QDX BS-170 replacement suggestions #magicsmoke #qdx


Roy Appleton
 

A couple of weeks ago I built my QDX V1 without incident or problems. Last week I spent the better part of the week testing it before putting it on the air and I was quite pleased with the results. I've now used it off and on for 4 or 5 days and it has been working perfectly fine on 20m, 30m and 40m. I haven't used it on 80m but it's output tested just fine on 80m. 

I'm running it on 12v. To be precise 12.06v.
The output into a dummy load was as follows.
20m - 4.0w
30m - 4.9w
40m - 3.8w
80m - 5.1w

Today I was using it on 20m (swr 1.05)for about an hour intermittently and then switched to 30m (swr 1.15) and had been operating for about an hour intermittently when it simply quit transmitting. Continued to receive just but no output on any band. When I say working intermittently I mean I was not transmitting continuously on every cycle. 

So I have to assume that the BS-170s are shot. Which brings me to the real question if the QDX is going to eat transistors what is the best technique for setting up the PCB for multiple replacements of the transistors. The pcb pads are simply too small to take repeated heating to replace the transistors! I've got a bag of BS-170s. So I can just keep shoving in more transistors until I figure out why or finally destroy the PCB in the process.

Any ideas?


Also any suggestions on tracing the transmitter chain, just in case it's not the BS-170s. I have to go read through the manual and is if there's any troubleshooting suggestions for transmit failures.

Thanks,
Roy
WA0YMH


George Korper
 

Is your QDX in a case? I have been told the QDX may draw
more current on 30 meters. Small case........


Curt wb8yyy
 

Two ways to zap bs170, too much heat or too much voltage. The former often involves some smoke, the latter just happens. But possible a different type of failure, even a solder connection. So it deserves a careful look before presuming bs170. Wait for help here before replacing those. 

Curt


George Korper
 

I have sockets that I purchased on Amazon that fit and work. Email me for link.

My first thought is that if on 30 the current is as high as reported on 30 meter transmit the overall case internal temperature will be to high if unventilated. This occurred on my Mini when using the GPS on WSPR at 4 watts out.
I released the BS 170's from the heat sink which had become a heat source and removed the back of the case.

I report this cure may be unique to my situation and not to propose anyone follow suit. 


Johan Bodin
 

You mentioned QDX V1. Did you upgrade the QDX firmware from the one shipped in the kit? There was a problem in early versions, including the version shipped with QDX batch #1. That problem was fixed in v1.02. Make sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:

So I have to assume that the BS-170s are shot.
...
Any ideas?


Jim Strohm
 

One possible replacement for the BS170 may be the 2N7000.  These are cheap, plentiful, and have similar characteristics. 

One hitch, though -- the pins are reversed, exactly left to right, from the BS170.  So this is potentially an issue, depending on how the devices are cooled.

On both devices, they appear to be running at or above max dissipation for 4 watts out. 

73
Jim N6OTQ


On Mon, Jan 24, 2022 at 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







George Korper
 

Interesting idea. If this is a solution that would be amazing. Does this fix it, when everything quits? 


Roy Appleton
 

Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.


On Mon, Jan 24, 2022, 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







Ronald Taylor
 

Check this post from sometime back regarding these transistors. 

Ron



On Mon, Jan 24, 2022 at 07:08 Roy Appleton <twelveoclockhigh@...> wrote:
Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.

On Mon, Jan 24, 2022, 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







Michael Black <mdblack98@...>
 

On Monday, January 24, 2022, 08:31:52 AM CST, Ronald Taylor <wa7gil@...> wrote:


Check this post from sometime back regarding these transistors. 

Ron



On Mon, Jan 24, 2022 at 07:08 Roy Appleton <twelveoclockhigh@...> wrote:
Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.

On Mon, Jan 24, 2022, 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







Nick Norman
 

On 24/01/2022 14:37, Michael Black via groups.io wrote:
The IRFZ44N looks like overkill and just takes a little more drive voltage.
https://www.componentsinfo.com/irfz44n-pinout-equivalent/
https://pdf1.alldatasheet.com/datasheet-pdf/view/17807/PHILIPS/IRFZ44N.html
However have you looked at the input capacitance presented to the drive system?

1n8F vs max 40pF

Regards

Nick
M0HGU
--
'What can I do? I'm only human,' he said aloud. Someone said, Not all
of you.
(Pyramids)
Mon 10373 Sep 14:45:01 GMT 1993
14:45:01 up 2 days, 20:05, 6 users, load average: 0.64, 0.58, 0.56


--
73 Nick M0HGU


Michael Black <mdblack98@...>
 

Nope -- didn't notice -- amplifier design not my forte' but the IRFZ44N was listed an equivalent.  "close enough for government" maybe.

So what is the impact of the capacitance difference?

Mike W9MDB




On Monday, January 24, 2022, 08:51:18 AM CST, Nick Norman <m0hgu@...> wrote:


On 24/01/2022 14:37, Michael Black via groups.io wrote:
> The IRFZ44N looks like overkill and just takes a little more drive voltage.
> https://www.componentsinfo.com/irfz44n-pinout-equivalent/
> https://pdf1.alldatasheet.com/datasheet-pdf/view/17807/PHILIPS/IRFZ44N.html

>

However have you looked at the input capacitance presented to the drive
system?

1n8F vs max 40pF

Regards

Nick
M0HGU
--
'What can I do? I'm only human,' he said aloud. Someone said, Not all
of you.
(Pyramids)
Mon 10373 Sep 14:45:01 GMT 1993
14:45:01 up 2 days, 20:05, 6 users, load average: 0.64, 0.58, 0.56


--
73 Nick M0HGU





Roy Appleton
 

Okay, I don't know if there's any way to edit my original post or not but I am not looking for a substitution for the transistors. I'm looking for a different way of mounting them so that I don't eventually destroy the printed circuit board from repeated replacement of the transistors!

Roy
WA0YMH

On Mon, Jan 24, 2022, 8:31 AM Ronald Taylor <wa7gil@...> wrote:
Check this post from sometime back regarding these transistors. 

Ron



On Mon, Jan 24, 2022 at 07:08 Roy Appleton <twelveoclockhigh@...> wrote:
Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.

On Mon, Jan 24, 2022, 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







Nick Norman
 

On 24/01/2022 14:55, Michael Black via groups.io wrote:
Nope -- didn't notice -- amplifier design not my forte' but the IRFZ44N was listed an equivalent.  "close enough for government" maybe.
So what is the impact of the capacitance difference?
Mike W9MDB
Mike,

The driver has to charge & discharge that capacitor every time the output level changes, it needs a much higher current capability or the gate won't keep up with the RF signal, i.e very poor 'higher' frequency operation (by higher I mean may be <10MHz??? not looked that hard) think RC filter type effect.

Regards

Nick
M0HGU


--
'Things either exist or they don't,' said Jeremy. 'I am very clear about
that. I have medicine.'
(The Thief of Time)
Mon 10373 Sep 15:05:01 GMT 1993
15:05:01 up 2 days, 20:25, 6 users, load average: 0.93, 0.83, 0.74


--
73 Nick M0HGU


William Smith
 

Pin sockets carved from a machined IC socket?

73, Willie N1JBJ

On Jan 24, 2022, at 10:02 AM, Roy Appleton <twelveoclockhigh@...> wrote:

 I'm looking for a different way of mounting them so that I don't eventually destroy the printed circuit board from repeated replacement of the transistors!


Yannig - F4IUJ
 

On Mon, Jan 24, 2022 at 04:02 PM, Roy Appleton wrote:
I'm looking for a different way of mounting them so that I don't eventually destroy the printed circuit board from repeated replacement of the transistors!
I have a bit of an history destroying transistors on my QCX+ (after several sets I realised that the coax between my ATU and the TRX was intermittently faulty :-o ) and replacing them with the right technique (at about the 3rd set!) is not that bad. I add lot of flux on the rear side of the PCB, remove as much solder as possible with a solder pump then wiggle out the transistors while heating... sometimes breaking them. If you struggle removing them, adding fresh solder can help but I don't like that as it heats up the PCB badly. I then add more flux, heat, open the holes with the solder pump from the other side and once clean resolder new transistors.

73,
Yannig, F4IUJ


William Smith
 

For components like that I usually start by cutting the leads off close to the package, removing the leads one at a time, and then desoldering the holes with braid, bulb, or pump.

73, Willie N1JBJ

On Jan 24, 2022, at 10:39 AM, Yannig - F4IUJ via groups.io <yannig.robert@...> wrote:

wiggle out the transistors while heating... sometimes breaking them


James Daldry W4JED
 

Uh, Guys

The input capacitance of 3 BS170's in parallel is 120 pf, max. The input capacitance of the IRFZ44 is 1900 pf average. That much cap looks like a 10 ohm resistor at 40 meters. You may be able to drive one with the 3 BS170's you already have, but it would end up class C and using about twice the power. Multiple band usage would require bandswitching the drive circuit.

73

Jim W4JED

On 1/24/22 09:37, Michael Black via groups.io wrote:
On Monday, January 24, 2022, 08:31:52 AM CST, Ronald Taylor <wa7gil@...> wrote:


Check this post from sometime back regarding these transistors. 

Ron



On Mon, Jan 24, 2022 at 07:08 Roy Appleton <twelveoclockhigh@...> wrote:
Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.

On Mon, Jan 24, 2022, 3:21 AM Johan Bodin <jbodin@...> wrote:
You mentioned QDX V1. Did you upgrade the QDX firmware from the one
shipped in the kit? There was a problem in early versions, including the
version shipped with QDX batch #1. That problem was fixed in v1.02. Make
sure that you have firmware v1.02 or later installed in your QDX.

73 SM6LKM

Roy Appleton wrote:
> So I have to assume that the BS-170s are shot.
> ...
> Any ideas?







Roy Appleton
 

Well I got the BS-170s out without permanently destroying the PCB! 🤣


Just used my $19 vacuum solder iron from Amazon!


Just need to find socket pins for plugging in the new BS-170s! 

Roy
WA0YMH


 

Excellent job! I'm pickin' up one of those things right away
--
Julian, N4JO.