Author Topic: Technosonic 1908 ticking (Read 6129 times)

simondgoodman · « **on:** February 08, 2009,10:45:39 »

I have a Technosonic 1908 and there is ticking coming from the motherboard around the area of the psu.
I have replaced the two three pin diodes, but still ticks. Any advice really welcome.

Mulja tv repair portal · « **on:** February 08, 2009,10:45:39 »

tv tony · « **Reply #1 on:** February 09, 2009,09:02:37 »

the two surface mount diodes that kick start the psu fail, about 330k each, also the 5.6ohm that is the feedback resistor goes oc, if you want circuit refs i will give you them when i return to work
is the standby led flashing or steady
tv tony

tv tony · « **Reply #2 on:** February 09, 2009,09:03:57 »

that should read resistors, and also the two diodes on the sink are schottky type

Mulja tv repair portal · « **Reply #2 on:** February 09, 2009,09:03:57 »

Turnip · « **Reply #3 on:** February 09, 2009,11:43:18 »

Hi, have had this problem with a couple of Technica (Tesco) sets, where it is difficult to remove the diode fixing screws as access is fouled by the chopper transformer. In both cases it was the LH side double shottky that was S/C and was replaced by a shottky with a higher voltage rating - no comebacks yet.

Turnip

tv tony · « **Reply #4 on:** February 09, 2009,16:32:16 »

yes but he said hes replaced the diodes, we bought all semssens stock when they folded, and the 3 resistors do fail, two in the start up straight from the 330v line and the one in the feedback 5.6ohm

Turnip · « **Reply #5 on:** February 11, 2009,12:25:01 »

Thanks Tony,
Realise you have met more of these sets that me. But I thought that it should be emphasised that not every 'three pin diode' is the correct Shottky for the job, ensuring the right sort is used which could save some headscratching.

Thanks again - Turnip

Mulja tv repair portal · « **Reply #5 on:** February 11, 2009,12:25:01 »

tv tony · « **Reply #6 on:** February 11, 2009,16:18:20 »

its a pleasure, ill look in rs tomorrow and get you pt no, they are are a bit critical
tony waker

Turnip · « **Reply #7 on:** February 13, 2009,09:24:14 »

Hi Tony,

When I had my first duff one, I checked it's spec and found I still had a pile of BYQ28 from Sendz years ago, Possibly now obsolete and requiring isolation, the spec seemed OK however.

Not useful perhaps - Turnip.

tv tony · « **Reply #8 on:** February 14, 2009,04:35:48 »

now theres a name from the past, early 70s at least

Mulja tv repair portal · « **Reply #8 on:** February 14, 2009,04:35:48 »

Mulja tv repair portal

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