Andres' H5 B1 Build

[exxos]

R21 and R22 measure 470 Ohms (and, at least in the schematics I have for the H5A, they are spec as 470 Ohms).

That is correct then. You must have a bad connection or something somewhere... As when the jumper is set, the clock output of the GAL is bypassed... So having the GAL in and floppy not working does not make sense...

[AndresPlazaR]

That is correct then. You must have a bad connection or something somewhere... As when the jumper is set, the clock output of the GAL is bypassed... So having the GAL in and floppy not working does not make sense...

Well, but this is the situation: having all floppy/1772 jumpers in the same position and GAL installed, if I boot TOS 1.04, the floppy works. If I boot TOS 2.06, the floppy doesn't work.

This behavior is the same whatever JP22 is in 1&2 or 2&3.

So, it does not seems to me it is a bad connection. But what is it? Don't know.

[AndresPlazaR]

OK, looking around with the oscilloscope, the signals coming from the Yamaha chip for floppy operations are VERY different for TOS 1.04 (floppy working) and TOS 2.06 (floppy not working):

pin 19 & 20: both TOS have activity in those pins, but different behavior.
pin 21: no activity at all on TOS 2.06

Will connect the logic analyzer and try to get something there.

[AndresPlazaR]

Here it is a comparison of pins 19 (DRIVE1_SEL), 20 (DRIVE0_SEL) and 21 (SIDE0_SEL) of the Yamaha chip, between TOS 1.04 and 2.06:

YMH_104_vs_206.jpg

When pin 21 goes up, the H5 has been powered on. Top is 1.04; bottom is 2.06.

I imagine that it is OK they are not exactly the same, but clearly the behavior is very different.

Ideas? :-)

[exxos]

Just to confirm... You got the gal from my store ?

Have you checked those signals on the gal ?

I just thought that the GAL drives signals on pins 18,19,22 so lift them out of the socket one by one and see if one of those has any effect. All 3 should be switching I think...

[AndresPlazaR]

Just to confirm... You got the gal from my store ?

Have you checked those signals on the gal ?

I just thought that the GAL drives signals on pins 18,19,22 so lift them out of the socket one by one and see if one of those has any effect. All 3 should be switching I think...

Interesting, I did not remember where I got the GAL, so I had to search in my emails, and I got it from your store. BUT, I now for a fact that, a few days ago, the GAL was not producing the right signal (8 MHz) on pin 14. I did not know (at the time) that GAL needed to be programmed (didn't know what GAL meant) so @Icky provided me with the JED code, that I uploaded to the GAL; at that point pin 14 is producing 8 MHz.

I will check the GAL signals on pins 18, 19, and 22 with the logic analyzer (that's what you meant with "lift", right?) and report back.

Thank you so much!!!

[exxos]

What I mean is carefully bend those pins out of the socket and see if the floppy starts working...

Those 3 signals control 2 datalines and the WP signal. So if there is a improvement then we know where to look better...

Of course if that does solve the problem, then check all the GAL inputs are switching... As a bad input will of course cause a bad output...

[AndresPlazaR]

What I mean is carefully bend those pins out of the socket and see if the floppy starts working...

I tried lifting the following combinations:
18
19
22
18&19
18&19&22
19&22

without change of behavior (aka, floppy does not work on TOS 2.06). :-(

[exxos]

I really dont know what to suggest then.. With the GAL acting as input only (with outputs isolated) it doesn't do anything when in the MB. You probably would have to ship it to @Steve to see if he can find anything amiss.

[AndresPlazaR]

I really dont know what to suggest then.. With the GAL acting as input only (with outputs isolated) it doesn't do anything when in the MB. You probably would have to ship it to @Steve to see if he can find anything amiss.

Mmmhhh... For the moment I will keep looking, I find this problem very educational. Until it gets frustrating. :-D

Do you think that the lack of the independent 16 MHz oscillator may have an impact? Because, as I mentioned before, I don't have it installed (but SJ3 is bridged).

Thanks again for all your help!