Sunday, 13 April 2014

Tekronix 2465CTS scope fixed


The two mains PCB filter caps had detonated...

So bit of fun taking it all apart.... earlier blog post.

But got it working again.... used two 0.1uF 250V X2 caps instead of original 0.068uF as I had some identical make etc....

Anyway seems to work again.

K2 fully loaded with 100W nd ATU build

Got  fully loaded build of K2 , 100W and ATU in separate EC2 just arrived.Was part built already so just going through what is there now.

G4PTH Mag Loop - Clive M5CHH (SK) version

Was asked to give some info on Clive's build as given this away....

He had made his up so that it could be used on all bands between 40m - 10m.

Follow the rest of the G4PTH article first from RadCom October 2008 (copyright so will not repeat it here). Pretty self explanatory really.

The build quality might not be quite as good as the commercial product but for us it worked fine all the same (it worked well). I look mine out to ON and was qrv with it from apartment out there. The mag loop ability to null out noise or pick up a station just by simply rotating it through the vertical axis has to be heard to be believed.

10 Ali rods 400m x 12mm x 2mm Pretty sure B&Q was the source

Stainless M6 Blots, split washers and wing nuts to fit together (Cambridge Mackays) these MUST be tight and the ends of the ali rods you may need to clean with a light sanding. You need LOW resistance all the way around the loop.
Clive and I had messed with radio and antenna setups since our little DX trip to EU-011 in 2005 when we took two homebrew dipoles and a mag loop. So we had a few IP56 enclosures for use for all things external in the junk box. You can use almost anything PLASTIC as long as rigid.  In it Clive fitted a 8-150pF capacitor. Not this is not one that stops you can go around and around.... so marking the outside of the IP56 box was essential for use. To be honest you tune using an analyser or VSWR meter not selecting a capacitor setting. The rods connect to the two M6 bolts that seem too long.

The straps were made from brass shim, RG58/RG213 coax braid (fresh) would have done, and did on another version... the object is minimum resistance.

Coupling baluns

You couple the RXTX (FT817 in our case) using RG58 coax to the max loop. The feed is using BNC sockets. For other SDR projects we had bought a load of insulated ones... normal ones are fine as long as can connect to BOTH the centre and the shield. The insulated ones are bit more expensive but easier to use.

40m FT150A ferrite (what was available) 5 turns of the green wire from 3 core 13 amp mains flex.
10m FT150A ferrite and 5 turns of the green wire from 3 core 13 amp mains flex.
 Common alignment

It used some small 8cm x 6cm x 4cm ABS potting boxes.... not important what they are as long as plastic.  You drill a hole right through so that the ali rods will slide through (do not do with the Ferrite in place!)

The best location was to have this hung from a telescoping fishing rod so bottom about 4 feet AGL, on the beach.

In use to tune was using either MFJ269, KD1JV antenna tuner or a simple vswr, tuning was sharp the band width not more that 5-6 khz.

Friday, 11 April 2014

Were you qrp?

I need to find out were you qrp when you contacted me on any of my somewhat crazy qrp trips ? I was always /M1KTA, sometimes /P
The prefix were VE7-3, W1, W5, W6, ON, PA, F, DL, OE, EA, CT7, DL, HB9, HB0, SM7, OZ, 3B8, C5, 6W, KH6 or KH8?
Trying to find out how many of these contacts were 2xqrp for Rev George Dobbs (G-QRP club).
Any interesting stores about the contact? Some I know waited decades for 3B8 and KH8 to appear with ops running qrp.

Thursday, 10 April 2014

Confused by X2 / Y2 gobbledegook

I think this sort of summarises it ...
All safety capacitors should have certifier’s symbols on their casing. For example UL (for USA), CSA (for Canada), VDE (for Germany), etc. To ensure you are using properly certified safety capacitors check that certification symbols (see below) are on the cases.
The different types are easily seen in this diagram.

C1 is X type, C2 and C3 are Y type.

I believe:
"Across-the-line” capacitors (X type) should be replaced with type X2, X1/Y2 or Y2 safety capacitors.

“Line-to-ground” line filter capacitors (Y Type) should be replaced with Y2 or X1/Y2 safety capacitors. (do not use X2 type).

As got to replace two 0.068uF X2 in oscilloscope looked to see what did I have before having to buy new ones.... and found some....  but are they the right sort?

Oscilloscope Tektronix 2465CTS Ressurection part 1

Time to fix the scope...

So this was the process to diassemble (where I got to anyway).

There are power supply problems (old capacitors).

1. A some what terminal step but got to do this turn it on and wait, self checks fine then sure enough blue smoke from the rear..... so turn it off, unplug and wait (any C that might have charged up need to be discharged).

2. Remove the rear panel

3. Side off the case (I will photo this)
4. The top of the scope internal, mine is a CTS so has the GBIC module.... filling where most have empty space.

5. Detach the leads marked CDE

6. Detach the leads I marked -++ GBIC rear interface

7. Remove the GBIC front LED jumpers

8. Remove the small 3x2 and 2x1 jumpers, last is a small RG174 coax connection. The leads are fitted so that the 1 is visible on the 3x2 and the coax inner fits furthest from the PCB

9. Remove the ribbon cables I have marked I, II and III

10. Remove the PSU board screws on strip with TO220 regulators

11. On case outer remove fan cover screw and remove (hold fan in place with bit of tape.)

12. remove screws holding PSU PCB in place (by fan)

13. Remove the black mains input cover holding screws

14. pull the spades off the mains input

15. unscrew the mains input and pull it out (care not 100% as there is an earth wire soldered to it. Put screws back on it once out... this is so you can then...
No photo.
16. pull off spades to the mains inline fuse holder.

17. Unplug the multi colour and gret leads connected to two SIL on the PSU PCB

18. Unplug the grey lead on the CPU board that provides power from the PSU
No photo
19. Pull the PSU PCB assemblies out (care do not flatten the electrolytics doing it)
No photo
20.The black flying lead that powers the fan goes to the feed through will still be securing the PSU modules to the scope

20. Desolder the black lead
No photo

The PSU PCB are now free.

Quick visual inspection shows the site of the blue magic smoke.... the paper 0.068uF X2 caps in the mains input filter section had detonated!

It just remains to take the cover off the pcb, separate the boards, de-solder and then replace the faulty capacitors, test and reverse the above :-)
Some of the 20V silver electrolytics look a bit suspect.... will test with esr meter. The green, black or brown can ones 'look' OK but will test them as well.

Wednesday, 9 April 2014

KX3 and DXlabs

The Command screen and configuration for my KX3