Bush DAC90A. Apparently dead. - UK Vintage Radio Repair and Restoration Discussion Forum

stm__uk · 16th Jan 2018, 3:56 pm

We just carefully applied power to a DAC90a and saw absolutely nothing -- no lights. I notice it was set to 250V internally whereas now we are supposed to be 230V. Would this explain lack of lights or is it likely to be more generally kaput?

I don't particularly want to mess with anything mains voltage but I am curious about some very simple checks. I've read the tops of the valves shouldn't be white (and they don't appear to be although they are dusty). Is it possible to test unplugged valves in any useful sense with a simple battery multimeter?

If all else fails and we remove everything (as is likely) and replace with a Raspberry Pi Radio and everything at 5V are the removed chassis and components likely to be of interest to others as spares?

Nuvistor · 16th Jan 2018, 4:27 pm

I suggest you start here if you want to try and get the radio working.
https://www.vintage-radio.com/repair...ion/index.html

Unless there is a fault in the voltage selector circuit, 250 or 230 it should work, I also suspect that your power will be nearer 240 than 230, mine ususally is around 250vac.

If there as been no refurbishment of the Radio it will require quite a bit of work to get it going properly.

Station X · 16th Jan 2018, 4:32 pm

Have you checked the fuse in the plug, which I hope isn't a 13 amp one? Try a fuse which works in another appliance.

Do the valves light up? You may have to view them in a darkened room.

Herald1360 · 16th Jan 2018, 4:57 pm

One little warning..... before you attempt to remove any valves from this set, carefully remove the spring retaining clip from the valve socket collar. These have a well known propensity to break the little retaining pip on the side of the valve which lets air in destroying the vacuum necessary to their function.

About the only meaningful test with valves removed is to check heater continuity. All the valves in the set have heaters between pins 1 & 8 (the pins either side of the pip when viewed end on).

Most likely cause of nothing at all will be dirty contacts in the on/off switch- you could try repeated on/off operation to see if any life results, but beware- you may be rewarded by a bang and a flash as a well known capacitor inside across the mains lets go! Even if it all lights up with no drama and even works, there will be some parts (relatively cheap but vital to reliable operation) which must be replaced.

Normally I'd be in shock/horror mode at the idea of upcycling a vintage set as you describe, but iconic or not, there's plenty of DAC90As out there (unless it's the rarer cream coloured one) and passing the guts on for spares may get another one restored anyway. Unfortunately, being a "live chassis" set, there's no simple way to play external music sources through the vintage electronics safely unless you invest in a low powered transmitter (same idea as the little adaptors for I-player and the like to FM radios only operating on medium wave AM instead of VHF FM).

TrevorG3VLF · 16th Jan 2018, 5:40 pm

With the set unplugged and switched on, measure the resistance between the line and neutral pins on the plug. If infinite resistance, you will have to work through the heater/resistance chain. The neutral will probably go to the chassis and you can then look at the top of the heater chain, Then look at the other end of the dropper resistance, that leaves the voltage selector, the switch and plug fuze. Once there is a connection through this, there should be some light from the dial bulbs and valve heaters.

Gentle persistance is required.

Freya · 16th Jan 2018, 6:23 pm

Quote:

Originally Posted by stm__uk

I don't particularly want to mess with anything mains voltage but I am curious about some very simple checks.

Lets not get to carried away with the advice here, I just looked at the post and sighed.
I'm not saying its impossible to guide the OP through the process but it could end up 200 posts just resulting with a raspberry pi just bundled in anyway.

Boater Sam · 17th Jan 2018, 8:46 am

Echo of Stephen.
The OP obviously has no equipment, no idea, wishes not to work on mains, and would like a magic wand fix which we cannot give.
I'm out of here, fast.

Station X · 17th Jan 2018, 8:59 am

I was trying to suggest some simple checks which could be done without test gear.

I'll leave it to someone else to take on the role of mentor.

stm__uk · 17th Jan 2018, 9:28 am

Quote:

Originally Posted by Station X

I was trying to suggest some simple checks which could be done without test gear.

I'll leave it to someone else to take on the role of mentor.

This is exactly the sort of advice I hoped for.

I'm not expecting to be talked through step by step.

Thanks for all the helpful posts.

Herald1360 · 17th Jan 2018, 10:40 am

Quote:

Originally Posted by stm__uk

Is it possible to test unplugged valves in any useful sense with a simple battery multimeter?

He has some test equipment and doesn't sound stupid, just not au fait with valve kit and sensibly cautious. A reasonable start, methinks!

16th Jan 2018, 3:56 pm	#1
stm__uk Retired Dormant Member Join Date: Jan 2018 Location: Suffolk, UK. Posts: 2	Bush DAC90A. Apparently dead. We just carefully applied power to a DAC90a and saw absolutely nothing -- no lights. I notice it was set to 250V internally whereas now we are supposed to be 230V. Would this explain lack of lights or is it likely to be more generally kaput? I don't particularly want to mess with anything mains voltage but I am curious about some very simple checks. I've read the tops of the valves shouldn't be white (and they don't appear to be although they are dusty). Is it possible to test unplugged valves in any useful sense with a simple battery multimeter? If all else fails and we remove everything (as is likely) and replace with a Raspberry Pi Radio and everything at 5V are the removed chassis and components likely to be of interest to others as spares?

16th Jan 2018, 4:27 pm	#2
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: DAC90a Apparently Dead I suggest you start here if you want to try and get the radio working. https://www.vintage-radio.com/repair...ion/index.html Unless there is a fault in the voltage selector circuit, 250 or 230 it should work, I also suspect that your power will be nearer 240 than 230, mine ususally is around 250vac. If there as been no refurbishment of the Radio it will require quite a bit of work to get it going properly. __________________ Frank

16th Jan 2018, 4:32 pm	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush DAC90A. Apparently dead. Have you checked the fuse in the plug, which I hope isn't a 13 amp one? Try a fuse which works in another appliance. Do the valves light up? You may have to view them in a darkened room. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

16th Jan 2018, 4:57 pm	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Bush DAC90A. Apparently dead. One little warning..... before you attempt to remove any valves from this set, carefully remove the spring retaining clip from the valve socket collar. These have a well known propensity to break the little retaining pip on the side of the valve which lets air in destroying the vacuum necessary to their function. About the only meaningful test with valves removed is to check heater continuity. All the valves in the set have heaters between pins 1 & 8 (the pins either side of the pip when viewed end on). Most likely cause of nothing at all will be dirty contacts in the on/off switch- you could try repeated on/off operation to see if any life results, but beware- you may be rewarded by a bang and a flash as a well known capacitor inside across the mains lets go! Even if it all lights up with no drama and even works, there will be some parts (relatively cheap but vital to reliable operation) which must be replaced. Normally I'd be in shock/horror mode at the idea of upcycling a vintage set as you describe, but iconic or not, there's plenty of DAC90As out there (unless it's the rarer cream coloured one) and passing the guts on for spares may get another one restored anyway. Unfortunately, being a "live chassis" set, there's no simple way to play external music sources through the vintage electronics safely unless you invest in a low powered transmitter (same idea as the little adaptors for I-player and the like to FM radios only operating on medium wave AM instead of VHF FM). __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

16th Jan 2018, 5:40 pm	#5
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Bush DAC90A. Apparently dead. With the set unplugged and switched on, measure the resistance between the line and neutral pins on the plug. If infinite resistance, you will have to work through the heater/resistance chain. The neutral will probably go to the chassis and you can then look at the top of the heater chain, Then look at the other end of the dropper resistance, that leaves the voltage selector, the switch and plug fuze. Once there is a connection through this, there should be some light from the dial bulbs and valve heaters. Gentle persistance is required.

17th Jan 2018, 8:46 am	#7
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Bush DAC90A. Apparently dead. Echo of Stephen. The OP obviously has no equipment, no idea, wishes not to work on mains, and would like a magic wand fix which we cannot give. I'm out of here, fast.

17th Jan 2018, 8:59 am	#8
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Bush DAC90A. Apparently dead. I was trying to suggest some simple checks which could be done without test gear. I'll leave it to someone else to take on the role of mentor. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.