Radio stuff

[mick2me 3,033]

I finished the day of by setting up all my listening gear.

Yaesu FRG-8800 and Icom IC-R7000

First time I had it set up since the 1980s

Currently listening to a guy in CoCo Florida N4LEN

[Ayupmeducks 1,730]

What frequency was that on Mick and what time??? This solar cycle has been a fizzer to say the least, late start and only a few openings on the 10 and 15 metre bands to Europe. It's been so bad I never bothered to get an antenna up.

[mick2me 3,033]

Around 23:00 gmt

either 7 or 14 meg

7190 or 7390 comes to mind.

He was talking to someone in OO1A who I couldn't hear,

and another yank I could only just hear AA1QM

I could be wrong about any of these calls as the yank spoke so quick.

I am sure the guy he said was in Belgium but the call gives Holland?

Could have been mobile?

[Ayupmeducks 1,730]

Chances are 20 metres then at that time Mick (14Mhz) the other bands are too low for that time of night. 20 metres is "our" long haul band any time of the day.

[mick2me 3,033]

Also found and set up an old valve HF receiver that I bought on ebay some years ago.

Star DX Mates SR-48, fires up but nothing picked up till I rig up a long wire.

[Ayupmeducks 1,730]

I'd get all the capacitors replaced in that radio Mick, especially the high voltage electrolytics which would have become very leaky. One failure of one of those in the filtering circuit of the power supply could take the main transformer out!!.

It also sounds like you have some "soft" tubes in it, it should put some good output out the speaker using a wire coat hanger!

Are they the "miniture" tubes or full sized tubes??

One QRZ forum, there is a good "Boat Anchor" section with many tips on restoring old tube equipment from guys all over the world who are experts on tube gear, with many links to suppliers of parts for those radios.

[mick2me 3,033]

I would not have a clue about what to replace?

Or the tubes?

The coathanger is a good idea.

It does fire up.

I will try a short antenna

I did think at first it was not working but forgot how you have to wait for

valves to warm up, like the old Tellehs.

[Ayupmeducks 1,730]

Well you know what capacitors look like, didn't you do a brief electronics course as an apprentice???

The large capacitor in the filtering circuit usually has two or three caps in one aluminium can from 1 inch to 2 inches diameter mounted on the chassis. Check the side of it for voltage ratings and values. Replace all the tubular caps, some are prone to exploding as they get old and showering everything in "confetti"

Find a local Ham, they usually have tube testers, especially the ones our age group Mick, ask him to test the tubes for you, he will give you advice on restoration and may even help you give it a new lease on life!! Well worth it, old tube radios just "sound different"!

[mick2me 3,033]

I'll get a screwdriver on it when I am not so busy

I have the Yaesu an Icom to be going on with

[mick2me 3,033]

Oh yes I also found the ERA Micoreader.

And the rare ERA rs232 LCD display

[mick2me 3,033]

Micro Reader MkII must be early 80s.

Managed to download a User Manual from mods.dk

A good site for old manuals

[mick2me 3,033]

I did take te cover off the star reciever.

The Tubes are, 12AV6 12BE6 12BA6 & 50C5

Any capacitors I can see appear in good order with no leakage or splitting.

There id a large Can with Microfarad figures on, it appears to be in a mount

but if its soldered in there are a lot of components soldered on to the base?

There are quite a few small capacitors which my soldering skill would not be up to replacing.

at a range of 2-100, I would rate my skills as 2.

I took some photos and will upload them when I get time.

You've now got me paranoid to turn it on!

[Ayupmeducks 1,730]

Electrolytic caps usually dry out with age Mick, that being the problem, I'm surprised your soldering skills are almost nil, mine were pretty good even before I started working. But in my side of the trade I did tons of soldering both with an iron and oxy, ie sweating joints on cables and motor terminations, so on your scale I must be at 200 then...LOL

Believe me it's not hard, first step is make a not of all the tubulars caps and electrolytics, ie capacity and voltage, get them ordered, when they arrive, cut the old cap leads as close to the joint as possible, slip some insulation on the new cap leads, tine the ends and wrap them around where they need to be and solder them in, use rosin cored solder!!! Also make sure you note polarity of the electro caps!! Very important.

You may have to finish up finding a ham who has a tube tester and get those miniature tubes tested, they have to be tested on a tube tester.

I have my own, it tests several tube functions, most common failure is they are just plain worn out, no or low cathode emission.

You may also need to ask a ham to do a quick re alignment, ie set the mixer/ oscillator and IF circuits up, you need a signal generator and scope for that, a signal tracer can be used in place of a scope, but not as good or accurate.

Then after that lot, you'll have learned the basic principles of radio!! And have a pretty sensitive receiver to boot!

Most is just common sense Mick, nothing hard or too difficult.

[mick2me 3,033]

Well you make it sound easy

[Ayupmeducks 1,730]

Been playing with radios for some 50 plus years now, plus I know a lot more theory than when I first started as a teenager Mick.

There's nothing difficult about repairing and restoring old tube radios and early solid state radios, common sense, experience is gained on each radio, and a little know how of how they work helps fault finding.

Modern radio's common fault is dry solder joints, that goes for modern amplifiers too!

Another common fault I have found with these mini shelf stereos is the owners think they can improve the output by adding parallel speaker.....OOOOOOOOOOO one stereo module burned out!

[dgbrit 258]

Watch out Mick VERY HIGH VOLTAGE in tube stuff dont want to loose you now

Remember the one hand tied behind your back technique

Ayup did you say you worked at Redifusion, I knew a guy Named Johnny Roberts worked there in the 50-60s

Do you get your tubes from the Tube Store ,I got some nos for my guitar amp.Did all the mods but it just made my playing sound worse lol

[mick2me 3,033]

Good point

Thanks for the reminder.

HV Stored by the Capacitors

[Ayupmeducks 1,730]

No, I served my elec apprenticeship with the NCB, only ever worked as an electrician or an elec fitter.

All my electronic experience has been learned as a hobby, books and practice, and of course exams to get my amateur radio ticket.

I do have a well equiped workshop, albiet some dated gear but with a digital frequency meter, quite adequate. My scopes a twin trace 100Mhz so does me for repairs to HF radios and will work for me on 2 metre rigs.(144Mhz) at a push.

Tubes are getting expensive as there are only a couple of companies making them these days, the Chinese crap Taylor Tubes, and a Russian company, they only make a few types, but are reliable..

I have a good stock of new and pulls I got off my late BIL after he retired and sold his TV repair shop.

[dgbrit 258]

Ayup ? If i put 2- 10uf caps in series does that equal a 20uf

Or is it parallel

[Ayupmeducks 1,730]

Series in caps halve the capacitance, opposite of resistance. To increase capacitance, add them in parallel, but the voltage of each must be the same rating!! So two 400 microfarads in series =200 microfarads or two in parallel = 800 microfarads.

Resistance two 400 ohms in series =800ohms two in parallel = 200 ohms.

It's not an accepted practice to either parallel or series caps!!! Get the right value for safety, and remember most are 10% rating, so you have a lot of leeway eitherway!

The only time you really have to stick to set or low tolerance values with caps is in RF circuits, ie mixer oscillator stages and IF stages of receivers, and critical stages in transmitters, like the master oscillators or PLL circuits...(Phase Lock Loop)

Reservoir circuits, like the filter, of other circuits using electrolytic caps aren't that fussy within 20% tolerance.

But again, an elec cap in any RF circuit in transmitters MUST be within the designers tolerances, or they could go into self oscillation destroying that circuit.

Tubes go into melt down states....I've seen vacuum tubes as flat as pancakes, solid state devices, power transistors and power modules just burn out.

[dgbrit 258]

Thanks Ayup maybe i should call you the Captain

It was in a motor circuit start cap

[Ayupmeducks 1,730]

My large compressor uses two caps in parallel.

[dgbrit 258]

Ok still alive only one big blue flash & a melted plug

Working on a German built machine that inside looks like a death trap ( You mean i paid $5000 for this)

Just a mess of wires with spade conneectors that are not insulated & over time have become very loose

It is a boil out machine 220v that has a pump & heater inside, The cap on the pump was bad so the pump wouldnt start.

Easy enough to replace the cap BUT on removing the cover quite a few wires came adrift as the spade connectors had lost tension

And of course they are all the same colour & not cut to length just bundled up like spagetti

I got everything hooked back up but on putting the cover back on there was a reason that some of the spade connectors were bent as they touch the tank & short out as i found out

So a 5 min job turned into a 2day affair but it is up & running better than before & much safer that when it was built

[Ayupmeducks 1,730]

You should have been with me when I was working on replacing a 24 volt power supply on a coal cutting shearer on a face many years back....Stupid manufacturer put all three power supplies right at the back of the control chamber. Oh they will never fail, they are heavy duty power supplies, yeah right, BUT, what happens if they do I asked the engineer from Anderson Strathclyde, he talked down to me and implied I was an idiot!!

I hope he woke up that night when I had umpteen hundreds of thousands of dollars worth of machine guts stacked on the coal face while I replaced a faulty power supply.

A full shift of work I could have been doing preventative maintenance...