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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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16th Sep 2017, 8:28 am | #21 |
Heptode
Join Date: Oct 2008
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Re: Audio use of the ECL80 valve.
ECL80 still attractive for DIY projects as late as 1984, see the attached.
Looks a lot like the Ferguson circuits Also, Funk Technik in 1952 had a ECL80 SE circuit with fixed bias and grounded cathodes. I believe I read somewhere doing this in Push-Pull is quite problematic because of instability. I imagine grid-stoppers and RF anode-chokes would improve matters if you want to go down that road. |
16th Sep 2017, 8:45 am | #22 |
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Re: Audio use of the ECL80 valve.
A bit off topic but Mullard did a design for a 12 volt portable oscilloscope using an ECL80 and a DH3_91 I have always considered it a very versatile little valve.
Cheers Mike T
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Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk Last edited by Cobaltblue; 16th Sep 2017 at 8:51 am. |
16th Sep 2017, 10:00 am | #23 |
Dekatron
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Location: Lynton, N. Devon, UK.
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Re: Audio use of the ECL80 valve.
I like G6tanuki's transmitter concept, and ParcGwyn's scope! Really uses the separate g3 pin constructively!
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22nd Mar 2018, 1:50 am | #24 |
Dekatron
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Alba portable mini radiogram with ECL80 output
I've had this Alba portable radiogram in for repair. There's no visible model number that I can see. The valve line up is ECL80, EBF89, ECH81, the latter had gone to air and needed replacement. The pickup arm was smashed in half with some of the plastic missing, so its owner had fitted the arm from a Fidelity. He'd fitted a Chinese black and red cartridge and soldered the wires directly onto the cartridge pins, which hadn't done it a lot of good! I've donated a BSRX5M as a replacement which the owner is at the moment using in another record player which I'll be given as part payment when the Alba is returned. I've also been given the rather nasty Fidelity HF.22 that the arm had been borrowed from and as many 78s as I can accommodate.
This chap had recently answered an add on Facebook for the free collection of thousands of 78s and it turned out that these three record players came with them (I don't 'do' Facebook myself). He wanted a working record player to go through them and play ones he wanted to keep for himself. He has a Hi-Fi system which obviously doesn't have the 78 speed and it would have been hard work on his 'wind-up' gramophone with changing needles and what with it also having a slipping spring. He told me I could help myself to as many 78s as I wanted and I took two boxes full when I collected the record player and he also let me have the Fidelity. I can't remember what the record player was that he's using the BSR X5M cartridge in, other than it's another rather nasty portable only slightly better refined than the Fidelity. None of the players had working cartridges as you would expect. He's not planning to keep many of the records and it looks like what I don't take will be dumped, so it's looking a bit like I'm going to be overwhelmed with records and will have a few happy hours playing them, as I think he's already got a bit fed up with going through them himself. There were other 'gifts' to tempt me to repair the radiogram including a very nice book on classic cars which also came with the records, a near mint copy of Pink Floyds Dark side of the Moon album and a set of three hand held radio transceivers on 173 MHz complete with charging stations - not that I've got an immediate use for these! I've repaired and filled the arm, although it really needs some colouring to match the plastic filler to the rest of the plastic. He says he's not bothered about this as long as it works. I've made a bit of a clip for the arm rest as it was missing on the original one. The grid coupling capacitor "That Cap" I identified as the RS 0.005uf replacement that can be seen in the first picture below - just below the volume on/off control. Being a 0.005 rather than a 0.0047, it would seem that this is quite an old repair and the fact that it's been soldered to the leads of the old one on the component side of the board indicates that the brittle tuning and volume knobs were stuck fast then, as they are now, so the board cannot be removed without possible breakage. This capacitor was good with no leakage and looks like a ceramic type? The HT was down to 26 volts and it was actually working at that and he was playing records on it with that part destroyed Chinese cartridge in the Fidelity arm. It even worked to an extent on radio when I replaced the broken ECH81 valve, however, once the selenium rectifier had been bypassed with a new diode and resistor, it worked much better. Those ECH81 valves were used in early car radios and worked at low HT voltages and the valve I fitted was a used 'pull', so was doing well. Having this player in for repair also gave me the opportunity to test a few of my spare ECL80 valves in the best way you can, and that is in an actual circuit. It showed that I had two duffs, one which developed a purple glow after about half a minute as the sound faded out and another with a few internal flash overs. So all in all an interesting trade. I've already got thousands of 78s and it looks like I may end up with a few more, so all good fun! The 78s that he still has are all in his car port and apparently the recent snow has blown in on some of the many hundreds that are left, although he says it hasn't harmed them. This is the same chap that I sold that radiogram to and then got all the innards back a few months later that I mentioned in another thread a while ago. I've done a few repairs for him over the last several years that usually involve interesting free gifts as payment rather than money, although he always askes me what he owes me, having already listed all the free gifts - I think he knows that I'm going to say that the 'goodies' will probably be payment enough Last edited by Station X; 22nd Mar 2018 at 9:29 am. Reason: Threads merged. |
22nd Mar 2018, 2:54 am | #25 |
Dekatron
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Re: Alba portable mini radiogram with ECL80 output
Ha-ha! Having said there's no model number that I could see, I've only just noticed that it says "SIX-0-SIX" on the tuning dial.
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22nd Mar 2018, 9:18 am | #26 |
Rest in Peace
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Re: Alba portable mini radiogram with ECL80 output
One small correction(nothing to do with the Alba as such) Hybrid car radios used the ECH83.. The ECH81 is, as I hope we all know, the standard AM radio F.C. valve of the 1950s/early 60s, operated at normal H.T. Voltage
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22nd Mar 2018, 1:17 pm | #27 |
Rest in Peace
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Re: Audio use of the ECL80 valve.
Many ECH83 were in fact selected ECH81, it is alleged.
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22nd Mar 2018, 2:53 pm | #28 |
Dekatron
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Re: Audio use of the ECL80 valve.
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22nd Mar 2018, 3:39 pm | #29 |
Dekatron
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Re: Audio use of the ECL80 valve.
Thanks for merging the threads, Graham.
That's correct about it being the ECH83 in car radios and it was the fact that it's thought that top performing ECH81 valves were labeled as ECH83 valves that was making me think they were used in these radios. Having said that, I'm sure I've come across an ECH81 being used in a car radio before now, probably in place of an ECH83. I'll have to go into the loft and check a valve car radio of that type now and see what valve it's using. The owner of this player wasn't really too bothered about whether the radio could be got working and he'd pointed out that there was a valve that had gone white and that the unit was still producing audio as regards records. I explained that the valve in question was connected to radio operation only, he then asked me why it stopped working as a record player when he pulled it out. I told him it was because it has a series heater chain and that pulling it out had interrupted the heaters for the other valves. I then had to tell him off as politely as I could about pulling valves out of live chassis equipment while stood on a concrete floor with it probably still connected to the supply. He hadn't appreciated the dangers of live chassis construction and I note that this one seems to use an auto wound transformer rather than a dropper. He'd also bypassed the pickup isolation when he swapped the arms and connected directly to the amplifier input as he thought it sounded a bit better like that. Not to worry too much I suppose, as that Fidelity doesn't seem to have any isolation whatsoever, with a length of single insulated un-colour coded twin lamp flex as the mains lead as original fitment. The Alba at least has a double insulated colour coded twin flex, although I did have to fit a 3 amp fuse in place of the original 13 amp MK one in the original fit vintage MK mains plug. The pickup has been wired back as original and I've told him it's up to him if he decides to change it back again and why it's wired as it is - I've fitted insulators on the cartridge tags. These things are what they are and will never meet modern standards. Another thing as regards the ECH81 valve, when he said he didn't want me to go to any expense getting the radio working, I told him that I'd got a valve that I'd removed from a radio some time back and replaced it as it had stopped oscillating on lower frequencies in that long wave had stopped working on the radio that it was removed from, so I would fit this valve and he'd have medium wave only. The funny thing was that after fitting this valve and leaving the radio on for an entire day, I switched to long wave and found it had started working with this valve, and it worked fine on long wave the next day when switched on. It seems the valve 'woke up' with use, perhaps a bit of cathode poisoning as regards the way the valve was used in the radio that it was originally fitted to that had VHF. This is also a classic example of putting a still partially working valve back in the box in case it comes in useful for something, only for someone to find it decades later and sell on to some poor unsuspecting person as NOS, as we all know happens all to frequently. Not in my case though, as I always write on the valve with felt tip pen what the fault is, as I had done in this case, and this particular valve has gone on to give further unexpected service. Now I see the model number of this Alba set, I see that there's an example on 'Radio Museum', before this I'd been searching for information on Alba portable radiograms and turned up nothing relating to this set. I can't believe I didn't spot that model number, perhaps it was the way it was written, I'd even taken a close look at the station markings to check that the stations (such as those that are left) were actually tuning in on roughly where they were supposed to be on the dial - can't see for looking, as the saying goes. I think that as this particular example of a radio/recordplayer has come to light using an ECL80 as an output valve, that there are likely to be others that are right under our noses that we just haven't thought about. The one on 'Radio Museum' had probably been there for quite a while with its valve line up listed, but no one had noticed it. Edit to say - better try to stick to the topic of just ECL80 valves used in audio output stages and not get too tied up with the ECH81/83, although as in this case, it does relate to this particular items circuitry. Last edited by Techman; 22nd Mar 2018 at 3:55 pm. |
22nd Mar 2018, 5:25 pm | #30 |
Heptode
Join Date: Jan 2008
Location: Sheffield, South Yorkshire, UK.
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Re: Audio use of the ECL80 valve.
Sounds like you could be given it back in a few months when he gets bored of playing the 78s!
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22nd Mar 2018, 6:42 pm | #31 |
Dekatron
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Re: Audio use of the ECL80 valve.
Looking at the photos of the radiogram, it really does look like the cheapest of the cheap in terms of design and features! I recognise the deck - motor left permanently running, just an idler disengagement to stop the turntable.
Its saving grace is that it probably gives a fair account of itself, and I'll bet the hours-pleasure-per-£ ratio is quite high! This sort of product, designed down to a price, do have a certain charm! |
23rd Mar 2018, 3:13 pm | #32 | |
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Re: Audio use of the ECL80 valve.
Quote:
As regards the deck, the Fidelity version has that arrangement with the motor running all the time with a neutral position on the speed selector and a tap off the motor windings for the valve heaters. However, although using 'nearly' the same deck, the Alba has no neutral position, but has a lever on the speed selector operating a switch that switches the motor off and disengages the deck when switched to radio. The motor still has the tapping that would be used for valve heaters in a different model type, but the wire is just left dangling - as usual. I've added heat shrink to the end of the wire for added safety should the original insulation ever shrink back with age and expose the inner conductor. The input impedance of the cartridge connection seems a little low for your average crystal cartridge, even with the original fit series 470K resistor on the tag strip (one of the items previously bypassed by the owner). I've disconnected one end of this resistor, leaving it still in place for future use if necessary and fitted a 1M resistor in series with the cartridge connection. I'll tell the owner that he has three choices of no resistor, half a meg or one meg, depending on whether he wants loud and no bass, or not so load with marginally better sound. He can lift the end of the 1M resistor and re-solder the 470K or go directly to the input, so long as he doesn't bypass the capacitor on the ground side (like he did before). I was very surprised to see this record player used an ECL80 as an audio amplifier and output, as I was used to them being usually used in old TVs. I had been following this thread when it was originally opened and was wondering how many examples of the audio output use of the ECL80 would turn up - and it looks like not very many so far, although this Alba had been waiting in the wings to be discovered, plus having an example already on Radiomuseum. |
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1st May 2018, 1:40 am | #33 |
Dekatron
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Re: Audio use of the ECL80 valve.
You were right, I got it back yesterday as a gift for helping him out with an odd fault on a radio transceiver. That's just over a month. I also got a few other electronic bits and pieces and a few more records
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