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Output transistors BS170 replacement

 

My antenna broke and high SWR caused my QCX to cook and smell and at least one BS170 is visibly blown. Seems cannot find these locally, is 2N7000 as good? What alternatives can be used that will not reduce power or be more likely to blow?
 

2N7000 has an opposite pinout to the BS170... so the transistors have to be inserted into the board with the flats "the other way" around. Also the 2N7000 does not have such a high dissipation rating as the BS170. So is not really a good substitute.?

BS170 is quite a common transistor! I'd be surprised if you cannot find them locally!

73 Hans G0UPL

On Mon, Nov 6, 2017 at 8:18 AM, VK5EEE <vk5eee@...> wrote:
My antenna broke and high SWR caused my QCX to cook and smell and at least one BS170 is visibly blown. Seems cannot find these locally, is 2N7000 as good? What alternatives can be used that will not reduce power or be more likely to blow?


 

Thank you Hans, I did indeed manage to find a shop selling them!
w7aqk
 

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Possibly they aren¡¯t readily available in VK, but if you have Amazon, they sell them for a very small price.? One listing shows them at about $15 for 100 of them, and they are supposedly Fairchild brand, so should be decent.
?
Dave W7AQK
?
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From: Hans Summers
Sent: Monday, November 6, 2017 12:06 AM
Subject: Re: [QRPLabs] Output transistors BS170 replacement
?
2N7000 has an opposite pinout to the BS170... so the transistors have to be inserted into the board with the flats "the other way" around. Also the 2N7000 does not have such a high dissipation rating as the BS170. So is not really a good substitute.?
?
BS170 is quite a common transistor! I'd be surprised if you cannot find them locally!

73 Hans G0UPL
?
On Mon, Nov 6, 2017 at 8:18 AM, VK5EEE <vk5eee@...> wrote:
My antenna broke and high SWR caused my QCX to cook and smell and at least one BS170 is visibly blown. Seems cannot find these locally, is 2N7000 as good? What alternatives can be used that will not reduce power or be more likely to blow?
?
 

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available in VK from Element14 (Farnell) for about 15c.? Problem is, if you only order under $45 you get hit with $12 shipping

glenn

vk3pe



Virus-free.

 

you might use any mosfet, say even IRF510.
?Only issue is its placement and mounting. Of course you , if one hand, can use 2n7000 taking care of pinouts.

?All said, please remove the broken device, The unit used to have three such.
?and test once. Even with two, it would run,

Finally should sell these.


?of course it takes a month.

all the best
sarma
?vu3zmv

regards
Sarma
?

On Mon, Nov 6, 2017 at 1:19 PM, Glenn <glennp@...> wrote:

available in VK from Element14 (Farnell) for about 15c.? Problem is, if you only order under $45 you get hit with $12 shipping

glenn

vk3pe



Virus-free.


 

Have you try to check at rs-online.com? I think there is available in VK also.? I bought many component form this seller and free shipping to Thailand.

73 de E29AHU
Choke
 

Thank you dear OM Choke,

Yes I found RS-online.com from a search, good prices, and very good to know free shipping to HS because I hope to be home in HS next year.

I found here BS170 from a shop, it was more expensive, but I wanted quickly.

But now I found that also IC3 is blown, so I have to replace IC3. I think I will get holder as well as IC3 in case I blow it again.

I think IC3 was affected by the 3 transistors Q1-3 explosion from high SWR.

I hope will QSO with you, my QCX is 30m, which is your QCX? I will have 2nd QCX, I did not 100% decide if 40m or 20m, and you?

73 de Lui
 

Hi OM Lui,

My QCX is 20m version with output power ~2w? (@13.8v) by modify a turn from LPF L1, L2, L3.
I have ordered MPS751 from RS-online.com for plan to replace to Q6 by this coming weekend and will see how it change.

Good to know your home available in HS also, hope to use QCX find you on the band in some day. and sadness for your IC3 cooking.?

73 de E29AHU
Choke

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