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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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18th May 2006, 8:39 pm | #1 |
Pentode
Join Date: May 2006
Location: South West London, UK.
Posts: 201
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DAC90A Ballast resistor connections
Hello
This is my first post after having acquired a DAC90A - it is complete but partly dismantled. I have replaced C22 and now need to reconnect R17 - the question I have is how many of the tags on R17 should be connected Currently I have three wires with ring tags but four tags on R17 ! Thanks in advance Graham |
18th May 2006, 9:10 pm | #2 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: DAC90A Ballast resistor connections
Welcome to the forum.
My circuit diagram gives R17 as a 150Ω (with the usual 2 wires), but gives R15 as the mains dropper with sections of 950Ω, 150Ω and 150Ω. The 950Ω end connects to heater of V5. The next tap (210V) connects to R17 (the other end of which connects to pin 2 (anode) of V5). The other end connects to C22 and the mains input. The two 150Ω sections of R15 are shorted out for 210V operation, or just one for 230V, so can presumably be ignored (and left unshorted). I hope that helps. |
18th May 2006, 9:19 pm | #3 |
Pentode
Join Date: May 2006
Location: South West London, UK.
Posts: 201
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Re: DAC90A Ballast resistor connections
Dave
Thanks for the reply, my cct diagram has it as R17 - but we are talking about the same resistor. It does help as I can't see where I would get some more connections from. thanks Graham |
19th May 2006, 10:09 am | #4 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,967
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Re: DAC90A Ballast resistor connections
Hi Graham. It would be well worth £2 to order some proper service info from Paul Stenning: http://www.service-data.com/email/list/bush.htm He has both the Trader sheet and the original Bush service info available. I've used this service and can recommend it.
Good luck, Paul |
19th May 2006, 8:29 pm | #5 |
Pentode
Join Date: May 2006
Location: South West London, UK.
Posts: 201
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Re: DAC90A Ballast resistor connections
Dave/Paul
Are there different DAC90A cct diag versions ? The one I have is Trader service sheet 1161 from sept 1954, this is the one that shows the ballast resistor as R17. R15 on this diag is 10k/HT smoothing ?? Also - I have replaced the mains RF bypass with a 1000v dc type - It is not an X or Y type - this should be ok Ta Graham |
19th May 2006, 8:58 pm | #6 | |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,967
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Re: DAC90A Ballast resistor connections
Quote:
I'd expect the Trader/manufacturer's info to show the dropper connections, which is why I suggested getting hold of it, but it sounds as if you have the trader sheet and it doesn't give this info. Your 1000V cap will probably work without problems, but it would be illegal in modern equipment. X/Y capacitors are designed to fail open circuit, whereas standard ones aren't, and the X/Ys are tested to ensure they self heal after quite big voltage spikes. That said, modern polyester film caps will generally fail open circuit anyway, and even if it shorts out it should only blow the plug fuse (don't forget to fit a 3A fuse BTW ) You will find lots of X2 250VAC caps in a scrap switch mode power supply such as a computer PSU. The value of this capacitor isn't critical - indeed, radios will often work perfectly well with this capacitor removed. Good luck, Paul Last edited by paulsherwin; 19th May 2006 at 9:07 pm. |
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20th Jul 2007, 2:16 pm | #7 |
Retired Dormant Member
Join Date: Apr 2003
Location: Blackpool, Lancashire, UK.
Posts: 4,061
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Re: DAC90A Ballast resistor connections
Attached below is the dropper section of the original Bush cct, with R15 and R17 highlighted in bolder text.
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