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what really happened during the late 70s early 80s in the hifi press

I keep an eye ope for a pair of ESL63s or later versions, but never see them in Malaysia. Tropical humidity seems to be incompatible. I see plenty of the amplifiers still in circulation.
I don’t know how anyone tolerates the miserable and oppressive humidity levels in Malaysia.
 
If you look back at that period you can see various other perhaps good UK items that appeared and then vanished again. Quite possibly for much the same reasons. It's impossible to quantify the damage it did to UK hifi design and making.
I have never seen an Armstrong in the flesh, which is odd. I have seen many old Quads, Sugdens, A60s etc

Every so often the press would latch onto a new kid on the block, NAD3020, Videoton Minimax (though Hungarian).
These were competent products, but not really the giant killers we were lead to believe at the time.
 
I don’t know how anyone tolerates the miserable and oppressive humidity levels in Malaysia.
It can be a nuisance for clothing, shoes and glue, but it has held off my arthritis for more than 20 years. I used to live next to the River Kennet and that could be miserable on a January morning with freezing fog.
 
I have never seen an Armstrong in the flesh, which is odd. I have seen many old Quads, Sugdens, A60s etc

Do you mean a 600? If so, quite suprising as there were many dealers and they exhibited at many shows during the 60s and into 70s. That tailed off towards when the factory closed, though.

Not surprising if you've never seen the 730/732. Only around 40 pairs were made.
 
Sounds like someone got two base pans swopped over!

Do you have the info on how to pop the lid and undo the plastic base pan?

I was rather wondering if it could have been a factory error or not!?

I've worked on several before so yes I know how to get the lid off.... Has to be the easiest access on any amp ever!

Have one plastic Dzus fastener missing on the bottom.

Most recent date is sept 77 on output caps so assuming 78 for year of manufacture. It has the Alps pots but the RCA decoder IC (I presume the TI decoder is not a pin compatible exchange?).

Smoothing cap and output caps are well dodgy looking and have blebed up rather with slight leakage... as usual they still work though! First try out, through headphones, and apparently the first time it's been powered up in 25 years, showed this it kinda works after a fashion.... vol control very noisy and only got output (on FM with a few foot of wire as a test aerial) on one channel but crackles from vol control present on both channels so it looks like the power amps work anyway. It seemed rather deaf even for just a few foot of wire as an aerial.

All I've done so far is give all the pots and switches a good squirt of contact cleaner and a thorough work out but I didn't give it another go after that.

Were encapsulated bridge rectifiers fitted to the last ones? I vaguely remember one with a bright green bridge fitted to the chassis around the power amp board area...

They are a typically British mix of "great!" and "what were they thinking?" in one unit.... For the time, impressive industrial design and styling.... but all sorts of femur aspects and obvious afterthought bodges as well!

Things like a single thin wire as the speaker earth return shared by left and right and speakers 1 and 2 are not good but easily modified.

plans after some more thought are now to not go as far as redesigning the power amp and going fully complementary etc but to re-cap it, including making the smoothing cap something like 15000uF as it should be about the same size as the original 7500uF item. Replace the leaky output caps but with standard value (4700uF anyway as 4000uF non standard today) to keep the clever "tuned damping factor" feature and find a way of mounting the new output caps as they will be a fraction of the size of the originals, then re-align the tuner section (which looks easy... famous last words! Only IF can on front end and discriminator can as Denco coils so not much to go wrong... plus front end itself of course... which has a coil in it with the ferrite core almost entirely unscrewed which looks a bit suspect!).
I'll also put right anything which is just not good engineering practice, ie the single shared earth for the speakers, and hopefully end up with a somewhat better than brand new one. May need to get another "spares or repairs" donor unit as the centre tune meter is buggered so I'll prob need to get another 625/6 just for a tuning meter!

I'd quite like a 626 for the novel and sophisticated AM section, even though I'm not likely to ever listen to AM!

I'm surprised we do not see more interest and demand for this British classic TBH. I love the styling, the features are well thought out, it's pretty powerful for the time (actually about 50WPC I believe), they were well reviewed, and I was impressed with the performance of a mates 625 which he had for years after he got it second hand in about 1984 ish and partnered it with B & W DM4 speakers. Excellent FM tuner performance from memory and amp to rival the likes of A & R A60 and similar in many ways.

oh, LOVE the styling of the 400 series! The pinky/purple circular FM tuning dial and all that! Power amp design looks rather dodgy though....
 
The Alps pots sound like it is from the era when I'd been fiddling with it. Does it have a thermal delay? Probably not if from when I worked on it as I dumpted that early on. If it does, replace the delay with a wire and uprate the diodes to cope with the surge. But I can't recall if they were individuals or a bridge in one pack. The peak and sustained powers did go up a bit as things got changed. But it mainly comes out for low impedance loads and allowing hotter heatsinks without thermal runaway. Alas, no getting away from the fact that the heatsinks are more R2/3 than R1!

I think the decoder pinouts were different. The TI one also had Toko MPX filters with their outer case removed as there wasn't enough space without that! I think I have some photos of the TI MPX but no diagrams.

If it is still denco coils, then not one of the later versions.
 
In the early '80s I bought an LP12 and never had it serviced until a few months ago.
It never had feedback issues as far as I ever noticed.

Interestingly, when returned from service its resistance to feedback was slightly worse I thought.
The engineer told me that the new springs, etc. would settle down.

Conversely, my very old AR XA which I’d cleaned and serviced, still passed the ‘hammer and wood block’
test.
 
The Alps pots sound like it is from the era when I'd been fiddling with it. Does it have a thermal delay? Probably not if from when I worked on it as I dumpted that early on. If it does, replace the delay with a wire and uprate the diodes to cope with the surge. But I can't recall if they were individuals or a bridge in one pack. The peak and sustained powers did go up a bit as things got changed. But it mainly comes out for low impedance loads and allowing hotter heatsinks without thermal runaway. Alas, no getting away from the fact that the heatsinks are more R2/3 than R1!

I think the decoder pinouts were different. The TI one also had Toko MPX filters with their outer case removed as there wasn't enough space without that! I think I have some photos of the TI MPX but no diagrams.

If it is still denco coils, then not one of the later versions.

It has the thermal delay yes (it even still works!) and removing it plus fitting bigger rectifiers were already on the to do list! They are separate diodes on the regulator board here but as I said I vaguely remember seeing one with a bridge.... which may have been fitted by an owner or repairer at a later date. The thermal delay on this one failed after a couple of months and I bypassed it. It worked reliably for many years after this in my mates system.
One of the factory bodges is apparent on the regulator board with the mounting of the series pass transistor.... which was no longer mounted! The fishie I bought it from had thoughtfully sellotaped the mica insulator, metal block and nylon nut to the innards. Although the reg still works fine I'll replace the pass transistor and make up a better arrangement to heatsink the transistor. Oh yeah! While at that board... what the hell is the thing that looks like the eraser on a pencil but dark grey/black and with no markings that's on that board?

It has a Japanese MPX filter on a small SRBP board piggybacked on the decoder board.

heatsinks are indeed inadequate but no more so than on many many other amps, A & R A60 being one of them, and better than some... My mate used to sometimes play his loud and it never shut down or complained.
 
Dunno about the 'eraser' as my visual memory is poor. Does the unit have the TI decoder chip? I don't have any photos that I can find of the track-side of it's board but I think it was essentially the standard circuit they gave with the added Toko filter and a dropper resistor for the power rail. Had a small amp stage alongside it.

I once used a 626 at full belt all evening at a party we had to celebrate the 'Last Night of the Proms'. Used 602 speakers.

Because of the heatsinks I used the amp on a shelf with its lid removed. 8-] Warned people NOT to try standing their drink on it, or pouring any into the set as it would end hearing the music! :) It played loud all night, just got hot. I think that was the last year I lived in London.
 
The 'piggybacked' board for the filter is just the base of the filter unit as it came. Normally it would be enclosed with the top cover - which we removed so it would fit!
 
Dunno about the 'eraser' as my visual memory is poor. Does the unit have the TI decoder chip? I don't have any photos that I can find of the track-side of it's board but I think it was essentially the standard circuit they gave with the added Toko filter and a dropper resistor for the power rail. Had a small amp stage alongside it.

I once used a 626 at full belt all evening at a party we had to celebrate the 'Last Night of the Proms'. Used 602 speakers.

Because of the heatsinks I used the amp on a shelf with its lid removed. 8-] Warned people NOT to try standing their drink on it, or pouring any into the set as it would end hearing the music! :) It played loud all night, just got hot. I think that was the last year I lived in London.

The 'piggybacked' board for the filter is just the base of the filter unit as it came. Normally it would be enclosed with the top cover - which we removed so it would fit!

No it has the RCA CA3090AQ decoder. The MPX filter has two blue cores and two red cores if that jogs the memory any...

I could see no sign of thermal compound on the OPT's and certainly non on the reg pass transistor... maybe just not enough to squeeze any out the sides and be visible... the mounting of the OPT's with self tappers into plastic TO3 holders does not inspire confidence either...
 
Just an even more uncomfortable pair of headphones as far as I’m concerned! The quality can be truly superb, but the presentation of music inside your head never becomes natural no matter how clean, detailed and accurate it is from a distortion/response perspective. I can never relax with headphones long-term and I’ve never found any IEMs that don’t actually hurt!

Not for everyone; but having reviewed maybe 20-30 different earphones in the last year or two I feel much more positive about them. A good fit is essential and everyone has different ears so that is a problem. But when the fit is right and the earphones are high quality they can sound excellent and do solve a lot of problems, no room effects to worry about.

Tim
 
But when the fit is right and the earphones are high quality they can sound excellent and do solve a lot of problems, no room effects to worry about.

I seem to have narrow ear canals so find IEMs very uncomfortable, as I do ear-plugs for gigs (though I always use them, albeit a small size). I like headphones though and consider my HD-600s a reference when setting a system up etc. The only headphones I’ve ever owned I’d actually rate as comfortable are the old HD-414s from the 70s with the yellow foams. So light and so little clamping, yet they stay in place fine. I wish there was a reference-grade headphone that comfortable!
 
No it has the RCA CA3090AQ decoder. The MPX filter has two blue cores and two red cores if that jogs the memory any...

I could see no sign of thermal compound on the OPT's and certainly non on the reg pass transistor... maybe just not enough to squeeze any out the sides and be visible... the mounting of the OPT's with self tappers into plastic TO3 holders does not inspire confidence either...

This shows the topside of the L15 decoder board. Annoyingly, I don't have a photo of the track side, nor a diagram! Wish I had. However I think it was essentially what was on the TI datasheets.

http://jcgl.orpheusweb.co.uk/temp/L15pic.jpeg

I can't recall when, but I think some 600s used some soft 'plastic washers' that took the place of mica insulators + heatsink compound. The idea being that they were soft enough to act as both. The were opaque. But I have no idea how they might have aged over this many decades!
 
WRT the 400 range. The problem was that the finish for the fascia tended to be quite uneven, so in the shop or on show looked cheap and tatty. Not easy to sell, particularly to a skeptical spouse! In essence the 500 was a rebranded 400 and sold like hot cakes.

Personally, I think the 600 range was one of the best styled audio units ever designed and sold. Can say that because I had nothing to do with the external design. The snag was the impact on transformer and heatsink sizes. And led Ted to put the output devices well out of thermal contact with what drove them. Shame heatpipes weren't around when it was developed.
 
It can be a nuisance for clothing, shoes and glue, but it has held off my arthritis for more than 20 years.
Records go mouldy in high humidity. Loudspeaker foam surrounds rot in record time. Class-A amps? Just don't go there.
 


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