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Old 16th Feb 2019, 10:35 am   #21
PJL
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Default Re: Hacker Cavalier with dimming output

..or C8 is leaky
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Old 16th Feb 2019, 9:29 pm   #22
opus242
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Default Re: Hacker Cavalier with dimming output

HI All
once again many thanks for your time on this.
have included a picture of the latest findings -
point a - 253 vdc
b 271
g 199
h 249
i 4.5
j 0
k 4.7

c and e both hit around 50 then nose-dived d and f hit the 20's then went south too
l onward where 0v
x 191 and y 21 with this measuring 1k9
the resisters at i and k both measured 189 ohms which I don't think is good.


the 10k R10 couldn't be found on the part of the board I have been looking at.
R15 came in at 949 ohm the rest are in the picture.
c8 is next on the hit list.

as for meter - I use a fluke 12b which is autosensing since the last set of batteries died in my avo.
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Old 16th Feb 2019, 10:08 pm   #23
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Default Re: Hacker Cavalier with dimming output

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Originally Posted by opus242 View Post
x 191 and y 21 with this measuring 1k9
That's the formula for smoke....

Lawrence.
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Old 16th Feb 2019, 10:11 pm   #24
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Default Re: Hacker Cavalier with dimming output

lol - thats good news . ... not
ok where should I be going from here
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Old 16th Feb 2019, 10:14 pm   #25
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Default Re: Hacker Cavalier with dimming output

Quote:
Originally Posted by opus242 View Post
HI All
once again many thanks for your time on this.
have included a picture of the latest findings -
point a - 253 vdc
b 271
g 199
h 249
i 4.5
j 0
k 4.7

c and e both hit around 50 then nose-dived d and f hit the 20's then went south too
l onward where 0v
x 191 and y 21 with this measuring 1k9
the resisters at i and k both measured 189 ohms which I don't think is good.


the 10k R10 couldn't be found on the part of the board I have been looking at.
R15 came in at 949 ohm the rest are in the picture.
c8 is next on the hit list.

as for meter - I use a fluke 12b which is autosensing since the last set of batteries died in my avo.
It's hard to make head or tail out of this. Can we have some readings of voltages on the valve pins as requested in post #19 please.
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Old 17th Feb 2019, 8:22 am   #26
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Default Re: Hacker Cavalier with dimming output

Morning opus,
That pretty well confirms what we are all thinking, C8, the blue 8uF one, has failed seriously and gone low resistance. It will need to be replaced by a 10uF 300 volt cap.

The 10K resistor R10 is the one I marked on the picture last time (post no. 19?)
and is the one you have between x and y. That too will be a dead duck now, so order a 10k ohm 2 or 3 watt replacement.

While you wait for parts, you could try removing one leg of the blue cap and see if the voltages improve.

Station X, yes a bit of a jigsaw, but we at least know what opus is referring to using his 'method'

Alan

PS, forgot to say about the resistors marked i and k, they are the cathode resistors R13 and R14. I would replace them too with the correct value, 220 ohms 2 or 3 watt types, as it will run the valves just a little 'cooler'.

And I have re-posted the location drawing so we can all see what is what... A
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Last edited by snowman_al; 17th Feb 2019 at 8:38 am. Reason: PS added
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Old 17th Feb 2019, 9:02 am   #27
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Default Re: Hacker Cavalier with dimming output

R15 a 1.5k seems low according to the photo, shown as 900ohms.
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Old 17th Feb 2019, 9:41 am   #28
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Default Re: Hacker Cavalier with dimming output

Many thanks to everyone.
What wattage are looking for r15.?
Don't think I have had a resistor go like r10 before
Thanks again
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Old 17th Feb 2019, 10:29 am   #29
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Default Re: Hacker Cavalier with dimming output

Hi opus,
May I suggest that before you order a new R15, you measure its resistance 'out of circuit' ? It might be that C11 and C12 are also leaking electrically, as well as C8, and are effectively in series with R12 when in circuit.
Unsolder one end of R12 and then take a reading.
That way it is not connected to other components and will give you a true measurement.
If it is closer to 1.5K out of circuit it does not need changing. If it stays at 900 or so ohms then a 3 watt 1.5K ohm replacement will be fine.
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Old 17th Feb 2019, 5:52 pm   #30
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Default Re: Hacker Cavalier with dimming output

Thank you all.
As per Alan and Nuvistor I have swapped out the resistors and caps( a tad over the top as had a selection of 5watts and 350v parts ) and joy of joys I have noise.
Many thanks to you all...
Now where is that Dynatron..😁
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Old 18th Feb 2019, 7:51 am   #31
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Default Re: Hacker Cavalier with dimming output

Good news.
Just one more thing before you leave it, just make sure the big can capacitor, C11 and C12, is not getting warmer (or hot even) than the chassis. If it is, best to replace it/them.

Alan
Now where is that Dynatron...
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Old 18th Feb 2019, 11:16 am   #32
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Default Re: Hacker Cavalier with dimming output

Quote:
Originally Posted by opus242 View Post
Thank you all.
As per Alan and Nuvistor I have swapped out the resistors and caps( a tad over the top as had a selection of 5watts and 350v parts ) and joy of joys I have noise.
Many thanks to you all...
Now where is that Dynatron..😁
that's good, I love a happy ending
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Old 18th Feb 2019, 11:58 am   #33
opus242
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Default Re: Hacker Cavalier with dimming output

Quote:
Originally Posted by snowman_al View Post
Good news.
Just one more thing before you leave it, just make sure the big can capacitor, C11 and C12, is not getting warmer (or hot even) than the chassis. If it is, best to replace it/them.

Alan
Now where is that Dynatron...
Hi Alan
I didn't notice last night but then wasn't looking for that.
I did see that is a dual/double cap and was surprised not to see it leaking when I first fired up, so will double check.
thanks
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