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Beomaster 5500 type 2332 no lights

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Philreck
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Philreck posted on Wed, Aug 31 2016 3:59 PM

Hi All,

I am struggling to get a Beomaster 5500 back to life. 

Initially the overload relay was energising, but I traced this to a bit of track that was damaged between R34 and earth. Now that is OK, but still no lights.

All the DC power supplies are a bit high:

I get

41.4v instead of 40v
37.8v instead of 28v
16.2v instead of 12v

16.4v instead of 13v
11.4v instead of 8v
7v instead of 5v.

The transformer output is 61v &11.3v ac.

I guess this is probably why it's not working, and may have damaged some components already. Any ideas why?

The other problem is that the manual on Beoworld shows the processor board as 8002607 whereas the board in this Beomaster is 8002675F and it does not have the large 8031 chip - it has TC9184P, TC9177P & TC9164N chips.

Cheers

Philip

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Philreck
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Update

My mistake - it does have the 8002607 board - I was looking in the wrong place!

Cheers

Philip

Dillen
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Dillen replied on Wed, Aug 31 2016 5:43 PM

Check your ground reference. And ground in general.

Overload relay? - Where is that?

Martin

Philreck
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Hi Martin,

Thanks for your quick reply. I was using the earth connection on the junction of the 2 large electrolytics (C6 & C7) on the 40v supply. Can you suggest a more reliable place?

The relay that I referred to is switched by the StandBy / On/Off signal from the processor, I think it can also be activated when the protect circuit in either power amp is activated - I guess it's known as something else. It is RL1 on the power board and cuts the power to the 40v supply.

Cheers

Philip

Dillen
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Dillen replied on Wed, Aug 31 2016 6:59 PM

Check that the ground connection is in fact carried on to the boards, voltage regulators etc.
I like to use the screening can on the processor board for connecting the scope and meter ground leads.

That relay is merely controlling the power to the amplfiiers.
When mains is connected, the display should intially show nothing but a red dot (and in some cases a timer status).
Do you have this dot?

Martin

Philreck
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I'll try measuring using the can as ground. I don't have the stand by dot, there is no sign of life at all externally.

Cheers

Philip

Philreck
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The voltages are the same using the can as earth.

Cheers

Philip

Dillen
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Dillen replied on Wed, Aug 31 2016 8:29 PM

If you can measure the 28V and the 40V, then the relay for the power supply must be on.
This again means, that it's contacts are either shorted or its coil powered.
37V instead of 28V is not a little to high. It's way to high.
And if you have 7V instead of 5V (that's 40% overvoltage), then most of the ICs operating off the 5V line will have died (in which case the Beomaster
is a write-off).
Check the voltage regulators (TR12, TR16 etc.) for shorts and check the ground connections around that area.

Martin

Beobuddy
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The 7V is indeed far to high. I front of the processor and other IC's there is a fuse. It might be shot as the zener shortens at a higher voltage (5.6V)

Dillen
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Dillen replied on Wed, Aug 31 2016 9:18 PM

Beobuddy:

The 7V is indeed far to high. I front of the processor and other IC's there is a fuse. It might be shot as the zener shortens at a higher voltage (5.6V)

Yes, but the voltages must be correct before eventually replacing that fuse (and zener).

Martin

Philreck
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Philreck replied on Wed, Aug 31 2016 10:21 PM

The fuse is indeed blown and the zener diode looks a bit cooked, so maybe the ICs have been saved?

I will need to sort out why the voltages are too high as Martin says, before fixing those. Any pointers about which transistors are the most likely suspects would be much appreciated. Looks like TR12-TR18 are all candidates. There is also another zener diode D5?

Thanks for the help so far. I hope this might have a happy ending.

Cheers

Philip

Beobuddy
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Dillen:

Beobuddy:

The 7V is indeed far to high. I front of the processor and other IC's there is a fuse. It might be shot as the zener shortens at a higher voltage (5.6V)

Yes, but the voltages must be correct before eventually replacing that fuse (and zener).

Martin

The tricky thing is that you can't measure this voltage with the upc-board disconnected. It will give a false reading.

So, measuring should be done by connecting the board with a replaced zener and fuse.

But the first culprit could be the zener D5 in the powersupply.

To go for the save version, change Tr 16, 17 and 18. They might be still ok, but just to be sure.

A Variac is a very helpfull instrument with this kind of problems.

Philreck
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I am struggling with getting the voltages correct on the power supplies.

I have replaced TR 16,17 & 18 plus the 3v3 zener D3. I also replaced the 5v6 zener and fuse (which had blown) on the upc board.

Unfortunately I do not have a variac, but on connecting up I briefly saw the standby led light up before the fuse blew again.

I have now replaced all the transistors in the low voltage power supply, but I still have:

10.8V on the 8V supply
6.7V on the 5V supply
13.3V on the 13V supply

TR13 has:
C 0.1v  B 12v  E 12.7 (so within 2%)

TR14 has:
C 12v  B  6.55v  E 6.17v

TR15 has:
C 7.2v  B 6.7v  E 6.17v

TR17 has:
C 0.2v  B 12.2v  E 12.7v

TR18 has:
C 12.2v  B 2.93v  E 2.4v (should be 0.3v)

I have checked diodes D4, D11 & D14

On the other power supply the voltages are also too high:

40v rail is 41.4v
28v rail is 37.8v
12v rail is 16.2v

Should it be possible to get these voltages correct when the fuse is blown in the upc board? With the upc connected and the fuse blown the relay RL1 does not activate and the 40V supply is active. If the voltages on the lower power supply are corrected, will that change the voltages in the 40/28/12v supplies?

Cheers

Philip

 

Philreck
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Well I have wasted a lot of time because I was convinced that I had replaced the D5 zener, but it turns out I hadn't !

Once that was done the voltages returned to spec.

The chips on the upc board seem to have been protected by the fuse and zener on that board as outwardly the BM now seems to be operating - the display is OK and it can be controlled from a MCP with 2 way comms. Selecting different inputs shows the correct display.

However no inputs produce any sound. When a CD is connected I can see signal on pin 21 of IC1 of the program select chip but not on pin 19 or 20 which I presume should be switched to connect the input to the preamp. With radio selected there is no signal at pin 18.

Applying a signal at C228 produces a result in the speakers, but not at C224 (before the tone control opamp).

Is there any other reason for this, apart from the over voltage destroying all the ICs on the preamp board and the tuner board?

I did have a look at the max supply voltages for some of the chips and it looked like they might be higher than the voltages I was measuring.

I suppose that if the tuner section is blown then the BM is a write off - also the program select chip (TC9184P) seems to be obsolete.

 

Philreck
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Update

I have now found and repaired 3 tracks which had hairline cracks in the top left of  pcb 3 and now signal is good from pin 12/17 of the input select IC 1 through to the speakers.

It seems that IC1 is not working though. I have checked that supply, strobe, clp & data connections are ok, but I cannot get any signal through any inputs to the preamp.

There also appears to be no radio signal (when radio is selected) at IC1 either. Tuning to a known frequency does not show 'locked' on the display as would be expected with a good stereo signal.

This Beomaster is certainly a challenge!

 

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