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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 28th Jun 2021, 9:56 pm   #1
Michael Maurice
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Default Beomaster 5000

I am trying to repair one of these which when first looked at the standby light flashed.

I changed the electrolytics in the output stages together with the two presets, adjusting them to the same resistance as the ones they replaced.

The unit is now stuck on standby, the standby light is steady but dim.

I have gently heated the microprocessor board just in case it was capacitors but it made no difference.

I then bypassed the relay to get the amplifier switched on and measured the voltage on the output transistors, both channels were close to 0V as expected. The fault line was high as expected, forcing it low caused the standby light to flash.

Can anyone shed some light on what’s causing this?
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Old 29th Jun 2021, 9:47 am   #2
Max Ripple
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Default Re: Beomaster 5000

Is the 5v supply to the upc module robust?The reset cap for the upc is a notorious troublemaker.
Do you have the Master Control Panel remote to operate the unit,or are you just using the drop down keyboard?It would be interesting to learn if you have comms between the unit and the MCP(if available?)
The protection circuit kicks in if dc appears at the speaker terminals,you may be confusing the system by bypassing the start up procedure?
Generally a reliable unit,but several "usual suspects" in there too!

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Old 14th Oct 2021, 12:47 am   #3
lawrenceenglish
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Default Re: Beomaster 5000

Hi I have got a circuit diagram .and all v are as listed good .I think that my problem if the Toshiba tmp 8355p as only 2 buttons on the front panel are working.the amp the speaker relay is working. The amplifier only works with the pre in with a good sound. I can only turn but no up or down volume .so if you no how to reset tmp chip it may set it right. I am going to buy another 5000 for the parts .but if I could get the tmp working. It would save me £40. The front panel and display only half work . I have tracked it back to the main computer chip .as I do not have a scope.thr trace ends there. Anyway I have gone on long enough. Can you be a bit more in detail about what you said .all the best to you Lawrence
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Old 14th Oct 2021, 9:20 am   #4
Beobloke
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Default Re: Beomaster 5000

Quote:
Originally Posted by lawrenceenglish View Post
Hi I have got a circuit diagram .and all v are as listed good .I think that my problem if the Toshiba tmp 8355p as only 2 buttons on the front panel are working.the amp the speaker relay is working. The amplifier only works with the pre in with a good sound. I can only turn but no up or down volume .so if you no how to reset tmp chip it may set it right. I am going to buy another 5000 for the parts .but if I could get the tmp working. It would save me £40. The front panel and display only half work . I have tracked it back to the main computer chip .as I do not have a scope.thr trace ends there. Anyway I have gone on long enough. Can you be a bit more in detail about what you said .all the best to you Lawrence
For the front panel buttons issue, have you checked the flexible lead between the panel and the main PCB? This is a very common problem and is nearly always caused by the flexible connection lead de-laminating due to it flexing over the years, which breaks the contacts between the front panel and the main board.

It can be replaced easily enough with a length of IDC ribbon cable.
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