UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 18th May 2006, 8:39 pm   #1
Graham-R
Pentode
 
Graham-R's Avatar
 
Join Date: May 2006
Location: South West London, UK.
Posts: 201
Default 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
Graham-R is offline  
Old 18th May 2006, 9:10 pm   #2
Dave Moll
Dekatron
 
Dave Moll's Avatar
 
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
Default 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.
Dave Moll is offline  
Old 18th May 2006, 9:19 pm   #3
Graham-R
Pentode
 
Graham-R's Avatar
 
Join Date: May 2006
Location: South West London, UK.
Posts: 201
Default 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
Graham-R is offline  
Old 19th May 2006, 10:09 am   #4
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default 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
paulsherwin is offline  
Old 19th May 2006, 8:29 pm   #5
Graham-R
Pentode
 
Graham-R's Avatar
 
Join Date: May 2006
Location: South West London, UK.
Posts: 201
Default 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
Graham-R is offline  
Old 19th May 2006, 8:58 pm   #6
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: DAC90A Ballast resistor connections

Quote:
Originally Posted by Graham-R
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
I don't have the different circuits to hand, but it's normal for there to be minor differences between different circuit diagrams, sometimes indicating model revisions and sometimes indicating mistakes The component numbering will also be different.

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.
paulsherwin is offline  
Old 20th Jul 2007, 2:16 pm   #7
Darren-UK
Retired Dormant Member
 
Join Date: Apr 2003
Location: Blackpool, Lancashire, UK.
Posts: 4,061
Default Re: DAC90A Ballast resistor connections

Attached below is the dropper section of the original Bush cct, with R15 and R17 highlighted in bolder text.
Attached Thumbnails
Click image for larger version

Name:	DAC90A cct.JPG
Views:	244
Size:	14.9 KB
ID:	11024  
Darren-UK is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:40 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.