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Beomaster 8000 restoration #3

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ALF
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ALF posted on Tue, Jun 4 2019 9:38 AM

Hi All,

its sometimes really good to have a donor unit at hand.....

as today, the fm-signal on the recently restored BM8000 sounded distorted, no matter which station

and the volume of that signal was quite loud even at vol setting 1 ?!

after checking that other inputs are ok I decided to swapp over the fm-related boards #2 & 1 from the donor unit and everything sounded fine again....😁🙏

but,.....

where to look for the most likely problem source on those two boards ??

as I have decided to go for another restoration project I want those fm- boards to work again.

the tuning voltage was set correctly.....other trim pots on the tuner boards I won’t dare to touch 😳

the donor unit is in far too very nice condition - so, its worth it to put in the work.

could someone throw some pointers in my direction.....pleeeease 🙄

ALF

 

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ALF
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ALF replied on Sun, Jun 16 2019 10:36 AM

Sadly the resistor trick - lifting 4R143/145 etc - has no impact on that static crackling noise when switching inputs and adjusting the volume.

I decided its time to revisit the uP-board after studying some of Beolover’s blogs reflowing a number of suspicious joints.

the memory issue, storing FM stations, seems cured and the static crackling noise is much better, although not entirely gone.

an interesting but annoying new issue turned up: 

When turning the BM on the balance setting is right over to the left channel - I can correct the setting on the tone/filter board again, fine

all sounds normal.

switching off the BM and start again the same issue is present ???

looks like I have another inspection of the uP-board checking on the soldering !??

sadly still no “sound” from the tuner ...... as said, I can dialing in FM stations, but silence is the answer 😡

desperately need some assistance here - so far I only replaced 2IC6 with no outcome......

anyone ??

ALF

 

chartz
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chartz replied on Mon, Jun 17 2019 9:45 PM
You have to press the memory button (volume store) if you want the balance setting to hold.

😎

Jacques

ALF
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ALF replied on Tue, Jun 18 2019 5:04 AM

Thanks Jacques - problem solved🙏🤗

ALF

ALF
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ALF replied on Tue, Jun 18 2019 5:16 AM

Looks like I arrived at the perhaps last major roadblock ??      !! the tuner !!

a quick recap:

FM stations can be tuned in and stored but no audible signal output ??

MPX lights up once a station/frequency is detected but signal strength meter is not moving

as mentioned previously, I should measure +-15VDC at 2IC6 pin8/6 but it is not there.

these voltages are however present at 2P8 - 1 and 3 but somehow don’t get through ???

I also mentioned earlier the replacement of 2IC6 !!

who could give some helping advice here ??

ALF

 

chartz
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chartz replied on Tue, Jun 18 2019 6:01 AM

Well, check for broken tracks. I’ve had some broken just at the limit of the solder joint, quite impossible to see even with a magnifying glass. 

Jacques

Dillen
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Dillen replied on Tue, Jun 18 2019 6:15 AM

Some bottom plate screws are long enough to reach through to the underside of the tuner boards.
One screw sits exactly where it can cause the tuner to go silent. Worth checking,
Also, check or replace the two boards inter-connecting plugs/sockets. They may look fine but they usually aren't.

Martin

ALF
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ALF replied on Wed, Jun 19 2019 10:55 AM

Ok, time to report back:

first, no screws sighted - good news

where the boards #1 & 2 connect I inspected the solder joints again, two looked suspect and were reflown - the plugs itself git the deoxit

treatment.

surprisingly the two tantal caps 2C21 & 23 were put in the wrong way - I wonder whether in this instance it is important or not ??

naturally I replaced both and pit them in according to the circuit diagram !!

next I discovered the connector 1P2 was loose, not providing a secure connection to 9P84 - reflown and back in business.

I also verified continuity between 2IC6, Pin8 and its +15VDC supply, again a suspect solder joint was detected and reflown.

with all that activities finished it was time to put the tuner-boards to the test.....success, FM has been restored 🙏🤗🍷

Detecting suspect solder joints is indeed a big task and even bigger is it importance....!!

still a few “building sites” to rectify - Not yet the clean bill of health, but out of intensive care......wonderful 🤙

I shall be back with another report, for now:

big THANK YOU to all actively involved members, contributing their knowledge & experience.

ALF

chartz
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chartz replied on Thu, Jun 20 2019 7:14 AM

Well done Alf 👍🏻👍🏻

Jacques

ALF
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Hi All,

when is a project ever finished............? I won't answer that !

finally had the courage in a moment of madness - had to wait for that though - and attacked the faulty display.....!

this had to be the most punishing job I have ever done...YES, it was.....but now it looks like that....still waiting for the black glue

to seal and close the three displays properly, however a giant leap for ME - believe me!

I have attached a couple of pics.......enjoy......you should try it one day.

at this point one thing is bugging me and that is the failing memory for the FM pre-sets - I replaced the memory IC in the uP box

but sadly that did not help ?!

perhaps one of the famous fake ICs and/or perhaps another source.

would be great to get some suggestions / pointers to help....anyone ??

thanks ALF


ALF
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and another one.....


ALF
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and a last one....you will notice some stray light escaping...that is because the displays are in testing and not yet sealed !


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