Its working but not perfectly

Well here is the capacitors that were stripped out most were a bit leaky and affecting the biasing on the valves. After they were all changed with new, much smaller, ones from RS Online the set actually started to work and recieve on all bands. Some of the valve bases were a bit noisy so some cleaning fluid fixed them, the volume does not seem very loud nor the receiver that sensitive.

So the next next steps are to check the IFs are tuned up and check all the voltages are now correct (I checked the values of all the resistors whilst checking out the caps)

I went to the QRP rally at Alfreton looking for Wander Plugs and a Signal Generator. I looked in all the component bins not a Wander Plug to be found but I got an Old Eagle TE-188 Sig Gen complete with its manual for a Fiver and my friend Geoff M5GAC fixed me up with some miniature coax to use with the phono sockets. I checked it when I got home (removing the case to check for faulty mains cable and dodgy electrolytics and all was ok and it produced signals ok. The next problem of course is calibration of the IF frequency, so rather than buy a frequency counter I bought a ceramic 465khz filter from an on line company I found call Electrojumble.org.uk they even list thermistors for dial lamp protection..!!

Original

 I've added a before and after picture of the underside, now I'm just waiting for some Wander Plugs from Ebay, expensive but they save me having to modify the back panel of the set. Its turning out a little more expensive than I would like but it is certainly exercising my mind.

Re Capped

First Switch On for the 870

Yesterday, after I had replaced the Electrolytic and what is often referred to "That Capacitor" (the paper capacitor of the mains filter), I switched it on for the first time.

No smoke, bad smells or exploding capacitors, always a good start, the panel lamps seemed a bit dim but otherwise OK. Waiting a minute or so, for the heaters to warm up and get those electrons moving, then crackles were heard a bit of switch cleaner on the volume pot fixed that. I tried an aerial and get a slight increase in noise but nothing seemed to tune on any band.

Testing with a screwdriver on the slider of the volume pot produced a reasonable hum so the amp seems good, just waiting for a cheap analogue meter to come in the post so I can do a few measurement. I did look at old Avo's on EBay but they go for silly money.


 
Changing the caps was an interesting exercise especially the 32 + 32 mFd smoothing cap, the only ones I could find were of a bolt through type that would have needed a slightly larger hole and cost around £20. I decide to try taking apart the old one and found a couple of 32 mfd caps that would fit in side the tube when I got it apart it was fairly well dried up, obviously the right thing to do. Soldering the new caps to the original connectors proved a problem as the internal wires were crimped to the solder tags and the wires would not solder; in the end i had to make small holes in the end plate to feed the new wires through and wrap them round the tags. To get the innards out I had to lever back the flange using a pair of fine cutters so when I reassemble it the flange looked a bit rough   (see picture)
























Following on from that Smoothing Capacitor rebuild I had to decide whether I was going to treat the other the same way, as in a restoration or a repair, so I compromised and replaced the rest with modern ones and saved the parts so I could perhaps restore it later (as if that will ever happen..!!) Just for completeness here is a before and after pic

Next step do some measurements of voltage etc when the analogue multimeter turns up, I do have and all singing and dance digital one but its a bit confusing so as its an old set back to old technology.

First Steps

I'd been looking at the mains connector, a quick trawl in all the usual places didn't throw up any spare connectors, so I decided to look for an alternative. As shown I found a G6 chassis socket and associated G5 moulded mains lead, these are the type used on in line laptop psu and I found them at Rapid. They nicley take up the hole left by the original polarized 2 pin , I did have to make a new backing plate which was fixed to the two existing mounting holes. When the original cover was fitted the mains lead connected perfectly with no need to mod the cover.

So if anyone wants the old chassis socket on the right let me know and I'll post it off.

The next area of work was the tuning mechanism as it had jammed this required a bit of oil and some filing to remove some rust that a oiling the drive mechanics made the tuning indicator move smoothly. I will have to remove it later as the scale is a bit dirty and dusty.

At some time in the past someone had fitted a phono socket for audio out this was connected to an additional isolation transformer that connected across the speaker. I've removed both of these so now the unit is back to original.
I think the next phase will be to check out the  resitors and capacitors to see what needs replacing. If anyone knows a source of 32 + 32mfd 350v smoothing caps please let me know.

More later

Eddystone S870 Restoration ?

I have have just bought an Eddystone S870 reciever from Ebay it looks good for its age but needs quite a lot of work doing on it to make it work. (sounds just like me, new heart valve , pacemaker, cateract repair and hearing aid + a general lack of performance due to a stroke..!!)

Hopefully it will be esaier than me to fix. From the photos it looks as though I need to clean up the rusting and the funny white deposits, free off the tuning pointer and perhaps change the mains to an IEC connector.

Then start on checking the resistors and capcitors etc and perhaps see if I can find/fix a small mains transformer and make it safe rather  than the existing AC/DC direct connection.

Should anyone be interested that since my last Blog I have change my computer to an Apple Mac Mini running Snow Leopard and I've not had a "Blue Screen of Death" or never ending updates since 2009 it just works and iPhoto is really great for photos and restoring old 35mm slides.


Anyway watch this space as I have found the Eddystone User Group site and download the service handbook. If you have already restored an old Eddystone like this I'd be pleased to hear from you

73's Phil G6AKK

(sort of qrt now RF can Upset Pacemakers if you are too close like bench testing and fiddling inside transcievers)