4th Dec 2020, 7:22 pm | #21 | |
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Re: Armstrong 600 series tuners and receivers
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4th Dec 2020, 7:38 pm | #22 |
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Re: Armstrong 600 series tuners and receivers
It was not a good time to be in the hifi business, when your produce became judged on parameters you could not measure objectively and you could not yourself discern, and you didn't even believe in. The fickleness of fashion.
A colleague had Armstrong 600 series tuner and amplifier. They worked well for him and sounded OK. He was quite keen on having equipment he liked (Hydraulic reference, SME 3009, V15 and Leak 2075 speakers) The little Armstrong looked a bit small. The circuitry I saw of the 700 series made it a shame that it didn't make it as a product. But I understand their feelings. My amplifier is something I would not have chosen to throw into the bearpit that the hifi world was becoming at that time. A small run of them was made at HP and that's been it. It sits there in the lounge and just works. I'm happy with it.... It does also contribute one extra bit of entertainment - whenever an audio aficionado meets it, it's hilarious to watch them completely sieze-up. There are no badges, it's not recognisable. It's obviously special and very professional, and the poor souls haven't a clue what they are supposed to say about it. They daren't say what they hear because they might say the wrong thing and be found out at a later date. But Armstrong came from being a radiogram chassis firm and their earlier amplifiers were not much removed, but with the 600 series, they had made a big jump in what they produced, and you have to respect that. David
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4th Dec 2020, 11:23 pm | #23 |
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Re: Armstrong 600 series tuners and receivers
Agree, no better or worse than other British amplifiers at the time. They all seemed to use the same resistors, Iskra carbon film I believe, and many used miniature Hunts green sleeved capacitors. They could be a problem in that the leads seemed to part company with the body a bit too easily. Certainly sold well as they were different styling to most other products. Usually reliable but the output capacitors seemed to suffer mainly.
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5th Dec 2020, 9:09 am | #24 | |
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Re: Armstrong 600 series tuners and receivers
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5th Dec 2020, 10:36 am | #25 |
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Re: Armstrong 600 series tuners and receivers
Output coupling capacitors generate some distortion even when in perfect condition - see Self for the details - and a leaking cap isn't going to improve matters, particularly in the matter of bass distortion as its capacitance will have decreased - and distortion products can easily have a subjective effect on treble clarity. So I wouldn't say that was audiophoolery, especially as measurements would have confirmed what was going on.
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5th Dec 2020, 11:05 am | #26 |
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Re: Armstrong 600 series tuners and receivers
Reduced ESR, so reduced output impedance.
David
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5th Dec 2020, 11:11 am | #27 | |
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Re: Armstrong 600 series tuners and receivers
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5th Dec 2020, 12:59 pm | #28 |
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Re: Armstrong 600 series tuners and receivers
The Armstrong do in fact include the output capacitor in the feedback loop so in some respects it effects are mitigated
But lets be honest these are getting on for 40 years old not unreasonable to replace at this time I feel Trev |
5th Dec 2020, 2:15 pm | #29 |
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Re: Armstrong 600 series tuners and receivers
Given that the 626 had a long life span in the shops, there are/were quite a few variants of data and schematics over that time. I have a service information document that says set quiescent current to 5mA. I have a schematic that says 20mA. What to do? 10mA?! Oh, the documents aren't dated, plus circuit changes were made as I say above.
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7th Dec 2020, 7:30 pm | #30 |
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Re: Armstrong 600 series tuners and receivers
Having changed the two output caps, I've just done the main smoother too. In all cases the new caps were at least half the size of the originals. This has never been a problem to me, a joy in fact (more space to work in!), I've never seen the point of stuffing caps on a piece of 70s or 80s hifi. The two speaker caps were 30mm diameter as opposed to 45, so I used 35mm cap mounting clips and filled in the gap with a short length of plastic plumbing pipe. I filed semicircular slots into the sides of the original caps chassis holes to accommodate the mounting nuts and bolts. The originals were a push fit into clips. The main smoother simply tie wraps onto the side of the chassis so no issues there. Before and after photos below. Incidentally, I did these repairs on separate days and in both cases the sound and general performance was improved.
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7th Dec 2020, 7:45 pm | #31 |
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Re: Armstrong 600 series tuners and receivers
Good piece of work !These units deserve to be maintained they were at the time medium high end I do rather get fed up of people knocking British audio Armstrong always strived for quality Dealing with the factory was never less than a pleasure they were always helpful re service tec.
I also liked the earlier 400/ 500 series very innovative Trev |
7th Dec 2020, 8:23 pm | #32 |
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Re: Armstrong 600 series tuners and receivers
Now on to the next fault. AM does not work, no rushing, tuning noises, nothing. But not quite.. if I turn the volume up FULL, the set sits there vibrating like an expectant spaceship seconds before take off (actually that's just a bit of theatre added for interest), I can just about, at less than a gnat's whisper volume, tune in to and 'hear' Radio 5 live (my strongest MW channel), though I cannot hear what they're saying it's so quiet. Strangely, this through one speaker only, and the other speaker sounds like it would with an unused line level input selected but with the volume up full ie amp noise. Interestingly, there's no AM noise, no tuner noise. This suggests to me that the tuner and agc are working but further down the line the signal level is being lost. FM works fine.
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8th Dec 2020, 9:09 pm | #33 |
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Re: Armstrong 600 series tuners and receivers
EI can remember as a 19 year old looking into a 626 receiver taking the lid off and gazing into the works! All modular construction gone were the unreliable connectors of the 400/500 series I could see how all was built as sub assemblies looking at the schematic with its enhanced VAS stage I really felt I was looking into the future
Build quality seemed to be good and the deign was brilliant the slim looking design was a master of subterfuge I sold as many as we could get Trev |
8th Dec 2020, 9:25 pm | #34 |
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Re: Armstrong 600 series tuners and receivers
Any ideas about the AM fault?
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8th Dec 2020, 10:04 pm | #35 |
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Re: Armstrong 600 series tuners and receivers
look at the diode logic switching you can use a scope or signal tracer to see if it has Am output I leaky capacitor may be the problem
Trev |
8th Dec 2020, 10:07 pm | #36 |
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Re: Armstrong 600 series tuners and receivers
Thanks Trevor. Which board is that?
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8th Dec 2020, 10:10 pm | #37 |
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Re: Armstrong 600 series tuners and receivers
If you look at this site under Armstrong
http://ukhhsoc.torrens.org/AudioDocs.html you will find the full schematic and this shows the board top left hand side Trev |
8th Dec 2020, 10:14 pm | #38 | |
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Re: Armstrong 600 series tuners and receivers
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9th Dec 2020, 7:20 pm | #39 |
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Re: Armstrong 600 series tuners and receivers
the diode logic switching board is the one with the din inputs on it below the chasis
Trev |
9th Dec 2020, 7:45 pm | #40 |
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Re: Armstrong 600 series tuners and receivers
Are there separate switches for AM & FM? If not it would suggest that the AM only fault is further back
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