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Internal Fire - Museum of Power

6599 Views 33 Replies 8 Participants Last post by  Michael Oceanspan
Found this amazing museum during holiday in Pembrokeshire last week.
They also have a couple of radio room displays.
Worth a visit if you are in the area.
There is even a morse key that has a loud side tone if you want to impress someone !
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I thought it might be bit of a stretch!! I seriously considered going to Colwyn Bay Wireless College in the mid-60s, but ended up serving an apprenticeship at Hawker Siddeley instead.
My usual day is Wednesday, in fact my wife is there too on Wednesdays. I'm usually there other days too. Opening hours are 10:30 to 5:00pm Wednesday to Sunday (Closed Mon and Tues). Best to drop me a PM on this site or send me an eMail via GB2MOP website and I'll try and be there to meet up with them. However, bear in mind that we will be away in France from 2nd to 22nd September. Perhaps a suggestion: October 12th and 13th are our big end of season "Crank-Up" days on both days we will have as many engines as possible running including the Proteus gas turbine. The Radio room will also, of course, be active. The museum is really buzzing on these days. Alternatively, for a more relaxed time, on 26th October we have a Museums at Night" event. This is a very pleasant evening fancy dress is optional we will be running engines: the proteus is even more spectacular at night. Again, the radio rooms will be active.
Plenty to think about!
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de GRUA...

Tks Mr. Oceanspan; I'll pass that information on and hopefully they will be able to visit and see how a real radio room looked back in the day.

#12 Too soon, too soon. Noticed absence of friendly tlick this AM to find the Maste5r has jammed - the stepper is the same model as the slaves but ticks every half second instead of half a minute. A lifetime spend at double speed takes its toll as does searching for a less worn 'spare' - I think now all 'used but good'. As the slaves are driven directly from the electronics it remains a good time keeper.

Repair will have to wait a bit I have two pairs of RN Bridge/E-R telegraphs to cobble together first.
Sidetone etc.

Spent the day at the Museum today. Amongst other things, put the Oceanspan into CW mode. "Sidetone" is present in both Atalanta and Mercury. I have not specifically wired it that way as there is no sidetone output from the Oceanspan. The sidetone is present only by virtue of the local signal being sufficient to overcome the de-sense and is, of course, adjustable in frequency by the BFO. This is probably OK while working the same TX and RX frequencies. If operating cross channels you wouldn't hear yourself.
Aside from that had a good day with a handful of contacts around the country on 80 and 40 on the Oceranspan and then later switched over to the Rohde and Schwartz 2100 for some SSB contacts. Throw in a bit of useful tinkering, sunshine and a few visitors make sit a very pleasant day.
Oceanspan Circuits.

Hi Andrew,
I promised you a copy of the Oceanspan circuits. Herewith, Transmitter and Control units.
N.B. I couldn't see how to include these in a PM.


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de GRUA...

Hello again, Mr. Oceanspan, Sir. Just wondering how things are on the 'ranch'. Desperate for an update on the Challenger and Oceanspan, and all things to do with that.

I got a couple of what look like brand new EF85's from a U.K. company for the Atalanta front end, but haven't got round to putting them in yet. Somehow find myself scared to do so, in case there's no improvement! How wimpish is that?

Best regards, Paul
Hi Paul,

You'll have to be patient! my wife and I are in the middle of a three week holiday in France (courtesy of my sister who lives in France). We'll be landing back at Poole on 22nd, then onwards to wonderful West Wales!

Really, you've nothing to loose by fitting the EF85s and maybe something to gain. Do you have a signal generator? I won't get round to realigning ours until the Winter shutdown (November 2019 to Easter 2020). Before that the HT supply needs sorting out. You probably know that the Atalanta has 110V LT - heaters in series via a varistor to limit inrush current and 110V HT. Ours has been modified by a previous owner for 240VAC mains operation by fitting an autotransformer: the 110VAC tapping goes to the filaments and also to a full wave silicon bridge rectifier consequently the HT is closer to 150VDC than 110VDC. From a purely electrical point of view it probably does no harm as all the capacitors are rated for 250V and the resistors should stand the extra few milliamps. However, from an RF and AF point of view I'm not so sure. The operating voltages; anode, screens and cathodes will be kept in proportion but elevated by nearly 50%. The set does have a tendancy to motor boat at maximum gain and stations are frequently accompanied by a hetrodyne. I'm hoping that sorting the HT and then re-alignment will resolve these issues.

As for the Challenger, I'm hoping to find a nice MRF393 or 392 waiting for me at the museum to replace the deceased BAL0000L10 in the driver section. The way will then be open to start checking the 4CX350s finals, one at a time. Then the fun begins!

Thanks for your interest - Michael.
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Thanks Michael
It looks like adjusting L27 core might bring 8 MHz down to 7, (or 6 up to 7) but a tedious procedure without extender leads. Alternative add some fixed capacitors. You do have it working on 3.5 MHz don't you? Sounds like a winter job as you suggested
Hi Andrew,
Oceanspan works on 1.8, 3.5, 5 and 7MHz. 3.5 is very good, tuning on 5 and 7 is critical but do-able! Its debateable how useful the higher frequencies will be on AM, but it might make life easier for visiting CW operators who want to use the higher bands. Once the Challenger is up and running I might return to the Oceanspan in the Winter - unless Paul (curator) has some other winter projects to distract me!
Hi Mike. Hope you're enjoying your holidays.

Nope, I don't have a sig gen. In fact, I'm almost back to what was commonly available at sea, namely, an AVO8! (In fact, not as good as it was, as I've got no spares at all, not even suspect ones: 'used but good', was a common note to find written on valve boxes in those days).

My Atalanta has always been very well behaved indeed. I don't have your motorboating or whistling heterodyne problems at all, not even on max gain, and apart from the usual slight drift effects on listening to SSB, which is normal for that vintage set, there's been no hint of a problem, other than the occasional 'locking up' of the tuning control at one extreme end, when she sticks and won't come out of some internal detent. Easily fixed. I just talk to her nicely and she's right.

Even the dial cords are in exactly the right position and no trouble with the bandspread locking or use. Very accurate, in fact. I haven't measured the HT or LT lines, but that's interesting, what you say about the 110V. She can be a bit of a biter, the Atalanta; lots of opportunities to get a hefty belt if you're not careful. Especially on a rolling ship when you've got one hand clamped firmly around one of the chrome handles on the front panel, a gert big screwdriver in the other, forgetting that the inset screws for the knobs on 110V DC mains were live....

Your holiday in France will no doubt recharge you, ready to fit the part you mentioned in the big fella. Sounds like great fun, getting them up and running again.

Best of, as always, Paul
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Hi Paul,

The Atalanta does bite! When it first arrived, I turned it on, twizzled the tuning knob as one does, found a station and just tuning in when the knob fell off. No worries, I thought, nearly got it, and took hold of the shaft to fine tune and you guessed it all the lights went out! Not mine - the RCD kicked in and saved the day, still got a healthy(?) belt though. A lesson well learned and not forgotten!

An isolation rather than autotransformer does have advantages Michael !

One of the first valves in the heater chain has a max heater to cathode voltage near 150v. My Atalanta had an intermittent heater wiring fault. My home made psu then rose from 110 to 160v off-load. The valve failed and burnt out the cathode resistor then the heater. I bypassed the faulty wiring.

With the Oceanspan on 7 mc/s it would be perfect for EU activity on a maritime activity day. Great to get it on 14 though.
I'll bear that in mind Andrew. Looks like another good reason to sort out the PSU section.
Marconi Challenger

Paul, and others interested in the Challenger, can I refer you to the thread on the Marconi Challenger rather than repeat the story here?
In a nutshell, the replacement driver transistor arrived and is now OK. 4 new 4CX350s also arrived and am in the process of carefully fitting and setting them up. It's going well - so far!
73 Michael
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