So coming soon with pictures and information ....
- (161.37 KiB) Downloaded 1465 times
- (192.08 KiB) Downloaded 1465 times
Not managed to get it going (yet), there seems to be a problem with the clock oscillator, I have the 6.5MHz out of Q1 once I realized that the silk screen for the transistor was the wrong way round ! But it only produces a vmax of 1.6V, the signal out of pin 8 of IC23 (LS86) is only 3.6V As is the divided 3.25MHz fed through R7/C4 to Q2. Putting the scope on the base of Q2 I get absolutely nothing, which is why no Z80 clock.
Having checked with my Real Ace board, the signal levels out of the oscillator and out of the LS86 seem correct, so it seems the problem lies around Q2 somewhere.
I do get a display of random bitmaps (as the character RAMS are uninitialized at this point) though it is not syncing properly.
I do wonder why some of the R and C values have been changed from the original circuit ? Also Q2 is a 2N2369 in the original but another 2N3904 in the kit.
I do have an original JA board which is currently not working so I'll cross check with that and hopefully end up with both working
I think the solution to this is to alter the value of R7, I'll do some experements this evening and post my results here.