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Saturday, 10 September 2011

KWS AMA 210S


Hi,

Recently I bought a second-hand KWS AMA 210S. While I got it for a very cheap price, it did have some issues:
  • Functional CRT, but with splintered glass;
  • Functional LCD, but with a stain on the inside, covering about 10mmx10mm of the display;
  • Difficulty in turning on and frequent self-reset: this got worse over a few days, at the end the device would not turn itself on any more.
The reason I still went for the purchase was that this model has full options fitted:
  • FM/VHF/UHF/SAT (standard)
  • Videotext (standard)
  • Spectrum analyzer (standard)
  • Printer (standard)
  • SCART in/out (standard)
  • RS-232 (standard)
  • Digital measurements: BER/MER (option)
  • QAM with constellation display (option)
  • MPEG2 decoder (option)
  • ADR decoder: Astra Digital Radio - still available, to be ceased April, 2012 (option)
  • Polarizer control, both mechanical and magnetic (option)
This is a whopping amount of functionality, i.e. compared to my Hirschmann UPM1800 (aka KWS AMA 214S), which only has:
  • FM/VHF/UHF/SAT (standard)
  • RS-232 (option)
My original idea was to make one fully working instrument of both of them. However, dispite the fact that they look similar on the outside, the fitted cards are different generations and it is not possible to exchange boards.

The main concern was that the KWS AMA 210S would not turn itself on anymore. After much research, without having any schematics, I found that the fault was actually on the frontend-board. This board has the keyboard and an I2C-controller, responsible to turn the main CPU-board on. One electrolytic capacitor had swollen and on a different region of the board, one trace of the PCB oxidized. After exchanging the capacitor and fitting a wire to fix the broken trace, the instrument was working again!

Now, I never messed around with CRT tubes and I know they pose a potential health hazzard due to extremly high voltages (up to 25.000V). But after looking inside both meters, I noticed that both share the same CRT tube: a VTM M15-125W.

After reviewing videos on Youtube about how to safely discharge a CRT-tube and having seen it in real life, I decided to go for it. To make it short: it worked well and nothing big happend (I was mentally prepared for major explosions).

This allowed me to exchange tubes and the LCD display. KWS used an MGLS32064-HT-HV-EL LCD graphic module. Unfortunatly this one is not produced anymore. But I believe that chinese manufacturer Hoon has a similar, compatible, module: the HMB32064A. I am in process of trying to order one of these, to find out.

Right now I ended up with:

1 - Fully working KWS AMA 210S with full extras. CRT in good shape, LCD in good shape. The device does not have any defect and is clean.

Todo: I would like to have a paint-job done, using the original color, so that the device looks as new.

2 - Working Hirschmann UPM 1800, without any extras, except the RS232 option I fitted myself (you just need to fit a MAX232 and solder the RS232 DB9 connector). This device has a splintered CRT, which is still fully operational. The defect is only of cosmetic nature. It also has a stained LCD display. The stain is within both glasses of the LCD display itself. There is no way to clean it, without destroying the display (I had a closer look at it).

Todo: Try to purchase a new or second hand VTM M15-125W and one or two display modules, compatible with the MGLS32064-HT-HV-EL (to replace the stained one and because the good one has a somehow dimm backlighting - it is OK, but the stained one is brighter). Also, I would like to have a paint job done on this device, as well as, replace the rubber feet.

Here is a picture of my repaired and maintained KWS AMA 210S:


Notice the splintered CRT on the Hirschmann UPM 1800 below the KWS AMA 210S. Amazingly, the CRT is fully operational.

Cheers,
vma

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