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 15th Jul 2022, 8:57 pm   #1
TomB1979
Diode
 
Join Date: Jul 2022
Location: Cardiff, Wales, UK.
Posts: 5
Default HMV 1134 Magic Eye

Hello all, firstly many thanks for all the informative resources on here, where I have lurked for some time. I’m hugely grateful, and hope I can ask for some advice about my HMV 1134. It works well, and sounds great. I’ve replaced a few components including a particularly sticky Hunts smoothing capacitor, and a clean of the wave change switch fixed a disappearing VHF band the other day.

Now, though, the magic eye is giving me some trouble. It’s pretty dim, but also doesn’t indicate full signal strength on LW/MW even though the radio gets a strong signal.it never gets above a weak indication. Strangely, it works even less well on VHF. I changed the 470k resistor R35 on the valve socket as it was measuring about 1.2M but it doesn’t seem to have had an effect.

Before I investigate R33/34 and C61 which are in close proximity, I thought I’d see if anyone has any other ideas, particularly whether the valve itself needs replacing.

Thanks for any advice!
TomB1979 is offline  
Old 15th Jul 2022, 9:36 pm   #2
Gabe001
Octode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
Default Re: HMV 1134 Magic Eye

I've done two of these for friends in the last 6 months, they are good looking sets. How's the veneer of yours?

You should be getting full or almost full detection on strong FM stations -in my case the BBC stations come through strongest. I dont remember the deflection on Am but I don't think it was particularly impressive.
From memory I don't think r33 and R34 can be reliably measured in situ and c61 isn't a hunts.

I think you've done everything right. Can I double check that you've replaced c49 and that's you've connected it positive to chassis? You can measure the negative volts there on a strong FM station to get an idea of the expected deflection, and at pin 1 of the em81

I also had a disappearing FM and weak FM deflection in one of my HMV 1134s. In my case it was a weak ecc85. The waveband switch was blameless. I suspect you also have a weak ecc85

As you may have found out, replacement em81s are quite expensive. If you're planning on buying a replacement, the Russian equivalent works really well and is much more affordable, but always buy new old stock.

Last edited by Gabe001; 15th Jul 2022 at 9:44 pm.
Gabe001 is offline  
Old 15th Jul 2022, 10:10 pm   #3
TomB1979
Diode
 
Join Date: Jul 2022
Location: Cardiff, Wales, UK.
Posts: 5
Default Re: HMV 1134 Magic Eye

Thank you - some good pointers for me to go on here!

The veneer (and indeed the whole set) is in a surprisingly good state; in fact I suspect some good work has taken place inside the set to keep it working well. There was only the one wax capacitor which was c60, now replaced. I will double check c49 tomorrow and see if it looks like a recent replacement - I suspect it must have been as I didn’t see any more dodgy looking ones. Will replace if I spot anything worrying! I did spot a modern-looking electrolytic inside so I wonder if that was it, and it’s already been replaced. On the list for the morning…

The radio itself picks up beautifully on VHF, especially BBC R3 and R4, it’s purely the display on the magic eye which is suddenly not deflecting strongly on AM, and not at all on VHF, so not a huge issue, but it would be nice to have it working. Probably a ridiculously basic question, but what sort of ball park of negative voltage should be present at pin 1 of the EM81 for full deflection? Sorry, very unfamiliar with the magic of the magic eye!

I have a new ECC85 so will try swapping that out tomorrow, and have also bitten the bullet and ordered a new EM81 (thanks for that advice re Russian equivalent!)

Sound quality and appearance are really nice on his set so it would be great to keep it in tip-top shape. Will update as and when - thanks again!
TomB1979 is offline  
Old 16th Jul 2022, 1:16 pm   #4
Gabe001
Octode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
Default Re: HMV 1134 Magic Eye

-1v on a strong station not good

You need -10.5v for full deflection. You should be seeing at least -7/8 on a strong signal. Try the new ecc85 and report back.

When my FM failed, it worked perfectly well until it didn't. Changing band switch or the Set on and off seemed to restore fm temporarily

Have you replaced the bridge rectifier or are you going to keep the old one?

I've got high resolution underchassis pictures of mine if you want them pm me your email
Gabe001 is offline  
Old 16th Jul 2022, 6:38 pm   #5
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,173
Default Re: HMV 1134 Magic Eye

Poor performance can often be leakage on the caps on the AVC line or resistors gone high in that area
It is a high impedance point so slight leakage in a cap can have a large effect

Ed
Ed_Dinning is offline  
Old 16th Jul 2022, 7:32 pm   #6
Gabe001
Octode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
Default Re: HMV 1134 Magic Eye

Tom, if you haven't don't so already, all the Hunts caps need to be replaced, not just the smoothing cap. There are about 4 or 5 in total. They will all be leaky
Gabe001 is offline  
Old 16th Jul 2022, 8:02 pm   #7
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: HMV 1134 Magic Eye

You may just be living in a weak signal area of course, or be using an inadequate aerial arrangement. 1950s radios were intended to be used with serious aerials.

Magic eyes are just voltage indicators. You can confirm it's working with a 1.5V or 9V battery on the grid.
paulsherwin is offline  
Old 16th Jul 2022, 8:20 pm   #8
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: HMV 1134 Magic Eye

The discriminator-capacitor [the odd electrolytic with its +ve terminal connected to earth] can also cause 'perplexing' issues with recovered-audio and FM AGC/tuning-signal if it has decided to try and emulate a resistor as a side-hustle.
__________________
I'm the Operator of my Pocket Calculator. -Kraftwerk.
G6Tanuki is offline  
Old 16th Jul 2022, 10:20 pm   #9
TomB1979
Diode
 
Join Date: Jul 2022
Location: Cardiff, Wales, UK.
Posts: 5
Default Re: HMV 1134 Magic Eye

Thank you all, this is really helpful. I’ve had the opportunity today to try the radio in a much stronger signal area, and the magic eye is now showing a much stronger deflection on VHF. So I suspect I was receiving a relatively weak signal but being bamboozled by the very good sound quality I was still experiencing!

Thank you for the warning about the Hunts capacitors and the electrolytic. The single wax one is gone and replaced by a suitably period-looking newer one. I have noted the other small brown hunts capacitors, and will put them on the list for replacement, along with the Plessey electrolytic, which I couldn’t find a suitable replacement for in my boxes of bits today! Replacement is on order.

To summarise, the following components have been replaced so far:

- wax capacitor across the mains
- resistor on the magic eye socket
- capacitor connected to the magic eye

Other maintenance:

- wave change switch cleaned
- some valve pins cleaned

Preventative maintenance on the list:

- Plessey electrolytic
- remaining (brown) hunts capacitors
- clean power/tone switch as the radio sometimes stays on when this switch is turned off

No valves replaced so far, but have around four of them available as spares.

Sound quality currently excellent, but I fully appreciate the importance of ensuring the capacitors are in good condition to keep it that way and avoid major damage, as I have reconsidered my original opinion and decided that there have not been any replacements of original components before I got it.

Huge thanks to all!
TomB1979 is offline  
Old 17th Jul 2022, 10:08 am   #10
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: HMV 1134 Magic Eye

If the radio is working well and the circuit voltages are reasonably close to where they should be, there's nothing to be gained by changing valves.
paulsherwin is offline  
Old 17th Jul 2022, 11:07 am   #11
TomB1979
Diode
 
Join Date: Jul 2022
Location: Cardiff, Wales, UK.
Posts: 5
Default Re: HMV 1134 Magic Eye

Thanks Paul, I felt the same. The radio is full of nice old Marconi valves so I was keen to leave them in situ if possible, but glad to have some spares on hand in case I get any issues further down the line.

I may try the replacement EM81 when it comes, just because I suspect the one I have is quite dim and it would be interesting to compare. But if it’s not significantly brighter I’ll probably ultimately leave the old one in.

Grateful to everyone for your generosity in pitching in useful info!
TomB1979 is offline  
Old 17th Jul 2022, 1:50 pm   #12
Gabe001
Octode
 
Join Date: Oct 2019
Location: Stockport, Greater Manchester, UK.
Posts: 1,612
Default Re: HMV 1134 Magic Eye

Tom I would strongly recommend you replace c50, the grid coupling cap also known as 'that' capacitor. It's a hunts and will almost certainly be leaky, which can cause damage the output valve or output transformer. You may have done so already.
Gabe001 is offline  
Old 17th Jul 2022, 2:57 pm   #13
TomB1979
Diode
 
Join Date: Jul 2022
Location: Cardiff, Wales, UK.
Posts: 5
Default Re: HMV 1134 Magic Eye

Thanks Gabe, excellent point. I haven't done this one yet, but will get on it as a priority. Thanks for the reminder!
TomB1979 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 10:29 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 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.