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Philips K80

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acj1980
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Yesterday a friend of mine came with this Philips S26K1144, better known as K80 chassis. Last time it was used was in 1986, so the most of the day I turned very slowly on the power, and got picture on the screen, but it has some fault. Very similar to another K80 I had 1 year ago where the EHT fault and the HV drops like someone cut the voltage and the PY500 glows up. Unfortunately I don't have a schematic, but it seems to be a oscillator issue? Maybe it stops?!.

im trying to get some pictures in my thread, but i wont work tonight, so i try tomorrow

 
Posted : 01/09/2019 7:31 pm
crustytv
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Posted by: @acj1980

i dont have a schematic,

The K80 service data is in this sites data library and you do have access. ? 

Posted by: @acj1980

im trying to get some pictures in my thread, but i wont work tonight, so i try tomorrow

I checked the upload library and can see two photo's you tried to load. One had a ridiculously long file name and was very close to the maximum file size allowed. The second was a shorter name and half the size. Both however were corrupt as when I downloaded them and tried to view them, they were unrecognised as a valid format, despite their extensions being .jpeg and .jpg something has corrupted them. Its not the forum as I test loaded a photo and it was fine. must be something local to you.

I recommend you recheck the photo your end before attempting to re-upload. Keep the file name short and the file size under the max allowed.  

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Posted : 01/09/2019 7:35 pm
acj1980
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@crustytv

Hi, hmm i forgot how to enter the VIP area, its beind a long while since i was there, and yes i think it could be the fault about the pictures, i transferred them from my cellphone to my computer via Facebook, FB makes something to the name and size 🙁 

 
Posted : 01/09/2019 7:50 pm
crustytv
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Posted by: @acj1980

hmm i forgot how to enter the VIP area, its beind a long while since i was there

Data library is accessed via the "Hot Link" bubbles (see below). 

If you're on a PC/Laptop they will appear on the right-hand side menu. If on a mobile or tablet, swipe down until you see the bubbles.

eg1

Hot Link Bubbles

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Crusty's TV/VCR Collection: View my collection
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Posted : 01/09/2019 7:53 pm
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acj1980
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@crustytv

Oh yes now i remember, thanx mate 🙂 

i take a look on the schematic, it´s really strange, 2 K80 with same EHT fault :-/ 

 
Posted : 01/09/2019 7:57 pm
acj1980
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my K80 is similar to this, http://www.timonradiosivut.fi/Philips_K80NF.html

 

Alex 🙂 

 
Posted : 01/09/2019 7:59 pm
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PYE625
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Sounds like a capacitor breaking down....possibly in the boost HT line at a guess?

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 01/09/2019 7:59 pm
acj1980
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@pye625

thanx 🙂 i check it out on thuesday/wednesday whem i´m of from work 🙂

 
Posted : 01/09/2019 8:15 pm
Nuvistor
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I will check the circuit, be interesting to look it over.

Frank

 
Posted : 01/09/2019 8:28 pm
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PYE625
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It is fairly complex and needs some time and care taken to check the voltages and possibly waveforms by the circuit data. At least there is a tripler, rather than the valve shunt-stabilsed PD510/GY501 arrangement like the K70 chassis, so a bit safer. ? 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 01/09/2019 8:40 pm
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PYE625
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Alex.... I am sure you know, but be careful not to have the set switched on for long if the PY500 is glowing red hot. ? 

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 01/09/2019 9:00 pm
Nuvistor
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The set has two PL509 valves, normally with no line Oscillator drive both the output valve and boost diode would overheat and glow red. However with two output valves this may not occur and although drawing two much current the output valves may not glow.

 

The output valves G1 should be  about -60 volts, if that is ok, you could always check the wave shape and frequency with a scope, it would appear the line drive is ok. If you have a lack of line drive, remove the screen feed resistors on the output valves, this will reduce the current through them to a safe value while fault finding on the line Oscillator drive circuit.

 

If you have line drive, then like Andrew states I would be checking the capacitors in the line output stage.

 

 

 

Frank

 
Posted : 02/09/2019 9:05 am
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acj1980
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@nuvistor

well i measured -58 volt on both PL509/19 at G1, and there was a fine waveform, so im not concerned about the oscillator circuit, and i tryed wit tripler  off, and the py500A is still getting red, i noticed that there i still a kind of small voltage out from the line transformer, if i place my screwdriver on the tripler input i can se small sparks.

i guess maybe the py500 is faulty, because i notice some stranges behavier before it overheat, it have some white light behind the anode end cathode,  maybe it could possibly leak in the wrong direction, that fault will overheat py500A i think?

 

@Pye625 Andrew, yes i know, i only have the TV set switched on for few seconds when the tubes are placed with top connections mounted on, i remove them if i have the TV turned on for more than that :-), i dont want to damage more.

 

I have to get 2 x pl519 and a new py500A , just i case, i notice both pl519 have marks inside the tube, (marks after long time using) 

 

Sincerely Alex

 
Posted : 03/09/2019 9:22 pm
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Nuvistor
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Has a complete guess check C1699 0.1ufd probably 1250-1500vw, a leak in that will overload the PY500.

 

Frank

 
Posted : 03/09/2019 9:59 pm
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PYE625
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Posted by: @acj1980

 

i guess maybe the py500 is faulty, because i notice some stranges behavier before it overheat, it have some white light behind the anode end cathode,  maybe it could possibly leak in the wrong direction, that fault will overheat py500A i think?

Hi Alex, it is more likely that a circuit fault is causing too much current through the PY500. It could explain why you saw the valve arc internally with a light between anode and cathode. Before fitting a new one, best to check for any shorts elsewhere in the circuit. The PL519's are probably OK, some marks and staining inside the glass is normal after long use. But I would replace the PY500 as it could contain gas after it has been overloaded.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 04/09/2019 8:10 am
Cathovisor
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Posted by: @pye625

I would replace the PY500 as it could contain gas after it has been overloaded.

Now, I'd have thought that any outgassing of the electrode structure (up to a point) would be taken care of by the gettering? 

 
Posted : 04/09/2019 12:46 pm
PYE625
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Yes indeed, it does under normal operating conditions and the PY500 is a tough valve. But severe overload will certainly damage the cathode material and possibly the anode too, releasing quite a bit of gas from the vaporised material.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 04/09/2019 3:50 pm
acj1980
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@nuvistor

i think you´re right about it, i check it tomorrow, today i have a day off from work and was in the radio museum and get some new tubes ( 2x pl519 ans 1x py500a) , 🙂 

 

thanx for all your great answers, 

Alex

 
Posted : 04/09/2019 8:59 pm
acj1980
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@nuvistor

i replaced c1699 this evening, but the same fault, maybe it´s the line transformer ? 

 
Posted : 11/09/2019 9:42 pm
PYE625
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Hi Alex,

Try disconecting the tripler from the line transformer and see if the PY500 then stops overheating.

To understand the black art of electronics is to understand witchcraft. Andrew.

 
Posted : 12/09/2019 5:46 am
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