8mm Forum: B&H 2592: no sound

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Posted by John Wilton (Member # 395) on July 18, 2005, 06:55 PM:

Picked up a promising Craig's List Fimosound 2592, that seller said was working OK when last used 18 months ago. I bought some films to feed it but a bit of a setback with the projector...no sound. The exciter lamp works; troubleshooting says, if you pass a card quickly between exciter lamp and its little lens, you should hear a thump...no thump means 'internal failure'. Tried plugging in an external speaker in case it was the switch in the jack; no good. Any suggestions as to cause/prognosis?

Posted by Dan Lail (Member # 18) on July 18, 2005, 07:13 PM:

John, have you checked the fuses? Hold them up to a light or if you have a meter that's even better.

Posted by John Wilton (Member # 395) on July 18, 2005, 11:06 PM:

Dan, you are good! Took the side cover off, not a fuse in sight; leftside baseplate, one good fuse; controlside baseplate; and voilá! Will look for fuse tomorrow and see what happens. This one is marked "250V 2A"; circuit board "replace with E83880"; should be easy to find.

Posted by John Wilton (Member # 395) on July 19, 2005, 12:24 PM:

I put a new 'slow-blow' 250V2A fuse in, but it popped the moment I turned projector on. Where to look next? (I have a multimeter)

Posted by John Whittle (Member # 22) on July 19, 2005, 06:37 PM:

Check at the beginning .... check the diodes and make sure they're ok. Sounds like short which could easily be the diodes or maybe there is something shorting the amp so look for a previous "fixer" who might have dropped a screw or something else. If that fails, you're going to need the schematic (you can check www.kmr.com and see if it's listed there for download) or a manual. The "thump" test is just the effect of cutting the exciter lamp off from the solar cell or phototube and is a quick test for any optical sound projector. Blown fuses and power supply problems are usually the easiest to fix, more difficult are intermittent noise or distortion.

John

Posted by John Wilton (Member # 395) on July 19, 2005, 11:19 PM:

Thanks for the advice...what does a diode look like, and how does one test it...is one visible in above closeup of fuses? I could post a photo of more of the board.

The leads coming from one of the power connecting blocks were bent to be very close together, I thought they might be arcing so straightened them...new fuse blew right away. I realised this time that the thump sound accompaning the fuse blow was not from the fuse; it came from the speaker.

Posted by John Wilton (Member # 395) on July 24, 2005, 12:57 AM:

I found the burnt-out diode, it's one of the silver and grey diodes next to the fuses in the photo above; CR7 on the board, the part is marked IN5402. Googling this part number suggests it is a 200V 3A silicone rectifier. Is this (or suitable replacement) likely to be found at Radio Shack; if not can any New Yorkers point me to any remaining electronic parts stores in the city?

Being a bit intimidated by removing the circuit board, I'm considering simply clipping off the burnt out diode, and soldering the new one to the leads of the old one sticking out of the circuit board, unless there's a good reason not to (other than inelegance). Sorry to be such a baby.

Posted by John Whittle (Member # 22) on July 24, 2005, 11:55 PM:

Actually cliping and replacing is an age old technique that was almost always used in hard wired tube chassis and should work ok for you as long as you don't get the clipped leads too hot and lose contact with the board.

If you remove the board, becare you don't over head and raise traces on the board. Hopefully the diode (and the radio shack replacement will be fine as will any of the common replacement lines such as ECG or the like) will fix your problem. If it goes again, there may also be a shorted capacitor as well. But start with the thrity cent parts and move up.

John

Posted by John Wilton (Member # 395) on July 27, 2005, 06:54 PM:

God said, let there be sound, and it was good, very good...This is the first time I've located a faulty component on a circuit board and replaced it, and it feels really good! Thanks very much for all the help.

Posted by John Whittle (Member # 22) on July 29, 2005, 09:18 AM:

John,

Congratulations. Welcome to the club. Nowdays you really have to be "your own" repairman for these things since the cost of getting one repaired is more than you can buy two or three more for.

John

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