Amstrad PC1640 fault. - UK Vintage Radio Repair and Restoration Discussion Forum

Outrun_uk · 29th May 2013, 11:06 pm

Hi all,

I have been asked to look at a faulty Amstrad PC1640. The fault is with the monitor, there is no life on the screen at all. There's no EHT and the heaters aren't lit but it is partially working as the base unit is powering up/floppy drives responding (base unit gets it's power from the monitor). I've checked around the diodes, high wattage resistors and a few transistors and looked for bulging caps etc but nothing obvious looks amiss.

I was wondering if there are any common component failures that could cause this? The only other option I can see is to find an 8-bit compatible VGA card and hack a standard ATX power supply onto it but would like to get it functioning as it should be.

Many thanks,

Kev

g8jzyian · 30th May 2013, 10:02 pm

Hi

I found the circuit diagram if will help, It's at http://archive.org/details/amstrad-p...service-manual

Best of luck

Ian

Outrun_uk · 30th May 2013, 11:30 pm

Many thanks Ian

I lucked out, found another monitor with opposite fault, tube working but no supply for the base unit. Dead STK regulator and o/c feed resistor. Manual will be help as I will hopefully be able to get the original one working too!

Cheers,

Kev

Outrun_uk · 6th Jun 2013, 8:59 pm

Hi all,

Quick update, success at last with the unit that had no EHT. Again a dead STK regulator and o/c feed resistor were replaced but it still refused to power up. After much head scratching and going around the circuit a couple of times it turned out to be a 0.22uF 50v electrolytic cap next to the STK. I had already checked this, it read ok on the LCR bridge and the ESR looked fine but after replacement it fired up just fine

Cheers,

Kev

29th May 2013, 11:06 pm	#1
Outrun_uk Heptode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 705	Amstrad PC1640 fault. Hi all, I have been asked to look at a faulty Amstrad PC1640. The fault is with the monitor, there is no life on the screen at all. There's no EHT and the heaters aren't lit but it is partially working as the base unit is powering up/floppy drives responding (base unit gets it's power from the monitor). I've checked around the diodes, high wattage resistors and a few transistors and looked for bulging caps etc but nothing obvious looks amiss. I was wondering if there are any common component failures that could cause this? The only other option I can see is to find an 8-bit compatible VGA card and hack a standard ATX power supply onto it but would like to get it functioning as it should be. Many thanks, Kev

30th May 2013, 10:02 pm	#2
g8jzyian Pentode Join Date: Jan 2009 Location: Liverpool, Merseyside, UK. Posts: 149	Re: Amstrad PC1640 fault. Hi I found the circuit diagram if will help, It's at http://archive.org/details/amstrad-p...service-manual Best of luck Ian

30th May 2013, 11:30 pm	#3
Outrun_uk Heptode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 705	Re: Amstrad PC1640 fault. Many thanks Ian I lucked out, found another monitor with opposite fault, tube working but no supply for the base unit. Dead STK regulator and o/c feed resistor. Manual will be help as I will hopefully be able to get the original one working too! Cheers, Kev

6th Jun 2013, 8:59 pm	#4
Outrun_uk Heptode Join Date: Aug 2009 Location: Liverpool, Merseyside, UK. Posts: 705	Re: Amstrad PC1640 fault. Hi all, Quick update, success at last with the unit that had no EHT. Again a dead STK regulator and o/c feed resistor were replaced but it still refused to power up. After much head scratching and going around the circuit a couple of times it turned out to be a 0.22uF 50v electrolytic cap next to the STK. I had already checked this, it read ok on the LCR bridge and the ESR looked fine but after replacement it fired up just fine Cheers, Kev