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Old 7th Jul 2021, 12:15 am   #1
bionicmerlin
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Default Ekco T542 (Pye 169 chassis)

I didn’t really want this set as I got to many other sets, but if it wasn’t for me it would of gone to landfill. I couldn’t let that happen so being the only bidder I won it. It’s got the original legs and in excellent condition apart from a chip on the front .
I believe it’s basically a Pye with different war paint .

All ready I’m stuck..
I snipped the main filter cap and slowly powered up on a Variac. Nearing full voltage hey presto nothing happened except R32 started smoking. It's not dust it’s overload. I tried the set 3 times and quickly had to switch off.
I can’t see anything why it would do this. Components near by look and test OK apart from a cooked C34 near a wire wound resistor. That’s now been replaced.
VT5 transistor has in the past been replaced.
I’m stuck so hopefully someone can help
Andy
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Last edited by bionicmerlin; 7th Jul 2021 at 12:26 am.
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Old 7th Jul 2021, 12:36 am   #2
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Default Re: Ekco T542 (Pye 169 chassis)

Just a couple more pics . Hopefully jog a few memories.
Showing R32.
Andy
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Old 7th Jul 2021, 6:52 am   #3
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Default Re: Ekco T542 (Pye 169 chassis)

First , I would remove VT5. Is it S/C?

Then power up and check your HT lines, and the voltage at the junction of R32 & R33.

Good luck.

Cheers. SimonT.
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Old 7th Jul 2021, 8:04 am   #4
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Default Re: Ekco T542 (Pye 169 chassis)

VT5 was a stock fault but usually O/C base emitter but no reason it cannot be S/C.

When you say nothing happened did that include no heaters lit up?
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Old 7th Jul 2021, 9:25 am   #5
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Default Re: Ekco T542 (Pye 169 chassis)

BF178 is a bit close to its limits here.

I would have used a BF259 or BF337 as replacement back then.
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Old 9th Jul 2021, 2:25 am   #6
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Default Re: Ekco T542 (Pye 169 chassis)

Bit of a update..
And thanks so far.
I removed the said transistor. Testing it on a meter I would say it’s ok. Not shorted. But it appears to be a BF257. Not One that you recommended.
By removing the transistor R32 its not smoking. Having said that it’s still running very hot.
Due to the smoking I probably didn’t give the set a chance to warm up . The valves lite up and I am now getting sound..
I have measured the HT results showing in the picture. According to the reading they are much to high. Andy
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Old 9th Jul 2021, 9:45 am   #7
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Default Re: Ekco T542 (Pye 169 chassis)

I liked the 169 chassis it gave very good pictures. What are the Voltages like around VT5? It could be being turned hard on either due to a problem around the contrast control RV3, C31 being leaky or if you are unlucky to high a voltage on pin12 of the IC.
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Old 9th Jul 2021, 2:17 pm   #8
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Default Re: Ekco T542 (Pye 169 chassis)

The voltage without the transistor at R32/33 is 156 volts. . I have had a little look and test around the contrast . It seems in order . I will have a better look later and maybe put the transistor back in and test again and voltages . Thanks everyone Andy
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Old 9th Jul 2021, 2:53 pm   #9
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Default Re: Ekco T542 (Pye 169 chassis)

257 just a lower gain version of 259. If the transistor runs a bit hot, try one of the
push on corrugated metal heatsinks for TO-5/TO-39 transistors - you may have one.
As the can is collector voltage, ensure it can't touch any other component.
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Old 10th Jul 2021, 2:02 am   #10
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Default Re: Ekco T542 (Pye 169 chassis)

Well THE GOOD ,BAD and probably THE UGLY
The good bit . I put the transistor back in with a heat sink as suggested. I did check C31 it appears ok , the contrast pot is abit suspect so turned it to its lowest setting and switched on
Chassis hinged down looking out for smoke . This time no smoke and also I got a picture and sound. Great. After a few mins no smoke , even better.
Now the BAD bit . Stupid me, with the chassis still down and the set still working I push the chassis back towards the upright position . There is a pop and I loose sound and picture.
Now the Ugly bit. I don’t know what I done wrong to cause the pop , I can’t see any reason or any loose wiring. Or maybe just coincidence it would of gone anyway. I guess the fault is in the IF stage as I get a blank screen and a hiss from the volume so the amps working.
It’s getting late so I will have look later. Andy
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