Date   
Re: Just finished old TennaDipper Deluxe

ajparent1/kb1gmx
 

I have one with the then vendors case and its a handy item for check and tuning
mobile whips without bringing the MFJ259B.

Enjoy!

Allison

Just finished old TennaDipper Deluxe

 

Great little kit I got off a ebay sale. Wish it had the original case but the one I got works out pretty good, no internal battery.

Case is not a the type I normally get with the top and bottom separate but it worked out nice.

 

https://www.ebay.com/itm/Aluminum-Enclosure-Electronic-DIY-PCB-Instrument-Project-Box-Case-100x74x29mm/380783805864?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Re: Troubleshooting the SB II

John AE5X
 
Edited

I will pull the processor out and re-install with the socket - didn't mean to skip the socket the first time around. I can remove it fairly easily with Chip-Quick that I have on hand. The Si5351 chip and display are installed correctly.

Re: Troubleshooting the SB II

Don, ND6T
 

Lacking a good variable supply for testing, try this instead: With pin 3 of U7 still isolated, attach a 100 ohm resistor from it to ground while measuring the voltage on the pin. This will provide a 33 ma current load. The chip is rated to 50 ma. It should present a nice 3.3 volts. If not, then replace the bad chip. If the voltage holds at 3.3 volts, remove the display and test.

Re: Troubleshooting the SB II

Steven Weber
 

 

Unless the display is in the wrong way around, I doubt that’s it. It’s a shame you didn’t socket the processor as pulling that could be telling. I doubt it’s the regulator, those are nearly indestructible. Could be the Si5351 chip is in the wrong way around.

 

There are only three things connected to the 3.3V supply, the processor, the display and the Si5351. Sorry I didn’t make the 3.3V supply track more accessible otherwise you could cut the track between the different pieces and see which one is pulling down the supply. Does the regulator get hot?

 

 

 

Two possibilities spring to mind: One is that the failure is a load with a breakdown voltage below 3.3 volts. That would look good on a low-voltage ohm meter but present an excessive current drain under operating voltage. This might be seen (or may not) by using the diode function on your DMM. Some DMMs have highter diode test voltages than others.
The other possibility is a bad regulator chip. It just might THINK that the load exceeds that 50ma rating and shuts down. Were you able to substitute the 3.3 volts and monitor the current as you increased it slowly from zero?
I would still suspect that the fault lies within the LCD display. I would remove it before anything else. Just a feeling.
Voltage regulators are extremely reliable.

 

Re: Troubleshooting the SB II

Don, ND6T
 

Two possibilities spring to mind: One is that the failure is a load with a breakdown voltage below 3.3 volts. That would look good on a low-voltage ohm meter but present an excessive current drain under operating voltage. This might be seen (or may not) by using the diode function on your DMM. Some DMMs have highter diode test voltages than others.
The other possibility is a bad regulator chip. It just might THINK that the load exceeds that 50ma rating and shuts down. Were you able to substitute the 3.3 volts and monitor the current as you increased it slowly from zero?
I would still suspect that the fault lies within the LCD display. I would remove it before anything else. Just a feeling.
Voltage regulators are extremely reliable.

Re: Troubleshooting the SB II

John AE5X
 
Edited

I finally had time to return to this...

With the output pin of the 3.3V regulator lifted I get 3.7V as shown in photo above. With it re-soldered to the board, I only get 0.4V indicating to me that something downstream is loading it down or shorted to ground. Ohmmeter readings of the pad show that not to be the case - I get from 800k-ohms to ground on the output pad (this value rises as C73 and C76 charge as a result of the meter's voltage).

I'm baffled...

Re: Blank display on SBII

Don, ND6T
 

I just realized that I had not tied up this string of messages. Please forgive me.
The issue was caused by a defective display. A new one, ordered from Amazon, performed just fine.
My groping about in the dark caused me further problems, though. When I "erased" the EEPROM settings upon re-loading the firmware I used the Arduino default of loading all zeros into EEPROM. Wrong! You need to load all ones for this firmware. Duh! Read the code, Don!
Dissection of the original display revealed a microscopic crack in the substrate of the LCD (not the carrier board). Likely it worked through any QC tests before it opened. The SB2 is an incredible rig. No one can tell that I am not using an Elecraft. AGC is superb. CW operation is a dream. This was a really fun build.

Re: SB II Final Transistor Heat Sink

ajparent1/kb1gmx
 

I said I didn't take a picture of SB-1 and SBII is uncased and pending so I've left it stock for now.
Likely I'll do something but first I want to decide if it  will stay on 40 or move to 80 or maybe
elsewhere.

No fan, on the SB1 or likely for SBII as I really am onto into FT-8, I'd rather plant grass and
watch it grow.

Allison

Re: SB II Final Transistor Heat Sink

n9dxp
 

Thank you very much Allison! That it all very helpful information. Would you by any chance have a picture of your radio? Did you use a fan?

 

Thanks,

 

George

Re: SB2 Q6 failure

ajparent1/kb1gmx
 

I went with the 4148. 

Based on older experience (and the SB1) I was more comfortable with that.


Allison

Re: SB II Final Transistor Heat Sink

ajparent1/kb1gmx
 

On my  SB1 20M whch had a very similar outline and layout just different display.

I used a block of aluminum behind the final to couple it to the aluminum front panel 
in place of a spacer and an Lshaped aluminum (1" Angle alumnum) to go from
behind the irf510 to the block on the other side of the board.  The Angle aluminum
was about .1 thick. The idea was conduct the heat to the front panel (.080 aluminum)
and take advantage of the surface area.  For voice it never even got warm.   
Sorry no pictures.

For digital work the heat sink must be huge compared to the supplied one as the
full power transmit time is 100% effectively.   Voice work the average power is
under 20% often less.  Also the box must have air flow to allow heat from the final
and its larger heatsink to escape the case.  Consider using a small 40 to 60mm
fan for cooling as well. The major trick is do not make the IRF510 leads longer
or stability may be compromised. also note the tab is the drain connection so
it has the main power on it and RF so it must be insulated from any cooling
structure (it must conduct heat) and that structure must be grounded.

The IRF510 can stand up and have a block of aluminum to couple the
heat to the back  of the case.  For that I'd say a block .625"W x1"D x1"H
might do well to get to the edge of the board and couple heat to a larger
finned heatsink.   the IRF510 is mounted to the .625" wise face and the
1"x1" face to the heatsink.  Again insulating kit and ground the heatsink.

Allison

SB II Final Transistor Heat Sink

n9dxp
 

Hello all,

 

I have enjoyed following the updates on the new Slop Bucket II projects. I have S/N 120 which will be used on 40 meters mostly digital modes. I have almost all of the surface mount components installed (I do them by hand). I am wondering if anyone might have any thoughts or suggestions on a more substantial heat sink for the digital modes.

 

Thanks,

 

George, N9DXP

Johnson City,TN

Re: SB2 Q6 failure

Steven Weber
 

 

Couldn’t hurt.

 

So, not having built my SB2 yet and planning on 40 meters, should I simply replace Q6 with a 4148?

 

Re: SB2 Q6 failure

ohwenzelph
 

So, not having built my SB2 yet and planning on 40 meters, should I simply replace Q6 with a 4148?

Re: Troubleshooting the SB II

Don, ND6T
 

It could still be the regulator. It looks like you decided not to socket U8? That socket would be very helpful for several reasons.
If you have a really good bench supply you could try substituting the 3.3 volts (with the regulator still isolated) by gently bringing it up from zero while monitoring the current. That would exonerate the regulator. I'm not sure what current would be normal but it is reasonable to assume that it will be below 30 milliamps. The rest of the board left de-powered, of course. If it acts like it will draw more than that, remove the display module and try again. My display came damaged internally so I am suspicious of it more than anything else.

Re: Troubleshooting the SB II

John AE5X
 

With pin 5 lifted I'm now showing the correct voltage. I was hoping I wouldn't as I would then know the problem :-(

So either something downstream is loading it down or is wasn't soldered properly in the first place. C73 and C76 are not shorted, neither are R56 or R57, and U28 pins 27 and 28 are not shorted to ground or each other.

I'll solder pin 5 back tomorrow, can't troubleshoot further tonight. Thanks for the suggestions, I appreciate it.

73 - John

Re: SB2 Q6 failure

Don, ND6T
 

Indeed. The voltage on that end is just about that level, too. I had to try, but yes, the next occupant of those pads will be a good ol' 1N4148.
The simplest of things often prove to have an incredible complexity.
Thanks Allison. Nothing beats experience.

Re: Troubleshooting the SB II

Don, ND6T
 

Next step would be to lift pin 5, slip insulation beneath, and test. Sounds like you have it cornered.

Re: SB2 Q6 failure

ajparent1/kb1gmx
 

On a technicality it would seem that way but gate to source or gate to drain is the same based on over voltage on the gate
relative to any pin (FYI that's 20V).  Its something that is variable in some circuits due to gate to source(or drain)
capacitance making a RF voltage divider.  It may be more likely due to two things your at 75M and likely the
IRF510 tends to put out a bit more power there.

Its a bit of nastiness I got to see doing some class D and E amplifier work.  Punch the gate oxide
and bad things happen.  Most of the time I got to see that when the drain exceeded the drivers
ability to keep the gate below 20V due to Miller capacitance.  Near instant poof.  It tended to
happen more at 6.77mhz than at 13.55 or 27mhz.   

Allison