Topics

Help on parts and or repairs !

chuckr@hostu.org
 

What a trip! Got my kit a few months back and even before I stared the
build I came across KD8CEC mods and followed that until I had that done,
built my case installed (may have buggered something at this time) the
board etc. Receive works, but the finals blew on first ptt, repalced,
check all and again blew burning trace to pa. fixed trec replaced pa's
third time and again the same. Tried checking things but nothing found,
Did fine one leg of bias pot missing ??? On fourth try after replacing
pa's and 10k bias pots there was no smoke, actually nothing, no current
draw, my circuit diagonis and my age is getting worse and older :). I have
come to this, I want to just buy a new board and drop it in my case and
should be good to go.. Where and how do i go about just ordering a main
board... thanks for reading this kind of long post and any help
appreciated.

chucck

Curt
 

Chuck

A new board can be ordered from hfsignals.com

I am mystified by the finals, I wonder if you have a shorted pot or just too much current.

I suggest getting it working in stock form before any mods, including adding kd8cec firmware. Take small steps in your build.

Curt

Timothy Fidler
 

Chuck I am sitting here on the side but this has happened before.
1. The uBitx as it comes from factory,  (you may have a Bitx40 you are not specific) is supposed to be biased correctly and the bias
instructions are supposed to be for set up a new pair of Mosfets. HOWEVER it would only take someone at the factory to be asleep and you could be where you are.
2. There have been a  vast number of IRF510 mafrs over years and they are not all born equal.  If you bought second tier components you may still have issues.
3. (the most useful one - possible GET OUT OF Jail ) . There are or used to be (Ashar Farhan does not ring me up to tell me every PCB rev) a number of top to bottom vias on the PCB around the IRFs.  If you look front to back and against the schema you will pick em up. Some are carring a lot of RF.  These have a rather sensitive plated through hole.  Clearly it is hard to test them with a DVM unless you have a known good PCB along side - ie a reading non Zero on ohms may still be acceptable.  However if fully toasted then putting through a bit of say Cat5e wire or a component lead and soldering both sides may just may get you out of jail. BUT at 30 Mhz the impedance of the fix will not be the same as a thin Cu PCB layer so you still may have a Princess board. 

Enough.

chuckr@hostu.org
 

On Tue, December 25, 2018 8:14 pm, Curt via Groups.Io wrote:
Chuck


A new board can be ordered from hfsignals.com

I could only find link to complete kit, is their a link to just the parts
ie: main board as it comes in a kir ?

I did send an email a couple of weeks back to hfsignals but have heard
nothing back... Thanks






I am mystified by the finals, I wonder if you have a shorted pot or just
too much current.

I suggest getting it working in stock form before any mods, including
adding kd8cec firmware. Take small steps in your build.

Curt





chuckr@hostu.org
 

I could only find link to complete kit, is their a link to just the parts
ie: main board as it comes in a kit ?

I did send an email a couple of weeks back to hfsignals but have heard
nothing back... Thanks

Dexter N Muir
 

Reviewing this tale of woe, I find no mention of initial bias. It's a common failing that people will 'zero' the pots before power-on, and *before* RTFM! Reading that fine manual will reveal the bias pots to be wired the 'wrong' way, i.e. fully clockwise to zero. Leaving them with factory-setting is recommended until either 'fine-tuning' with meter in *each* FET's supply (difficult, not for the newcomer) or complete 're-do from start'.
Hopefully helpfully - and "Best'v the Festive"!
Dex, ZL2DEX

Timothy Fidler
 

Basis of  above  rabbit out of the hat statement Drive power  in this case 25 mW =  10 Wout  x Alog  ( - 26/10)

Timothy Fidler
 

Chuck, 

there are cases where people have wanted a new Raduino and hfsignals has allegedly sold one of those , independently of other hardware (via an email enquiry to the gmail.com  letterbox ).  That was $25 USD plus shipping last I saw.  Subtract that from what you paid for your board and that will give you an idea of the cost you are up for.   (A fair proportion of the original price )
2. Re contacting HF signals - you could get cheeky and sniff around for a recent post/ans by A. Farhan on this wunnerful (sic)  BBS and reply to him about cost and arrangements for getting a new main board. 

3. There is another option (but with greater technical risk)  if you have not put it into a min. size case and if the board works fine on Rx. http://www.qrp-labs.com/linear.html  It needs 25 mW to drive it . You will need to ensure you have somewhere on the existing PCB that has this power available.  He does not state the input impedance of the  .... hust ma mouth... look at the input Z measurements by Fred  down the bottom of the referenced page.  BTW others (AN Other) AKA the mad radio modder has allegedly had the modified kit working on 6m SSB and it appears that the Hans 10 W kit is the one to do just that (with other mods on the HF signals board and firmware  too)

Mike Lichtman
 

Chuck,
Check to see if you have the heat sinks on the finals touching the case. That will blow them. 73 Mike KF6KXG