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Saturday, 24 January 2015

Ekco U353 Basket Case repaired!

There's a lovely chap at work called Terry, who likes to restore old radios and record players. He arrived with this old Ecko U353 in bits in a box. "It's got cut wires and labels and has been got at. Would you like it?" Why not ...


 Wires cut. Looks like someone was going to change the mains smoothing capacitor.
 UL84 getter looks bad.
Most of the white lettering from the scale has gone...
... but on the whole the chassis looks reasonable.










The mains smoothing cap is not original, has been disconnected and is dated Feb '65. It has poor ESR....











.. so each of it's 3 sections is given a few hours on the ole' MK87 Dreadnaught capacitor reformer.....









 .... meanwhile the sad looking UL84 is tested on the AVO two-panel valve tester...

A sad 1.5 mA per Volt. Minimum for a new valve is 9 mA per Volt. No good at all....


Thankfully, we have a NOS replacement. Just look at the difference in the gettering (that's the shiny bit at the top). The new valve is on the left. The gettering is bright and has a nice sharp edge. The blacker the gettering is, the better. This new valve reads 15mA per Volt on the AVO!





Stamped on the chassis is a date ... 1st Sept ...19 ?? 1957 perhaps? Seems a bit early for this receiver...








There were many leaking and cracked Hunts capacitors to be changed, along with some suspect TCC electrolytics. The cathode bypass capacitor for the UL84 was short-circuit. That's probably why the valve was worn out.






 Remembering how there was a small decoupling capacitor in the U319 VHF tuner, which caused issues, I removed the cover to this unit (a much easier job that the U319!!!)
But the decoupling caps are Eire types, and all read in very good condition...


So, after leaving the mains smoother on the reformer with all 3 sections in parallel, the leakage had dropped to a very low 50uA!  ESR was good too, so it was re-installed and connected up. So all in all, 1 valve and 9 capacitors, and we're ready to go! Connect to the safety mains isolation transformer, switch on ....






... and after a few minutes warm up time, the DM70 indicator tube lights, and the set performs well...








In common with most mains sets of the period, the metal chassis is connected straight to one side of our AC line (in normal practice, the neutral)... this is referred to as a "live chassis" (even if it is neutral) , which mean the shafts for the controls are also "live". Now, until a set of insulating knobs can be found, this set can only be safely operated though an isolation transformer.


I did locate a nice shiny set of plastic knobs at a dealer locally. Whilst the knobs are plastic, the shiny coating must be metallic, as they conduct very well! These will NOT be safe!







Anyways, here's some good-looking chap to explain the set to you!

Wednesday, 14 January 2015

Hello!

I'd like to say a big "Hello" to Nicu from Romania, who's taken the pond pump controller and added a DHT11 to it to make a weather station.

You can read more here:

http://nicuflorica.blogspot.ro/2015/01/ceas-rtc-cu-ds1307-si-date-mediu-cu.html

Sunday, 11 January 2015

Sony KV1320 UB MKI restoration.

This has to be the shortest restoration ever. I normally like a bit of a fight from my restorations! A few juicy faults, but not this one! Testament to the quality of late 60's Japanese Engineering.

Now back in the day, set manufacturers had to pay a license fee to Telefunken to use the PAL system, rumoured to be about £30 a set. Sony got around this by decoding the colour signal in a manner which didn't infringe Telefunken's patents. Sony used a modified NTSC decoder, which had an additional delay line, and the colour was repeated from the previously decoded line, reducing the colour resolution, but on such a small screen this isn't noticeable. Any problems with phase could be corrected with the provided hue control, which PAL receivers didn't have, nor need.

Most of these sets died due to being worn out. It is very rare to find one with a decent CRT in, so I wasn't hoping for much, and anyways I paid little money for it, and it's a KV-1320 MKI, a very early one, as several revisions were made.

Being an early model, it has a 3AT2 EHT rectifier valve, and has the CRT heaters permanently connected and warm (not good for CRT longevity!) , regardless of the mains switch position.

This one arrived dead. No tube heaters, nothing.





Opening the mains plug... and the fuse is open circuit!







Replacing that and great pictures!!



 A quick tweak to the frame height and centering


Sit down, and watch telly! A sticker on the chassis show the manufacturing date as June 1969! Fantastic tube which these pictures really don't do justice to.








This sticker is intriguing. Most sets in the UK of this vintage had "live" chassis working, that is one side of the chassis tied to the neutral of the supply, and this has a warning sticker to that effect, but the set doesn't have this! It's a fully isolated design!

Friday, 9 January 2015

Workshop video rack.

Whilst I don't get as much time as I'd like to "play tellys", the state of the workshop video sources has been plaguing me recently.

For those outside the UK, I'll explain a little. All TV transmissions in the UK are now digital. They're delivered in Band IV UHF.

In times gone by, there used to be a 405 line black and white only service (System A). This existed  from 1936 until 1984 and started out in Band I VHF, and then expanded into Band III when ITV started in 1955. 625 lines (System I) was introduced for the start of the BBC2 service in 1964, in UHF only (it went colour (PAL) in 1967, and all services moved to UHF 625, both in bands IV and V (Band V has now been flogged off to the mobile phone operators for 4G etc.) )

Now, to run my old tellys we need to generate at least some of these signals. The UHF 625 line colour stuff is easy, just get a DVB receiver (Freeview) with a modulator built in. 405 lines is a little more tricky, but thankfully there exists a small box called an Aurora, which is a 625 line to 405 converter (there are other types available too, to convert between almost anything!)  with a built in VHF modulator. It's superb. Auroras (Auroae?) can be found here. If you are inside the EU, you can order them from Crowthorne tubes here.

The big problem is this motly collection  of boxes and power  supplies, the odd DVD player etc, has just been jury rigged as required. Not a satisfactory situation.

So, I designed myself a little rack to house it all.





 All connections are made on the front panel. This is a workshop piece of equipment, and you don't want to go fiddling around the back. The signal from our aerial (with our digital TV signal on) feeds the top Belling Lee socket, this is passed to a "4G" filter to remove any signals from band V. The RF then feeds the two freeview boxes and the outputs from these (in Band V) are mixed and sent to the mixer in a UHF modulator. The band I output from the Aurora standards converter feeds an attenuator (it's output is hot!) and a low pass filter, this is then combined with the UHF RF and passed (finally!) to the lower Belling Lee locket for connection to the set or sets.





Video to the standards converter is switchable from nothing (which causes the Aurora to output test card C), the Aux input sockets on the front, the DVD or either freeview receivers. Video to the UHF modulator can be switched from the Aux sockets or the DVD player (The freeview is already modulated)





 Much neater and I'm rather pleased with how it's all come out.











I've subsequently added a small Sumvision Cyclone media player to the set up, which is great for playing video files and test cards from a USB memory stick.