I'll get back on that later I'm not home right now
AU-X1
- Thread starter Willy6
- Start date
I guess it's back to the drawing board
Ronito6
Super Member
"Back to the drawing board" meaning just retesting the transformer?
Or is it a bit more serious?
Like abandoning the first project X1 and moving on to the 100v version?
No that transformer is good I need to put it back in and figure out where the short circuit is.I think it's on f-2781 somewhere so I have a few ideas for trouble shooting I'm gonna try
Those are the only diodes I didn't test cause I wasn't to sure how to go about testing them
Ronito6
Super Member
Those diodes are pretty reliable. Although Amp8 did change them out in his most recent X11 restoration.
l see what you're saying about the ground tab and I'll put some type of insulator between there but I think I'm gonna go thru things again and put new transistors and diodes in like John did.You wouldn't happen to have a diode and transistor replacement list handy would ya?
Ronito6
Super Member
Sorry, but the list I created was deemed unsafe by EchoWars.
So I dare not share it any longer.
BUT what I actually ended up doing was leave in most of the diodes. With painstaking testing I found that they were all good anyway.
I only swapped out all the Zener diodes, and two old germanium diodes for new ones on the driver board, and traded all VD1212 for two 1N4148's in series, and all MV 103 with three 1N4148's in series.
Tried and tested upgrades only
So I dare not share it any longer.
BUT what I actually ended up doing was leave in most of the diodes. With painstaking testing I found that they were all good anyway.
I only swapped out all the Zener diodes, and two old germanium diodes for new ones on the driver board, and traded all VD1212 for two 1N4148's in series, and all MV 103 with three 1N4148's in series.
Tried and tested upgrades only
The reason I suspect F-2781 is because when I unplugged the wire plugs that the arrows are pointing at the dbt still glowed bright and when I put the plugs back in and unplugged the red wire (circled)the dbt went dim and the soft start relay clicked and lights on the front panel came on.And that was also the reason I suspected that transformer. 
That pic is of the old board before I started
I'm at least gonna replace all of the 2sa992,2sc945 and 2sc1845's and the zener's and vd1212 and 1s2473's also the mv12 and mv103 with in series 1n4148s
Yes they all tested good with high current gain up around 105 hfe
I checked just about every transistor and they all checked good on my peak tester
That is a bridge rectifier, they don't usually blow, there is a direct replacement but you have to swap all 4 leads so the pin-out matches. You should 'Google' how to test them - it might come in handy - but it is best to remove them to test, otherwise you will get confusing readings.
That connector you pulled off is one of the feeds to the power amplifiers if I am not mistaken - the kind of thing that would cause an issue would be a short on an OP transistor or on one or more of the main capacitors? or maybe a trapped wire somewhere?
So, it is fairly unlikely that your issue was caused by something on the F-2781 board itself.
Yes I also suspected the main caps but my dmm measures OL so I'm not sure if they're bad or my dmm can't handle that high of capacity
