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  1. ATU100
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Burned up cap

 

Hi folks,i was trying my atu-100 on my doublet/ocfd on 80m,it tuned down to about 1.2-1,then after a min of key down it smoked,heres a pic of the cooked cap,dous anyone know the value and type so i can repair it,cheers Paul.73 also the possible cause..
 

or where i can find? replacement,nothing on ebay.
 

Hi paul?

go on digikey and get silver mica caps > 500v .. chinese atus use 50v or 100v? versions which fail.

73's?
Jason 9H5BM




On Tue, Mar 21, 2023 at 10:53?AM paul larner <quadzillatech@...> wrote:
or where i can find? replacement,nothing on ebay.

 

any idea of the c value?
 

Paul,

As others have recommended I would use the Vishay or Mica Capacitors.

I have a Chinese made ATU-100 and run a maximum of 50 watts since I don't trust the quality of the capacitors.

Mike N2MS

On 03/20/2023 9:21 PM Paul M3VUV <nanovnauser@...> wrote:


Hi folks,i was trying my atu-100 on my doublet/ocfd on 80m,it tuned down to about 1.2-1,then after a min of key down it smoked,heres a pic of the cooked cap,dous anyone know the value and type so i can repair it,cheers Paul.73 also the possible cause..
 

Hi,

220pF

73

BOTTOM.png
TOP.png

 

Paul,

The schematic should be in this GitHub link:


73
Evan
AC9TU
 

Hi,

220pF
 

well i replaced the cap with 3 mica caps in parelell totaling 218pf,now tho i have no oled display,i have tried good known replacements but nothing,it has the 5v supply going to it,any ideas?.73
 

also digikey have some listed but none in stock and saying backorder not possible,any ideas where i can get replacements but possibly 750v versions?,cheers Paul.
 

Hi, Paul
Farnell
Mouser
Stores
 

Hi Paul,?
Was the OLED display working before and after the capacitor was burnt out?
Are you able to verify that the PIC is programmed correctly using a PICkit 2 or PICkit 3 interface?
It may be the case that the PIC was damaged or corrupted when the fault occurred.
73, Dave
 

yes it was working ok,i cant find my pikit3 to check yet,i have another kit,i have fitted the vreg diode and caps,that does nothing on the display either,i havent fitted relays or torroids yet but guess it should display something,i have tried 3 oled displays so far all look dead.
 
Edited

Hi Paul,
Not sure which firmware you are using, but the EEPROM defaults for the N7DDC software is not set for the OLED display, but if it is a kit, I would expect it should have been updated accordingly prior to shipping.
Generally for the OLED display, EEPROM Addr 0x00 = 78 and Addr 0x01 = 05.
Yes, the display should work with just the reverse voltage protection diode and regulator fitted, that's how I initially tested the kit I received.
Just double check the connections between the ATU and the OLED are correct.
73, Dave
 

i now have another cap cooked off,its the 470pf next to the one already cooked,i have 220pf caps,will 2 in paralell work?.
 

Hi Paul,
I would expect 440pF (220pF//220pF) to be okay provided the capacitors have a good voltage rating.
73, Dave
 

well it seems the cap tookout the 7805 and alsop nuked the oled,i expect the pic is toast too.

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