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Not a diode. That's a Transient Voltage Suppressor (TVS). Acts like a Metal Oxide Varistor (MOV - red discs in outlet strips) but can withstand a higher jolt without sacrificing itself. But, it sounds like yours has sacrificed itself in an attempt to protect your machine. The part number is...

I change my batteries when I change the smoke alarm batteries - new years. I use a remote battery holder in the base of the machine. I also use memcaps with good hold times in one of my machines. The voltage doesn't matter that much if you are changing from NiCAD to alkaline. Most memories...

Yeah... but Jameco doesn't offer NOS parts, only pulls (used). For comparison, Big Daddy parts are 68B21's at $5 ($7 for NOS), Jameco has 68B21's at $4.95. OK, Jameco also has 6821's - pulls for cheaper. Luckily, these parts are still made by one manufacturer. You don't see them often...

I agree. With the JEDEC files published 'somewhere' - GAL replacements for these old PAL's would be a dime-a-dozen. J

Yup, clone. EF prefix means the part came from ST Microelectronics. ST was probably the last company to discontinue these. J

Blank PAL's are pretty cheap at less than a buck apiece. Has anybody ever tried extracting the JEDEC data from one of these programmed PALs? Security fuses blown? J

It isn't uncommon for older EPROMS to erase and then not be programmable again - I've had it happen to me on several occasions (yes, I select correct part for programming voltages). Just be aware that any 2764's you buy are most probably old and used. 2764's have not been made in years. No...

Correct. Always beware of the super cheap stamped sockets - you will get what you pay for. These are almost always single wipe and won't last long. For me, I always use machine pin sockets. These typically have three or four tines. J

update to older post... I saw this old post and have the answer as to why these boards do this. In the olden days - the bare board was etched, tin/lead plated and then soldermasked. The soldermask was applied directly over the tin/lead plating. During the soldering process when parts are...

The tolerance on those caps is so wide that 27000 should be close enough... J

Not really a big deal cost wise... But, after the Chinese electrolyte fiasco - I avoid these and other Chinese names like the plague. I didn't notice you went with the Nichicons on the 4900 kit... I only looked at the 4600 and 'assumed' the 4900's followed. My mistake...

The guys that offer them up in kits probably get their caps from Mouser or Digikey as well. These two buy in huge quantities and get nice price breaks so it's tough for the little guys to compete with them...especially if they are buying them from Mouser or Digikey. Unfortunately, I think many...

Try here: http://www.greatplainselectronics.com/ribbon_categories.asp They start at 4" but I'll bet you can get one at 3" J

The little ones were 8 amp rated parts if I remember correctly. Direct replacements are typically 10 amp rated bridges such as part number MB104. The MB104's are usually just under $2 each. You can also use 35 amp bridge rectifiers but these require mounting to the top of the board. For...

$6 - Yeow!!!! Normal price on these is in the $2.50 range. For example see GBPC3504W at www.greatplainselectronics.com - diodes category. This is a 35 amp rated version for use on these boards. J

....pretty lame. Neither one gave you a list of which caps are included, type, age or anything else useful. Maybe if you ask why theirs is worth about $60 more - then you might get an answer. Schematics and tagged parts sure aren't worth it if that's the only difference. J

Real good question for which I have no answer. Not a single one of those sources list how many and which caps are included nor do they mention manufacturer or age of caps (i.e. cheap old NOS Chinese caps A.K.A. eBay caps versus brand new, high quality caps). Might try emailing them and asking...

Boards are washed when they're built -- ran thru large washers that look like dishwashers. BUT - they never ran certain items thru the board washers. I.e. DIP switches and several other components. I worked for an electronics company several years ago. They had a production line and a small...

Ice cube type relays will trap water and corrode. DIP swithes are notorious for tapping water inside. You will eventually get nice, blue-green colored contacts within them. If you have unsealed components such as relays, etc - don't wash this way. J

A lot of older standoffs had 0.156" holes for both ends of the standoffs. All the newer ones have 0.18" for one end and 0.156" for the other end. Finding 0.156" both end standoffs has become impossible. Curious, what was the desired length for this board? J