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Old 17th Oct 2020, 1:12 am   #1
Kyle__B
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Default Blaupunkt Orbis transistor portable

Just picked up this beauty from a few streets over. It's in beautiful condition, not a mark on it and not a spec of dust anywhere on it, inside or out.

Since it looked good and the seller told me it was working I didn't waste much time in powering it up. Picture came through reasonably good and improved after it'd been on for ten minutes or so. No sound though, completely mute from the speaker.

After about four hours it started getting a bit funny, picture was horizontally jagged across the screen, and it was only happening in bright parts. I turned the brightness down and it would tidy up, only for it to gradually need making darker and darker.

Four and a half hour mark there's a click and the raster vanished. The tube heater is dim. No bangs happened, no foul smoke.

So, is anyone familiar with Blaupunkt tellies from the mid 70s? I'm trying to find a service manual but nothing much is turning up. I suppose it'd help if I knew the name of the chassis, but I haven't found an identifying mark. This set just says "Orbis" on it.
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Old 17th Oct 2020, 9:08 am   #2
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Default Re: Blaupunkt Orbis transistor portable

Hi Kyle

Is this the one in the Radiomuseum?

https://www.radiomuseum.org/r/blaupu...160767216.html

As a non member you can download a limited amount of the circuit/service

Hope that helps

Cheers

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Old 17th Oct 2020, 7:19 pm   #3
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Default Re: Blaupunkt Orbis transistor portable

Yep that's the one, only that circuit diagram is the wrong one. Shows a valve hybrid but this telly is completely solid state.

Found another model that has the right chassis (except different tuner controls) but I'm out of downloads.

https://www.radiomuseum.org/r/blaupu...?language_id=2
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Old 18th Oct 2020, 6:58 pm   #4
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Default Re: Blaupunkt Orbis transistor portable

Got it apart now, I think found why the speaker is silent. One of the transistors is missing it's heatsink and probably toasted itself, some of the electrolytics have got gunk coming out.

Would I be alright fitting a BD507 in place of a BD505? Doesn't seem much difference between them.

The volume control is part of a combined IF amp/demodulator chip (TBA120S), it just has a pin going to earth through a pot. Since they're not massively expensive I'll pick up a spare, just in case.

___

Regarding the line output packing in, not sure of myself. Just been using my multi-meter on bits around the LOPT.

The resistor between lopt and tube heater is reading about 16 ohms, but on the schematic (R401) it's meant to be 8.2 ohms.

Part is stamped KH16018 X, 9R1 10%. So definitely reading about twice what it should.

Could be significant? Or just my meter being a bit rubbish? All suggestions welcome.
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Old 19th Oct 2020, 5:31 am   #5
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Default Re: Blaupunkt Orbis transistor portable

Turns out multimeter was going erratic, put a new battery in and it's being sensible, the heater resister reads 11ohms now.

Checked the lopt windings and there's no breaks, and no shorts between primary/secondary or anode cap. So I assume it's fine.

What else, worked my way down the "quick fault finding" service manual page, checked all fuses, checked transistors aren't shorted. Still need to check voltages but have to wait for my croc clips to show up again.

What's got my attention is two odd parts I've never seen before in transistor packages, locations D551 and D552 labelled "flyback switch". These parts are drawn as diodes, but they're in TO-66 packages, and are stamped TD3F600.

Radio museum refers to them as "Silicon controlled rectifiers", which isn't something I'm familiar with, but the TV service manual suggests to check them.

So how do I do that?
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Old 19th Oct 2020, 4:03 pm   #6
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Default Re: Blaupunkt Orbis transistor portable

Those are thyristors. The output stage had a somewhat higher efficiency than a normal transistor stage, but was more complicated. First thing would be to check the thyristors or short circuits. That's easy without even taking them out of the circuit for the first measurement.

There's also some impulse capacitors in this circuit. I don't think they broke down often in the first 10 to 20 years, but there's a possibility that some of them are paper or mixed dielectric capacitors. When they go leaky or change capacity with age, they could probably cause the destruction of the thyristors.
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Old 19th Oct 2020, 6:27 pm   #7
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Default Re: Blaupunkt Orbis transistor portable

Hey Maarten, good seeing you again. Got that traffic simulator going?

re: impulse capacitors, that would be all the ones on the horizontal module (C301, etc) right? They're blue wima fkp-1, and they're all cracking a bit on the top corners and near the bottom.

How do I test a thyristor?
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Old 20th Oct 2020, 12:01 am   #8
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Default Re: Blaupunkt Orbis transistor portable

Hi Kyle,

FKP1 should be mostly allright. Those are already propylene capacitors so generally pretty reliable, but if they're cracked they might go open circuit slowly when exposed to moisture. The first test for thyristors would be for shorts, by putting your meter in diode mode and measuring across the conncections. If one of the measurements is low, tens of millivolts or less, there's a good chance of a short. In that case the measurement should be repeated outside the circuit. Basic functionality is a bit harder to test but can be done with a DC power supply, maybe 12V is enough so you can use a car backlight bulb or something siilar. Cathode to -, anode via a light bulb to +. Then use a resistor of maybe 1k to touch the gate to the anode. The light bulb should then turn on and stay on until you disconnect the supply.

P.S. The traffic control thingy was missing too many parts, so I stored it as a a curiosity. I'll let you know once I get to your old F6.
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Old 20th Oct 2020, 5:53 am   #9
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Default Re: Blaupunkt Orbis transistor portable

Thanks for the advice, shame about the trafficmachine.

I'd misread the circuit slightly, what I thought was D552 was actually D553 "scanning switch". The real D552 (and D554 even) are plain diodes, and also aren't fitted to this set in the first place.

In circuit test you described gives me this:

D551

cathode-gate (any direction) 0.042
Red annode black cathode no connection
red annode black gate no connection
black annode red cathode 0.456
black annode red gate 0.486

cathode-gate (any direction) 0.034
Red annode black cathode no connection
red annode black gate no connection
black annode red cathode 0.426
black annode red gate 0.451

Cathode to gate on both is a lot lower than the other results, is that alright, or should I pull them out and do the 12V and bulb test?

I tested the voltages that the fault finding page suggested.

U3 supposed to be 21V, U5 supposed to be 19V, U7 supposed to be 20.8V, but all are 4V when the multi-meter starts to settle down, and slowly go down about 0.1V every second.

Results are bad, but to be expected, because these voltages come from the secondary of the LOPT. So it's seeing some juice, but not much.
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Old 21st Oct 2020, 4:44 am   #10
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Default Re: Blaupunkt Orbis transistor portable

More poking:

U1, supposed to be 220V, sitting at 277V. Removing the horizontal control board (so it has no load whatsoever) rises to 330V.

Checked all resistors and diodes on horizontal board and around LOPT on main board found 4 duff parts, D306 shorted, R301 0.1ohms instead of 6.8ohms. R398 447 Ohms instead of 1.1K, R375 1ohm (!!) instead of 33K.

So will replace those parts, all pulse caps on horizontal board, and if nobody objects, the thyristors too.

It really can't be more complicated than that, can it?
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Old 21st Oct 2020, 11:30 am   #11
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Default Re: Blaupunkt Orbis transistor portable

The thyristors seem fine on a first glance, the low measurement on the gates could be the drive transformers. I'll try to have a look at the schematic tonight. The shorted diode is clearly a clue. The resistor measurements seem strange, if you measured them in circuit, they're likely fine or could even be open circut, but a short or 0.1 ohm measurement could point to a short in a nearby part.
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Old 21st Oct 2020, 2:44 pm   #12
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Default Re: Blaupunkt Orbis transistor portable

This is interesting. I've never heard of a mono portable with a thyristor line output stage before.
The fact your tube heaters are dim suggests to me that the line stage is operating to a limited extent. From your description of the fault, I'd be inclined to suspect the EHT rectifier. If you remove the final anode cap from the CRT, insulate well and power up, do the heaters glow brighter?
If the rectifier diode in the transformer has shorted, you could always fit one in series with the EHT cable. This was a common repair over here for the Thorn 1690 series of portables.
Like Maarten, I'm a little confused by your resistor readings. I'd remove them from circuit and re-test them - also compare with new ones just in case your meter is playing tricks.
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Old 21st Oct 2020, 7:04 pm   #13
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Default Re: Blaupunkt Orbis transistor portable

ok mr anorak we might be getting somewhere. Did exactly what you said with the anode cap, heater came up hotter! Not by much, it just has a tiny glow now. Telly also made a high pitched whine so I turned it off quick and didn't test any voltages.

The diode inside the lopt is only written D561 on the schematic, and it's encased in resin. However, it's in series with a resistor (also inside the resin), value of 8.2k 1/4W, and the HT is marked 18kV.

So if I put a diode into the cable, what would be an appropriate one, and what should I use to insulate the splice in the cable? I don't think normal heat shrink is good for near 20,000 volts?
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Old 22nd Oct 2020, 12:38 am   #14
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Default Re: Blaupunkt Orbis transistor portable

Quote:
Originally Posted by Kyle__B View Post
More poking:

Checked all resistors and diodes on horizontal board and around LOPT on main board found 4 duff parts, D306 shorted, R301 0.1ohms instead of 6.8ohms. R398 447 Ohms instead of 1.1K, R375 1ohm (!!) instead of 33K.
If you measured this in circuit these results would be normal
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Old 22nd Oct 2020, 1:06 am   #15
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Default Re: Blaupunkt Orbis transistor portable

Might well be, hans. But every other part I tested gave the numbers on the schematic.

EHT diode recommendations? I can't find anything rated for 18kv in my catalogues.
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Old 22nd Oct 2020, 1:51 am   #16
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Default Re: Blaupunkt Orbis transistor portable

I've looked at the schematic. All measurements make sense in circuit, except maybe the K-G measurement of the thyristors of which I'm not 100% sure. D306 is across a coil hence will always measure short in circuit, similar conditions apply to the resistors.

So no need to replace the resistors and diode. Since there's some activity I assume the thyristors are also working, though I lack experience with this kind of deflection circuit.

There's a small chance something is wrong with a capacitor, but since disconnecting the anode connection makes a difference, that might be the first symptom to look into a bit further. With disconnected anode, what voltages are on the U2, U3 and U7 lines? They should be at their full voltage if the EHT rectifier is the cause of the problem.

Last edited by Maarten; 22nd Oct 2020 at 2:06 am.
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Old 22nd Oct 2020, 3:16 am   #17
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Default Re: Blaupunkt Orbis transistor portable

I'm glad that component tests with multimeter turned out to be ok.

about voltages

U2 135V
U3 24.5V
U5 22.7V
U5 21.7V

supposed to be

U2 145V
U3 21V
U5 19V
U7 20.8V

It came to me without sound working, so I think that's a missing load effecting results a little, but otherwise good results?

Makes a loud high pitch squeal with anode connected, don't like that much.
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Old 22nd Oct 2020, 9:38 am   #18
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Default Re: Blaupunkt Orbis transistor portable

Those voltages seem close enough to the manual, and prove that the output stage is working and not being loaded down by a short on the LT lines.
The EHT diode's a bit tricky. The ones I mentioned earlier had the diode in the anode cap which was slightly bigger than usual to accomodate it, but it's only small. You could possibly use a couple of lower voltage rated ones on series just to check whether you get a raster.
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Old 22nd Oct 2020, 3:09 pm   #19
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Default Re: Blaupunkt Orbis transistor portable

I've just found some 20KV diodes up on a high voltage specialist site in germany, wasn't even that expensive, about a quid each. Good for 30mA and 100ns response time.

Question is, what can I use to insulate it? Most heat shrinks I can find aren't branded, or else don't have a listed breakdown voltage.
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Old 22nd Oct 2020, 4:08 pm   #20
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Default Re: Blaupunkt Orbis transistor portable

Depends on what you can get. For a quick test, I would put 20 pieces of UF4007 (NOT 1N4007!) in series, they are 1kV diodes and widely available. For a more peranent solution, a 20kV diode would be ideal, but I would have to look up whether those are readily available.
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