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U3s was working with one BS170

 

I have searched this forum to find out a solution to my problem so please bear with me. I had my U3S working just fine, transmitting on 40m WSPR and being heard as far as Canada from here in Virginia, putting out 500mw with the bifilar toroid and one BS170. However, I thought I would add two more BS170's and use 13.8v to "bump" up power out. I put them in without soldering and took off the jumper from PA to 5v, add 5v to 5v and 13.8v to the PA. Was putting out close to 4watts out. Then I soldered the BS170s in and then it happened, no more power out on my watt meter. So...I removed all three of the BS170s and replaced one back in Q1 with a new one, put the jumper back on and running off of 5v and still no power out. I can hear the oscillator on my other radio and and can decode a WSPR with it but no more power out. Someone please help.
 

Also, this might help someone help me more, the BS170 is hot or very warm to touch even when not in transmit.
 

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Your bias is probably set too high and it's self oscillating

October 28, 2017 at 7:08 PM
Also, this might help someone help me more, the BS170 is hot or very warm to touch even when not in transmit.

 

Yeah, it was, I turned it down but still I have no power out on the wattmeter. I did something wrong but just dont know what.
 

Note that compared to operating a bs170 on 12 volts, excessive dissipation is reached at a much lower rf output at 5 volts. For one device, 300 mW is a good place to stop at 5 volt operation. If you don't have an accurate qrp wattmeter you may wish to monitor bias current. Its easy to smoke a bs170 even at 5 volts.

Curt
 

Thanks, My problem is I was putting out close to 500mw, however now the meter does not move and I get no WSPR decodes. I replaced all three BS170 with a single new one. still nothing. I dont know what to do. I have checked continuity of toroids and power on the new BS170 with my DMM. Maybe I can order a new board from Hans if he sells them separately a part from the lcd, and oscillator.?
 

Robert

Possibly its just battle damage from your repair work. First check continuity through the LPF and bias choke in case it is now open. Next possibility is an open joint somewhere.? been there done that. Its a simple PA so troubleshoot when you are patient. Damage to a bs170 can't damage the board. Do stick with one bs170 for now.? 300 mW crosses oceans on wspr. If you need more help okay to email me direct.

Curt
 

Curt, thanks for your reply. I checked continuity on both the lpf and board T1 and they are good. Also replaced the BS170 again with a new one and still no power at all out. I will certainly stick with one transistor though, learned my lesson, if it aint broke dont fix it, hi hi.anyway I am a novice with kit building but am learning, albeit the hard way. There must be something simple I am overlooking. Anyway, thanks again. I may contact you via email later if I am still unsuccessful. 73, Robert N4SWD
 

I suggest you check continuity of the surrounding circuitry to each of the BS170's legs and not just at their pads. That would be Common/Ground to Source, C1 and R6 to Gate and T1 to Drain. I'm just expanding on what Curt suggested. Good luck & 73!

--Al
WD4AH

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Oh thank you so much. I was wondering what else to check. My problems are now confounded after reflowing solder joints and now only getting error si5351a. I am so frustrated.
 

I've posted before about the header socket pins being difficult to solder (and not worry about it melting). That's not to say you're having this trouble as well, but it wouldn't hurt to go over the boards with a good magnifying glass and look for cold solder joints.

I'm a big fan of the Optivisor line of headband magnifiers; I have one my dad used from the 70's and picked up a couple more at a garage sale. The 5x I use for normal work and 10x is good for checking fine detail. But, my close-up vision isn't what it used to be. Remember to breathe and again, good luck!
 

Thanks, my vision to be honest is also not like it was. I did look at it with my small magnifying glass but i do need a visor like yours because its not easy looking through the small one. I have reflowed the headers and other joints but gettimg the si5351a error.
w7aqk
 

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I would echo the compliment about Optivisor magnifiers.?? I got mine, a 2.5X from my father-in-law.? Later I picked up a 2nd one that was a bit stronger¡ªabout 3.5X? I think.? The nice thing about Optivisor vs. many of the other cheaper versions you see, is that the Optivisor lenses don¡¯t degrade as you look towards the edges of the lens.?
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More recently I¡¯ve found another method that works pretty well¡ªusing strong reading glasses.? I use readers anyway, so I¡¯m comfortable using them, even if they have a stronger diopter rating.? Sometime back I ran across a type of reading glasses that I really found to be handy.? They are called ¡°Clics¡±, and they have a lightweight collar that goes around you neck, and the two lenses separate in the middle as they are held together by a magnet!? So, when not in use, you just pop the lenses apart, and let the glasses hang around your neck.? When you want to use them, you just ¡°click¡± the two parts together magnetically.? They are really very handy.? The Clic brand is? bit expensive, but I found some knock offs that are almost identical and far cheaper (on Amazon).? So, I picked up a stronger pair¡ªabout 3.5X, and use that pair quite often for soldering work.?
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If I need something much stronger than 3.5X, like to give close inspection to a solder joint or SMD connection, I just use one of the loupes I picked up at Harbor Freight¡ªthey were cheap, but work pretty well.
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Dave W7AQK
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From: Al Holt
Sent: Tuesday, October 31, 2017 8:13 AM
Subject: Re: [QRPLabs] U3s was working with one BS170
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I've posted before about the header socket pins being difficult to solder (and not worry about it melting). That's not to say you're having this trouble as well, but it wouldn't hurt to go over the boards with a good magnifying glass and look for cold solder joints.

I'm a big fan of the Optivisor line of headband magnifiers; I have one my dad used from the 70's and picked up a couple more at a garage sale. The 5x I use for normal work and 10x is good for checking fine detail. But, my close-up vision isn't what it used to be. Remember to breathe and again, good luck!
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