I've tried to run the output stage standalone. I put 10K resistors in series with the input rail power connector. The bulb lit bright. Next I tried 22k in series with the 15V input connector. Still bright. Nothing showing on the output now.
I've found the issue. The pattern is backwards for Q12 in the layout. We can either hack some traces or install Q12 upside down.
You could. Just remember the square pad is emitter, not base. Bias still isn't completely off even after this correction. I've got 1k2 for R34. I was going to change the pot to a 200R next. It's almost off.
I have no doubt the NS will show better numbers once it's properly tuned. There's a lot less parts to the mini board and it fits in a smaller area
I'm going to wait for Jeff to get the OPS working before I make any changes to mine. Meanwhile, yesterday, while trying to find the issue I started testing the IPS boards to see if that was my problem and had a probe slip and saw a puff of smoke so I know I have blown something but I can't see any damage. So, having said that, is there another schematic for the x4 that is different from the PDF Jeff sent to me? It has a lot of traces that overlay other traces and it is making it very difficult to see what goes where? It is too difficult to probe the tiny pins on the dual transistors.
Thanks, Terry
Thanks, Terry
Don't probe the tiny pins on the dual transistors,using very thin probe just probe resistors where they fit😉
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It's a lot easier to see what's happening by checking voltage drops on resistors instead of trying to probe transistors. The resistors themselves act as fuses a lot of times. There's a good chance you blew a resistor and it's now open circuit.
That is what I am trying to do but I cant read the schematic to see what each pin connects to.
I agree, but on this X4 with the large heatsinks, it is really difficult to get the probes to everything. I didn't want to do that while powered up. with through hole parts you can choose which side of the board you want to probe but with SMD you are limited. Just a learning curve for me.
I'll try to shuffle parts around a bit on the schematic and see if I can make it easier to read. This is a real sore spot with Diptrace. Schematics are ugly!
Agree,eagle eye is what you need.
Difficult to read those schematics especially when these printed😡
Well, it looks like I won't be testing a stereo set of the x4 boards. I had damaged Q7 but when removing it so I could replace it the pad for pin 5 came off with the part. I'm afraid the pins are just too tiny to try to attach a lead of any kind so this board is likely done for. I also learned that I need to use through bolts to attach the little heatsinks since the heads of the screws are facing each other. 😉
There's a new version of the VZ-X4 coming. I'm going to shuffle the output end around to fit a large single heat sink.
Reworking gets easier with practice. The remains of your board might be good for this. Blob lots of solder across the pads and pluck it off with two irons. The pads normally only lift if one is too cool.
Reworking gets easier with practice. The remains of your board might be good for this. Blob lots of solder across the pads and pluck it off with two irons. The pads normally only lift if one is too cool.
Well I was bored so I went ahead and cut the traces and installed jumpers to reverse Q12. I also installed a 200R trimmer and changed R34 to 1.2k. One of my boards is drawing way too much current, (the light bulb shines brightly), even with no IPS in place. The other board fires up but I can't get any bias at all, even with the trimmer set to 0R. I may try to put 1k1 back in R34. Still not sure why the one board doesn't work. I haven't found any shorts and all the transistors test fine with diode test. The two boards are slightly different since one is left hand and the other right hand. I wonder if there could be another mistake in the layout in that one. I'll keep hunting.