Author
|
Topic: Another Eumig S940 problem - now its the amp!
|
|
|
|
|
|
|
|
|
Phil Slater
Expert Film Handler
Posts: 161
From: Norwich, United Kingdom
Registered: Jan 2011
|
posted October 02, 2013 11:33 AM
Maurice, Yes that was the one. The seller told me before he shipped it that the on off switch wasn't working, ie it was permenantly on, and he had installed an inline switch on the mains cable. I negotiated a partilal refund for this. I'm just wondering whether operating that switch had anything to do with it, such as causing a power surge.
It still works as a silent machine, with the amp fuse removed. Does that sould like the chip has failed? If so, what are the chances of finding a new chip?
I will probably get it checked out, just incase it turns out to be something more simple to fix.
Thanks to everyone who has respond so far. If anyone has any further thoughts, please let me know.
| IP: Logged
|
|
|
|
Paul Browning
Phenomenal Film Handler
Posts: 1006
From: West Midlands United Kingdom
Registered: Aug 2011
|
posted October 02, 2013 03:02 PM
Phil, I had this on projector a while back, where the replaced fuse as you say in the amplifier stage kept blowing when you replaced it, I thought it was the power supply to this stage( the bit that changes it to dc), not that either. Its something that draws enough current to take out that fuse when switched on?. The output stages of an amplifier have transistors to drive the speaker or speakers on anything audio, and my guess is its one of them that's failed, in my case this was shorting one of the pins on the transistor to ground taking the fuse out. I feel sure someone on here could tell you more, perhaps martin who's already chipped in here, as a tele repair man retired, he's trained to component level testing, could tell how to safely test it.
| IP: Logged
|
|
|
Martin Jones
Phenomenal Film Handler
Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008
|
posted October 03, 2013 03:40 AM
Thank you, Paul. Yes, I probably could, because I've actually done it before...
Not long after I joined this Forum I helped someone (nameless!) to repair the amplifier of a 926. Because of the complexity of doing it, and because he was located elsewhere in the world, it was done through a very large number of emails containing photographs and detailed step by step instructions, .
I had a circuit diagram and another board of the same type, he had a soldering iron and solder and a Multirange meter, both of which he said he could use. And he was sure he could follow my remote instructions (he was a trained medical practitioner in a surgical discipline).
The faulty component was traced by a logical step by step series of measurements on the board with no power applied, involving isolating sections of the circuit in turn, then individual components in turn. Fortunately it didn't take long to find the fault which was fortuitously early in the very long series of tests envisaged. The process was assisted by the owner following my instructions TO THE LETTER, no variations or short cuts on his part... and EVERY measurement or observed effect reported back before a further instruction was sent. The spare was obtained and fitted... and the board worked first time.....BUT! After refitting, it didn't work! Out it came and the answer was obvious. Yes, the gentleman could use a soldering iron, but his soldering skills were sadly lacking when it came to electronic circuitry! Bad joints, lifted printed wiring, all disturbed and damaged when replacing the board.
There's no way that can be dealt with at a distance. I offered to repair the board at no charge if he could send it to me, but I heard no more.
The moral: to repair an electronic item you require the Knowledge, tools, skills to use them properly, the relevant information and the ability to interpret it properly. And it helps to be able to remove and replace boards without causing further problem! There are MANY competent amateurs (that's how I started and I am almost exclusively self taught on the practical side) but you need to know who they are, which is why I would always recommend using a professional with a good track record. There are a number of people on this Forum who will agree with the foregoing... and agree with my position on such remote repairs. Regrettably, I would NEVER repeat that kind of exercise! And although I have on occasions repaired members' machines in my own workshop my advancing years are affecting my best tools (My eyes and my fingers) adversely. These days I only try to please the wife! However, advice is still available. Regards, Martin
-------------------- Retired TV Service Engineer Ongoing interest in Telecine....
| IP: Logged
|
|
|
|
|