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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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18th Apr 2018, 4:34 pm | #1 |
Dekatron
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Homemade record player
I've just come back from an auction with an interesting job lot including the record player in question, Sharp music centre, old school portable typewriter, a VERY sticky Ferguson tape recorder and a load of records.
I've not had a proper look at any of it yet, but it was the homemade record player that I wanted. I was the only bidder, so all's good on that front. It'll be interesting to see what's inside, as the control panel is labeled as Elpico AC15 which sounds as if a small early sixties guitar amplifier has been used as the electronics, but we'll see when we open it up. I was surprised when I just did a very quick internet search for the Elpico AC15 and found nothing about it, but it was a VERY quick search, although I'm sure I've read about them before in the distant past somewhere on the net. It looks like someone has gone to a lot of trouble to make this unit in the long past. The usual mains lead has been cut off (strangely it wasn't cut off on the Sharp), the platter mat on the Garrard TA MK11 is good, but the centre circlip is missing (as usual), I always seem to end up having to make replacement platter clips for these single players! Pictures so far - below:- |
18th Apr 2018, 4:55 pm | #2 |
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Re: Homemade record player
Elpico made a lot of small amps and complete record players. The amp may have a high gain if it was a made as a Guitar amp - so do check that (stereo compatible) Acos cartridge is a GP91-1SC or 2SC as the GP91-3SC is liable to overload it. That might explain the resistor fitted into the head.
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18th Apr 2018, 5:23 pm | #3 |
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Re: Homemade record player
I've opened it up. The deck is solid and will need the usual servicing and the inside of the case is full of fluff etc., so I will now take it outside for a good 'blow out' with the air blower to get rid of it all.
Nice little amplifier:- |
18th Apr 2018, 5:30 pm | #4 | |
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Re: Homemade record player
Quote:
There's actually two resistors in the head shell, one in series and one in parallel. |
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18th Apr 2018, 5:42 pm | #5 |
Hexode
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Re: Homemade record player
The last one of these record players that I repaired was at the local county school, they had one in each class room. Plenty of good sound, I think that it was a copy of the Mullard 10-12W amp.
Bob
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18th Apr 2018, 5:44 pm | #6 |
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Re: Homemade record player
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18th Apr 2018, 6:48 pm | #7 |
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Re: Homemade record player
And you may well be right. I'm guessing from the size of the valves and the OPTX this is a 2 x ECL82 + EZ80 amp. Six watts in PP and a nice sized, large magnet speaker. Should sound really good.
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18th Apr 2018, 7:41 pm | #8 |
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Re: Homemade record player
The wooden case just looks as if it's just been treated with a single coat of wood stain. It could be a single coat of varnish stain that's soaked right into the wood. The light colour on the inside of the lid and where the deck sits is bare wood and has never been treated with anything, so definitely homebrew, but never completely finished.
I've removed the amplifier for service and given it a clean, but no other testing has been performed as yet. It'll need at least a couple of capacitors replacing. The valves are ECC83, EL84, EZ80 and probably based on the Mullard 3-3 amplifier design. Two out of the three knobs have broken on removal, so will need the glue - the plastic has gone VERY brittle with age. Some more pictures below:- |
18th Apr 2018, 7:57 pm | #9 |
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Re: Homemade record player
Actually, I've changed my mind about it being a Mullard 3-3 type amplifier as it uses an ECC83 rather than an EF86.
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18th Apr 2018, 8:00 pm | #10 |
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Re: Homemade record player
Given that the amp, has a socket marjed "gram motor" I guess it was designed for this duty rather than being a guitar amp. In your amp, I see some of the dreaded Hunts, and a couple of those Plessey electrolytics with red-and-black ends and a yellow printed band giving the ratings.
It's *always* time to replace these! |
18th Apr 2018, 8:04 pm | #11 |
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Re: Homemade record player
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18th Apr 2018, 8:09 pm | #12 |
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Re: Homemade record player
Anyone else spotted the 100K 2 watt resistor with a salmon pink band...indicates high stability. Haven't seen one of them used for many years although I do have one in my resistor box. I wonder where it is used in the circuit?
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18th Apr 2018, 8:22 pm | #13 |
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Re: Homemade record player
Those two 100k resistors (pink band) look as though they're the anode loads for the ECC83 so far as I can make out.
Lawrence. |
18th Apr 2018, 8:56 pm | #14 |
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Re: Homemade record player
Yes, I can confirm they are the two anode loads for the ECC83 and the two associated 0.1uf 400 volt black hunts, both 100k being returned to HT via the 47k. I think I may also have some of those pink banded types like the ones in the amp in my (old) spares stock.
Clarke & Smith was exactly what I first thought when I saw it until I realised it was a homebrew. |
18th Apr 2018, 9:08 pm | #15 |
Heptode
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Re: Homemade record player
Well the knotted mains lead is original - see pictures of new unit:-
http://www.vintagehofner.co.uk/brita.../elpico21.html
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18th Apr 2018, 10:14 pm | #16 |
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Re: Homemade record player
Thanks for that link. I think that's the web page that I remember reading a few years ago that I mentioned previously, but didn't seem to come up when I did a quick search.
It's strange that they use the model number AC15, as you would think from that it would be twin EL84s in push pull, but probably thinking of a Vox AC15. I've already got an Elpico tape recorder from the same sort of date as this amp. |
18th Apr 2018, 11:54 pm | #17 |
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Re: Homemade record player
There are two 68K pink band resistors as anode and cathode loads in the phase splitters in the mono blocks I use as a front room stereo.
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19th Apr 2018, 9:17 am | #18 |
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Re: Homemade record player
It looks quite like a schools record player.
http://viyoutube.com/video/eQ4mTFLXt...ecord%20player Peter |
19th Apr 2018, 2:59 pm | #19 |
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Re: Homemade record player
I get the impression that there's a thought that this could be a Clarke & Smith schools player, but would they really have made something so 'unfinished'?
The one in the previous link looks to have quite a basic cabinet finish, but it does seem to have some sort of colouring to all the exposed woodwork and also has name plates attached. It's a bit similar to the Grampian that some of you may remember, that I worked on a year or so back. The Grampian had major design faults, one of which was a severe lack of cabinet ventilation. Particularly there was no lid rear ventilation which is the same as with the one we're looking at now, the one in the video linked to in the previous post does have the rear lid ventilation. The ventilation to the rest of the cabinet in this particular player is good, though. It may well be that a school teacher decided that it would be a good project to make a copy of a 'schools' record player for use in the school. A woodworking student could have been tasked with making the cabinet and the electrical bits were bought in and the whole lot assembled in the science lab. This is just a thought and it's something that certainly wouldn't be allowed today. I gave the amplifier full mains in several short, sharp shots, the way I always do, letting the HT rise a bit at a time while monitoring its rise and fall as it dies away between switch on and offs. I didn't give it very long as there's over a volt positive on the grid of the EL84, likely to be mainly due to leakage in one of those black Hunts. The HT is rather high for the rating of some of the components with almost 400 volts on the reservoir and something over 350 volts on the first smoother (these voltages were taken quickly yesterday and are from memory). These two capacitors are the 50-50uf two in one can which is rated at 425 surge and 350 volt normal working, however, it's dated Sep 1960 so it's stood up to it for a while while it was in use and seems to be still good. I wondered whether the HT wasn't being fully loaded, so took some other quick readings around the EL84. There was (from memory) just over 350 volts on the anode and 370 volts on the screen. There was around 13 volts on the cathode and the 220 ohm cathode resistor had risen in value to 257 ohms, which is a significant rise for a component of this value in this position. This equates to around 50mA of current so is very close to what would normally be expected and even with that higher cathode resistor value, the leaky grid coupler will be over compensating for that, so the loading on the HT looks normal. There won't be anything significantly wrong in any preceding stages that could lessen HT loading, so it looks like this is just how it is. I wondered whether the mains transformer was wound for a slightly lower mains voltage. There's no tapping adjustment, but a check on the heater voltage found this voltage to be correct, so that ruled out that one. The amplifier seems to have loads of gain and seems to be designed to run the significant components at their maximum ratings, so it should pack quite a punch for what it is - any thoughts? |
19th Apr 2018, 3:21 pm | #20 |
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Re: Homemade record player
Given both stages of the ECC83 are in use, there should be ample gain and enough for a ressonable degree of NFB.
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