Unica UNR-30 - UK Vintage Radio Repair and Restoration Discussion Forum

dragonser · 19th Jul 2025, 4:20 pm

Hi, I got offered this radio and as it looked nice I thought, why not ?
After taking off the bottom panel I looked at the circuitry and wiring.
Worryingly there are two ceramic caps from either side of the mains supply to the chassis ! So which ever way the mains is connected the chassis may float at 115v ac..
I think I am going to carefully remove these two caps before powering it up. Any other things I should check before powering up ?

Cobaltblue · 19th Jul 2025, 8:55 pm

What's the value of the caps?

Difficult to see in the pics

Cheers

Mike T

Terry_VK5TM · 19th Jul 2025, 10:28 pm

Those caps markings appear to be .01MF (.01uF).

If the chassis is earthed properly, it shouldn't be floating at 115V.

its ur aerial · 20th Jul 2025, 8:00 am

I think Terry`s correct, I would also guess at 0.01 mf, but I assume like most imported equipment at the time, its only got two a core mains lead.
Are these caps connected to input of the mains Transformer or the HT secondary ? If I ever I need to power up any thing of dubious integrity, I always do a few cold resistance checks first and then power it up on a Variac and or Lamp Limiter .
If I recall correctly they used valves and were retailed by GW Smith, with branches in Tottenham Court Rd, Lisle St

and possibly also one in the Edgware Rd, can't remember now: shrug:
Ken G6HZG.

dragonser · 20th Jul 2025, 8:47 am

Hi, just to clarify, the radio has a 2 core mains lead. The ceramic caps are 10nf and are on the mains side of the transformer !
If they were on the ht side I would not be so worried.
Thank you for all your help.

davidw · 20th Jul 2025, 9:01 am

If it helps the circuit is down the page here https://g4aqb.wordpress.com/2023/08/11/unica-unr-30/ However, it only shows one cap on the mains side to earth at the aerial coupling winding.

Terry_VK5TM · 20th Jul 2025, 10:37 am

Quote:

Originally Posted by dragonser

Hi, just to clarify, the radio has a 2 core mains lead.

I would be inclined to fit a 3 core mains lead and earth the chassis - the schematic linked to does show the power supply negative side is earthed via the connection at the antenna coil.

If you just want to test it, disconnect the caps, they are for mains interference suppression, just be aware there may be a bit of mains fed interference.

g4wim_tim · 20th Jul 2025, 7:36 pm

This was my first commercial HF rx over 50 years ago and I can confirm that without a proper earth the chassis is likely to be floating live as I discovered the hardway.

As an rx it drifts alot and with no band spread it makes resolving ssb nigh on impossible much above 7MHz but as I used it as a tuneable IF for 2Mtrs tuning 2-4MHz AM it was ok.

I also recall the HT was poorly filtered resulting in mains hum of the LO.

its ur aerial · 20th Jul 2025, 7:38 pm

If that circuit is correct, the switch is only single pole and only switches the N conductor

, I again agree with Terry, chop the caps out for test purposes, then fit 3 core flex and earth the chassis, I personally, would also fit a double pole switch and replace those caps with one cap across the replacement's Switched terminals.
According to that advert link they retailed at 13 Gns

I think that equates to £13.65, in present money.
Ken G6HZG.

Mark GØOIW · 9th Aug 2025, 12:40 pm

I had one circa 1972, consuming a lot of my pocket and Christmas money.
Usually called Unica UNR-30 in Britain, though Laskys sold a virtually identical own-brand one, Skyrover Mk2. Olson RA-48 in the USA.

Yep, 2-core mains lead, touch the case and an earthed point and you'll jump a bit.

Don't get excited - they're a pretty awful set. As G4WIM says, drifts like the clappers. It's also deaf as a post on the higher frequencies, and riddled with images: not just the usual 2 x IF away, but numerous variations on LO x n +/-IF, e.g. 9MHz broadcasters appearing above 4 MHz [((4000 + 455) x2) + 455 = 9365 etc]. Also, mine had weird whistling on the MW band, almost like the BFO was switched on, so you had to carefully zero-beat.

The regenerative IF / BFO / Q-multiplier was fun, though. Very familiar to us who started with HAC one valvers etc which had a reaction control. Set the knob just short of oscillation for maximum sensitivity and selectivity, a bit further and it acts as a BFO.

Cheap and nasty little set, though I wish I still had mine for nostalgic value.

19th Jul 2025, 4:20 pm	#1
dragonser Heptode Join Date: Aug 2009 Location: Carshalton, Surrey, UK. Posts: 759	Unica UNR-30 Hi, I got offered this radio and as it looked nice I thought, why not ? After taking off the bottom panel I looked at the circuitry and wiring. Worryingly there are two ceramic caps from either side of the mains supply to the chassis ! So which ever way the mains is connected the chassis may float at 115v ac.. I think I am going to carefully remove these two caps before powering it up. Any other things I should check before powering up ? Attached Thumbnails __________________ Regards Peter B

19th Jul 2025, 8:55 pm	#2
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 7,708	Re: Unica UNR-30 What's the value of the caps? Difficult to see in the pics Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

19th Jul 2025, 10:28 pm	#3
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,820	Re: Unica UNR-30 Those caps markings appear to be .01MF (.01uF). If the chassis is earthed properly, it shouldn't be floating at 115V. __________________ Terry VK5TM https://www.vk5tm.com/

20th Jul 2025, 8:00 am	#4
its ur aerial Heptode Join Date: May 2009 Location: Ryde, Isle of Wight, UK. Posts: 606	Re: Unica UNR-30 I think Terry`s correct, I would also guess at 0.01 mf, but I assume like most imported equipment at the time, its only got two a core mains lead. Are these caps connected to input of the mains Transformer or the HT secondary ? If I ever I need to power up any thing of dubious integrity, I always do a few cold resistance checks first and then power it up on a Variac and or Lamp Limiter . If I recall correctly they used valves and were retailed by GW Smith, with branches in Tottenham Court Rd, Lisle St and possibly also one in the Edgware Rd, can't remember now: shrug: Ken G6HZG. __________________ Life is not Hollywood, life is Cricklewood. Last edited by its ur aerial; 20th Jul 2025 at 8:07 am.

20th Jul 2025, 8:47 am	#5
dragonser Heptode Join Date: Aug 2009 Location: Carshalton, Surrey, UK. Posts: 759	Re: Unica UNR-30 Hi, just to clarify, the radio has a 2 core mains lead. The ceramic caps are 10nf and are on the mains side of the transformer ! If they were on the ht side I would not be so worried. Thank you for all your help. __________________ Regards Peter B

20th Jul 2025, 9:01 am	#6
davidw Heptode Join Date: Sep 2006 Location: Woodbridge, Suffolk, UK. Posts: 656	Re: Unica UNR-30 If it helps the circuit is down the page here https://g4aqb.wordpress.com/2023/08/11/unica-unr-30/ However, it only shows one cap on the mains side to earth at the aerial coupling winding. __________________ Dave G1AGK. My perception is my reality! Last edited by davidw; 20th Jul 2025 at 9:03 am. Reason: addition

20th Jul 2025, 7:36 pm	#8
g4wim_tim Hexode Join Date: Nov 2018 Location: Freckleton, Lancashire, UK. Posts: 273	Re: Unica UNR-30 This was my first commercial HF rx over 50 years ago and I can confirm that without a proper earth the chassis is likely to be floating live as I discovered the hardway. As an rx it drifts alot and with no band spread it makes resolving ssb nigh on impossible much above 7MHz but as I used it as a tuneable IF for 2Mtrs tuning 2-4MHz AM it was ok. I also recall the HT was poorly filtered resulting in mains hum of the LO. __________________ Building and tinkering for over 50 years, from 807's to digital amateur TV. Last edited by g4wim_tim; 20th Jul 2025 at 8:04 pm. Reason: typo

20th Jul 2025, 7:38 pm	#9
its ur aerial Heptode Join Date: May 2009 Location: Ryde, Isle of Wight, UK. Posts: 606	Re: Unica UNR-30 If that circuit is correct, the switch is only single pole and only switches the N conductor, I again agree with Terry, chop the caps out for test purposes, then fit 3 core flex and earth the chassis, I personally, would also fit a double pole switch and replace those caps with one cap across the replacement's Switched terminals. According to that advert link they retailed at 13 Gns I think that equates to £13.65, in present money. Ken G6HZG. __________________ Life is not Hollywood, life is Cricklewood.

9th Aug 2025, 12:40 pm	#10
Mark GØOIW Tetrode Join Date: Jul 2007 Location: Caversham, Berkshire, UK. Posts: 54	Re: Unica UNR-30 I had one circa 1972, consuming a lot of my pocket and Christmas money. Usually called Unica UNR-30 in Britain, though Laskys sold a virtually identical own-brand one, Skyrover Mk2. Olson RA-48 in the USA. Yep, 2-core mains lead, touch the case and an earthed point and you'll jump a bit. Don't get excited - they're a pretty awful set. As G4WIM says, drifts like the clappers. It's also deaf as a post on the higher frequencies, and riddled with images: not just the usual 2 x IF away, but numerous variations on LO x n +/-IF, e.g. 9MHz broadcasters appearing above 4 MHz [((4000 + 455) x2) + 455 = 9365 etc]. Also, mine had weird whistling on the MW band, almost like the BFO was switched on, so you had to carefully zero-beat. The regenerative IF / BFO / Q-multiplier was fun, though. Very familiar to us who started with HAC one valvers etc which had a reaction control. Set the knob just short of oscillation for maximum sensitivity and selectivity, a bit further and it acts as a BFO. Cheap and nasty little set, though I wish I still had mine for nostalgic value.