Newbie help required. Bush DAC70. - UK Vintage Radio Repair and Restoration Discussion Forum

peterpiper2727 · 14th Jul 2019, 9:26 pm

Hello there, I am totally new to this hobby and I have a Bush DAC70 C.

I know it's a silly question, but could someone please tell me what the "C" denotes as all the pics I can find online are all type 70 without the "C"

The radio did work then one day nothing, any help would be really appreciated.

Thanks, Peter.

Station X · 14th Jul 2019, 9:33 pm

Hello and welcome to the forums.

What is your skill level and what test equipment do you have?

ms660 · 15th Jul 2019, 10:21 am

https://www.radiomuseum.org/r/bush_dac70c.html

Lawrence.

paulsherwin · 15th Jul 2019, 11:50 am

It's just a slightly revised version of the DAC70. I'm not aware there ever was an A or B model.

music-centre · 15th Jul 2019, 1:28 pm

I think the DAC70C was a black case with chrome trim and the DAC70 was a Brown case with Brass trim otherwise the same.
Steve.

ms660 · 15th Jul 2019, 2:16 pm

Tape out as well so far as I can make out.

Lawrence.

peterpiper2727 · 15th Jul 2019, 4:30 pm

Thank you so much for your quick replies! Looks like its the same as the 70 then. I am complete newb, I did a skill centre course at Milbrook in Southampton many many years ago and covered lots of stuff about valves, but you know I have forgotten 99 % of it. Came out with City & Guilds certificates, and was basically trying to get employment in TV servicing. Never got job. Any way have no test gear but could easy get a multi meter.
To be honest was thinking of buying a working DAC70 off eBay and swap out components until I found what was gone on mine. I know its a cack handed way of doing it so would be glad of any helpful advice. Many thanks in advance.

Station X · 15th Jul 2019, 5:04 pm

Quote:

Originally Posted by peterpiper2727

To be honest was thinking of buying a working DAC70 off eBay and swap out components until I found what was gone on mine. I know its a cack handed way of doing it so would be glad of any helpful advice. Many thanks in advance.

You'll probably end up with two dead radios!

I suggest you download the service sheet and study it:-

https://www.service-data.com/product.php/600/945/m10600

Once you understand the operation of the circuit, particularly the power supply and output stages, get yourself a meter and start fault finding.

You'll find plenty of people here willing to assist, but they'll expect you to do some thinking for yourself and not just respond to an answer with another question.

Wellington · 15th Jul 2019, 5:17 pm

Quote:

Originally Posted by peterpiper2727

I am complete newb, I did a skill centre course at Milbrook in Southampton many many years ago and covered lots of stuff about valves, but you know I have forgotten 99 % of it. Came out with City & Guilds certificates, and was basically trying to get employment in TV servicing.

Not a complete newb, then!

Quote:

Originally Posted by peterpiper2727

To be honest was thinking of buying a working DAC70 off eBay and swap out components until I found what was gone on mine. I know its a cack handed way of doing it so would be glad of any helpful advice.

There's some good stuff here to refresh your memory: http://www.vintage-radio.com/repair-...ion/index.html

TonyDuell · 15th Jul 2019, 5:58 pm

Quote:

Originally Posted by peterpiper2727

To be honest was thinking of buying a working DAC70 off eBay and swap out components until I found what was gone on mine. I know its a cack handed way of doing it so would be glad of any helpful advice. Many thanks in advance.

I think that is one of the quickest ways known to end up with _two_ defective DAC70s!

You'll need a multimeter, but probably not much else in the way of test gear to get started. The manufacturer's service manual is available 'up top' and is worth buyng (or buy the DVD of all the manuals). It looks to be a convnetional design so shouldn't cause too many problems.

A couple of points :

1) This is a 'live chassis' set meaning the circuitry is directly connected to the mains. The valve heaters are in series across the mains with a series resistor (R19 on the manfacturer's circuit), the HT+ supply for the anodes is obtained by half-wave rectifying the mains using the UY85 valve.

2) Change C18 (Manufacturer's circuit) before you do anything else. It's commonly called 'That Capacitor' here. If it goes electrically leaky (and it will!) it can damage the UL84 output valve, maybe the UY85 rectifier, and more seriously the output transformer.

14th Jul 2019, 9:26 pm	#1
peterpiper2727 Retired Dormant Member Join Date: Jul 2019 Location: Fordingbridge, Hampshire, UK. Posts: 2	Newbie help required. Bush DAC70. Hello there, I am totally new to this hobby and I have a Bush DAC70 C. I know it's a silly question, but could someone please tell me what the "C" denotes as all the pics I can find online are all type 70 without the "C" The radio did work then one day nothing, any help would be really appreciated. Thanks, Peter.

14th Jul 2019, 9:33 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Newbie help required. Bush DAC70. Hello and welcome to the forums. What is your skill level and what test equipment do you have? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

15th Jul 2019, 10:21 am	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Newbie help required. Bush DAC70. https://www.radiomuseum.org/r/bush_dac70c.html Lawrence.

15th Jul 2019, 11:50 am	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Newbie help required. Bush DAC70. It's just a slightly revised version of the DAC70. I'm not aware there ever was an A or B model.

15th Jul 2019, 1:28 pm	#5
music-centre Heptode Join Date: Sep 2007 Location: Brentwood, Essex, UK. Posts: 687	Re: Newbie help required. Bush DAC70. I think the DAC70C was a black case with chrome trim and the DAC70 was a Brown case with Brass trim otherwise the same. Steve.

15th Jul 2019, 2:16 pm	#6
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Newbie help required. Bush DAC70. Tape out as well so far as I can make out. Lawrence.

15th Jul 2019, 4:30 pm	#7
peterpiper2727 Retired Dormant Member Join Date: Jul 2019 Location: Fordingbridge, Hampshire, UK. Posts: 2	Re: Newbie help required. Bush DAC70. Thank you so much for your quick replies! Looks like its the same as the 70 then. I am complete newb, I did a skill centre course at Milbrook in Southampton many many years ago and covered lots of stuff about valves, but you know I have forgotten 99 % of it. Came out with City & Guilds certificates, and was basically trying to get employment in TV servicing. Never got job. Any way have no test gear but could easy get a multi meter. To be honest was thinking of buying a working DAC70 off eBay and swap out components until I found what was gone on mine. I know its a cack handed way of doing it so would be glad of any helpful advice. Many thanks in advance.