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Beomaster 8000 Project

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sonavor
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sonavor posted on Tue, Aug 6 2013 8:28 AM

Here is the Beomaster 8000 that I acquired as part of an 8000 system earlier this year. I have been wanting to get this receiver working again but kept getting side-tracked. I think it is now time to dive into it. I have the service manual so I think I am set.

 

 


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Søren Mexico
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chartz:
Tim is the best!

Consider the hours he must have used for this project, not to speak of the time used before and during the project, thinking about it. I have a couple of times done "impossible" repairs on printing m/cs, reaching sometimes the point where the client declines to pay for my time. But as you have an idea and you are sure the solution is around the corner, you just goes on, not thinking about time and effort (or payment). Some of the members on this forum, has the same attitude as Tim, we never give up, and looks for solutions for the "impossible" . You dont have to be crazy to do it, but it helps.Smile

Collecting Vintage B&O is not a hobby, its a lifestyle.

chartz
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chartz replied on Tue, Nov 25 2014 11:04 PM

Crazy eh? Yes, possibly so. But I feel a bit like Steve Jobs in a reverse kind of way, we are the crazy ones, the misfits who believe that ancient devices still have something valuable in their guts, that they still have something to say. They have a soul.

Tim, Martin et al, great purveyors of parts and advice, believe in that too, and keep helping us, day in, day out. Let me thank them for that!

Back to business then.

A change of U264 - I had one spare - has not resolved my tuner issue. No control over input voltage to the varicaps, whilst displaying the whole frequency range.

I feel that I am on my own here. 

Jacques

sonavor
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What are some more details of the failed tuner?  You're getting the FM station but not the correct display?  Or are you not getting anything from the tuner? 

I just got a Beomaster 6000 back to full operating condition last night. The last thing I had to do on that one was replace the tuner signal cable (the 2-wire one inside from the tuner board to the processor board) because the cable was bad. So double-check the cable in the BM8000 if you haven't already. Also, the cable from the control panel to the processor board in the BM8000 can start breaking at the board connection. Sometimes it is hard to see that one of those connections is broken. If you are seeing the frequency jumping around it could be that control panel board connection to the processor board. On my BM8000, I finally just detached that cable, stripped new leads and re-attached it.

chartz
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chartz replied on Wed, Nov 26 2014 7:18 AM

Thank you John.

Every single wire was duly checked. In fact, they are the first elements I verified. I know about the BM6000 cable, I had the same problem, with the digits displaying 74 MHz or something like that.

I get static (hiss) in manual, and no MPX or multipath signal. Of course, no radio. The galvanometer is good though.

I will have to test the tuner boards. 

By the way, what do you say to a TP2 input that has less treble on both channels, along with a narrowed stereo image, than TP1? 

The preamp boards were fully re-capped, but it made no difference whatsoever.

Jacques

sonavor
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chartz:

By the way, what do you say to a TP2 input that has less treble on both channels, along with a narrowed stereo image, than TP1? 

The preamp boards were fully re-capped, but it made no difference whatsoever.

Does the Phono input work okay?  If the phono path is fine then I guess I would check out and try replacing 3IC1 OpAmp. You've already cleaned the input level trim pots (3R122 and 3R222), right?

chartz
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chartz replied on Wed, Nov 26 2014 8:14 AM

So I'll try replacing the op-amp then, the rest being okay. I was thinking along the same lines here, input electronic switch IC, then op-amp on TP2 line. Still I wonder how a partially defective LF can degrade sound quality that way...

Thanks! 

Jacques

chartz
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chartz replied on Sat, Nov 29 2014 3:08 PM

I thought I was about to solve the tuner issue. I found that the tuning voltage was never arriving from the connector to the front end. So I grabbed a magnifying glass and found this.

False hopes... After repair, still nothing but static. I can now see voltage at the right places, but all I can get is Vmax (22V) and Vmin (3V) before and after about 91 MHz. But this time, no zooming of radio stations.

The signal meter stays idle. It is good and the needle responds to voltage from an exterior source.

I did replace the pre-scaler (twice so I'm sure) and the 4013 flip-flops.

Jacques

chartz
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chartz replied on Sat, Nov 29 2014 4:28 PM

We have a shorted TDA1062! The 47Ω protection resistor was duly burnt, but it was difficult to see. A voltage test revealed that.

Mmmm... Don't have that in stock Angry

I'm not sure what caused the internal transistors to burn. It is shorted between PIN13 and ground. What are R6 and R11 anyway?

Is it a fragile chip? B&O fitted a protection resistor for a reason, didn't they? They knew something that we don't!

Jacques

Menahem Yachad
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Right here for you, in France.

http://www.ebay.com/itm/TDA1062-Tuner-FM-CTDA1062-/180788694030

I've bought from him a few times - quite reliable, and has most of these obsolete B&O parts.

Menahem

chartz
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chartz replied on Sat, Nov 29 2014 4:49 PM

Hi Menahem,

I've already ordered from him too! Thanks for the link! Smile

Jacques

chartz
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chartz replied on Sat, Nov 29 2014 4:49 PM

Ordered placed! (in fact, double post but I've found something else to say Stick out tongue)

Jacques

chartz
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chartz replied on Sun, Nov 30 2014 2:15 PM

One more component to replace. Let's hope it's the last one... There must be some logic here, but I don't see it.

The other transistors appear to be fine. I have tested the coils as well: I had a doubt about L7 but it is fine.

Jacques

Menahem Yachad
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Did you replace those trimmer potis?

chartz
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chartz replied on Sun, Nov 30 2014 2:37 PM

I usually let the tuner trimmers well alone. I don't have suitable equipment to handle FM circuits.

Jacques

chartz
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The new TDA1062 arrived yesterday. Then again, B&O fitted a protection resistor (R21) for a reason, I'm pretty sure that they knew the failure mode of that Telefunken chip! I think this is a first on the forum!

And the repair is a success!  Smile

The tuner now works (as usual, even without any aerial, it pulls in a few stations) and the meter and MPX beacon are back.

Pre-sets work to.

I now have a rather tatty Beomaster 8000 that is fully functional. I need new wood trims (the right one is fine, the reveiver was stocked standing on its left side, oh dear, can you imagine? Well, I sore it! (for Brits only) and the display misses a few segments.

The top is okay, not sctatched or anything, except that someone tried to lift the middle bar with a screwdriver. Sometimes... Angry

Jacques

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