I have talked to Rich Comeau and explained our requirements. He is looking
for one that will work. 

Jed

Dennis, this is from my status report:

As a result of a meeting with various people alleged to be involved with the
project, it was discovered that the new higher current thyristors they were 
unable to get were, in fact, SCRs, and would not have worked. 

I have been in contact with Rich Comeau of Motorola. It seems that they
are in the process of making extensive changes to the fabs that make their 
thyristors and, basically, they can't deliver parts until October.

Rich Comeau checked all around and the ONLY Triacs he could find are
MAC223A10s from Future Electronic in Boston. They have 4,000 parts.
(The MAC223A10 is 25 Amps and 800 Volts.) Note, there are no MAC15A6s to be
had.

According to MANMAN we have 141 MAC223A8s in inventory (132004-001). They are
rated for 25 Amps and 600 Volts and were used in the Rump Thump Board.

SGS-Thompson also makes Triacs and someone could check with them if they
wanted to.


Motor Amp, Continued:
--------------------
At 60 Hz a half cycle is 8.33 ms. 

The counter that determines the conduction angle has a maximum length of 
8.19 ms.

At 50 Hz a half cycle is 10 ms. 

Therefore, what would be a low-power cycle at 60 Hz will be 2 ms 
(out of 10 ms) at 50 Hz.

If this needs to be fixed in hardware there are three options:

	1. Change the 1 MHz oscillator oscillator to 830 KHz.

		Not a standard frequency.

	2. Change the Divide Ratio from 64 to 78	[Board Change]

		Requires changing LS393 to GAL16V8.

	3. Change Divide Ratio to 128.			[One Cut, One Jumper]

		Reduces Programmable range from 128 to 78.

Jed

I just talked with Mark Sherman about some thoughts he has concerning 
the Motor Driver (Numfa) board.

. He requested the use of metal screws (with nylon insulators if 
  necessary) for mounting the Triacs to the heatsinks. He said that 
  the Nylon screws can not be tightened sufficiently, ant that they 
  get damaged too easily.

. Fuse holder mounting. He said that one of the fuseholders arrived 
  in France broken. He thought that the mounting for the fuseholder in 
  the board was not sufficient for the amount of pressure required to 
  get the fuse out of the holder.

. He reiterated the concern about the orientation of the triac 
  heatsinks. The triacs can not be replaced without removing one of 
  the heatsinks completely.

His comments were given for consideration in future designs, and 
where possible for consideration in the existing design.

This is a communication message, not an action request.
					Pat.