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

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Success Stories

Notices

Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

Reply
 
Thread Tools
Old 11th Dec 2018, 2:46 pm   #1
mark2collection
Pentode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 224
Default Bush DAC90A, Write-off to Worker in no easy steps.

Ordinarily, I wouldn't write up about the repair of such a popular set. As the festivities beckon, making our way to 2019, the supply of Bush DAC90A's, repair advice, general interest, seemingly never fading.

Why would my story of 'yet another' be worthy of a write-up? Whilst most points may have been covered in the past, this may prove inspiring, or at least, an interesting tale.

It all began earlier this year, as spring 'sprung', the Daffodils showing promise of warmer days ahead; we made our way to an open-air antique fair. You know the ones, vast open field, cold, raining sideways, with dealers offering their 'wares' under some of the worlds flimsiest temporary structures!

Nestled under one such structure, sat on a raised part of a table, was indeed, the Bush radio I now write about, looking in fantastic cosmetic condition, externally. With a thumbnail-sized white label tied around a vent-slot in the back cover and slightly smudged ink, I enquired whether the price tag read £5 or 15, as I was unsure if it was supposed to be a 'one' digit, or a Pound sign. 'Fifteen pounds' was the reply. I went on to ask 'what can you tell me about the set?'

'You would have spotted the mains connector with one pin having been ripped out & the remains of some mains cabling poked through the hole, snipped level with the back cover' … the chap went on to say he'd owned the set for 10 years as a display only item, the current antique seller said the previous owner was 'into' radios and had removed two valves plus a transformer. Looking through the back cover under the gloomy clouds, hopelessly failing staying warm, never mind dry, I pointed out the dreadful condition of the rubber wiring and the fact the steel parts of the chassis looking very badly corroded, plus I could indeed see vacant valve sockets, where a rectifier and output device should live. Both I.F.T's looked original, could just about make out a gap where the output transformer should've been, under the gloom.
The seller was quick to point out he knew how much 'these go for' on eBay. Hmmm, since the only items of any value in these sets (if those items were in good condition) are now missing, 'will you accept £10?'

Needless to say, the deal was done at £10, and I was happy, the sellers’ wife put the set in a carrier bag to 'keep it dry' too.

Once home, set on the bench, back off and oh-my … it wasn't a pretty lot. Clearly the set had shared a home with smokers, possibly had a life in the kitchen too. It was grubby, sticky and had a bouquet of its own. Out came the chassis, the rubber insulation falling away as the ‘speaker leads were extended. The output transformer had, by the looks of things, been unceremoniously removed by wire cutters and a pair of Stilsons! Looking underneath the chassis, it clearly hadn't been touched since leaving the factory, things were looking up. My thinking was, if someone went to the trouble of removing the rectifier, output valve and output transformer, the radios’ biggest downfall must be the rotten wiring, as the sleeving on the wiring around the dropper was also a crumbly mess, the same could have been said for the internal aerial wiring. Looking deeper, all the rubber grommets where shot too, plus the dial glass channels, this set was decomposing!

Checking the coils, including the 'speaker proved these were good, the wave-change switch clearly hadn't seen any action for a good number of years, the contacts were green. Amazingly though, all the resistors were within specification, the waxies looked ok on my cap-meter, all reading roughly in the right-order of uF's, my DMM telling a different story on the ohms setting, the waxies ranged from 2-Megs up to around 7-Megs. The HT electrolytic(s) read about 4 Megs.

The loudspeaker was removed from the cabinet, sure enough the bellows had detached from the basket. Cleaning debris away as best I could, then using some contact adhesive, I applied some glue to the surfaces of the bellows & basket via a long cotton bud, the type with wooden stems, then laid the 'speaker facing upwards, carefully placing a reel of solder dead-centre, ensuring the voice coil made no contact with the magnet, and left to dry.

Taking further pity and a chance, over the course of the following months during summer, I gathered some spares from various events, on-line auctions & even made some parts with a view to returning the radio into a fully functioning set again.

I later removed the lamp diffuser panel only to discover the two lamps were also missing. I went on to remove the steel-work for the internal aerial, dial lamp reflector and associated mountings, pointer runner, dial cord pullers, wave-change switch, tuning capacitor and volume control. The chassis steel-work, nuts and bolts plus dial lamp reflector, went into the ultrasonic bath for an hour at 30 degrees, thinking it'll remove some of 'the rust'. Turns out they were not so much rusty, but caked in so much muck, it had in many ways, preserved the metalwork underneath. While these parts were being cleaned, I continued with cleaning the muck off the chassis, replacing all the rubber grommets, especially the ones for the mains and HT/output wiring, terrible mess. Once the metalwork was out of the ultrasonic bath, the paint for the dial lamp reflector had, in a number of places, come off. Oooops, oh well, it was off-brown to begin with, so I removed the remaining paint, made the surfaces clean/smooth, repainting the reflector white, aerosol Hammerite, smooth, about 3 coats. Whilst the paint was drying, I made a new decal to replace the missing 'Calibration Key'. This was printed, laminated & then double-sided tape applied to the rear. Once the paint had dried, the decal was trimmed, then fitted roughly where the original would have been (you could see the outline of the original).
The diffuser itself was also very yucky, both sides were cleaned with anti-static foaming cleanser, the smooth side came up lovely, the coarse side required a few goes with some T-Cut. Just before re-fitting the now clean metalwork to the shiny chassis, I fitted my spare output transformer that Ed Dining had previously rewound, about a year or two previous, merrily replacing the duff/too short wiring with PTFE sleeved wiring, of identical colours to the original, where possible. I also removed the dropper plus associated mountings.

The upper part of the Paxolin board was scorched, and so needed decarbonising plus careful Araldite reinforcement. All electrical connections were cleaned & the lot rewired in PTFE sleeved wiring, keeping to the original colour-code, where possible. With the chassis hardware refitted, time to see if the HT capacitor would reform.

Over the course of a day, drawing hardly any current, we reached 250 volts on my home-made variable DC bench supply, day two we ended up at 350 volts. Re-checking the value of the capacitor(s), it was within specification & read initially 25 Megs, but soon crept passed 40 Megs and beyond. The capacitor was cleaned up then refitted to the chassis. The date on the capacitor read 'May 1954'.

Having read a thread on wax capacitor re-stuffing (thank you John – Heatercathodeshort for the inspiration/guidance in your thread) I decided to give it a go. Best to use a cloth to grip the outer sleeve and keep any wax which forms on the vice, comes in very handy to plug the ends of the re-stuffed bodies, since my new capacitors were a bit smaller than the originals. I checked each waxie before removing, and indeed, each was more a resistor than a capacitor.

Replacement valves were sourced, again through the usual channels, days out, on-line etc, and whilst some parts were en route, a chap at work made a new mains connector mount on his lathe to replace the damaged original. Carefully removing the original and using its dimensions as a template, a new disc was made from Paxolin with a couple of mounting holes and a hole made for a Heyco cable grommet. I also bought some braided 2-core cable later to find in my stash, a modern, 3-pin safety plug, of the 'hot-condition' variety, which looks like black bakelite. Maybe I should've grounded the 'speaker grille, but I didn't.

Whilst cleaning all the valve pins, including my recently purchased replacements, I used cut-off guitar strings to clean out the socket pins. That's when I noticed one half of a pin missing from one of the heater legs, maybe this is why the set was taken out of service (?) Luckily I had a spare socket, simply de-soldering the duff leg inside the set & carefully removing a good leg from my spare socket, then fitting the good leg to the set … optionally, there would soon be a spare leg on the output valve socket, as I always follow Kalee20's advice by not using pin 4 as an anchor point.

With a clean, assembled chassis, waxies re-stuffed, HT cap reformed, new grommets throughout, lightly oiled tuning cap, new dial cord (the original was solid and didn't respond well to cleaning), new rubber wire for the 'speaker and aerial, PTFE wiring for the mains/HT and check after check to ensure all had gone back as per the diagram/my photos, it was time to apply power via my Variac, monitoring the current as we went, with the volume turned down.

Over the course of some 15 anxious minutes, we reached around 170 volts AC … nothing untoward to report and, out of the loudspeaker, I could hear the faint sound of 50Hz mains hum, I could see a very gentle glow from the dial lamps. Taking the set to 185 volts AC, selecting LW, turning the volume up a smidge & tuning until ….... Radio 4, we had sound!

Whilst listening to 'the radio' with its chassis and 'speaker on the bench, I went about cleaning the inside of the cabinet and later, switched the set off and gave the 'speaker basket a spruce-up. The date code for the loudspeaker was also May 1954.

The following day, the set was reassembled, captive mains lead fed through the back cover, plug refitted and a 1A fuse installed, the set then spent the following day running at full mains, with no issues to report, it's a great performer. Although the original mains RFI capacitor has been retained, it serves only a visual function, a modern X2 takes its place, electrically.

I'm glad I cleaned the lamp diffuser and repainted the dial reflector, the lamps are the brightest I've seen in an unmodified set. The outside of the cabinet was given a light dusting, as really, that's all it needed.

Given the current trend to turn old items into lamps, (this set would have been perfect fodder and would have taken all of 45 minutes to convert) this little radio has given me a day out in a muddy field, engage with like-mined souls on the forum whose skills and expertise made this project viable, it has made me attend various events/rallies in search of parts, meeting new people along the way, nattering, laughing and sharing experiences, plus making parts. After all this hard work, which was some months in the making, I now have a fine example of its type, rewarding me with a gentle hum, glow, warm aroma and hours of further entertainment, through listening enjoyment. The only real modifications being the tone corrector capacitor at 390pF & not using pin 4 of the UL41 as an anchor point.

The humble Bush DAC90a … no lamp conversion could ever come close, surely?

Thank you for your time reading all this, I hope it inspires and maybe, brought on a smile or two. Many thanks due to Kaylee20 & John (heatercathodeshort) for their write-ups which went some way into turning this set around, thank you to Ed Dining for his time in rewinding my transformer and all those folk who make this forum and other event possible, a very Merry Christmas to one and all.

Before, during and after photos, follow.

Mark
Attached Thumbnails
Click image for larger version

Name:	01 Before.JPG
Views:	314
Size:	168.2 KB
ID:	174372   Click image for larger version

Name:	02 Chassis Overview.JPG
Views:	295
Size:	155.3 KB
ID:	174373   Click image for larger version

Name:	03 Where's The Transformer.JPG
Views:	278
Size:	140.6 KB
ID:	174374   Click image for larger version

Name:	04 Before, Under Chassis.JPG
Views:	297
Size:	182.2 KB
ID:	174375   Click image for larger version

Name:	05 Chassis Front.JPG
Views:	279
Size:	128.6 KB
ID:	174376  

mark2collection is offline   Reply With Quote
Old 11th Dec 2018, 2:47 pm   #2
mark2collection
Pentode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 224
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

After photos ...

Mark
Attached Thumbnails
Click image for larger version

Name:	06 During.JPG
Views:	285
Size:	123.6 KB
ID:	174377   Click image for larger version

Name:	07 During.JPG
Views:	284
Size:	90.6 KB
ID:	174378   Click image for larger version

Name:	08 Coming Together.JPG
Views:	290
Size:	133.5 KB
ID:	174379   Click image for larger version

Name:	09 After, Under Chassis.JPG
Views:	298
Size:	158.1 KB
ID:	174380   Click image for larger version

Name:	10 After.JPG
Views:	314
Size:	146.3 KB
ID:	174381  

mark2collection is offline   Reply With Quote
Old 11th Dec 2018, 2:48 pm   #3
mark2collection
Pentode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 224
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Calibration Labels, Word document, printed on standard A4, laminate it, apply double-side tape to the rear, jobs a good'n.

Mark
Attached Files
File Type: docx Calibration Label Modified.docx (32.0 KB, 121 views)
mark2collection is offline   Reply With Quote
Old 11th Dec 2018, 3:19 pm   #4
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 17,496
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Very nice job. I always like these "back from the dead" restorations.
paulsherwin is offline   Reply With Quote
Old 11th Dec 2018, 6:49 pm   #5
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 4,734
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Well done! Sometimes it's a duty to save a radio and bring it back to life, hopefully you will gain much enjoyment from it now though!
kalee20 is offline   Reply With Quote
Old 11th Dec 2018, 7:18 pm   #6
Nickthedentist
Dekatron
 
Nickthedentist's Avatar
 
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 14,067
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Lovely work!

I love these sets, and even rough ones can usually be spruced up and work well.

Hats off to you for restuffing the caps - I've never bothered in mine, but feel like I ought to have a go on the next one I do.

Cheers,

Nick.
Nickthedentist is offline   Reply With Quote
Old 11th Dec 2018, 8:52 pm   #7
HamishBoxer
Dekatron
 
HamishBoxer's Avatar
 
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 6,297
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Great little sets and a great job.Good enough write up I think to send to the BVWS bulletin.

There are always after articles.
__________________
G8JET BVWS Member and V.M.A.R.S
HamishBoxer is offline   Reply With Quote
Old 11th Dec 2018, 11:13 pm   #8
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 3,329
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

for a second or two I thought, pffft..he hasn't even changed 'that' capacitor! I think you'd call that a 'concours' job
__________________
Kevin
McMurdo is offline   Reply With Quote
Old 13th Dec 2018, 12:33 am   #9
johnny english
Pentode
 
Join Date: Nov 2013
Location: Liverpool, Merseyside, UK.
Posts: 159
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Great work Mark.
I love success restorations that have a beginning, middle and a good ending. Just one request could you upload a photo showing the radio in its cabinet.

Thanks Ed.
johnny english is offline   Reply With Quote
Old 13th Dec 2018, 1:00 am   #10
Lloyd 1985
Octode
 
Lloyd 1985's Avatar
 
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,463
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

A most enjoyable write up

I have a few spare bits I’ve been trying to turn into a working set for a while, I got a cracked cabinet for next to nothing and repaired the crack invisibly, got the mankiest chassis I could possibly get for it too! It was a golden colour from all the fag smoke, so I shoved the whole thing in the ultrasonic cleaner, came out really lovely and shiny! Haven’t got round to testing it yet though.

Regards
Lloyd
Lloyd 1985 is offline   Reply With Quote
Old 16th Dec 2018, 2:58 pm   #11
mark2collection
Pentode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 224
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Many thanks for the positive responses gentlemen, the set came together rather well, much better than initially hoped.

The write-up took some work too, trying to keep to the mains points without missing any details or drifting off into tangents. I'd not considered a BVWS write-up either, currently I'm not a member, am now rethinking this

Ed, I've just taken a few more photos this morning, including one of the dial, powered up. Taking my time to repaint the lamp reflector has paid off, the set is using original specification lamps, no other modifications. In the photo, the set had reached normal running temperature.

I've also included a better photo of the sets new mains lead, plug and cable grommet/retaining disc, taken at the time of the work.

The little plastic cover on the pins of the mains plug are for safety, saves accidentally plugging 'a work-in-progress' set directly into the mains. I do this at work too, as some of our test leads are mains leads, with mains plugs on but, open at the other end terminated by bootlace ferrules.

Mark
Attached Thumbnails
Click image for larger version

Name:	Mains Lead & Plug.JPG
Views:	135
Size:	182.7 KB
ID:	174714   Click image for larger version

Name:	Dial Illumination.JPG
Views:	133
Size:	136.5 KB
ID:	174715   Click image for larger version

Name:	Ready For Action.JPG
Views:	128
Size:	160.7 KB
ID:	174716  

Last edited by mark2collection; 16th Dec 2018 at 3:04 pm. Reason: Cannot spell :O)
mark2collection is offline   Reply With Quote
Old 16th Dec 2018, 5:42 pm   #12
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 8,097
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

I have often wondered what those plastic plug covers are for, I simply put the plug in question in a trouser pocket.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 17th Dec 2018, 1:59 pm   #13
ekcopyephilips
Hexode
 
ekcopyephilips's Avatar
 
Join Date: Dec 2006
Location: Norwich, Norfolk, UK.
Posts: 388
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Hi Mark

That looks wonderful. Where did you source your dial lamps from, ive got one of those radios too minus the dial lamps. So need to get some of the correct (or as near as possible) value.

Did you replace the lamp light diffuser with a modern material? Apparently the originals are made from Cellulose acetate sheet, so burn really quickly and ferociously if they get hot enough.

Cheers

Mike
ekcopyephilips is offline   Reply With Quote
Old 17th Dec 2018, 2:07 pm   #14
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 4,734
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Quote:
Originally Posted by ekcopyephilips View Post
Did you replace the lamp light diffuser with a modern material? Apparently the originals are made from Cellulose acetate sheet, so burn really quickly and ferociously if they get hot enough.
I think it's cellulose nitrate actually - and yes they do!! Burn very cleanly though.

I do have a small a small amount of 0.5mm translucent polyester sheet, which makes excellent diffuser material. It doesn't buckle, warp, shrink, etc. PM me if you would like a DAC90a-diffuser sized piece.
kalee20 is offline   Reply With Quote
Old 17th Dec 2018, 8:28 pm   #15
ColinB
Heptode
 
ColinB's Avatar
 
Join Date: Apr 2003
Location: Chineham, Basingstoke, Hampshire, UK.
Posts: 504
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Quote:
Originally Posted by mark2collection View Post
I do this at work too, as some of our test leads are mains leads, with mains plugs on but, open at the other end terminated by bootlace ferrules.

Mark

I know you know the risks, but be exceptionally careful of doing this type of thing. I'm certain it will be contrary to your employers H&S rules, and if anything goes wrong (or even if it doesn't), is unlikely to "go down well"...


We have to protect ourselves from time to time, unfortunately.


All that said, I like the restoration, did you reduce the HT through the OP TX primary by changing the cathode resistor to protect the TX a bit?


Cheers,
Colin
ColinB is offline   Reply With Quote
Old 18th Dec 2018, 12:24 pm   #16
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 12,744
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

The TX is an Ed rewind so it'll likely be happy enough anyway.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline   Reply With Quote
Old 18th Dec 2018, 11:27 pm   #17
mark2collection
Pentode
 
mark2collection's Avatar
 
Join Date: Jul 2010
Location: Royal Berkshire, UK.
Posts: 224
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

Mike, the lamps were purchased from Camber Television Centre, as they were doing kits a while back. The dial lamp diffuser is the original, it just needed a going over with anti-static foaming cleanser on the smooth side, T-Cut on the coarse side.

The biggest improvement was repainting the reflector itself.

Colin, a timely reminder on two counts. For one, I should have included in the write-up the idle current. The replacement/used UL41 was 25mA almost from the word go, & remained there. I then trialled a NOS CV1977, 1st 5 minutes was around 18mA, around 20 minutes later, it stabilised at 23mA. My meter was connected between the output valve anode & TX.

Count two, yes, the mains leads at work. We always have industrial instruments/units returned for repair with missing gland plates & hence, missing captive mains leads. We have the cables under lock & key for added safety, not ideal but it does make repairs easier. The look on the last PAT contractors face when I said 'at least the earth bond'll be a pass!'

I like merlinmaxwells idea of putting a plug in a pocket, though I've been caught out on a TV where the mains RFI cap was pre-power switch, & the jolt from the plug due to the charged cap taught me a lesson.

Mark
mark2collection is offline   Reply With Quote
Old 19th Dec 2018, 11:19 am   #18
AC/HL
Moderator
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 6,814
Default Re: Bush DAC90A, Write-off to Worker in no easy steps.

...and don't casually walk away!
__________________
Bill, BVWS member
AC/HL is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 9:27 am.


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 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.