DAC90A Lives again! - UK Vintage Radio Repair and Restoration Discussion Forum

Hunts smoothing bomb · 18th Jan 2006, 10:50 am

Hi all,

Two years ago I purchased a DAC90A from the NVCF at the bargain price of £35...yes £35. It had a label saying "not working". I decided to get it.
On handing over the cash the trader asked for another £10!

I said to him it's marked up at £35. He thought for some bizzare reason he marked it up at £45. anyway I have only just got around to looking at the set and on opening it up I was pleasantly surprised to see that someone with good skills had already fitted a black 3 core mains pvc lead and disconnected the mains input socket. Also it had a full complement of new caps (the little yellow ones from RS, the MKT series) I could see the person who had done this had good soldering skills and everything was neatly done, well this filled me with confidence and I decided to power up through my variac. Powering up brought forward no problems and after a few minutes crackles could be heard when adjusting the volume but no signals could be heard

I had a quick look round and dicovered that the UCH42 had no heater glow....HMmm, short circuit heater I thought so I whipped the valve out and couldn't believe my luck for this valve was not a UCH42 but an ECH42, now full of excitement I rushed up stairs to my valve stock and rumaged round and found a UCH42. Well what more is there to say, I popped the new valve in and switched on. After about 45 seconds I was rewarded with more than ample output and the little beast was pulling in plenty of stations on both MW and LW very clearly so I decided realignment was not necsasary. Must be my easiest restoration ever!

All the best
Lee

ppppenguin · 18th Jan 2006, 11:32 am

Excellent buy! I'd like to know where the earth core of the mains lead was connected.

paulsherwin · 18th Jan 2006, 12:07 pm

I know some people like to connect the metal speaker grille to an earth wire.

Paul

Hunts smoothing bomb · 18th Jan 2006, 12:30 pm

Crikey Moses!
I've just twigged.
The Earth I remember seeing it connected to chassis!

Obviously if I used an rcd when I first powered up (like I should) then I would have been aware of this dangorous mod.
I can't believe I didn't twig, i know only to well it has neutral connected to chassis!!
What a complete

Thanks for pointing that out, must change that tonight!!

Regards Lee

paulsherwin · 18th Jan 2006, 12:36 pm

I wouldn't call it dangerous... The worst that would happen would be a blown plug fuse or tripped breaker in the consumer unit.

Not exactly wise though

It's surprising that someone would be competent to recap a radio and still do something like this

Best regards, Paul

Ed_Dinning · 18th Jan 2006, 1:32 pm

Hi Lee it might also be worth checking that the output valve base has no connections to the IC/NC pins (4&5 I think) as these can cause problems if certain types of valve are fitted where there is an internal connection to that pin. It's a simple matter to lift the components in the air and leave them there.

Ed

Hunts smoothing bomb · 18th Jan 2006, 3:27 pm

Hi Ed,

Thanks for that tip, I will also check this when I rewire the earth to the speaker grill tonight.

Regards
Lee

JoshWard · 18th Jan 2006, 6:25 pm

Sounds like a nice restoration! Although I had a DAC90A for Christmas I know my parents did not spend less than £15 on it fully restored!

Danny · 19th Jan 2006, 12:50 am

Arr just a thought have thay done the schasis isolation trick i remember reading this somewhere ? Danny

zak · 19th Jan 2006, 2:09 pm

That is horrendus,I would have sorted out the mains lead first!To use 3 core lead on most radio sets is just not on,they are not classed as an appliance to be pat tested anyway.I have a few sets now that supposed to have been "restored" by a professional these have 3 core leads which are causing hum problems,these will be fitted with 2 core lead as intended.It scares me to see what these anti- restorers get up to.
As regards the DAC90A, I assume the safety connector has been removed also,what amazes me that so few people have accidents by all these dangerous mods that people are doing.
Only class 1 appliances require an earth,does not apply to vintage domestic radio. Where the case is not wood or bakelite,the only sets which are earthed are metal cased communication receivers.

DON THOMSON · 21st Jan 2006, 1:06 pm

Danny may be thinking of the article entitled "Safety First and a leaky DAC" by GaryTempest in the BVWS Bulletin for the Summer 2002,Vol 27 No.2.

Regards,

Don

18th Jan 2006, 10:50 am	#1
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	DAC90A Lives again! Hi all, Two years ago I purchased a DAC90A from the NVCF at the bargain price of £35...yes £35. It had a label saying "not working". I decided to get it. On handing over the cash the trader asked for another £10! I said to him it's marked up at £35. He thought for some bizzare reason he marked it up at £45. anyway I have only just got around to looking at the set and on opening it up I was pleasantly surprised to see that someone with good skills had already fitted a black 3 core mains pvc lead and disconnected the mains input socket. Also it had a full complement of new caps (the little yellow ones from RS, the MKT series) I could see the person who had done this had good soldering skills and everything was neatly done, well this filled me with confidence and I decided to power up through my variac. Powering up brought forward no problems and after a few minutes crackles could be heard when adjusting the volume but no signals could be heard I had a quick look round and dicovered that the UCH42 had no heater glow....HMmm, short circuit heater I thought so I whipped the valve out and couldn't believe my luck for this valve was not a UCH42 but an ECH42, now full of excitement I rushed up stairs to my valve stock and rumaged round and found a UCH42. Well what more is there to say, I popped the new valve in and switched on. After about 45 seconds I was rewarded with more than ample output and the little beast was pulling in plenty of stations on both MW and LW very clearly so I decided realignment was not necsasary. Must be my easiest restoration ever! All the best Lee __________________ Lee

18th Jan 2006, 11:32 am	#2
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: DAC90A Lives again! Excellent buy! I'd like to know where the earth core of the mains lead was connected.

18th Jan 2006, 12:07 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,936	Re: DAC90A Lives again! I know some people like to connect the metal speaker grille to an earth wire. Paul

18th Jan 2006, 12:30 pm	#4
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: DAC90A Lives again! Crikey Moses! I've just twigged. The Earth I remember seeing it connected to chassis! Obviously if I used an rcd when I first powered up (like I should) then I would have been aware of this dangorous mod. I can't believe I didn't twig, i know only to well it has neutral connected to chassis!! What a complete Thanks for pointing that out, must change that tonight!! Regards Lee __________________ Lee

18th Jan 2006, 12:36 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,936	Re: DAC90A Lives again! I wouldn't call it dangerous... The worst that would happen would be a blown plug fuse or tripped breaker in the consumer unit. Not exactly wise though It's surprising that someone would be competent to recap a radio and still do something like this Best regards, Paul

18th Jan 2006, 1:32 pm	#6
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: DAC90A Lives again! Hi Lee it might also be worth checking that the output valve base has no connections to the IC/NC pins (4&5 I think) as these can cause problems if certain types of valve are fitted where there is an internal connection to that pin. It's a simple matter to lift the components in the air and leave them there. Ed

18th Jan 2006, 3:27 pm	#7
Hunts smoothing bomb Octode Join Date: Oct 2005 Location: Wimborne, Dorset, UK. Posts: 1,407	Re: DAC90A Lives again! Hi Ed, Thanks for that tip, I will also check this when I rewire the earth to the speaker grill tonight. Regards Lee __________________ Lee

18th Jan 2006, 6:25 pm	#8
JoshWard Octode Join Date: Dec 2005 Location: Near Stowmarket, Suffolk, UK. Posts: 1,962	Re: DAC90A Lives again! Sounds like a nice restoration! Although I had a DAC90A for Christmas I know my parents did not spend less than £15 on it fully restored!

19th Jan 2006, 12:50 am	#9
Danny Heptode Join Date: Jul 2003 Location: North Walsham, Norfolk, UK. Posts: 516	Re: DAC90A Lives again! Arr just a thought have thay done the schasis isolation trick i remember reading this somewhere ? Danny

19th Jan 2006, 2:09 pm	#10
zak Retired Dormant Member Join Date: Feb 2005 Location: Monmouthshire,on South Wales border Posts: 85	Re: DAC90A Lives again! That is horrendus,I would have sorted out the mains lead first!To use 3 core lead on most radio sets is just not on,they are not classed as an appliance to be pat tested anyway.I have a few sets now that supposed to have been "restored" by a professional these have 3 core leads which are causing hum problems,these will be fitted with 2 core lead as intended.It scares me to see what these anti- restorers get up to. As regards the DAC90A, I assume the safety connector has been removed also,what amazes me that so few people have accidents by all these dangerous mods that people are doing. Only class 1 appliances require an earth,does not apply to vintage domestic radio. Where the case is not wood or bakelite,the only sets which are earthed are metal cased communication receivers.

21st Jan 2006, 1:06 pm	#11
DON THOMSON Retired Dormant Member Join Date: Nov 2005 Location: CHELMSFORD, ESSEX,UK Posts: 26	Re: DAC90A Lives again! Danny may be thinking of the article entitled "Safety First and a leaky DAC" by GaryTempest in the BVWS Bulletin for the Summer 2002,Vol 27 No.2. Regards, Don