8mm Forum: B&H Humming but no tune

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Posted by Robert Pitman (Member # 801) on April 08, 2008, 06:39 PM:

Wow its been a year since I last revisted. Why do I get the film bug at this time of year?
Looking for some advice on a B&H TQIII green [spew][/spew]. The sound suddenly stopped working and now I got a constant hum from the speakers that is not effected by volume or tone controls.
Disconnect speaker sound goes.
Exciter lamp lit fine.

Thanks in advance,
Rob

Posted by Simon McConway (Member # 219) on April 09, 2008, 02:39 AM:

You need a new amplifier board. Contact Gordon Ogbourne. Email me and I'll send you his details. smcconway at hotmail. com

Posted by John Whittle (Member # 22) on April 09, 2008, 09:41 AM:

If you have an amp schematic you can probably track this down. To me it sounds like an open cap or dried out cap. Don't know the cross between the US and UK models but some were tube some where hybrid (part tube part solid state) and some were solid state. If it's the third you also could have a bad transistor.

Since your problem doesn't change with the volume control or tone control, it's possible it's toward the final driver end of the amp and not the preamp section. If it were earlier, then turning down the volume control would remove the hum.

Good luck, don't know how hard it is to work on these if you require an extender card or if you have to have a bench with various power input and tests. Or you could just replace the amp as Simon said. Extra parts machines (especially ones with broken helical gears) are great cheap sources for parts.

John

Posted by Dan Lail (Member # 18) on April 09, 2008, 11:27 AM:

Robert! John is right. I have a couple of B&H projectors in running condition plus three junkers I bought very cheap just for parts. Sure saves a lot of headaches when somethng fails or breaks. Some people give these non-working projectors away.

A replacement sound board here in the US costs around $125.00 plus shipping. The working ones in my junkers cost next to nothing.

Good luck. [Smile]

Posted by Robert Pitman (Member # 801) on April 09, 2008, 02:13 PM:

Thanks everyone for the pointers.
Guess I really gotta decide which way to go on this.
It's not my main projector, but I'd still like to get it going again. If only just to get some peace in the garage while the kids are ripping the house apart [Smile]

Rob

Posted by Kevin Faulkner (Member # 6) on April 20, 2008, 04:49 PM:

This will be one of the all semiconductor versions. If you look in the Manuals section on the left I'm sure you will probably find a service manual to download for your machine.

As John says it will be in the output stage and more likely a dried up capacitor.

Kev.

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