Eddystone 888A: Turn it OFF, or leave it ON?

[carnivalpete]

This morning I was reading an interesting short article (Rob Mannion, PW, 2003) on the Eddystone S750 and he said he never turned it OFF unless he was doing something important, like moving house! It set me wondering. My son is seriously into computing rather than radio but also never turns his home or work computers OFF. I realise what is going on here and I have heard many people talk about the stresses involved in powering up and shutting down but I wonder if there is any consensus on this, especially with scarce vintage equipment. I always turn everything OFF when I've finished using it. What do others do? pete

[n_r_muir]

HI,

I switch things on and off as required, mainly to avoid using (and paying for) even more electricity than is actually required.

Not switching valves on and off does improve the overall reliability of the equipment; this was well demonstrated during WW2 by the Colossus code breaking machines. These used about 2500 valves and were run continuously. The mean time between failures was much longer than expected from an equivalent number of valves used in equipments that were switched on & off as required.

[HamishBoxer]

I certainly would not leave vintage gear running 24/7 in case of any major failure and or a fire.
Re computers I used to run mine 24/7 but they do need a restart from time to time. Now it's on from 0900 to 2200 aprox each day.

[G6Tanuki]

The only benefit I can think of from leaving a communications-receiver always on would be reducing thermal drift in the oscillators. I have memories somewhere of a recommendation to fit a small [15-watt] pygmy-type 240V bulb in the LO compartment of your radio if you had an unheated or outdoor 'shack': when you weren't using the radio you turned the bulb on to provide a bit of background heat to the LO components.

Me? I switch things on and off as needed. If power-cycling causes components to fail then I'd rather know about it and fix it ! A few resistors/capacitors over the years are cheap compared with paying to keep 100 Watts or more of radio on 24x7.

[paulsherwin]

Most electronic equipment is better kept running permanently, both valve and transistor. However, this is impractical in a domestic environment with electricity bills to pay, especially with valve stuff. The only equipment I run all the time is the ADSL router.

[mark pirate]

Actually there are many things in this house that run 24/7. 4 cordless phones, broadband router, wi-fi extender, 3 PVR's and two TV's are kept on standby.
Add a chest freezer, a fridge/freezer and two mains powered clocks!

It is quite shocking to see how many electricals are left running 24 hours a day in the average home, I even have two laptops that are left in standby.
But I would never leave anything valve powered running if I was not actually using it

I have actually found that it is more likely that modern equipment will fall victim to thermal stress rather than vintage gear, switched mode power supplies being high on the list.

Mark

[g4aaw pete]

Hello Pete

I would say turn it off when not in use.
If the mains transformer develops a fault & goes into melt down, it would be preferable it be there to switch it off.

Yes, the heater in-rush current at switch on will shorten the life of the valves, but replacements are plentiful.

Just a few half-baked theories from me.

Regards
Pete

[emeritus]

The data sheet of an early Texas Instruments "audio amplifier on a chip" ICs that I used in the 1970's specified the life as so many switch power on/off operations rather than so many hours use.

[Skywave]

The Eddystone 888A (and its companion, the 750) have a lot of components crammed into a case / chassis that is simply too small. Not only does that make maintenance difficult, but it also means that the under-chassis heat will not be readily removed to outside the case. That, in turn, will accelerate the demise of various passive components. So on that basis, my recommendation is to switch it off when not in use.
Finally - FWIW - on my 888A, I have relocated a few power resistors that do get hot to above the chassis.

Al.

[turretslug]

It seems that some 750s were supplied for coastal station use (particularly in Marconi HR101 guise) as watch receivers and it's likely that these would have been left on continuously- but "someone else" was picking up the electricity and maintenance bills. It's all a question of balance for a particular usage as to whether it's left on continuously- then, listening out for mariners or aviators had precedence over other considerations, in a domestic situation leaving an elderly, quite hot-running, 80W-consuming receiver on 24/7 would be pointless. That's about 2kWH a day. An additional argument against continuous powering is the consideration that valves that have considerable emission demanded of them (in this case the 5Z4 rectifier and N78 output) are likely to become weary this way over time, working against the surge-reduction case.

The 750/888 are good examples of Eddystone neat packaging and mechanical construction, making for an easily accommodated unit, but perhaps just too closely-packed and cheek-by-jowl inside. There's a bit of a "crisis corner" where mains transformer, smoothing choke and BFO valve all nestle closely up to each other- I stuck an easily available "hedgehog" processor heatsink to the top of the choke's brass can for a bit of cooling (easily removable should originality demand it). Diagonally opposite on the chassis, the N78's B7g socket mounting hole was punched out to 3/4", taking care to centre it between the existing mounting holes, and the holder raised on 1/8" spacers, thus the hot-running valve draws air up through the annular slot from beneath the chassis. Not reversible but it was a weak spot anyway. It's odd that Eddystone didn't put louvres in the bottom of the case, I haven't done so myself but a slice of 4U panel was screwed to the 2BA threaded bushes, this being fitted with 15mm high feet- the domes pressed into the case are pretty hopeless for allowing ventilation underneath.

There are a few misconceptions that have slipped through that in that PW article regarding the functions of V2, V3 and V4- V2 is used as an externally-fed hexode mixer, not as a mixer/oscillator. V3 is the local oscillator but it certainly doesn't run at 85kHz!. V4 is used as a mixer/oscillator, not as plain mixer in the way of V2.

[Skywave]

If you study the evolution of Eddystone comms. radios, you can see that the circuitry, cabinet size and the general construction is traceable back to their early sets, (even if those did have 'half-moon' dials) long before the 888A was born. Those early sets had far less within the cabinet, so in the best traditions of engineering*, when a new model was under design, the temptation to use parts of existing designs was simply too great to resist. It's always seemed to me that Eddystone reached the limit of just how much could be crammed into that case with the 888A. When later receivers came along - such as the 940 and the EA12 - a much larger cabinet was designed.

* Which I do realize is a highly contentious viewpoint.

Al.

[turretslug]

Indeed- the 750 comes across as very much an extensive re-visit of the 640, taking advantage of miniature valves to help squeeze in additional measures in the same volume to overcome its shortcomings. A separate LO valve and the inevitable additional HT burden of the shunt stabiliser bumps up the internal heat. Also, the 6BA6s that replaced the EF39s represent another 0.1A each of heater current and the N78 draws 0.2A more than the 6V6- each of these factors being small increments but adding up to appreciable extra heat.

I'm impressed that the 888 and -A successor squeezed 6 wavebands into the coil-box- it's not as if there's bags of room for 4 coils and associated trimmers in each of the 750's coil-box sections. Shame that the 5th, "Gram", position of the 750 bandswitch wasn't used for a 5th waveband- either LW, or to split the 12-32MHz band into two sections.

[Skywave]

Originally Posted by turretslug

Shame that the 5th, "Gram", position of the 750 band-switch wasn't used for a 5th waveband- either LW, or to split the 12-32MHz band into two sections.

But if the 12-32 Mc/s band had been so split, that would have required a larger under-chassis coil box - and there simply isn't the room for that. And that takes us back to where we were: a quart crammed into a pint pot. Nevertheless, splitting that band would have made tuning at the H.F. end of that band a lot easier, since despite Eddystone's excellent reduction drives, with all their traditionally-designed general coverage sets tuning above 20 Mc/s (or thereabouts) is always a tricky 'fine tuning' operation.

Al.

[Wendymott]

Being a Yorkshire person, being known for "thrift", my ultimate consideration is power useage, living is expensive enough without keeping my 750 and 770 on continuously. I fitted a computer PSU fan into the 750 above the mains transformer, which helps stability over the time required for use. The 770 is not used so much so no such mod was required. Also I concur with the feeling that if a fault occurred I would like to be within easy reach to attend.

[Andrew2]

Back in the late 60's, we had a customer who never switched his Bush telly off because he didn't know how to. This only came to light when he called us out for the very first time when the set was about 8 years old!

Our Freesat receiver ran faultlessly for 3 years until I unplugged it to go on holiday. When it was plugged back in it refused to start up. Duff electrolytics in the PSU. It probably would have carried on working if I hadn't powered it down.

[carnivalpete]

Surprising how much interesting stuff comes up on here when someone poses a simple query. Just shows the amazingly wide experience of the contributors. Until the comments stirred my muddled mind I hadn't realised just how many things in my home actually do stay powered up or on standby all the time - I make it 15 bits of gear! Seems the consensus view here edges towards leaving modern electronics ON if it suits your circumstances but turn vintage valve gear OFF in case something serious goes wrong. The thought that a simmering 888A could dangerously overheat in the event of a fault is what causes me to turn it OFF when I cannot watch it. If start-up stresses take out an occasional component I can live with that. This 888A is my third, and I got 25yrs out of my first one before I sold it on and it never suffered a single fault. It hadn't occured to me to fit additional heat sinks or fans but I have often left the lid open as I have heard others sometimes do. GL all, pete

[G6Tanuki]

Truth is, post-WWII Eddystone were caught in a quandary: were they in the "clipper-class" prestige ship-cruse radio-cabin market [which demanded fruitily-syllabic and loud audio hence push-pull output stages but whose costs could be reclaimed against tax if you were Cunard or White Funnel Line fitting-out your liner], the amateur sector [good LO stability and IF selectivity and image-rejection which meant dual-conversion and the likes of the 888], 'consumer' grade stuff like the 840 whose design-criteria were often driven by the purchase-tax classifications of the era [does it have a BFO? in which case it's a purchase-tax-exempt 'communications-receiver' - unless it also has a loudspeaker - in which case it's an enterntainment radio so gets the full whack of ~luxury rate~ purchase-tax!]

I'm happy to leave my Eddystone 840A switched-off for weeks/months at a time - and expect it to work sensibly within minutes when it's powered up. That's what would have been expected of it when it was new - why shouldn't I expect it to perform the same today?

[majoconz]

As a radio op in the UK Merchant and Royal Navies, the usual method was to turn everything on at the start of the trip and turn it off at the end - unless the new crew had turned up so you left it on... and on...

[Radio Wrangler]

I'd question whether you are always within easy reach.

I can be out in the garage for hours at a time, doing noisy things and might not notice even the outbreak of world war 3.

I was in the attic some years ago when I smelled burning. It took a while to get down the ladder and into the radio shack where a pretty new and very expensive computer monitor was emitting actual flames underneath a bookshelf. I hit the big switch and heaved the thing out the front door. You can't trust this new technology stuff. I took photos of all the UL, CSA etc markings on the melted back-shell of its case.

I really don't like having to leave an ADSL modem and router on when out.

And my Eddystone is off when I'm not using it. Only the bedside radio is left on power.

David

[M0ALK Richard]

Just a thought but...

Valve amplifiers often have a standby switch.
The valve heaters have power going to them but the high voltage supply to the amplifier is not connected.
If it is the thermal stress of warming up and cooling down that is the problem then I wonder if there is a case for leaving the receiver's heaters on even though the HT supply is off.