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Old 24th Jan 2021, 6:31 pm   #1
MeanDumpsterCat
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Default HMV 1115 General Advice

Hi everyone.

So i've just won an HMV 1115

There are a few things that need doing on it, and is not cosmetically great.

The seller has said it works (i'm assuming it wont to avoid disappointment) but the dial cord needs replacing.

As far as I understand these sets are a bit of a pain to work on. Is there anything I should be aware of in terms of disassembly and things to keep in mind when replacing components? I did notice that big (and presumably hot) mains dropper that is built into the chassis which looks like it needs to come out in order to get the radio out.

Also anything I should know about adjusting iron-dust transformers? I presume I should use a reasonably gentle plastic tool so to not break the slug.

Probably dont need to mention it but i am already aware of the live chassis of these older transformerless sets. Isolation transformer and variac supply will be used. Still need to build myself a light bulb limiter but that shouldnt be too hard.

Cheers.
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Old 25th Jan 2021, 1:32 pm   #2
Beardyman
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Default Re: HMV 1115 General Advice

I have one of these & the wiring to the dropper was very crumbly! There's a lot of heat in a small box! I didn't need to adjust the alignment so am unable to answer your question about the iron dust cores but common sense says you approaching it correctly, that said, if it doesn't need to be adjusted then leave well alone. These have a push pull output & the internal speaker is tiny, quite why they did that I don't know. Consequently the chassis is fairly compact so take lots of photos & I do mean lots. The service data sheet has a stringing diagram so you should be alright there. There's a fair bit of data available via the search facility regarding these sets not to mention photos. Best of luck chap!
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Old 25th Jan 2021, 2:10 pm   #3
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Default Re: HMV 1115 General Advice

I have one of these sets it needed a rewire, but works fine although does not do justice to the push pull output stage.
Here is a write up by another restorer.

http://www.vintage-radio.com/recent-.../hmv-1115.html

John
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Old 26th Jan 2021, 12:56 am   #4
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Default Re: HMV 1115 General Advice

Quote:
Originally Posted by Beardyman View Post
I have one of these & the wiring to the dropper was very crumbly! There's a lot of heat in a small box! I didn't need to adjust the alignment so am unable to answer your question about the iron dust cores but common sense says you approaching it correctly, that said, if it doesn't need to be adjusted then leave well alone. These have a push pull output & the internal speaker is tiny, quite why they did that I don't know. Consequently the chassis is fairly compact so take lots of photos & I do mean lots. The service data sheet has a stringing diagram so you should be alright there. There's a fair bit of data available via the search facility regarding these sets not to mention photos. Best of luck chap!
I just had a look at the schematic for the first time. I'm confused as to why they used two KT71's as the output. It seems like that would just make it more complicated and expensive. Perhaps they were tasked with getting rid of surplus valves left over from WWII? That would also explain the green paint.

Have to admit I kind of like it in an "ugly duckling" kind of way. Definitly some interesting design choices.
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Old 27th Jan 2021, 11:18 am   #5
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Default Re: HMV 1115 General Advice

Quote:
Originally Posted by MeanDumpsterCat View Post
I just had a look at the schematic for the first time. I'm confused as to why they used two KT71's as the output. It seems like that would just make it more complicated and expensive. Perhaps they were tasked with getting rid of surplus valves left over from WWII? That would also explain the green paint.

Have to admit I kind of like it in an "ugly duckling" kind of way. Definitly some interesting design choices.
I don't understand your comment, a push pull output was common in the higher quality radios. 2 x KT71 valves in PP would give a substantial increase in the audio power output, over using just a single KT71.
It would never be done to just use up valves.

Mike
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Old 27th Jan 2021, 11:53 am   #6
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Default Re: HMV 1115 General Advice

Completely agree Mike but this model has a tiny 5" speaker. It does seem a bit odd to go to the expense of the extra valve and components for such a small receiver. John.
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Old 27th Jan 2021, 12:14 pm   #7
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Default Re: HMV 1115 General Advice

The 1115 chassis was also fitted to the 1604 radiogram which had a 6.5 inch speaker, perhaps they had in mind the radiogram rather than a radio? I must admit I've always found the 1115 to be rather tinny but plenty of volume. And it is handsome in an ugly duckling kind of way!
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Old 27th Jan 2021, 11:13 pm   #8
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Default Re: HMV 1115 General Advice

I once had the radiogram version and it did sound good with the solid cabinet and fairly large speaker. There was plenty of space for heat dissipation but the turntable got rather hot. I also found that the rubber insulation on much of the wiring was crumbling. It wasn't difficult to work on.
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Old 28th Jan 2021, 1:35 am   #9
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Default Re: HMV 1115 General Advice

Well, it arrived at my door today. Very well packaged and in once piece (phew)

Here are some pictures.

Unfortunately as expected, a lot of the rubber wiring is decaying so i'm going to replace that with some modern heat resistant wire before I even think of powering this thing up.

Quite handily, there is a removable wooden panel on the bottom of the radio that allows one to have a peek at the electronics below the chassis. Neat!

All seems completely original to me. If there has been any repair work, it's very well camouflaged. Just look at all those original waxies .

I popped it out of its cabinet which was a little fiddly to do but not as difficult as I was led to believe. Valves all look original too. I didnt remove the X67M or W76 as I didnt feel like unscrewing delicate anode caps on the living room floor at midnight. Post work tired brain in full effect.

Dial string is indeed broken but the spring is still there. I might even get away with using the old string. If not, I may have to raid my dad's old fishing supplies.

But once i've replaced those wires, i'll give it a little juice on a current limited variac and see if anything happens. I will replace those waxies, but I would like to see what it does first before I start replacing things. According to its previous owner, they did power it up and it recieved stuff but then the dial string broke.

Annoyingly they cut the plug off. But I wouldnt want to plug anything in with flakey internal wiring anyway. Doesnt actually look too complicated to re wire. The main concern is the ones going from the main dropper. The rest seem okay.

It's going to be a fun project. If any unusual problem comes up I will make a new thread as to not make this one go too long and off topic.
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Last edited by MeanDumpsterCat; 28th Jan 2021 at 2:02 am. Reason: Added picture of decaying wires.
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Old 28th Jan 2021, 4:20 am   #10
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Default Re: HMV 1115 General Advice

Just to add to my previous post.
I know the tubular wax capacitors are molded paper but are the flat ones also molded paper just at a different value or are they mica capacitors coated in wax (and thus should avoid being replaced unless for a specific reason)
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Old 28th Jan 2021, 8:53 am   #11
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Default Re: HMV 1115 General Advice

The flat ones (with pF values) are waxed mica so I'd really not worry about those unless they are obviously damaged in some way. I'd remove the smoothing capacitor if it looks distressed (white deposits around the terminals or bulging of said terminal support), mine reformed well but it took a good few hours. As always, if in doubt then replace or re-stuff. I found a lot of the resistors in mine had gone high but only those over 100K?!? And by high I mean more than 50%. Oh, and I found a "dry" joint on the wave change switch that had been that way since it had been made, this gave intermittent operation on MW.
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Old 28th Jan 2021, 8:55 am   #12
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Default Re: HMV 1115 General Advice

Another thought came to me just after I'd posted! Be really careful of the frame aerial, they are rather delicate & will fall to pieces if handled too much, don't ask how I know that!
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Old 28th Jan 2021, 5:51 pm   #13
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Default Re: HMV 1115 General Advice

Quote:
Originally Posted by Beardyman View Post
Another thought came to me just after I'd posted! Be really careful of the frame aerial, they are rather delicate & will fall to pieces if handled too much, don't ask how I know that!
Thanks. I thought those were micas so I will leave well alone. I did also notice the antenna was rather delicate so I was careful when removing it from the chassis.

I've ordered some heat resistant wire so once i've fixed that up I will power it up slowly and see if it comes to life at all. I cant see anything obviously wrong so here's hoping theres at least some life.
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Old 28th Jan 2021, 6:20 pm   #14
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Default Re: HMV 1115 General Advice

I have restored one of these including re painting the cabinet with colour match paint , one thing to look out for is to check both the output transformer and driver transformer ,for o/c windings. Mick.
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