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A quick check of other components running very very hot include the Si5351 (oh dear!) and the D1 and D2. 73 Carl M0ICR

I would thoroughly visually inspect all parts and solder joints top and bottom if this has transitioned from working to non working. Worth checking the input current to the 7805 and output voltage of

Do you have access to a thermal imaging camera ? If you cant borrow one, or justify ?100+ to buy, build your own

So ... I have removed IC3, Q1, Q2, Q3, Q5 and Q6 and the 7805 regulator is still getting too hot to touch. Any thoughts please? 73 Carl M0ICR

Carl: Should be OK. Some variance with manufacturer Texas Instruments slightly faster than On Semiconductor. HCT fine to about 30 MHz, ACT to 50 MHz. 73 Fred WD9HNU

Hi Hans, ? Thanks I have just ordered a few of the correct devices and a bunch of other useful components for the parts bin. Excellent prices given the free international postage. Now to try and work

Alan, Many thanks. Progress report: I have removed IC3 and checked the 5V line which reads correctly at 5V off the regulator. I will need to get a replacement for IC3 but I do have a small stock of

Carl Remove IC3, check the 5V line and regulator is OK. Then you will possibly have to replace all items I mentioned. I do not know for sure without looking it up but maybe the ACT is faster, probably

Hi Carl A 74HCT00 is fine as far as the input voltage thresholds are concerned (it will convert the 3.3V output of the Si5351A nicely to 5V). But the 74ACT00 is a faster device and will do better

Thanks Alan, I think your theory is right, I need to replace IC3. I note that it appears easier to obtain a 74HCT00 rather than a 74ACT00 as originally supplied, do you or anyone else have any

His not being able to figure out why a certain post won't go, does not indicate he did something wrong. I am not moderator either; but it is unlikely that his post is being blocked *unless* there is

it would seem you did something wrong.? I am answering the latest post so you do have the ability to do so. I am not moderator. Allison

Dear All After one year of normal work even not having too much power ( not more than 1 W in 20 m band ) , now my QCX it is not working. I think the power transispor are off.? One year of experience

Jared- My build did the same thing with the exception of the volume being extremely loud. If I turn the gain off the lowest wetting, it is painfully loud. I’m watching your post for answers, as

I finished my 40 meter kit last night. When I powered it up (using 10 AA battery pack with 14.8 Volts) I was not able to align it. While calibrating I was able to maximize the out on 4.7 at 9 although

I recently posted a topic on Band Pass Filters and notice that it still hasn't appeared. How does the approval process work?? Thanks in advance. This is a very informative group.

Carl, My guess is IC3. You seem to have had the catastrophic failure reported here in the past. Q6, Q1, 2, 3 Q3. You might notice IC3 gets hot before IC11 blows if you just connect the power but I do

I have yet to build a QCX, but when I want to remove the varnish from wire, I scrape most of it off with a sharp knife. Bob AG7OZ

You might check with Mike at the old dog (the second address) address in my header. (I don't know how to copy and paste addresses in my iPad) He makes a beautiful 3D case and will sell you one or may

Also, clean the wire RIGHT UP TO THE BASE OF THE TOROID! Many times I thought I had cleaned it far enough but when I pulled it through with a little tension it went a little bit farther than I had