risking damaging things by fully stripping.

I'm waiting for the cabinet to fully dry before doing anything with that.

Tony was right about the UY41 as the HT was well down. Swapping that brought it up but it's still much quieter than my other ones; my first brown one is, if anything, too loud. Changing the UL41 made only a marginal difference so it looks like a session of 'Hunt the duff capacitor' will be in order.

- Joe

[tiv48]

hi joe i am looking forward to how you tackle the cracked cabinet all my attempts so far have been left wanting. because you seem to come up with original ideas i am waiting to to steel them and get some of my plastic sets looking as good as they sound.
rob t.