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Old 27th September 2010, 02:01 AM   #1
KevinC is offline KevinC  United States
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Default BEL 1001 repair info

I am helping a friend troubleshoot and repair his BEL 1001 Mk I amplifier (he's an original owner!). It's clear that the 2N6284 NPN output transistor in one channel is shorted internally. They are still readily available, but I suspect that there is some matching that needs to be done to preserve performance at the highest level. However, with Richard Brown's passing last October, there appears to be no source of info (schematic, etc.) available. Anyone have any ideas?

Thanks!
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Old 27th September 2010, 02:12 AM   #2
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A bit depends on what else has gone with the output transistor. I would be checking the driver transistors too.

If its just the output transistor then changing it and setting up DC offset and bias again is the way to go.
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Old 27th January 2013, 11:55 PM   #3
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Default Darlington device used in BEL2002

I am working on a BEL 2002. One of the outputs failed and I replaced it with ON semiconductor part 2N6287. I replaced the small electrolytics on the channel The amp lasted 4 months and failed again. I found 2 shorted devices and replaced them. It lasted for 3 hours and failed. I replaced all the devices in the output stage and it last 30 min. and failed. I mounted test points on the PCB to measure the emitter drop. I get 70-130 mV depending on device. The channels do not seem to get real warm. I measured 60 C on an output (not the one that fails) but that is within reason. DC offset is OK. There is no bias adjustment. Also peculiar is the heat sink configuration. Thermal coupling is not optimal. Does anyone know much about the design or the model?
I have no schematic or instructions. Would all be well if the devices were matched using a curve tracer? It seems oscillation may be the cause, but I have seen nothing to indicate that on the scope.
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Old 28th January 2013, 12:40 AM   #4
KevinC is offline KevinC  United States
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Default BEL amps repair

Ultimately, the amp I was looking at went to someone who has a schematic and repaired it so it continues to run. Contact Sal Zambrano at Audio Summa (Audio Summa | home) for BEL amp repair. For what it's worth I agree with your assessment of the need for matched devices and, in the absence of these, the resulting oscillation-mediated destruction.
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Old 1st April 2013, 11:32 PM   #5
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Does anyone know if there is someone looking after the company now? I sent the boards from my 1001 in for repair around 3 years ago, I didn't get them back before he sadly passed, I have the rest of the amp here but would like to get the boards back and fix them myself.
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Old 10th May 2013, 05:15 AM   #6
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I spoke to Sal regarding the Model 2002, but sadly I was unable to keep it working more then several hours or days. Sal has taken over the BEL 1001 products. Replaced diodes, measured all components over and over. This unit has no test points, no bias control, and many parts hanging in air on a large header for a terminal/PCB. A mystery to me.
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Old 31st December 2013, 07:18 PM   #7
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I've emailed Audio Summa several times to try and get my PCB's back but they haven't replied, I've been using info@audiosumma.com, does anyone have a recent status update? Hopefully my boards are still in the boxes of bits that got passed from BEL through to Audio Summa. Or even a schematic, a parts list (including how to set it up properly) and any pair of PCB's would be OK. I have a MK III sat here that has never worked
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Old 25th February 2014, 02:40 AM   #8
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I know this is an older thread but I am trying to contact Sal regarding a potential repair of a Bel 1001 mk II amplifier.

Does anyone know if he is still in business and his contact number?

If not are there any recommendations on repair tech that would be very familiar with this amplifier design?

Thanks for any assistance you can provide.

Amplifier is currently in Chicago area.

Best Regards,

Nick
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